Table of Contents
- 1 Description
- 2 Codec Options
- 3 Decoders
- 4 Video Decoders
- 5 Audio Decoders
- 6 Subtitles Decoders
- 7 Encoders
- 8 Audio Encoders
- 8.1 aac
- 8.2 ac3 and ac3_fixed
- 8.3 flac
- 8.4 opus
- 8.5 libfdk_aac
- 8.6 libmp3lame
- 8.7 libopencore-amrnb
- 8.8 libopus
- 8.9 libshine
- 8.10 libtwolame
- 8.11 libvo-amrwbenc
- 8.12 libvorbis
- 8.13 mjpeg
- 8.14 wavpack
- 9 Video Encoders
- 9.1 a64_multi, a64_multi5
- 9.2 Cinepak
- 9.3 GIF
- 9.4 Hap
- 9.5 jpeg2000
- 9.6 librav1e
- 9.7 libaom-av1
- 9.8 libsvtav1
- 9.9 libjxl
- 9.10 libkvazaar
- 9.11 libopenh264
- 9.12 libtheora
- 9.13 libvpx
- 9.14 libwebp
- 9.15 libx264, libx264rgb
- 9.16 libx265
- 9.17 libxavs2
- 9.18 libxvid
- 9.19 MediaFoundation
- 9.20 mpeg2
- 9.21 png
- 9.22 ProRes
- 9.23 QSV Encoders
- 9.24 snow
- 9.25 VAAPI encoders
- 9.26 vbn
- 9.27 vc2
- 10 Subtitles Encoders
- 11 See Also
- 12 Authors
1 Description
This document describes the codecs (decoders and encoders) provided by the libavcodec library.
2 Codec Options
libavcodec provides some generic global options, which can be set on all the encoders and decoders. In addition each codec may support so-called private options, which are specific for a given codec.
Sometimes, a global option may only affect a specific kind of codec, and may be nonsensical or ignored by another, so you need to be aware of the meaning of the specified options. Also some options are meant only for decoding or encoding.
Options may be set by specifying -option value in the
FFmpeg tools, or by setting the value explicitly in the
AVCodecContext
options or using the libavutil/opt.h API
for programmatic use.
The list of supported options follow:
- b integer (encoding,audio,video)
Set bitrate in bits/s. Default value is 200K.
- ab integer (encoding,audio)
Set audio bitrate (in bits/s). Default value is 128K.
- bt integer (encoding,video)
Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to min/max bitrate. Lowering tolerance too much has an adverse effect on quality.
- flags flags (decoding/encoding,audio,video,subtitles)
Set generic flags.
Possible values:
- ‘mv4’
Use four motion vector by macroblock (mpeg4).
- ‘qpel’
Use 1/4 pel motion compensation.
- ‘loop’
Use loop filter.
- ‘qscale’
Use fixed qscale.
- ‘pass1’
Use internal 2pass ratecontrol in first pass mode.
- ‘pass2’
Use internal 2pass ratecontrol in second pass mode.
- ‘gray’
Only decode/encode grayscale.
- ‘psnr’
Set error[?] variables during encoding.
- ‘truncated’
Input bitstream might be randomly truncated.
- ‘drop_changed’
Don’t output frames whose parameters differ from first decoded frame in stream. Error AVERROR_INPUT_CHANGED is returned when a frame is dropped.
- ‘ildct’
Use interlaced DCT.
- ‘low_delay’
Force low delay.
- ‘global_header’
Place global headers in extradata instead of every keyframe.
- ‘bitexact’
Only write platform-, build- and time-independent data. (except (I)DCT). This ensures that file and data checksums are reproducible and match between platforms. Its primary use is for regression testing.
- ‘aic’
Apply H263 advanced intra coding / mpeg4 ac prediction.
- ‘ilme’
Apply interlaced motion estimation.
- ‘cgop’
Use closed gop.
- ‘output_corrupt’
Output even potentially corrupted frames.
- time_base rational number
Set codec time base.
It is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented. For fixed-fps content, timebase should be
1 / frame_rate
and timestamp increments should be identically 1.- g integer (encoding,video)
Set the group of picture (GOP) size. Default value is 12.
- ar integer (decoding/encoding,audio)
Set audio sampling rate (in Hz).
- ac integer (decoding/encoding,audio)
Set number of audio channels.
- cutoff integer (encoding,audio)
Set cutoff bandwidth. (Supported only by selected encoders, see their respective documentation sections.)
- frame_size integer (encoding,audio)
Set audio frame size.
Each submitted frame except the last must contain exactly frame_size samples per channel. May be 0 when the codec has CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is not restricted. It is set by some decoders to indicate constant frame size.
- frame_number integer
Set the frame number.
- delay integer
- qcomp float (encoding,video)
Set video quantizer scale compression (VBR). It is used as a constant in the ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0.
- qblur float (encoding,video)
Set video quantizer scale blur (VBR).
- qmin integer (encoding,video)
Set min video quantizer scale (VBR). Must be included between -1 and 69, default value is 2.
- qmax integer (encoding,video)
Set max video quantizer scale (VBR). Must be included between -1 and 1024, default value is 31.
- qdiff integer (encoding,video)
Set max difference between the quantizer scale (VBR).
- bf integer (encoding,video)
Set max number of B frames between non-B-frames.
Must be an integer between -1 and 16. 0 means that B-frames are disabled. If a value of -1 is used, it will choose an automatic value depending on the encoder.
Default value is 0.
- b_qfactor float (encoding,video)
Set qp factor between P and B frames.
- codec_tag integer
- bug flags (decoding,video)
Workaround not auto detected encoder bugs.
Possible values:
- ‘autodetect’
- ‘xvid_ilace’
Xvid interlacing bug (autodetected if fourcc==XVIX)
- ‘ump4’
(autodetected if fourcc==UMP4)
- ‘no_padding’
padding bug (autodetected)
- ‘amv’
- ‘qpel_chroma’
- ‘std_qpel’
old standard qpel (autodetected per fourcc/version)
- ‘qpel_chroma2’
- ‘direct_blocksize’
direct-qpel-blocksize bug (autodetected per fourcc/version)
- ‘edge’
edge padding bug (autodetected per fourcc/version)
- ‘hpel_chroma’
- ‘dc_clip’
- ‘ms’
Workaround various bugs in microsoft broken decoders.
- ‘trunc’
trancated frames
- strict integer (decoding/encoding,audio,video)
Specify how strictly to follow the standards.
Possible values:
- ‘very’
strictly conform to an older more strict version of the spec or reference software
- ‘strict’
strictly conform to all the things in the spec no matter what consequences
- ‘normal’
- ‘unofficial’
allow unofficial extensions
- ‘experimental’
allow non standardized experimental things, experimental (unfinished/work in progress/not well tested) decoders and encoders. Note: experimental decoders can pose a security risk, do not use this for decoding untrusted input.
- b_qoffset float (encoding,video)
Set QP offset between P and B frames.
- err_detect flags (decoding,audio,video)
Set error detection flags.
Possible values:
- ‘crccheck’
verify embedded CRCs
- ‘bitstream’
detect bitstream specification deviations
- ‘buffer’
detect improper bitstream length
- ‘explode’
abort decoding on minor error detection
- ‘ignore_err’
ignore decoding errors, and continue decoding. This is useful if you want to analyze the content of a video and thus want everything to be decoded no matter what. This option will not result in a video that is pleasing to watch in case of errors.
- ‘careful’
consider things that violate the spec and have not been seen in the wild as errors
- ‘compliant’
consider all spec non compliancies as errors
- ‘aggressive’
consider things that a sane encoder should not do as an error
- has_b_frames integer
- block_align integer
- rc_override_count integer
- maxrate integer (encoding,audio,video)
Set max bitrate tolerance (in bits/s). Requires bufsize to be set.
- minrate integer (encoding,audio,video)
Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use elsewise.
- bufsize integer (encoding,audio,video)
Set ratecontrol buffer size (in bits).
- i_qfactor float (encoding,video)
Set QP factor between P and I frames.
- i_qoffset float (encoding,video)
Set QP offset between P and I frames.
- dct integer (encoding,video)
Set DCT algorithm.
Possible values:
- ‘auto’
autoselect a good one (default)
- ‘fastint’
fast integer
- ‘int’
accurate integer
- ‘mmx’
- ‘altivec’
- ‘faan’
floating point AAN DCT
- lumi_mask float (encoding,video)
Compress bright areas stronger than medium ones.
- tcplx_mask float (encoding,video)
Set temporal complexity masking.
- scplx_mask float (encoding,video)
Set spatial complexity masking.
- p_mask float (encoding,video)
Set inter masking.
- dark_mask float (encoding,video)
Compress dark areas stronger than medium ones.
- idct integer (decoding/encoding,video)
Select IDCT implementation.
Possible values:
- ‘auto’
- ‘int’
- ‘simple’
- ‘simplemmx’
- ‘simpleauto’
Automatically pick a IDCT compatible with the simple one
- ‘arm’
- ‘altivec’
- ‘sh4’
- ‘simplearm’
- ‘simplearmv5te’
- ‘simplearmv6’
- ‘simpleneon’
- ‘xvid’
- ‘faani’
floating point AAN IDCT
- slice_count integer
- ec flags (decoding,video)
Set error concealment strategy.
Possible values:
- ‘guess_mvs’
iterative motion vector (MV) search (slow)
- ‘deblock’
use strong deblock filter for damaged MBs
- ‘favor_inter’
favor predicting from the previous frame instead of the current
- bits_per_coded_sample integer
- aspect rational number (encoding,video)
Set sample aspect ratio.
- sar rational number (encoding,video)
Set sample aspect ratio. Alias to aspect.
- debug flags (decoding/encoding,audio,video,subtitles)
Print specific debug info.
Possible values:
- ‘pict’
picture info
- ‘rc’
rate control
- ‘bitstream’
- ‘mb_type’
macroblock (MB) type
- ‘qp’
per-block quantization parameter (QP)
- ‘dct_coeff’
- ‘green_metadata’
display complexity metadata for the upcoming frame, GoP or for a given duration.
- ‘skip’
- ‘startcode’
- ‘er’
error recognition
- ‘mmco’
memory management control operations (H.264)
- ‘bugs’
- ‘buffers’
picture buffer allocations
- ‘thread_ops’
threading operations
- ‘nomc’
skip motion compensation
- cmp integer (encoding,video)
Set full pel me compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- subcmp integer (encoding,video)
Set sub pel me compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- mbcmp integer (encoding,video)
Set macroblock compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- ildctcmp integer (encoding,video)
Set interlaced dct compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- dia_size integer (encoding,video)
Set diamond type & size for motion estimation.
- ‘(1024, INT_MAX)’
full motion estimation(slowest)
- ‘(768, 1024]’
umh motion estimation
- ‘(512, 768]’
hex motion estimation
- ‘(256, 512]’
l2s diamond motion estimation
- ‘[2,256]’
var diamond motion estimation
- ‘(-1, 2)’
small diamond motion estimation
- ‘-1’
funny diamond motion estimation
- ‘(INT_MIN, -1)’
sab diamond motion estimation
- last_pred integer (encoding,video)
Set amount of motion predictors from the previous frame.
- precmp integer (encoding,video)
Set pre motion estimation compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- pre_dia_size integer (encoding,video)
Set diamond type & size for motion estimation pre-pass.
- subq integer (encoding,video)
Set sub pel motion estimation quality.
- me_range integer (encoding,video)
Set limit motion vectors range (1023 for DivX player).
- global_quality integer (encoding,audio,video)
- slice_flags integer
- mbd integer (encoding,video)
Set macroblock decision algorithm (high quality mode).
Possible values:
- ‘simple’
use mbcmp (default)
- ‘bits’
use fewest bits
- ‘rd’
use best rate distortion
- rc_init_occupancy integer (encoding,video)
Set number of bits which should be loaded into the rc buffer before decoding starts.
- flags2 flags (decoding/encoding,audio,video,subtitles)
-
Possible values:
- ‘fast’
Allow non spec compliant speedup tricks.
- ‘noout’
Skip bitstream encoding.
- ‘ignorecrop’
Ignore cropping information from sps.
- ‘local_header’
Place global headers at every keyframe instead of in extradata.
- ‘chunks’
Frame data might be split into multiple chunks.
- ‘showall’
Show all frames before the first keyframe.
- ‘export_mvs’
Export motion vectors into frame side-data (see
AV_FRAME_DATA_MOTION_VECTORS
) for codecs that support it. See also doc/examples/export_mvs.c.- ‘skip_manual’
Do not skip samples and export skip information as frame side data.
- ‘ass_ro_flush_noop’
Do not reset ASS ReadOrder field on flush.
- ‘icc_profiles’
Generate/parse embedded ICC profiles from/to colorimetry tags.
- export_side_data flags (decoding/encoding,audio,video,subtitles)
-
Possible values:
- ‘mvs’
Export motion vectors into frame side-data (see
AV_FRAME_DATA_MOTION_VECTORS
) for codecs that support it. See also doc/examples/export_mvs.c.- ‘prft’
Export encoder Producer Reference Time into packet side-data (see
AV_PKT_DATA_PRFT
) for codecs that support it.- ‘venc_params’
Export video encoding parameters through frame side data (see
AV_FRAME_DATA_VIDEO_ENC_PARAMS
) for codecs that support it. At present, those are H.264 and VP9.- ‘film_grain’
Export film grain parameters through frame side data (see
AV_FRAME_DATA_FILM_GRAIN_PARAMS
). Supported at present by AV1 decoders.
- threads integer (decoding/encoding,video)
Set the number of threads to be used, in case the selected codec implementation supports multi-threading.
Possible values:
- ‘auto, 0’
automatically select the number of threads to set
Default value is ‘auto’.
- dc integer (encoding,video)
Set intra_dc_precision.
- nssew integer (encoding,video)
Set nsse weight.
- skip_top integer (decoding,video)
Set number of macroblock rows at the top which are skipped.
- skip_bottom integer (decoding,video)
Set number of macroblock rows at the bottom which are skipped.
- profile integer (encoding,audio,video)
-
Set encoder codec profile. Default value is ‘unknown’. Encoder specific profiles are documented in the relevant encoder documentation.
- level integer (encoding,audio,video)
-
Possible values:
- ‘unknown’
- lowres integer (decoding,audio,video)
Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.
- mblmin integer (encoding,video)
Set min macroblock lagrange factor (VBR).
- mblmax integer (encoding,video)
Set max macroblock lagrange factor (VBR).
- skip_loop_filter integer (decoding,video)
- skip_idct integer (decoding,video)
- skip_frame integer (decoding,video)
-
Make decoder discard processing depending on the frame type selected by the option value.
skip_loop_filter skips frame loop filtering, skip_idct skips frame IDCT/dequantization, skip_frame skips decoding.
Possible values:
- ‘none’
Discard no frame.
- ‘default’
Discard useless frames like 0-sized frames.
- ‘noref’
Discard all non-reference frames.
- ‘bidir’
Discard all bidirectional frames.
- ‘nokey’
Discard all frames excepts keyframes.
- ‘nointra’
Discard all frames except I frames.
- ‘all’
Discard all frames.
Default value is ‘default’.
- bidir_refine integer (encoding,video)
Refine the two motion vectors used in bidirectional macroblocks.
- keyint_min integer (encoding,video)
Set minimum interval between IDR-frames.
- refs integer (encoding,video)
Set reference frames to consider for motion compensation.
- trellis integer (encoding,audio,video)
Set rate-distortion optimal quantization.
- mv0_threshold integer (encoding,video)
- compression_level integer (encoding,audio,video)
- bits_per_raw_sample integer
- channel_layout integer (decoding/encoding,audio)
-
Possible values:
- request_channel_layout integer (decoding,audio)
-
Possible values:
- rc_max_vbv_use float (encoding,video)
- rc_min_vbv_use float (encoding,video)
- ticks_per_frame integer (decoding/encoding,audio,video)
- color_primaries integer (decoding/encoding,video)
Possible values:
- ‘bt709’
BT.709
- ‘bt470m’
BT.470 M
- ‘bt470bg’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘film’
Film
- ‘bt2020’
BT.2020
- ‘smpte428’
- ‘smpte428_1’
SMPTE ST 428-1
- ‘smpte431’
SMPTE 431-2
- ‘smpte432’
SMPTE 432-1
- ‘jedec-p22’
JEDEC P22
- color_trc integer (decoding/encoding,video)
Possible values:
- ‘bt709’
BT.709
- ‘gamma22’
BT.470 M
- ‘gamma28’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘linear’
Linear
- ‘log’
- ‘log100’
Log
- ‘log_sqrt’
- ‘log316’
Log square root
- ‘iec61966_2_4’
- ‘iec61966-2-4’
IEC 61966-2-4
- ‘bt1361’
- ‘bt1361e’
BT.1361
- ‘iec61966_2_1’
- ‘iec61966-2-1’
IEC 61966-2-1
- ‘bt2020_10’
- ‘bt2020_10bit’
BT.2020 - 10 bit
- ‘bt2020_12’
- ‘bt2020_12bit’
BT.2020 - 12 bit
- ‘smpte2084’
SMPTE ST 2084
- ‘smpte428’
- ‘smpte428_1’
SMPTE ST 428-1
- ‘arib-std-b67’
ARIB STD-B67
- colorspace integer (decoding/encoding,video)
Possible values:
- ‘rgb’
RGB
- ‘bt709’
BT.709
- ‘fcc’
FCC
- ‘bt470bg’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘ycocg’
YCOCG
- ‘bt2020nc’
- ‘bt2020_ncl’
BT.2020 NCL
- ‘bt2020c’
- ‘bt2020_cl’
BT.2020 CL
- ‘smpte2085’
SMPTE 2085
- ‘chroma-derived-nc’
Chroma-derived NCL
- ‘chroma-derived-c’
Chroma-derived CL
- ‘ictcp’
ICtCp
- color_range integer (decoding/encoding,video)
If used as input parameter, it serves as a hint to the decoder, which color_range the input has. Possible values:
- ‘tv’
- ‘mpeg’
MPEG (219*2^(n-8))
- ‘pc’
- ‘jpeg’
JPEG (2^n-1)
- chroma_sample_location integer (decoding/encoding,video)
Possible values:
- ‘left’
- ‘center’
- ‘topleft’
- ‘top’
- ‘bottomleft’
- ‘bottom’
- log_level_offset integer
Set the log level offset.
- slices integer (encoding,video)
Number of slices, used in parallelized encoding.
- thread_type flags (decoding/encoding,video)
Select which multithreading methods to use.
Use of ‘frame’ will increase decoding delay by one frame per thread, so clients which cannot provide future frames should not use it.
Possible values:
- ‘slice’
Decode more than one part of a single frame at once.
Multithreading using slices works only when the video was encoded with slices.
- ‘frame’
Decode more than one frame at once.
Default value is ‘slice+frame’.
- audio_service_type integer (encoding,audio)
Set audio service type.
Possible values:
- ‘ma’
Main Audio Service
- ‘ef’
Effects
- ‘vi’
Visually Impaired
- ‘hi’
Hearing Impaired
- ‘di’
Dialogue
- ‘co’
Commentary
- ‘em’
Emergency
- ‘vo’
Voice Over
- ‘ka’
Karaoke
- request_sample_fmt sample_fmt (decoding,audio)
Set sample format audio decoders should prefer. Default value is
none
.- pkt_timebase rational number
- sub_charenc encoding (decoding,subtitles)
Set the input subtitles character encoding.
- field_order field_order (video)
Set/override the field order of the video. Possible values:
- ‘progressive’
Progressive video
- ‘tt’
Interlaced video, top field coded and displayed first
- ‘bb’
Interlaced video, bottom field coded and displayed first
- ‘tb’
Interlaced video, top coded first, bottom displayed first
- ‘bt’
Interlaced video, bottom coded first, top displayed first
- skip_alpha bool (decoding,video)
Set to 1 to disable processing alpha (transparency). This works like the ‘gray’ flag in the flags option which skips chroma information instead of alpha. Default is 0.
- codec_whitelist list (input)
"," separated list of allowed decoders. By default all are allowed.
- dump_separator string (input)
Separator used to separate the fields printed on the command line about the Stream parameters. For example, to separate the fields with newlines and indentation:
ffprobe -dump_separator " " -i ~/videos/matrixbench_mpeg2.mpg
- max_pixels integer (decoding/encoding,video)
Maximum number of pixels per image. This value can be used to avoid out of memory failures due to large images.
- apply_cropping bool (decoding,video)
Enable cropping if cropping parameters are multiples of the required alignment for the left and top parameters. If the alignment is not met the cropping will be partially applied to maintain alignment. Default is 1 (enabled). Note: The required alignment depends on if
AV_CODEC_FLAG_UNALIGNED
is set and the CPU.AV_CODEC_FLAG_UNALIGNED
cannot be changed from the command line. Also hardware decoders will not apply left/top Cropping.
3 Decoders
Decoders are configured elements in FFmpeg which allow the decoding of multimedia streams.
When you configure your FFmpeg build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding --enable-lib
option. You can list all
available decoders using the configure option --list-decoders
.
You can disable all the decoders with the configure option
--disable-decoders
and selectively enable / disable single decoders
with the options --enable-decoder=DECODER
/
--disable-decoder=DECODER
.
The option -decoders
of the ff* tools will display the list of
enabled decoders.
4 Video Decoders
A description of some of the currently available video decoders follows.
4.1 av1
AOMedia Video 1 (AV1) decoder.
4.1.1 Options
- operating_point
Select an operating point of a scalable AV1 bitstream (0 - 31). Default is 0.
4.2 rawvideo
Raw video decoder.
This decoder decodes rawvideo streams.
4.2.1 Options
- top top_field_first
Specify the assumed field type of the input video.
- -1
the video is assumed to be progressive (default)
- 0
bottom-field-first is assumed
- 1
top-field-first is assumed
4.3 libdav1d
dav1d AV1 decoder.
libdav1d allows libavcodec to decode the AOMedia Video 1 (AV1) codec.
Requires the presence of the libdav1d headers and library during configuration.
You need to explicitly configure the build with --enable-libdav1d
.
4.3.1 Options
The following options are supported by the libdav1d wrapper.
- framethreads
Set amount of frame threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the global option
threads
instead.- tilethreads
Set amount of tile threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the global option
threads
instead.- filmgrain
Apply film grain to the decoded video if present in the bitstream. Defaults to the internal default of the library. This option is deprecated and will be removed in the future. See the global option
export_side_data
to export Film Grain parameters instead of applying it.- oppoint
Select an operating point of a scalable AV1 bitstream (0 - 31). Defaults to the internal default of the library.
- alllayers
Output all spatial layers of a scalable AV1 bitstream. The default value is false.
4.4 libdavs2
AVS2-P2/IEEE1857.4 video decoder wrapper.
This decoder allows libavcodec to decode AVS2 streams with davs2 library.
4.5 libuavs3d
AVS3-P2/IEEE1857.10 video decoder.
libuavs3d allows libavcodec to decode AVS3 streams.
Requires the presence of the libuavs3d headers and library during configuration.
You need to explicitly configure the build with --enable-libuavs3d
.
4.5.1 Options
The following option is supported by the libuavs3d wrapper.
- frame_threads
Set amount of frame threads to use during decoding. The default value is 0 (autodetect).
4.6 QSV Decoders
The family of Intel QuickSync Video decoders (VC1, MPEG-2, H.264, HEVC, JPEG/MJPEG, VP8, VP9, AV1).
4.6.1 Common Options
The following options are supported by all qsv decoders.
- async_depth
Internal parallelization depth, the higher the value the higher the latency.
- gpu_copy
A GPU-accelerated copy between video and system memory
- ‘default’
- ‘on’
- ‘off’
4.6.2 HEVC Options
Extra options for hevc_qsv.
- load_plugin
A user plugin to load in an internal session
- ‘none’
- ‘hevc_sw’
- ‘hevc_hw’
- load_plugins
A :-separate list of hexadecimal plugin UIDs to load in an internal session
4.7 v210
Uncompressed 4:2:2 10-bit decoder.
4.7.1 Options
- custom_stride
Set the line size of the v210 data in bytes. The default value is 0 (autodetect). You can use the special -1 value for a strideless v210 as seen in BOXX files.
5 Audio Decoders
A description of some of the currently available audio decoders follows.
5.1 ac3
AC-3 audio decoder.
This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet).
5.1.1 AC-3 Decoder Options
- -drc_scale value
Dynamic Range Scale Factor. The factor to apply to dynamic range values from the AC-3 stream. This factor is applied exponentially. The default value is 1. There are 3 notable scale factor ranges:
- drc_scale == 0
DRC disabled. Produces full range audio.
- 0 < drc_scale <= 1
DRC enabled. Applies a fraction of the stream DRC value. Audio reproduction is between full range and full compression.
- drc_scale > 1
DRC enabled. Applies drc_scale asymmetrically. Loud sounds are fully compressed. Soft sounds are enhanced.
5.2 flac
FLAC audio decoder.
This decoder aims to implement the complete FLAC specification from Xiph.
5.2.1 FLAC Decoder options
- -use_buggy_lpc
The lavc FLAC encoder used to produce buggy streams with high lpc values (like the default value). This option makes it possible to decode such streams correctly by using lavc’s old buggy lpc logic for decoding.
5.3 ffwavesynth
Internal wave synthesizer.
This decoder generates wave patterns according to predefined sequences. Its use is purely internal and the format of the data it accepts is not publicly documented.
5.4 libcelt
libcelt decoder wrapper.
libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
Requires the presence of the libcelt headers and library during configuration.
You need to explicitly configure the build with --enable-libcelt
.
5.5 libgsm
libgsm decoder wrapper.
libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
the presence of the libgsm headers and library during configuration. You need
to explicitly configure the build with --enable-libgsm
.
This decoder supports both the ordinary GSM and the Microsoft variant.
5.6 libilbc
libilbc decoder wrapper.
libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
audio codec. Requires the presence of the libilbc headers and library during
configuration. You need to explicitly configure the build with
--enable-libilbc
.
5.6.1 Options
The following option is supported by the libilbc wrapper.
- enhance
-
Enable the enhancement of the decoded audio when set to 1. The default value is 0 (disabled).
5.7 libopencore-amrnb
libopencore-amrnb decoder wrapper.
libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
Narrowband audio codec. Using it requires the presence of the
libopencore-amrnb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrnb
.
An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB without this library.
5.8 libopencore-amrwb
libopencore-amrwb decoder wrapper.
libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
Wideband audio codec. Using it requires the presence of the
libopencore-amrwb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrwb
.
An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB without this library.
5.9 libopus
libopus decoder wrapper.
libopus allows libavcodec to decode the Opus Interactive Audio Codec.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
--enable-libopus
.
An FFmpeg native decoder for Opus exists, so users can decode Opus without this library.
6 Subtitles Decoders
6.1 libaribb24
ARIB STD-B24 caption decoder.
Implements profiles A and C of the ARIB STD-B24 standard.
6.1.1 libaribb24 Decoder Options
- -aribb24-base-path path
Sets the base path for the libaribb24 library. This is utilized for reading of configuration files (for custom unicode conversions), and for dumping of non-text symbols as images under that location.
Unset by default.
- -aribb24-skip-ruby-text boolean
Tells the decoder wrapper to skip text blocks that contain half-height ruby text.
Enabled by default.
6.2 dvbsub
6.2.1 Options
- compute_clut
- -2
Compute clut once if no matching CLUT is in the stream.
- -1
Compute clut if no matching CLUT is in the stream.
- 0
Never compute CLUT
- 1
Always compute CLUT and override the one provided in the stream.
- dvb_substream
Selects the dvb substream, or all substreams if -1 which is default.
6.3 dvdsub
This codec decodes the bitmap subtitles used in DVDs; the same subtitles can also be found in VobSub file pairs and in some Matroska files.
6.3.1 Options
- palette
Specify the global palette used by the bitmaps. When stored in VobSub, the palette is normally specified in the index file; in Matroska, the palette is stored in the codec extra-data in the same format as in VobSub. In DVDs, the palette is stored in the IFO file, and therefore not available when reading from dumped VOB files.
The format for this option is a string containing 16 24-bits hexadecimal numbers (without 0x prefix) separated by commas, for example
0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b
.- ifo_palette
Specify the IFO file from which the global palette is obtained. (experimental)
- forced_subs_only
Only decode subtitle entries marked as forced. Some titles have forced and non-forced subtitles in the same track. Setting this flag to
1
will only keep the forced subtitles. Default value is0
.
6.4 libzvbi-teletext
Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
subtitles. Requires the presence of the libzvbi headers and library during
configuration. You need to explicitly configure the build with
--enable-libzvbi
.
6.4.1 Options
- txt_page
List of teletext page numbers to decode. Pages that do not match the specified list are dropped. You may use the special
*
string to match all pages, orsubtitle
to match all subtitle pages. Default value is *.- txt_default_region
Set default character set used for decoding, a value between 0 and 87 (see ETS 300 706, Section 15, Table 32). Default value is -1, which does not override the libzvbi default. This option is needed for some legacy level 1.0 transmissions which cannot signal the proper charset.
- txt_chop_top
Discards the top teletext line. Default value is 1.
- txt_format
Specifies the format of the decoded subtitles.
- bitmap
The default format, you should use this for teletext pages, because certain graphics and colors cannot be expressed in simple text or even ASS.
- text
Simple text based output without formatting.
- ass
Formatted ASS output, subtitle pages and teletext pages are returned in different styles, subtitle pages are stripped down to text, but an effort is made to keep the text alignment and the formatting.
- txt_left
X offset of generated bitmaps, default is 0.
- txt_top
Y offset of generated bitmaps, default is 0.
- txt_chop_spaces
Chops leading and trailing spaces and removes empty lines from the generated text. This option is useful for teletext based subtitles where empty spaces may be present at the start or at the end of the lines or empty lines may be present between the subtitle lines because of double-sized teletext characters. Default value is 1.
- txt_duration
Sets the display duration of the decoded teletext pages or subtitles in milliseconds. Default value is -1 which means infinity or until the next subtitle event comes.
- txt_transparent
Force transparent background of the generated teletext bitmaps. Default value is 0 which means an opaque background.
- txt_opacity
Sets the opacity (0-255) of the teletext background. If txt_transparent is not set, it only affects characters between a start box and an end box, typically subtitles. Default value is 0 if txt_transparent is set, 255 otherwise.
7 Encoders
Encoders are configured elements in FFmpeg which allow the encoding of multimedia streams.
When you configure your FFmpeg build, all the supported native encoders
are enabled by default. Encoders requiring an external library must be enabled
manually via the corresponding --enable-lib
option. You can list all
available encoders using the configure option --list-encoders
.
You can disable all the encoders with the configure option
--disable-encoders
and selectively enable / disable single encoders
with the options --enable-encoder=ENCODER
/
--disable-encoder=ENCODER
.
The option -encoders
of the ff* tools will display the list of
enabled encoders.
8 Audio Encoders
A description of some of the currently available audio encoders follows.
8.1 aac
Advanced Audio Coding (AAC) encoder.
This encoder is the default AAC encoder, natively implemented into FFmpeg.
8.1.1 Options
- b
Set bit rate in bits/s. Setting this automatically activates constant bit rate (CBR) mode. If this option is unspecified it is set to 128kbps.
- q
Set quality for variable bit rate (VBR) mode. This option is valid only using the
ffmpeg
command-line tool. For library interface users, use global_quality.- cutoff
Set cutoff frequency. If unspecified will allow the encoder to dynamically adjust the cutoff to improve clarity on low bitrates.
- aac_coder
Set AAC encoder coding method. Possible values:
- ‘twoloop’
Two loop searching (TLS) method. This is the default method.
This method first sets quantizers depending on band thresholds and then tries to find an optimal combination by adding or subtracting a specific value from all quantizers and adjusting some individual quantizer a little. Will tune itself based on whether aac_is, aac_ms and aac_pns are enabled.
- ‘anmr’
Average noise to mask ratio (ANMR) trellis-based solution.
This is an experimental coder which currently produces a lower quality, is more unstable and is slower than the default twoloop coder but has potential. Currently has no support for the aac_is or aac_pns options. Not currently recommended.
- ‘fast’
Constant quantizer method.
Uses a cheaper version of twoloop algorithm that doesn’t try to do as many clever adjustments. Worse with low bitrates (less than 64kbps), but is better and much faster at higher bitrates.
- aac_ms
Sets mid/side coding mode. The default value of "auto" will automatically use M/S with bands which will benefit from such coding. Can be forced for all bands using the value "enable", which is mainly useful for debugging or disabled using "disable".
- aac_is
Sets intensity stereo coding tool usage. By default, it’s enabled and will automatically toggle IS for similar pairs of stereo bands if it’s beneficial. Can be disabled for debugging by setting the value to "disable".
- aac_pns
Uses perceptual noise substitution to replace low entropy high frequency bands with imperceptible white noise during the decoding process. By default, it’s enabled, but can be disabled for debugging purposes by using "disable".
- aac_tns
Enables the use of a multitap FIR filter which spans through the high frequency bands to hide quantization noise during the encoding process and is reverted by the decoder. As well as decreasing unpleasant artifacts in the high range this also reduces the entropy in the high bands and allows for more bits to be used by the mid-low bands. By default it’s enabled but can be disabled for debugging by setting the option to "disable".
- aac_ltp
Enables the use of the long term prediction extension which increases coding efficiency in very low bandwidth situations such as encoding of voice or solo piano music by extending constant harmonic peaks in bands throughout frames. This option is implied by profile:a aac_low and is incompatible with aac_pred. Use in conjunction with -ar to decrease the samplerate.
- aac_pred
Enables the use of a more traditional style of prediction where the spectral coefficients transmitted are replaced by the difference of the current coefficients minus the previous "predicted" coefficients. In theory and sometimes in practice this can improve quality for low to mid bitrate audio. This option implies the aac_main profile and is incompatible with aac_ltp.
- profile
Sets the encoding profile, possible values:
- ‘aac_low’
The default, AAC "Low-complexity" profile. Is the most compatible and produces decent quality.
- ‘mpeg2_aac_low’
Equivalent to
-profile:a aac_low -aac_pns 0
. PNS was introduced with the MPEG4 specifications.- ‘aac_ltp’
Long term prediction profile, is enabled by and will enable the aac_ltp option. Introduced in MPEG4.
- ‘aac_main’
Main-type prediction profile, is enabled by and will enable the aac_pred option. Introduced in MPEG2.
If this option is unspecified it is set to ‘aac_low’.
8.2 ac3 and ac3_fixed
AC-3 audio encoders.
These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet).
The ac3 encoder uses floating-point math, while the ac3_fixed
encoder only uses fixed-point integer math. This does not mean that one is
always faster, just that one or the other may be better suited to a
particular system. The ac3_fixed encoder is not the default codec for
any of the output formats, so it must be specified explicitly using the option
-acodec ac3_fixed
in order to use it.
8.2.1 AC-3 Metadata
The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not affect the audio encoding itself. Some of the options do directly affect or influence the decoding and playback of the resulting bitstream, while others are just for informational purposes. A few of the options will add bits to the output stream that could otherwise be used for audio data, and will thus affect the quality of the output. Those will be indicated accordingly with a note in the option list below.
These parameters are described in detail in several publicly-available documents.
- A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard
- A/54 - Guide to the Use of the ATSC Digital Television Standard
- Dolby Metadata Guide
- Dolby Digital Professional Encoding Guidelines
8.2.1.1 Metadata Control Options
- -per_frame_metadata boolean
Allow Per-Frame Metadata. Specifies if the encoder should check for changing metadata for each frame.
- 0
The metadata values set at initialization will be used for every frame in the stream. (default)
- 1
Metadata values can be changed before encoding each frame.
8.2.1.2 Downmix Levels
- -center_mixlev level
Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo. This field will only be written to the bitstream if a center channel is present. The value is specified as a scale factor. There are 3 valid values:
- 0.707
Apply -3dB gain
- 0.595
Apply -4.5dB gain (default)
- 0.500
Apply -6dB gain
- -surround_mixlev level
Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo. This field will only be written to the bitstream if one or more surround channels are present. The value is specified as a scale factor. There are 3 valid values:
- 0.707
Apply -3dB gain
- 0.500
Apply -6dB gain (default)
- 0.000
Silence Surround Channel(s)
8.2.1.3 Audio Production Information
Audio Production Information is optional information describing the mixing environment. Either none or both of the fields are written to the bitstream.
- -mixing_level number
Mixing Level. Specifies peak sound pressure level (SPL) in the production environment when the mix was mastered. Valid values are 80 to 111, or -1 for unknown or not indicated. The default value is -1, but that value cannot be used if the Audio Production Information is written to the bitstream. Therefore, if the
room_type
option is not the default value, themixing_level
option must not be -1.- -room_type type
Room Type. Describes the equalization used during the final mixing session at the studio or on the dubbing stage. A large room is a dubbing stage with the industry standard X-curve equalization; a small room has flat equalization. This field will not be written to the bitstream if both the
mixing_level
option and theroom_type
option have the default values.- 0
- notindicated
Not Indicated (default)
- 1
- large
Large Room
- 2
- small
Small Room
8.2.1.4 Other Metadata Options
- -copyright boolean
Copyright Indicator. Specifies whether a copyright exists for this audio.
- 0
- off
No Copyright Exists (default)
- 1
- on
Copyright Exists
- -dialnorm value
Dialogue Normalization. Indicates how far the average dialogue level of the program is below digital 100% full scale (0 dBFS). This parameter determines a level shift during audio reproduction that sets the average volume of the dialogue to a preset level. The goal is to match volume level between program sources. A value of -31dB will result in no volume level change, relative to the source volume, during audio reproduction. Valid values are whole numbers in the range -31 to -1, with -31 being the default.
- -dsur_mode mode
Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround (Pro Logic). This field will only be written to the bitstream if the audio stream is stereo. Using this option does NOT mean the encoder will actually apply Dolby Surround processing.
- 0
- notindicated
Not Indicated (default)
- 1
- off
Not Dolby Surround Encoded
- 2
- on
Dolby Surround Encoded
- -original boolean
Original Bit Stream Indicator. Specifies whether this audio is from the original source and not a copy.
- 0
- off
Not Original Source
- 1
- on
Original Source (default)
8.2.2 Extended Bitstream Information
The extended bitstream options are part of the Alternate Bit Stream Syntax as
specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts.
If any one parameter in a group is specified, all values in that group will be
written to the bitstream. Default values are used for those that are written
but have not been specified. If the mixing levels are written, the decoder
will use these values instead of the ones specified in the center_mixlev
and surround_mixlev
options if it supports the Alternate Bit Stream
Syntax.
8.2.2.1 Extended Bitstream Information - Part 1
- -dmix_mode mode
Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt (Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.
- 0
- notindicated
Not Indicated (default)
- 1
- ltrt
Lt/Rt Downmix Preferred
- 2
- loro
Lo/Ro Downmix Preferred
- -ltrt_cmixlev level
Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lt/Rt mode.
- 1.414
Apply +3dB gain
- 1.189
Apply +1.5dB gain
- 1.000
Apply 0dB gain
- 0.841
Apply -1.5dB gain
- 0.707
Apply -3.0dB gain
- 0.595
Apply -4.5dB gain (default)
- 0.500
Apply -6.0dB gain
- 0.000
Silence Center Channel
- -ltrt_surmixlev level
Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lt/Rt mode.
- 0.841
Apply -1.5dB gain
- 0.707
Apply -3.0dB gain
- 0.595
Apply -4.5dB gain
- 0.500
Apply -6.0dB gain (default)
- 0.000
Silence Surround Channel(s)
- -loro_cmixlev level
Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lo/Ro mode.
- 1.414
Apply +3dB gain
- 1.189
Apply +1.5dB gain
- 1.000
Apply 0dB gain
- 0.841
Apply -1.5dB gain
- 0.707
Apply -3.0dB gain
- 0.595
Apply -4.5dB gain (default)
- 0.500
Apply -6.0dB gain
- 0.000
Silence Center Channel
- -loro_surmixlev level
Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lo/Ro mode.
- 0.841
Apply -1.5dB gain
- 0.707
Apply -3.0dB gain
- 0.595
Apply -4.5dB gain
- 0.500
Apply -6.0dB gain (default)
- 0.000
Silence Surround Channel(s)
8.2.2.2 Extended Bitstream Information - Part 2
- -dsurex_mode mode
Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX (7.1 matrixed to 5.1). Using this option does NOT mean the encoder will actually apply Dolby Surround EX processing.
- 0
- notindicated
Not Indicated (default)
- 1
- on
Dolby Surround EX Off
- 2
- off
Dolby Surround EX On
- -dheadphone_mode mode
Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone encoding (multi-channel matrixed to 2.0 for use with headphones). Using this option does NOT mean the encoder will actually apply Dolby Headphone processing.
- 0
- notindicated
Not Indicated (default)
- 1
- on
Dolby Headphone Off
- 2
- off
Dolby Headphone On
- -ad_conv_type type
A/D Converter Type. Indicates whether the audio has passed through HDCD A/D conversion.
- 0
- standard
Standard A/D Converter (default)
- 1
- hdcd
HDCD A/D Converter
8.2.3 Other AC-3 Encoding Options
- -stereo_rematrixing boolean
Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This is an optional AC-3 feature that increases quality by selectively encoding the left/right channels as mid/side. This option is enabled by default, and it is highly recommended that it be left as enabled except for testing purposes.
- cutoff frequency
Set lowpass cutoff frequency. If unspecified, the encoder selects a default determined by various other encoding parameters.
8.2.4 Floating-Point-Only AC-3 Encoding Options
These options are only valid for the floating-point encoder and do not exist for the fixed-point encoder due to the corresponding features not being implemented in fixed-point.
- -channel_coupling boolean
Enables/Disables use of channel coupling, which is an optional AC-3 feature that increases quality by combining high frequency information from multiple channels into a single channel. The per-channel high frequency information is sent with less accuracy in both the frequency and time domains. This allows more bits to be used for lower frequencies while preserving enough information to reconstruct the high frequencies. This option is enabled by default for the floating-point encoder and should generally be left as enabled except for testing purposes or to increase encoding speed.
- -1
- auto
Selected by Encoder (default)
- 0
- off
Disable Channel Coupling
- 1
- on
Enable Channel Coupling
- -cpl_start_band number
Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a value higher than the bandwidth is used, it will be reduced to 1 less than the coupling end band. If auto is used, the start band will be determined by the encoder based on the bit rate, sample rate, and channel layout. This option has no effect if channel coupling is disabled.
- -1
- auto
Selected by Encoder (default)
8.3 flac
FLAC (Free Lossless Audio Codec) Encoder
8.3.1 Options
The following options are supported by FFmpeg’s flac encoder.
- compression_level
Sets the compression level, which chooses defaults for many other options if they are not set explicitly. Valid values are from 0 to 12, 5 is the default.
- frame_size
Sets the size of the frames in samples per channel.
- lpc_coeff_precision
Sets the LPC coefficient precision, valid values are from 1 to 15, 15 is the default.
- lpc_type
Sets the first stage LPC algorithm
- ‘none’
LPC is not used
- ‘fixed’
fixed LPC coefficients
- ‘levinson’
- ‘cholesky’
- lpc_passes
Number of passes to use for Cholesky factorization during LPC analysis
- min_partition_order
The minimum partition order
- max_partition_order
The maximum partition order
- prediction_order_method
- ‘estimation’
- ‘2level’
- ‘4level’
- ‘8level’
- ‘search’
Bruteforce search
- ‘log’
- ch_mode
Channel mode
- ‘auto’
The mode is chosen automatically for each frame
- ‘indep’
Channels are independently coded
- ‘left_side’
- ‘right_side’
- ‘mid_side’
- exact_rice_parameters
Chooses if rice parameters are calculated exactly or approximately. if set to 1 then they are chosen exactly, which slows the code down slightly and improves compression slightly.
- multi_dim_quant
Multi Dimensional Quantization. If set to 1 then a 2nd stage LPC algorithm is applied after the first stage to finetune the coefficients. This is quite slow and slightly improves compression.
8.4 opus
Opus encoder.
This is a native FFmpeg encoder for the Opus format. Currently its in development and only implements the CELT part of the codec. Its quality is usually worse and at best is equal to the libopus encoder.
8.4.1 Options
- b
Set bit rate in bits/s. If unspecified it uses the number of channels and the layout to make a good guess.
- opus_delay
Sets the maximum delay in milliseconds. Lower delays than 20ms will very quickly decrease quality.
8.5 libfdk_aac
libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.
The libfdk-aac library is based on the Fraunhofer FDK AAC code from the Android project.
Requires the presence of the libfdk-aac headers and library during
configuration. You need to explicitly configure the build with
--enable-libfdk-aac
. The library is also incompatible with GPL,
so if you allow the use of GPL, you should configure with
--enable-gpl --enable-nonfree --enable-libfdk-aac
.
This encoder has support for the AAC-HE profiles.
VBR encoding, enabled through the vbr or flags +qscale options, is experimental and only works with some combinations of parameters.
Support for encoding 7.1 audio is only available with libfdk-aac 0.1.3 or higher.
For more information see the fdk-aac project at http://sourceforge.net/p/opencore-amr/fdk-aac/.
8.5.1 Options
The following options are mapped on the shared FFmpeg codec options.
- b
Set bit rate in bits/s. If the bitrate is not explicitly specified, it is automatically set to a suitable value depending on the selected profile.
In case VBR mode is enabled the option is ignored.
- ar
Set audio sampling rate (in Hz).
- channels
Set the number of audio channels.
- flags +qscale
Enable fixed quality, VBR (Variable Bit Rate) mode. Note that VBR is implicitly enabled when the vbr value is positive.
- cutoff
Set cutoff frequency. If not specified (or explicitly set to 0) it will use a value automatically computed by the library. Default value is 0.
- profile
Set audio profile.
The following profiles are recognized:
- ‘aac_low’
Low Complexity AAC (LC)
- ‘aac_he’
High Efficiency AAC (HE-AAC)
- ‘aac_he_v2’
High Efficiency AAC version 2 (HE-AACv2)
- ‘aac_ld’
Low Delay AAC (LD)
- ‘aac_eld’
Enhanced Low Delay AAC (ELD)
If not specified it is set to ‘aac_low’.
The following are private options of the libfdk_aac encoder.
- afterburner
Enable afterburner feature if set to 1, disabled if set to 0. This improves the quality but also the required processing power.
Default value is 1.
- eld_sbr
Enable SBR (Spectral Band Replication) for ELD if set to 1, disabled if set to 0.
Default value is 0.
- eld_v2
Enable ELDv2 (LD-MPS extension for ELD stereo signals) for ELDv2 if set to 1, disabled if set to 0.
Note that option is available when fdk-aac version (AACENCODER_LIB_VL0.AACENCODER_LIB_VL1.AACENCODER_LIB_VL2) > (4.0.0).
Default value is 0.
- signaling
Set SBR/PS signaling style.
It can assume one of the following values:
- ‘default’
choose signaling implicitly (explicit hierarchical by default, implicit if global header is disabled)
- ‘implicit’
implicit backwards compatible signaling
- ‘explicit_sbr’
explicit SBR, implicit PS signaling
- ‘explicit_hierarchical’
explicit hierarchical signaling
Default value is ‘default’.
- latm
Output LATM/LOAS encapsulated data if set to 1, disabled if set to 0.
Default value is 0.
- header_period
Set StreamMuxConfig and PCE repetition period (in frames) for sending in-band configuration buffers within LATM/LOAS transport layer.
Must be a 16-bits non-negative integer.
Default value is 0.
- vbr
Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty good) and 5 is highest quality. A value of 0 will disable VBR, and CBR (Constant Bit Rate) is enabled.
Currently only the ‘aac_low’ profile supports VBR encoding.
VBR modes 1-5 correspond to roughly the following average bit rates:
- ‘1’
32 kbps/channel
- ‘2’
40 kbps/channel
- ‘3’
48-56 kbps/channel
- ‘4’
64 kbps/channel
- ‘5’
about 80-96 kbps/channel
Default value is 0.
8.5.2 Examples
- Use
ffmpeg
to convert an audio file to VBR AAC in an M4A (MP4) container:ffmpeg -i input.wav -codec:a libfdk_aac -vbr 3 output.m4a
- Use
ffmpeg
to convert an audio file to CBR 64k kbps AAC, using the High-Efficiency AAC profile:ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
8.6 libmp3lame
LAME (Lame Ain’t an MP3 Encoder) MP3 encoder wrapper.
Requires the presence of the libmp3lame headers and library during
configuration. You need to explicitly configure the build with
--enable-libmp3lame
.
See libshine for a fixed-point MP3 encoder, although with a lower quality.
8.6.1 Options
The following options are supported by the libmp3lame wrapper. The
lame
-equivalent of the options are listed in parentheses.
- b (-b)
Set bitrate expressed in bits/s for CBR or ABR. LAME
bitrate
is expressed in kilobits/s.- q (-V)
Set constant quality setting for VBR. This option is valid only using the
ffmpeg
command-line tool. For library interface users, use global_quality.- compression_level (-q)
Set algorithm quality. Valid arguments are integers in the 0-9 range, with 0 meaning highest quality but slowest, and 9 meaning fastest while producing the worst quality.
- cutoff (--lowpass)
Set lowpass cutoff frequency. If unspecified, the encoder dynamically adjusts the cutoff.
- reservoir
Enable use of bit reservoir when set to 1. Default value is 1. LAME has this enabled by default, but can be overridden by use --nores option.
- joint_stereo (-m j)
Enable the encoder to use (on a frame by frame basis) either L/R stereo or mid/side stereo. Default value is 1.
- abr (--abr)
Enable the encoder to use ABR when set to 1. The
lame
--abr sets the target bitrate, while this options only tells FFmpeg to use ABR still relies on b to set bitrate.
8.7 libopencore-amrnb
OpenCORE Adaptive Multi-Rate Narrowband encoder.
Requires the presence of the libopencore-amrnb headers and library during
configuration. You need to explicitly configure the build with
--enable-libopencore-amrnb --enable-version3
.
This is a mono-only encoder. Officially it only supports 8000Hz sample rate, but you can override it by setting strict to ‘unofficial’ or lower.
8.7.1 Options
- b
Set bitrate in bits per second. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.
- 4750
- 5150
- 5900
- 6700
- 7400
- 7950
- 10200
- 12200
- dtx
Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).
8.8 libopus
libopus Opus Interactive Audio Codec encoder wrapper.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
--enable-libopus
.
8.8.1 Option Mapping
Most libopus options are modelled after the opusenc
utility from
opus-tools. The following is an option mapping chart describing options
supported by the libopus wrapper, and their opusenc
-equivalent
in parentheses.
- b (bitrate)
Set the bit rate in bits/s. FFmpeg’s b option is expressed in bits/s, while
opusenc
’s bitrate in kilobits/s.- vbr (vbr, hard-cbr, and cvbr)
Set VBR mode. The FFmpeg vbr option has the following valid arguments, with the
opusenc
equivalent options in parentheses:- ‘off (hard-cbr)’
Use constant bit rate encoding.
- ‘on (vbr)’
Use variable bit rate encoding (the default).
- ‘constrained (cvbr)’
Use constrained variable bit rate encoding.
- compression_level (comp)
Set encoding algorithm complexity. Valid options are integers in the 0-10 range. 0 gives the fastest encodes but lower quality, while 10 gives the highest quality but slowest encoding. The default is 10.
- frame_duration (framesize)
Set maximum frame size, or duration of a frame in milliseconds. The argument must be exactly the following: 2.5, 5, 10, 20, 40, 60. Smaller frame sizes achieve lower latency but less quality at a given bitrate. Sizes greater than 20ms are only interesting at fairly low bitrates. The default is 20ms.
- packet_loss (expect-loss)
Set expected packet loss percentage. The default is 0.
- fec (n/a)
Enable inband forward error correction. packet_loss must be non-zero to take advantage - frequency of FEC ’side-data’ is proportional to expected packet loss. Default is disabled.
- application (N.A.)
Set intended application type. Valid options are listed below:
- ‘voip’
Favor improved speech intelligibility.
- ‘audio’
Favor faithfulness to the input (the default).
- ‘lowdelay’
Restrict to only the lowest delay modes.
- cutoff (N.A.)
Set cutoff bandwidth in Hz. The argument must be exactly one of the following: 4000, 6000, 8000, 12000, or 20000, corresponding to narrowband, mediumband, wideband, super wideband, and fullband respectively. The default is 0 (cutoff disabled).
- mapping_family (mapping_family)
Set channel mapping family to be used by the encoder. The default value of -1 uses mapping family 0 for mono and stereo inputs, and mapping family 1 otherwise. The default also disables the surround masking and LFE bandwidth optimzations in libopus, and requires that the input contains 8 channels or fewer.
Other values include 0 for mono and stereo, 1 for surround sound with masking and LFE bandwidth optimizations, and 255 for independent streams with an unspecified channel layout.
- apply_phase_inv (N.A.) (requires libopus >= 1.2)
If set to 0, disables the use of phase inversion for intensity stereo, improving the quality of mono downmixes, but slightly reducing normal stereo quality. The default is 1 (phase inversion enabled).
8.9 libshine
Shine Fixed-Point MP3 encoder wrapper.
Shine is a fixed-point MP3 encoder. It has a far better performance on platforms without an FPU, e.g. armel CPUs, and some phones and tablets. However, as it is more targeted on performance than quality, it is not on par with LAME and other production-grade encoders quality-wise. Also, according to the project’s homepage, this encoder may not be free of bugs as the code was written a long time ago and the project was dead for at least 5 years.
This encoder only supports stereo and mono input. This is also CBR-only.
The original project (last updated in early 2007) is at http://sourceforge.net/projects/libshine-fxp/. We only support the updated fork by the Savonet/Liquidsoap project at https://github.com/savonet/shine.
Requires the presence of the libshine headers and library during
configuration. You need to explicitly configure the build with
--enable-libshine
.
See also libmp3lame.
8.9.1 Options
The following options are supported by the libshine wrapper. The
shineenc
-equivalent of the options are listed in parentheses.
- b (-b)
Set bitrate expressed in bits/s for CBR.
shineenc
-b option is expressed in kilobits/s.
8.10 libtwolame
TwoLAME MP2 encoder wrapper.
Requires the presence of the libtwolame headers and library during
configuration. You need to explicitly configure the build with
--enable-libtwolame
.
8.10.1 Options
The following options are supported by the libtwolame wrapper. The
twolame
-equivalent options follow the FFmpeg ones and are in
parentheses.
- b (-b)
Set bitrate expressed in bits/s for CBR.
twolame
b option is expressed in kilobits/s. Default value is 128k.- q (-V)
Set quality for experimental VBR support. Maximum value range is from -50 to 50, useful range is from -10 to 10. The higher the value, the better the quality. This option is valid only using the
ffmpeg
command-line tool. For library interface users, use global_quality.- mode (--mode)
Set the mode of the resulting audio. Possible values:
- ‘auto’
Choose mode automatically based on the input. This is the default.
- ‘stereo’
Stereo
- ‘joint_stereo’
Joint stereo
- ‘dual_channel’
Dual channel
- ‘mono’
Mono
- psymodel (--psyc-mode)
Set psychoacoustic model to use in encoding. The argument must be an integer between -1 and 4, inclusive. The higher the value, the better the quality. The default value is 3.
- energy_levels (--energy)
Enable energy levels extensions when set to 1. The default value is 0 (disabled).
- error_protection (--protect)
Enable CRC error protection when set to 1. The default value is 0 (disabled).
- copyright (--copyright)
Set MPEG audio copyright flag when set to 1. The default value is 0 (disabled).
- original (--original)
Set MPEG audio original flag when set to 1. The default value is 0 (disabled).
8.11 libvo-amrwbenc
VisualOn Adaptive Multi-Rate Wideband encoder.
Requires the presence of the libvo-amrwbenc headers and library during
configuration. You need to explicitly configure the build with
--enable-libvo-amrwbenc --enable-version3
.
This is a mono-only encoder. Officially it only supports 16000Hz sample rate, but you can override it by setting strict to ‘unofficial’ or lower.
8.11.1 Options
- b
Set bitrate in bits/s. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.
- ‘6600’
- ‘8850’
- ‘12650’
- ‘14250’
- ‘15850’
- ‘18250’
- ‘19850’
- ‘23050’
- ‘23850’
- dtx
Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).
8.12 libvorbis
libvorbis encoder wrapper.
Requires the presence of the libvorbisenc headers and library during
configuration. You need to explicitly configure the build with
--enable-libvorbis
.
8.12.1 Options
The following options are supported by the libvorbis wrapper. The
oggenc
-equivalent of the options are listed in parentheses.
To get a more accurate and extensive documentation of the libvorbis
options, consult the libvorbisenc’s and oggenc
’s documentations.
See http://xiph.org/vorbis/,
http://wiki.xiph.org/Vorbis-tools, and oggenc(1).
- b (-b)
Set bitrate expressed in bits/s for ABR.
oggenc
-b is expressed in kilobits/s.- q (-q)
Set constant quality setting for VBR. The value should be a float number in the range of -1.0 to 10.0. The higher the value, the better the quality. The default value is ‘3.0’.
This option is valid only using the
ffmpeg
command-line tool. For library interface users, use global_quality.- cutoff (--advanced-encode-option lowpass_frequency=N)
Set cutoff bandwidth in Hz, a value of 0 disables cutoff.
oggenc
’s related option is expressed in kHz. The default value is ‘0’ (cutoff disabled).- minrate (-m)
Set minimum bitrate expressed in bits/s.
oggenc
-m is expressed in kilobits/s.- maxrate (-M)
Set maximum bitrate expressed in bits/s.
oggenc
-M is expressed in kilobits/s. This only has effect on ABR mode.- iblock (--advanced-encode-option impulse_noisetune=N)
Set noise floor bias for impulse blocks. The value is a float number from -15.0 to 0.0. A negative bias instructs the encoder to pay special attention to the crispness of transients in the encoded audio. The tradeoff for better transient response is a higher bitrate.
8.13 mjpeg
Motion JPEG encoder.
8.13.1 Options
- huffman
Set the huffman encoding strategy. Possible values:
- ‘default’
Use the default huffman tables. This is the default strategy.
- ‘optimal’
Compute and use optimal huffman tables.
8.14 wavpack
WavPack lossless audio encoder.
8.14.1 Options
The equivalent options for wavpack
command line utility are listed in
parentheses.
8.14.1.1 Shared options
The following shared options are effective for this encoder. Only special notes about this particular encoder will be documented here. For the general meaning of the options, see the Codec Options chapter.
- frame_size (--blocksize)
For this encoder, the range for this option is between 128 and 131072. Default is automatically decided based on sample rate and number of channel.
For the complete formula of calculating default, see libavcodec/wavpackenc.c.
- compression_level (-f, -h, -hh, and -x)
8.14.1.2 Private options
- joint_stereo (-j)
Set whether to enable joint stereo. Valid values are:
- ‘on (1)’
Force mid/side audio encoding.
- ‘off (0)’
Force left/right audio encoding.
- ‘auto’
Let the encoder decide automatically.
- optimize_mono
Set whether to enable optimization for mono. This option is only effective for non-mono streams. Available values:
- ‘on’
enabled
- ‘off’
disabled
9 Video Encoders
A description of some of the currently available video encoders follows.
9.1 a64_multi, a64_multi5
A64 / Commodore 64 multicolor charset encoder. a64_multi5
is extended with 5th color (colram).
9.2 Cinepak
Cinepak aka CVID encoder. Compatible with Windows 3.1 and vintage MacOS.
9.2.1 Options
- g integer
Keyframe interval. A keyframe is inserted at least every
-g
frames, sometimes sooner.- q:v integer
Quality factor. Lower is better. Higher gives lower bitrate. The following table lists bitrates when encoding akiyo_cif.y4m for various values of
-q:v
with-g 100
:-q:v 1
1918 kb/s-q:v 2
1735 kb/s-q:v 4
1500 kb/s-q:v 10
1041 kb/s-q:v 20
826 kb/s-q:v 40
553 kb/s-q:v 100
394 kb/s-q:v 200
312 kb/s-q:v 400
266 kb/s-q:v 1000
237 kb/s
- max_extra_cb_iterations integer
Max extra codebook recalculation passes, more is better and slower.
- skip_empty_cb boolean
Avoid wasting bytes, ignore vintage MacOS decoder.
- max_strips integer
- min_strips integer
The minimum and maximum number of strips to use. Wider range sometimes improves quality. More strips is generally better quality but costs more bits. Fewer strips tend to yield more keyframes. Vintage compatible is 1..3.
- strip_number_adaptivity integer
How much number of strips is allowed to change between frames. Higher is better but slower.
9.3 GIF
GIF image/animation encoder.
9.3.1 Options
- gifflags integer
Sets the flags used for GIF encoding.
- offsetting
Enables picture offsetting.
Default is enabled.
- transdiff
Enables transparency detection between frames.
Default is enabled.
- gifimage integer
Enables encoding one full GIF image per frame, rather than an animated GIF.
Default value is 0.
- global_palette integer
Writes a palette to the global GIF header where feasible.
If disabled, every frame will always have a palette written, even if there is a global palette supplied.
Default value is 1.
9.4 Hap
Vidvox Hap video encoder.
9.4.1 Options
- format integer
Specifies the Hap format to encode.
- hap
- hap_alpha
- hap_q
Default value is hap.
- chunks integer
Specifies the number of chunks to split frames into, between 1 and 64. This permits multithreaded decoding of large frames, potentially at the cost of data-rate. The encoder may modify this value to divide frames evenly.
Default value is 1.
- compressor integer
Specifies the second-stage compressor to use. If set to none, chunks will be limited to 1, as chunked uncompressed frames offer no benefit.
- none
- snappy
Default value is snappy.
9.5 jpeg2000
The native jpeg 2000 encoder is lossy by default, the -q:v
option can be used to set the encoding quality. Lossless encoding
can be selected with -pred 1
.
9.5.1 Options
- format integer
Can be set to either
j2k
orjp2
(the default) that makes it possible to store non-rgb pix_fmts.- tile_width integer
Sets tile width. Range is 1 to 1073741824. Default is 256.
- tile_height integer
Sets tile height. Range is 1 to 1073741824. Default is 256.
- pred integer
Allows setting the discrete wavelet transform (DWT) type
- dwt97int (Lossy)
- dwt53 (Lossless)
Default is
dwt97int
- sop boolean
Enable this to add SOP marker at the start of each packet. Disabled by default.
- eph boolean
Enable this to add EPH marker at the end of each packet header. Disabled by default.
- prog integer
Sets the progression order to be used by the encoder. Possible values are:
- lrcp
- rlcp
- rpcl
- pcrl
- cprl
Set to
lrcp
by default.- layer_rates string
By default, when this option is not used, compression is done using the quality metric. This option allows for compression using compression ratio. The compression ratio for each level could be specified. The compression ratio of a layer
l
species the what ratio of total file size is contained in the firstl
layers.Example usage:
ffmpeg -i input.bmp -c:v jpeg2000 -layer_rates "100,10,1" output.j2k
This would compress the image to contain 3 layers, where the data contained in the first layer would be compressed by 1000 times, compressed by 100 in the first two layers, and shall contain all data while using all 3 layers.
9.6 librav1e
rav1e AV1 encoder wrapper.
Requires the presence of the rav1e headers and library during configuration.
You need to explicitly configure the build with --enable-librav1e
.
9.6.1 Options
- qmax
Sets the maximum quantizer to use when using bitrate mode.
- qmin
Sets the minimum quantizer to use when using bitrate mode.
- qp
Uses quantizer mode to encode at the given quantizer (0-255).
- speed
Selects the speed preset (0-10) to encode with.
- tiles
Selects how many tiles to encode with.
- tile-rows
Selects how many rows of tiles to encode with.
- tile-columns
Selects how many columns of tiles to encode with.
- rav1e-params
Set rav1e options using a list of key=value pairs separated by ":". See
rav1e --help
for a list of options.For example to specify librav1e encoding options with -rav1e-params:
ffmpeg -i input -c:v librav1e -b:v 500K -rav1e-params speed=5:low_latency=true output.mp4
9.7 libaom-av1
libaom AV1 encoder wrapper.
Requires the presence of the libaom headers and library during
configuration. You need to explicitly configure the build with
--enable-libaom
.
9.7.1 Options
The wrapper supports the following standard libavcodec options:
- b
Set bitrate target in bits/second. By default this will use variable-bitrate mode. If maxrate and minrate are also set to the same value then it will use constant-bitrate mode, otherwise if crf is set as well then it will use constrained-quality mode.
- g keyint_min
Set key frame placement. The GOP size sets the maximum distance between key frames; if zero the output stream will be intra-only. The minimum distance is ignored unless it is the same as the GOP size, in which case key frames will always appear at a fixed interval. Not set by default, so without this option the library has completely free choice about where to place key frames.
- qmin qmax
Set minimum/maximum quantisation values. Valid range is from 0 to 63 (warning: this does not match the quantiser values actually used by AV1 - divide by four to map real quantiser values to this range). Defaults to min/max (no constraint).
- minrate maxrate bufsize rc_init_occupancy
Set rate control buffering parameters. Not used if not set - defaults to unconstrained variable bitrate.
- threads
Set the number of threads to use while encoding. This may require the tiles or row-mt options to also be set to actually use the specified number of threads fully. Defaults to the number of hardware threads supported by the host machine.
- profile
Set the encoding profile. Defaults to using the profile which matches the bit depth and chroma subsampling of the input.
The wrapper also has some specific options:
- cpu-used
Set the quality/encoding speed tradeoff. Valid range is from 0 to 8, higher numbers indicating greater speed and lower quality. The default value is 1, which will be slow and high quality.
- auto-alt-ref
Enable use of alternate reference frames. Defaults to the internal default of the library.
- arnr-max-frames (frames)
Set altref noise reduction max frame count. Default is -1.
- arnr-strength (strength)
Set altref noise reduction filter strength. Range is -1 to 6. Default is -1.
- aq-mode (aq-mode)
Set adaptive quantization mode. Possible values:
- ‘none (0)’
Disabled.
- ‘variance (1)’
Variance-based.
- ‘complexity (2)’
Complexity-based.
- ‘cyclic (3)’
Cyclic refresh.
- tune (tune)
Set the distortion metric the encoder is tuned with. Default is
psnr
.- ‘psnr (0)’
- ‘ssim (1)’
- lag-in-frames
Set the maximum number of frames which the encoder may keep in flight at any one time for lookahead purposes. Defaults to the internal default of the library.
- error-resilience
Enable error resilience features:
- default
Improve resilience against losses of whole frames.
Not enabled by default.
- crf
Set the quality/size tradeoff for constant-quality (no bitrate target) and constrained-quality (with maximum bitrate target) modes. Valid range is 0 to 63, higher numbers indicating lower quality and smaller output size. Only used if set; by default only the bitrate target is used.
- static-thresh
Set a change threshold on blocks below which they will be skipped by the encoder. Defined in arbitrary units as a nonnegative integer, defaulting to zero (no blocks are skipped).
- drop-threshold
Set a threshold for dropping frames when close to rate control bounds. Defined as a percentage of the target buffer - when the rate control buffer falls below this percentage, frames will be dropped until it has refilled above the threshold. Defaults to zero (no frames are dropped).
- denoise-noise-level (level)
Amount of noise to be removed for grain synthesis. Grain synthesis is disabled if this option is not set or set to 0.
- denoise-block-size (pixels)
Block size used for denoising for grain synthesis. If not set, AV1 codec uses the default value of 32.
- undershoot-pct (pct)
Set datarate undershoot (min) percentage of the target bitrate. Range is -1 to 100. Default is -1.
- overshoot-pct (pct)
Set datarate overshoot (max) percentage of the target bitrate. Range is -1 to 1000. Default is -1.
- minsection-pct (pct)
Minimum percentage variation of the GOP bitrate from the target bitrate. If minsection-pct is not set, the libaomenc wrapper computes it as follows:
(minrate * 100 / bitrate)
. Range is -1 to 100. Default is -1 (unset).- maxsection-pct (pct)
Maximum percentage variation of the GOP bitrate from the target bitrate. If maxsection-pct is not set, the libaomenc wrapper computes it as follows:
(maxrate * 100 / bitrate)
. Range is -1 to 5000. Default is -1 (unset).- frame-parallel (boolean)
Enable frame parallel decodability features. Default is true.
- tiles
Set the number of tiles to encode the input video with, as columns x rows. Larger numbers allow greater parallelism in both encoding and decoding, but may decrease coding efficiency. Defaults to the minimum number of tiles required by the size of the input video (this is 1x1 (that is, a single tile) for sizes up to and including 4K).
- tile-columns tile-rows
Set the number of tiles as log2 of the number of tile rows and columns. Provided for compatibility with libvpx/VP9.
- row-mt (Requires libaom >= 1.0.0-759-g90a15f4f2)
Enable row based multi-threading. Disabled by default.
- enable-cdef (boolean)
Enable Constrained Directional Enhancement Filter. The libaom-av1 encoder enables CDEF by default.
- enable-restoration (boolean)
Enable Loop Restoration Filter. Default is true for libaom-av1.
- enable-global-motion (boolean)
Enable the use of global motion for block prediction. Default is true.
- enable-intrabc (boolean)
Enable block copy mode for intra block prediction. This mode is useful for screen content. Default is true.
- enable-rect-partitions (boolean) (Requires libaom >= v2.0.0)
Enable rectangular partitions. Default is true.
- enable-1to4-partitions (boolean) (Requires libaom >= v2.0.0)
Enable 1:4/4:1 partitions. Default is true.
- enable-ab-partitions (boolean) (Requires libaom >= v2.0.0)
Enable AB shape partitions. Default is true.
- enable-angle-delta (boolean) (Requires libaom >= v2.0.0)
Enable angle delta intra prediction. Default is true.
- enable-cfl-intra (boolean) (Requires libaom >= v2.0.0)
Enable chroma predicted from luma intra prediction. Default is true.
- enable-filter-intra (boolean) (Requires libaom >= v2.0.0)
Enable filter intra predictor. Default is true.
- enable-intra-edge-filter (boolean) (Requires libaom >= v2.0.0)
Enable intra edge filter. Default is true.
- enable-smooth-intra (boolean) (Requires libaom >= v2.0.0)
Enable smooth intra prediction mode. Default is true.
- enable-paeth-intra (boolean) (Requires libaom >= v2.0.0)
Enable paeth predictor in intra prediction. Default is true.
- enable-palette (boolean) (Requires libaom >= v2.0.0)
Enable palette prediction mode. Default is true.
- enable-flip-idtx (boolean) (Requires libaom >= v2.0.0)
Enable extended transform type, including FLIPADST_DCT, DCT_FLIPADST, FLIPADST_FLIPADST, ADST_FLIPADST, FLIPADST_ADST, IDTX, V_DCT, H_DCT, V_ADST, H_ADST, V_FLIPADST, H_FLIPADST. Default is true.
- enable-tx64 (boolean) (Requires libaom >= v2.0.0)
Enable 64-pt transform. Default is true.
- reduced-tx-type-set (boolean) (Requires libaom >= v2.0.0)
Use reduced set of transform types. Default is false.
- use-intra-dct-only (boolean) (Requires libaom >= v2.0.0)
Use DCT only for INTRA modes. Default is false.
- use-inter-dct-only (boolean) (Requires libaom >= v2.0.0)
Use DCT only for INTER modes. Default is false.
- use-intra-default-tx-only (boolean) (Requires libaom >= v2.0.0)
Use Default-transform only for INTRA modes. Default is false.
- enable-ref-frame-mvs (boolean) (Requires libaom >= v2.0.0)
Enable temporal mv prediction. Default is true.
- enable-reduced-reference-set (boolean) (Requires libaom >= v2.0.0)
Use reduced set of single and compound references. Default is false.
- enable-obmc (boolean) (Requires libaom >= v2.0.0)
Enable obmc. Default is true.
- enable-dual-filter (boolean) (Requires libaom >= v2.0.0)
Enable dual filter. Default is true.
- enable-diff-wtd-comp (boolean) (Requires libaom >= v2.0.0)
Enable difference-weighted compound. Default is true.
- enable-dist-wtd-comp (boolean) (Requires libaom >= v2.0.0)
Enable distance-weighted compound. Default is true.
- enable-onesided-comp (boolean) (Requires libaom >= v2.0.0)
Enable one sided compound. Default is true.
- enable-interinter-wedge (boolean) (Requires libaom >= v2.0.0)
Enable interinter wedge compound. Default is true.
- enable-interintra-wedge (boolean) (Requires libaom >= v2.0.0)
Enable interintra wedge compound. Default is true.
- enable-masked-comp (boolean) (Requires libaom >= v2.0.0)
Enable masked compound. Default is true.
- enable-interintra-comp (boolean) (Requires libaom >= v2.0.0)
Enable interintra compound. Default is true.
- enable-smooth-interintra (boolean) (Requires libaom >= v2.0.0)
Enable smooth interintra mode. Default is true.
- aom-params
Set libaom options using a list of key=value pairs separated by ":". For a list of supported options, see
aomenc --help
under the section "AV1 Specific Options".For example to specify libaom encoding options with -aom-params:
ffmpeg -i input -c:v libaom-av1 -b:v 500K -aom-params tune=psnr:enable-tpl-model=1 output.mp4
9.8 libsvtav1
SVT-AV1 encoder wrapper.
Requires the presence of the SVT-AV1 headers and library during configuration.
You need to explicitly configure the build with --enable-libsvtav1
.
9.8.1 Options
- profile
Set the encoding profile.
- ‘main’
- ‘high’
- ‘professional’
- level
Set the operating point level. For example: ’4.0’
- hielevel
Set the Hierarchical prediction levels.
- ‘3level’
- ‘4level’
This is the default.
- tier
Set the operating point tier.
- ‘main’
This is the default.
- ‘high’
- qmax
Set the maximum quantizer to use when using a bitrate mode.
- qmin
Set the minimum quantizer to use when using a bitrate mode.
- crf
Constant rate factor value used in crf rate control mode (0-63).
- qp
Set the quantizer used in cqp rate control mode (0-63).
- sc_detection
Enable scene change detection.
- la_depth
Set number of frames to look ahead (0-120).
- preset
Set the quality-speed tradeoff, in the range 0 to 13. Higher values are faster but lower quality.
- tile_rows
Set log2 of the number of rows of tiles to use (0-6).
- tile_columns
Set log2 of the number of columns of tiles to use (0-4).
- svtav1-params
Set SVT-AV1 options using a list of key=value pairs separated by ":". See the SVT-AV1 encoder user guide for a list of accepted parameters.
9.9 libjxl
libjxl JPEG XL encoder wrapper.
Requires the presence of the libjxl headers and library during
configuration. You need to explicitly configure the build with
--enable-libjxl
.
9.9.1 Options
The libjxl wrapper supports the following options:
- distance
Set the target Butteraugli distance. This is a quality setting: lower distance yields higher quality, with distance=1.0 roughly comparable to libjpeg Quality 90 for photographic content. Setting distance=0.0 yields true lossless encoding. Valid values range between 0.0 and 15.0, and sane values rarely exceed 5.0. Setting distance=0.1 usually attains transparency for most input. The default is 1.0.
- effort
Set the encoding effort used. Higher effort values produce more consistent quality and usually produces a better quality/bpp curve, at the cost of more CPU time required. Valid values range from 1 to 9, and the default is 7.
- modular
Force the encoder to use Modular mode instead of choosing automatically. The default is to use VarDCT for lossy encoding and Modular for lossless. VarDCT is generally superior to Modular for lossy encoding but does not support lossless encoding.
9.10 libkvazaar
Kvazaar H.265/HEVC encoder.
Requires the presence of the libkvazaar headers and library during configuration. You need to explicitly configure the build with --enable-libkvazaar.
9.10.1 Options
- b
Set target video bitrate in bit/s and enable rate control.
- kvazaar-params
Set kvazaar parameters as a list of name=value pairs separated by commas (,). See kvazaar documentation for a list of options.
9.11 libopenh264
Cisco libopenh264 H.264/MPEG-4 AVC encoder wrapper.
This encoder requires the presence of the libopenh264 headers and
library during configuration. You need to explicitly configure the
build with --enable-libopenh264
. The library is detected using
pkg-config
.
For more information about the library see http://www.openh264.org.
9.11.1 Options
The following FFmpeg global options affect the configurations of the libopenh264 encoder.
- b
Set the bitrate (as a number of bits per second).
- g
Set the GOP size.
- maxrate
Set the max bitrate (as a number of bits per second).
- flags +global_header
Set global header in the bitstream.
- slices
Set the number of slices, used in parallelized encoding. Default value is 0. This is only used when slice_mode is set to ‘fixed’.
- slice_mode
Set slice mode. Can assume one of the following possible values:
- ‘fixed’
a fixed number of slices
- ‘rowmb’
one slice per row of macroblocks
- ‘auto’
automatic number of slices according to number of threads
- ‘dyn’
dynamic slicing
Default value is ‘auto’.
- loopfilter
Enable loop filter, if set to 1 (automatically enabled). To disable set a value of 0.
- profile
Set profile restrictions. If set to the value of ‘main’ enable CABAC (set the
SEncParamExt.iEntropyCodingModeFlag
flag to 1).- max_nal_size
Set maximum NAL size in bytes.
- allow_skip_frames
Allow skipping frames to hit the target bitrate if set to 1.
9.12 libtheora
libtheora Theora encoder wrapper.
Requires the presence of the libtheora headers and library during
configuration. You need to explicitly configure the build with
--enable-libtheora
.
For more information about the libtheora project see http://www.theora.org/.
9.12.1 Options
The following global options are mapped to internal libtheora options which affect the quality and the bitrate of the encoded stream.
- b
Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode. In case VBR (Variable Bit Rate) mode is enabled this option is ignored.
- flags
Used to enable constant quality mode (VBR) encoding through the qscale flag, and to enable the
pass1
andpass2
modes.- g
Set the GOP size.
- global_quality
Set the global quality as an integer in lambda units.
Only relevant when VBR mode is enabled with
flags +qscale
. The value is converted to QP units by dividing it byFF_QP2LAMBDA
, clipped in the [0 - 10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63]. A higher value corresponds to a higher quality.- q
Enable VBR mode when set to a non-negative value, and set constant quality value as a double floating point value in QP units.
The value is clipped in the [0-10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63].
This option is valid only using the
ffmpeg
command-line tool. For library interface users, use global_quality.
9.12.2 Examples
- Set maximum constant quality (VBR) encoding with
ffmpeg
:ffmpeg -i INPUT -codec:v libtheora -q:v 10 OUTPUT.ogg
- Use
ffmpeg
to convert a CBR 1000 kbps Theora video stream:ffmpeg -i INPUT -codec:v libtheora -b:v 1000k OUTPUT.ogg
9.13 libvpx
VP8/VP9 format supported through libvpx.
Requires the presence of the libvpx headers and library during configuration.
You need to explicitly configure the build with --enable-libvpx
.
9.13.1 Options
The following options are supported by the libvpx wrapper. The
vpxenc
-equivalent options or values are listed in parentheses
for easy migration.
To reduce the duplication of documentation, only the private options and some others requiring special attention are documented here. For the documentation of the undocumented generic options, see the Codec Options chapter.
To get more documentation of the libvpx options, invoke the command
ffmpeg -h encoder=libvpx
, ffmpeg -h encoder=libvpx-vp9
or
vpxenc --help
. Further information is available in the libvpx API
documentation.
- b (target-bitrate)
Set bitrate in bits/s. Note that FFmpeg’s b option is expressed in bits/s, while
vpxenc
’s target-bitrate is in kilobits/s.- g (kf-max-dist)
- keyint_min (kf-min-dist)
- qmin (min-q)
Minimum (Best Quality) Quantizer.
- qmax (max-q)
Maximum (Worst Quality) Quantizer. Can be changed per-frame.
- bufsize (buf-sz, buf-optimal-sz)
Set ratecontrol buffer size (in bits). Note
vpxenc
’s options are specified in milliseconds, the libvpx wrapper converts this value as follows:buf-sz = bufsize * 1000 / bitrate
,buf-optimal-sz = bufsize * 1000 / bitrate * 5 / 6
.- rc_init_occupancy (buf-initial-sz)
Set number of bits which should be loaded into the rc buffer before decoding starts. Note
vpxenc
’s option is specified in milliseconds, the libvpx wrapper converts this value as follows:rc_init_occupancy * 1000 / bitrate
.- undershoot-pct
Set datarate undershoot (min) percentage of the target bitrate.
- overshoot-pct
Set datarate overshoot (max) percentage of the target bitrate.
- skip_threshold (drop-frame)
- qcomp (bias-pct)
- maxrate (maxsection-pct)
Set GOP max bitrate in bits/s. Note
vpxenc
’s option is specified as a percentage of the target bitrate, the libvpx wrapper converts this value as follows:(maxrate * 100 / bitrate)
.- minrate (minsection-pct)
Set GOP min bitrate in bits/s. Note
vpxenc
’s option is specified as a percentage of the target bitrate, the libvpx wrapper converts this value as follows:(minrate * 100 / bitrate)
.- minrate, maxrate, b end-usage=cbr
(minrate == maxrate == bitrate)
.- crf (end-usage=cq, cq-level)
- tune (tune)
- ‘psnr (psnr)’
- ‘ssim (ssim)’
- quality, deadline (deadline)
- ‘best’
Use best quality deadline. Poorly named and quite slow, this option should be avoided as it may give worse quality output than good.
- ‘good’
Use good quality deadline. This is a good trade-off between speed and quality when used with the cpu-used option.
- ‘realtime’
Use realtime quality deadline.
- speed, cpu-used (cpu-used)
Set quality/speed ratio modifier. Higher values speed up the encode at the cost of quality.
- nr (noise-sensitivity)
- static-thresh
Set a change threshold on blocks below which they will be skipped by the encoder.
- slices (token-parts)
Note that FFmpeg’s slices option gives the total number of partitions, while
vpxenc
’s token-parts is given aslog2(partitions)
.- max-intra-rate
Set maximum I-frame bitrate as a percentage of the target bitrate. A value of 0 means unlimited.
- force_key_frames
VPX_EFLAG_FORCE_KF
- Alternate reference frame related
- auto-alt-ref
Enable use of alternate reference frames (2-pass only). Values greater than 1 enable multi-layer alternate reference frames (VP9 only).
- arnr-maxframes
Set altref noise reduction max frame count.
- arnr-type
Set altref noise reduction filter type: backward, forward, centered.
- arnr-strength
Set altref noise reduction filter strength.
- rc-lookahead, lag-in-frames (lag-in-frames)
Set number of frames to look ahead for frametype and ratecontrol.
- min-gf-interval
Set minimum golden/alternate reference frame interval (VP9 only).
- error-resilient
Enable error resiliency features.
- sharpness integer
Increase sharpness at the expense of lower PSNR. The valid range is [0, 7].
- ts-parameters
Sets the temporal scalability configuration using a :-separated list of key=value pairs. For example, to specify temporal scalability parameters with
ffmpeg
:ffmpeg -i INPUT -c:v libvpx -ts-parameters ts_number_layers=3:\ ts_target_bitrate=250,500,1000:ts_rate_decimator=4,2,1:\ ts_periodicity=4:ts_layer_id=0,2,1,2:ts_layering_mode=3 OUTPUT
Below is a brief explanation of each of the parameters, please refer to
struct vpx_codec_enc_cfg
invpx/vpx_encoder.h
for more details.- ts_number_layers
Number of temporal coding layers.
- ts_target_bitrate
Target bitrate for each temporal layer (in kbps). (bitrate should be inclusive of the lower temporal layer).
- ts_rate_decimator
Frame rate decimation factor for each temporal layer.
- ts_periodicity
Length of the sequence defining frame temporal layer membership.
- ts_layer_id
Template defining the membership of frames to temporal layers.
- ts_layering_mode
(optional) Selecting the temporal structure from a set of pre-defined temporal layering modes. Currently supports the following options.
- 0
No temporal layering flags are provided internally, relies on flags being passed in using
metadata
field inAVFrame
with following keys.- vp8-flags
Sets the flags passed into the encoder to indicate the referencing scheme for the current frame. Refer to function
vpx_codec_encode
invpx/vpx_encoder.h
for more details.- temporal_id
Explicitly sets the temporal id of the current frame to encode.
- 2
Two temporal layers. 0-1...
- 3
Three temporal layers. 0-2-1-2...; with single reference frame.
- 4
Same as option "3", except there is a dependency between the two temporal layer 2 frames within the temporal period.
- VP9-specific options
- lossless
Enable lossless mode.
- tile-columns
Set number of tile columns to use. Note this is given as
log2(tile_columns)
. For example, 8 tile columns would be requested by setting the tile-columns option to 3.- tile-rows
Set number of tile rows to use. Note this is given as
log2(tile_rows)
. For example, 4 tile rows would be requested by setting the tile-rows option to 2.- frame-parallel
Enable frame parallel decodability features.
- aq-mode
Set adaptive quantization mode (0: off (default), 1: variance 2: complexity, 3: cyclic refresh, 4: equator360).
- colorspace color-space
Set input color space. The VP9 bitstream supports signaling the following colorspaces:
- ‘rgb’ sRGB
- ‘bt709’ bt709
- ‘unspecified’ unknown
- ‘bt470bg’ bt601
- ‘smpte170m’ smpte170
- ‘smpte240m’ smpte240
- ‘bt2020_ncl’ bt2020
- row-mt boolean
Enable row based multi-threading.
- tune-content
Set content type: default (0), screen (1), film (2).
- corpus-complexity
Corpus VBR mode is a variant of standard VBR where the complexity distribution midpoint is passed in rather than calculated for a specific clip or chunk.
The valid range is [0, 10000]. 0 (default) uses standard VBR.
- enable-tpl boolean
Enable temporal dependency model.
- ref-frame-config
Using per-frame metadata, set members of the structure
vpx_svc_ref_frame_config_t
invpx/vp8cx.h
to fine-control referencing schemes and frame buffer management.
Use a :-separated list of key=value pairs. For example,av_dict_set(&av_frame->metadata, "ref-frame-config", \ "rfc_update_buffer_slot=7:rfc_lst_fb_idx=0:rfc_gld_fb_idx=1:rfc_alt_fb_idx=2:rfc_reference_last=0:rfc_reference_golden=0:rfc_reference_alt_ref=0");
- rfc_update_buffer_slot
Indicates the buffer slot number to update
- rfc_update_last
Indicates whether to update the LAST frame
- rfc_update_golden
Indicates whether to update GOLDEN frame
- rfc_update_alt_ref
Indicates whether to update ALT_REF frame
- rfc_lst_fb_idx
LAST frame buffer index
- rfc_gld_fb_idx
GOLDEN frame buffer index
- rfc_alt_fb_idx
ALT_REF frame buffer index
- rfc_reference_last
Indicates whether to reference LAST frame
- rfc_reference_golden
Indicates whether to reference GOLDEN frame
- rfc_reference_alt_ref
Indicates whether to reference ALT_REF frame
- rfc_reference_duration
Indicates frame duration
For more information about libvpx see: http://www.webmproject.org/
9.14 libwebp
libwebp WebP Image encoder wrapper
libwebp is Google’s official encoder for WebP images. It can encode in either lossy or lossless mode. Lossy images are essentially a wrapper around a VP8 frame. Lossless images are a separate codec developed by Google.
9.14.1 Pixel Format
Currently, libwebp only supports YUV420 for lossy and RGB for lossless due to limitations of the format and libwebp. Alpha is supported for either mode. Because of API limitations, if RGB is passed in when encoding lossy or YUV is passed in for encoding lossless, the pixel format will automatically be converted using functions from libwebp. This is not ideal and is done only for convenience.
9.14.2 Options
- -lossless boolean
Enables/Disables use of lossless mode. Default is 0.
- -compression_level integer
For lossy, this is a quality/speed tradeoff. Higher values give better quality for a given size at the cost of increased encoding time. For lossless, this is a size/speed tradeoff. Higher values give smaller size at the cost of increased encoding time. More specifically, it controls the number of extra algorithms and compression tools used, and varies the combination of these tools. This maps to the method option in libwebp. The valid range is 0 to 6. Default is 4.
- -quality float
For lossy encoding, this controls image quality. For lossless encoding, this controls the effort and time spent in compression. Range is 0 to 100. Default is 75.
- -preset type
Configuration preset. This does some automatic settings based on the general type of the image.
- none
Do not use a preset.
- default
Use the encoder default.
- picture
Digital picture, like portrait, inner shot
- photo
Outdoor photograph, with natural lighting
- drawing
Hand or line drawing, with high-contrast details
- icon
Small-sized colorful images
- text
Text-like
9.15 libx264, libx264rgb
x264 H.264/MPEG-4 AVC encoder wrapper.
This encoder requires the presence of the libx264 headers and library
during configuration. You need to explicitly configure the build with
--enable-libx264
.
libx264 supports an impressive number of features, including 8x8 and 4x4 adaptive spatial transform, adaptive B-frame placement, CAVLC/CABAC entropy coding, interlacing (MBAFF), lossless mode, psy optimizations for detail retention (adaptive quantization, psy-RD, psy-trellis).
Many libx264 encoder options are mapped to FFmpeg global codec
options, while unique encoder options are provided through private
options. Additionally the x264opts and x264-params
private options allows one to pass a list of key=value tuples as accepted
by the libx264 x264_param_parse
function.
The x264 project website is at http://www.videolan.org/developers/x264.html.
The libx264rgb encoder is the same as libx264, except it accepts packed RGB pixel formats as input instead of YUV.
9.15.1 Supported Pixel Formats
x264 supports 8- to 10-bit color spaces. The exact bit depth is controlled at x264’s configure time.
9.15.2 Options
The following options are supported by the libx264 wrapper. The
x264
-equivalent options or values are listed in parentheses
for easy migration.
To reduce the duplication of documentation, only the private options and some others requiring special attention are documented here. For the documentation of the undocumented generic options, see the Codec Options chapter.
To get a more accurate and extensive documentation of the libx264
options, invoke the command x264 --fullhelp
or consult
the libx264 documentation.
- b (bitrate)
Set bitrate in bits/s. Note that FFmpeg’s b option is expressed in bits/s, while
x264
’s bitrate is in kilobits/s.- bf (bframes)
- g (keyint)
- qmin (qpmin)
Minimum quantizer scale.
- qmax (qpmax)
Maximum quantizer scale.
- qdiff (qpstep)
Maximum difference between quantizer scales.
- qblur (qblur)
Quantizer curve blur
- qcomp (qcomp)
Quantizer curve compression factor
- refs (ref)
Number of reference frames each P-frame can use. The range is from 0-16.
- sc_threshold (scenecut)
Sets the threshold for the scene change detection.
- trellis (trellis)
Performs Trellis quantization to increase efficiency. Enabled by default.
- nr (nr)
- me_range (merange)
Maximum range of the motion search in pixels.
- me_method (me)
Set motion estimation method. Possible values in the decreasing order of speed:
- ‘dia (dia)’
- ‘epzs (dia)’
Diamond search with radius 1 (fastest). ‘epzs’ is an alias for ‘dia’.
- ‘hex (hex)’
Hexagonal search with radius 2.
- ‘umh (umh)’
Uneven multi-hexagon search.
- ‘esa (esa)’
Exhaustive search.
- ‘tesa (tesa)’
Hadamard exhaustive search (slowest).
- forced-idr
Normally, when forcing a I-frame type, the encoder can select any type of I-frame. This option forces it to choose an IDR-frame.
- subq (subme)
Sub-pixel motion estimation method.
- b_strategy (b-adapt)
Adaptive B-frame placement decision algorithm. Use only on first-pass.
- keyint_min (min-keyint)
Minimum GOP size.
- coder
Set entropy encoder. Possible values:
- ‘ac’
Enable CABAC.
- ‘vlc’
Enable CAVLC and disable CABAC. It generates the same effect as
x264
’s --no-cabac option.
- cmp
Set full pixel motion estimation comparison algorithm. Possible values:
- ‘chroma’
Enable chroma in motion estimation.
- ‘sad’
Ignore chroma in motion estimation. It generates the same effect as
x264
’s --no-chroma-me option.
- threads (threads)
Number of encoding threads.
- thread_type
Set multithreading technique. Possible values:
- ‘slice’
Slice-based multithreading. It generates the same effect as
x264
’s --sliced-threads option.- ‘frame’
Frame-based multithreading.
- flags
Set encoding flags. It can be used to disable closed GOP and enable open GOP by setting it to
-cgop
. The result is similar to the behavior ofx264
’s --open-gop option.- rc_init_occupancy (vbv-init)
- preset (preset)
Set the encoding preset.
- tune (tune)
Set tuning of the encoding params.
- profile (profile)
Set profile restrictions.
- fastfirstpass
Enable fast settings when encoding first pass, when set to 1. When set to 0, it has the same effect of
x264
’s --slow-firstpass option.- crf (crf)
Set the quality for constant quality mode.
- crf_max (crf-max)
In CRF mode, prevents VBV from lowering quality beyond this point.
- qp (qp)
Set constant quantization rate control method parameter.
- aq-mode (aq-mode)
Set AQ method. Possible values:
- ‘none (0)’
Disabled.
- ‘variance (1)’
Variance AQ (complexity mask).
- ‘autovariance (2)’
Auto-variance AQ (experimental).
- aq-strength (aq-strength)
Set AQ strength, reduce blocking and blurring in flat and textured areas.
- psy
Use psychovisual optimizations when set to 1. When set to 0, it has the same effect as
x264
’s --no-psy option.- psy-rd (psy-rd)
Set strength of psychovisual optimization, in psy-rd:psy-trellis format.
- rc-lookahead (rc-lookahead)
Set number of frames to look ahead for frametype and ratecontrol.
- weightb
Enable weighted prediction for B-frames when set to 1. When set to 0, it has the same effect as
x264
’s --no-weightb option.- weightp (weightp)
Set weighted prediction method for P-frames. Possible values:
- ‘none (0)’
Disabled
- ‘simple (1)’
Enable only weighted refs
- ‘smart (2)’
Enable both weighted refs and duplicates
- ssim (ssim)
Enable calculation and printing SSIM stats after the encoding.
- intra-refresh (intra-refresh)
Enable the use of Periodic Intra Refresh instead of IDR frames when set to 1.
- avcintra-class (class)
Configure the encoder to generate AVC-Intra. Valid values are 50,100 and 200
- bluray-compat (bluray-compat)
Configure the encoder to be compatible with the bluray standard. It is a shorthand for setting "bluray-compat=1 force-cfr=1".
- b-bias (b-bias)
Set the influence on how often B-frames are used.
- b-pyramid (b-pyramid)
Set method for keeping of some B-frames as references. Possible values:
- ‘none (none)’
Disabled.
- ‘strict (strict)’
Strictly hierarchical pyramid.
- ‘normal (normal)’
Non-strict (not Blu-ray compatible).
- mixed-refs
Enable the use of one reference per partition, as opposed to one reference per macroblock when set to 1. When set to 0, it has the same effect as
x264
’s --no-mixed-refs option.- 8x8dct
Enable adaptive spatial transform (high profile 8x8 transform) when set to 1. When set to 0, it has the same effect as
x264
’s --no-8x8dct option.- fast-pskip
Enable early SKIP detection on P-frames when set to 1. When set to 0, it has the same effect as
x264
’s --no-fast-pskip option.- aud (aud)
Enable use of access unit delimiters when set to 1.
- mbtree
Enable use macroblock tree ratecontrol when set to 1. When set to 0, it has the same effect as
x264
’s --no-mbtree option.- deblock (deblock)
Set loop filter parameters, in alpha:beta form.
- cplxblur (cplxblur)
Set fluctuations reduction in QP (before curve compression).
- partitions (partitions)
Set partitions to consider as a comma-separated list of. Possible values in the list:
- ‘p8x8’
8x8 P-frame partition.
- ‘p4x4’
4x4 P-frame partition.
- ‘b8x8’
4x4 B-frame partition.
- ‘i8x8’
8x8 I-frame partition.
- ‘i4x4’
4x4 I-frame partition. (Enabling ‘p4x4’ requires ‘p8x8’ to be enabled. Enabling ‘i8x8’ requires adaptive spatial transform (8x8dct option) to be enabled.)
- ‘none (none)’
Do not consider any partitions.
- ‘all (all)’
Consider every partition.
- direct-pred (direct)
Set direct MV prediction mode. Possible values:
- ‘none (none)’
Disable MV prediction.
- ‘spatial (spatial)’
Enable spatial predicting.
- ‘temporal (temporal)’
Enable temporal predicting.
- ‘auto (auto)’
Automatically decided.
- slice-max-size (slice-max-size)
Set the limit of the size of each slice in bytes. If not specified but RTP payload size (ps) is specified, that is used.
- stats (stats)
Set the file name for multi-pass stats.
- nal-hrd (nal-hrd)
Set signal HRD information (requires vbv-bufsize to be set). Possible values:
- ‘none (none)’
Disable HRD information signaling.
- ‘vbr (vbr)’
Variable bit rate.
- ‘cbr (cbr)’
Constant bit rate (not allowed in MP4 container).
- x264opts (N.A.)
Set any x264 option, see
x264 --fullhelp
for a list.Argument is a list of key=value couples separated by ":". In filter and psy-rd options that use ":" as a separator themselves, use "," instead. They accept it as well since long ago but this is kept undocumented for some reason.
For example to specify libx264 encoding options with
ffmpeg
:ffmpeg -i foo.mpg -c:v libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
- a53cc boolean
Import closed captions (which must be ATSC compatible format) into output. Only the mpeg2 and h264 decoders provide these. Default is 1 (on).
- udu_sei boolean
Import user data unregistered SEI if available into output. Default is 0 (off).
- x264-params (N.A.)
Override the x264 configuration using a :-separated list of key=value parameters.
This option is functionally the same as the x264opts, but is duplicated for compatibility with the Libav fork.
For example to specify libx264 encoding options with
ffmpeg
:ffmpeg -i INPUT -c:v libx264 -x264-params level=30:bframes=0:weightp=0:\ cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:\ no-fast-pskip=1:subq=6:8x8dct=0:trellis=0 OUTPUT
Encoding ffpresets for common usages are provided so they can be used with the general presets system (e.g. passing the pre option).
9.16 libx265
x265 H.265/HEVC encoder wrapper.
This encoder requires the presence of the libx265 headers and library during configuration. You need to explicitly configure the build with --enable-libx265.
9.16.1 Options
- b
Sets target video bitrate.
- bf
- g
Set the GOP size.
- keyint_min
Minimum GOP size.
- refs
Number of reference frames each P-frame can use. The range is from 1-16.
- preset
Set the x265 preset.
- tune
Set the x265 tune parameter.
- profile
Set profile restrictions.
- crf
Set the quality for constant quality mode.
- qp
Set constant quantization rate control method parameter.
- qmin
Minimum quantizer scale.
- qmax
Maximum quantizer scale.
- qdiff
Maximum difference between quantizer scales.
- qblur
Quantizer curve blur
- qcomp
Quantizer curve compression factor
- i_qfactor
- b_qfactor
- forced-idr
Normally, when forcing a I-frame type, the encoder can select any type of I-frame. This option forces it to choose an IDR-frame.
- udu_sei boolean
Import user data unregistered SEI if available into output. Default is 0 (off).
- x265-params
Set x265 options using a list of key=value couples separated by ":". See
x265 --help
for a list of options.For example to specify libx265 encoding options with -x265-params:
ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4
9.17 libxavs2
xavs2 AVS2-P2/IEEE1857.4 encoder wrapper.
This encoder requires the presence of the libxavs2 headers and library during configuration. You need to explicitly configure the build with --enable-libxavs2.
The following standard libavcodec options are used:
- b / bit_rate
- g / gop_size
- bf / max_b_frames
The encoder also has its own specific options:
9.17.1 Options
- lcu_row_threads
Set the number of parallel threads for rows from 1 to 8 (default 5).
- initial_qp
Set the xavs2 quantization parameter from 1 to 63 (default 34). This is used to set the initial qp for the first frame.
- qp
Set the xavs2 quantization parameter from 1 to 63 (default 34). This is used to set the qp value under constant-QP mode.
- max_qp
Set the max qp for rate control from 1 to 63 (default 55).
- min_qp
Set the min qp for rate control from 1 to 63 (default 20).
- speed_level
Set the Speed level from 0 to 9 (default 0). Higher is better but slower.
- log_level
Set the log level from -1 to 3 (default 0). -1: none, 0: error, 1: warning, 2: info, 3: debug.
- xavs2-params
Set xavs2 options using a list of key=value couples separated by ":".
For example to specify libxavs2 encoding options with -xavs2-params:
ffmpeg -i input -c:v libxavs2 -xavs2-params RdoqLevel=0 output.avs2
9.18 libxvid
Xvid MPEG-4 Part 2 encoder wrapper.
This encoder requires the presence of the libxvidcore headers and library
during configuration. You need to explicitly configure the build with
--enable-libxvid --enable-gpl
.
The native mpeg4
encoder supports the MPEG-4 Part 2 format, so
users can encode to this format without this library.
9.18.1 Options
The following options are supported by the libxvid wrapper. Some of the following options are listed but are not documented, and correspond to shared codec options. See the Codec Options chapter for their documentation. The other shared options which are not listed have no effect for the libxvid encoder.
- b
- g
- qmin
- qmax
- mpeg_quant
- threads
- bf
- b_qfactor
- b_qoffset
- flags
Set specific encoding flags. Possible values:
- ‘mv4’
Use four motion vector by macroblock.
- ‘aic’
Enable high quality AC prediction.
- ‘gray’
Only encode grayscale.
- ‘gmc’
Enable the use of global motion compensation (GMC).
- ‘qpel’
Enable quarter-pixel motion compensation.
- ‘cgop’
Enable closed GOP.
- ‘global_header’
Place global headers in extradata instead of every keyframe.
- trellis
- me_method
Set motion estimation method. Possible values in decreasing order of speed and increasing order of quality:
- ‘zero’
Use no motion estimation (default).
- ‘phods’
- ‘x1’
- ‘log’
Enable advanced diamond zonal search for 16x16 blocks and half-pixel refinement for 16x16 blocks. ‘x1’ and ‘log’ are aliases for ‘phods’.
- ‘epzs’
Enable all of the things described above, plus advanced diamond zonal search for 8x8 blocks, half-pixel refinement for 8x8 blocks, and motion estimation on chroma planes.
- ‘full’
Enable all of the things described above, plus extended 16x16 and 8x8 blocks search.
- mbd
Set macroblock decision algorithm. Possible values in the increasing order of quality:
- ‘simple’
Use macroblock comparing function algorithm (default).
- ‘bits’
Enable rate distortion-based half pixel and quarter pixel refinement for 16x16 blocks.
- ‘rd’
Enable all of the things described above, plus rate distortion-based half pixel and quarter pixel refinement for 8x8 blocks, and rate distortion-based search using square pattern.
- lumi_aq
Enable lumi masking adaptive quantization when set to 1. Default is 0 (disabled).
- variance_aq
Enable variance adaptive quantization when set to 1. Default is 0 (disabled).
When combined with lumi_aq, the resulting quality will not be better than any of the two specified individually. In other words, the resulting quality will be the worse one of the two effects.
- ssim
Set structural similarity (SSIM) displaying method. Possible values:
- ‘off’
Disable displaying of SSIM information.
- ‘avg’
Output average SSIM at the end of encoding to stdout. The format of showing the average SSIM is:
Average SSIM: %f
For users who are not familiar with C, %f means a float number, or a decimal (e.g. 0.939232).
- ‘frame’
Output both per-frame SSIM data during encoding and average SSIM at the end of encoding to stdout. The format of per-frame information is:
SSIM: avg: %1.3f min: %1.3f max: %1.3f
For users who are not familiar with C, %1.3f means a float number rounded to 3 digits after the dot (e.g. 0.932).
- ssim_acc
Set SSIM accuracy. Valid options are integers within the range of 0-4, while 0 gives the most accurate result and 4 computes the fastest.
9.19 MediaFoundation
This provides wrappers to encoders (both audio and video) in the MediaFoundation framework. It can access both SW and HW encoders. Video encoders can take input in either of nv12 or yuv420p form (some encoders support both, some support only either - in practice, nv12 is the safer choice, especially among HW encoders).
9.20 mpeg2
MPEG-2 video encoder.
9.20.1 Options
- profile
Select the mpeg2 profile to encode:
- ‘422’
- ‘high’
- ‘ss’
Spatially Scalable
- ‘snr’
SNR Scalable
- ‘main’
- ‘simple’
- level
Select the mpeg2 level to encode:
- ‘high’
- ‘high1440’
- ‘main’
- ‘low’
- seq_disp_ext integer
Specifies if the encoder should write a sequence_display_extension to the output.
- -1
- auto
Decide automatically to write it or not (this is the default) by checking if the data to be written is different from the default or unspecified values.
- 0
- never
Never write it.
- 1
- always
Always write it.
- video_format integer
Specifies the video_format written into the sequence display extension indicating the source of the video pictures. The default is ‘unspecified’, can be ‘component’, ‘pal’, ‘ntsc’, ‘secam’ or ‘mac’. For maximum compatibility, use ‘component’.
- a53cc boolean
Import closed captions (which must be ATSC compatible format) into output. Default is 1 (on).
9.21 png
PNG image encoder.
9.21.1 Private options
- dpi integer
Set physical density of pixels, in dots per inch, unset by default
- dpm integer
Set physical density of pixels, in dots per meter, unset by default
9.22 ProRes
Apple ProRes encoder.
FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder.
The used encoder can be chosen with the -vcodec
option.
9.22.1 Private Options for prores-ks
- profile integer
Select the ProRes profile to encode
- ‘proxy’
- ‘lt’
- ‘standard’
- ‘hq’
- ‘4444’
- ‘4444xq’
- quant_mat integer
Select quantization matrix.
- ‘auto’
- ‘default’
- ‘proxy’
- ‘lt’
- ‘standard’
- ‘hq’
If set to auto, the matrix matching the profile will be picked. If not set, the matrix providing the highest quality, default, will be picked.
- bits_per_mb integer
How many bits to allot for coding one macroblock. Different profiles use between 200 and 2400 bits per macroblock, the maximum is 8000.
- mbs_per_slice integer
Number of macroblocks in each slice (1-8); the default value (8) should be good in almost all situations.
- vendor string
Override the 4-byte vendor ID. A custom vendor ID like apl0 would claim the stream was produced by the Apple encoder.
- alpha_bits integer
Specify number of bits for alpha component. Possible values are 0, 8 and 16. Use 0 to disable alpha plane coding.
9.22.2 Speed considerations
In the default mode of operation the encoder has to honor frame constraints (i.e. not produce frames with size bigger than requested) while still making output picture as good as possible. A frame containing a lot of small details is harder to compress and the encoder would spend more time searching for appropriate quantizers for each slice.
Setting a higher bits_per_mb limit will improve the speed.
For the fastest encoding speed set the qscale parameter (4 is the recommended value) and do not set a size constraint.
9.23 QSV Encoders
The family of Intel QuickSync Video encoders (MPEG-2, H.264, HEVC, JPEG/MJPEG and VP9)
9.23.1 Ratecontrol Method
The ratecontrol method is selected as follows:
- When global_quality is specified, a quality-based mode is used.
Specifically this means either
- - CQP - constant quantizer scale, when the qscale codec flag is also set (the -qscale ffmpeg option).
- - LA_ICQ - intelligent constant quality with lookahead, when the look_ahead option is also set.
- - ICQ – intelligent constant quality otherwise. For the ICQ modes, global quality range is 1 to 51, with 1 being the best quality.
- Otherwise, a bitrate-based mode is used. For all of those, you should specify at
least the desired average bitrate with the b option.
- - LA - VBR with lookahead, when the look_ahead option is specified.
- - VCM - video conferencing mode, when the vcm option is set.
- - CBR - constant bitrate, when maxrate is specified and equal to the average bitrate.
- - VBR - variable bitrate, when maxrate is specified, but is higher than the average bitrate.
- - AVBR - average VBR mode, when maxrate is not specified, both avbr_accuracy and avbr_convergence are set to non-zero. This mode is available for H264 and HEVC on Windows.
Note that depending on your system, a different mode than the one you specified may be selected by the encoder. Set the verbosity level to verbose or higher to see the actual settings used by the QSV runtime.
9.23.2 Global Options -> MSDK Options
Additional libavcodec global options are mapped to MSDK options as follows:
- g/gop_size -> GopPicSize
- bf/max_b_frames+1 -> GopRefDist
- rc_init_occupancy/rc_initial_buffer_occupancy -> InitialDelayInKB
- slices -> NumSlice
- refs -> NumRefFrame
- b_strategy/b_frame_strategy -> BRefType
- cgop/CLOSED_GOP codec flag -> GopOptFlag
- For the CQP mode, the i_qfactor/i_qoffset and b_qfactor/b_qoffset set the difference between QPP and QPI, and QPP and QPB respectively.
- Setting the coder option to the value vlc will make the H.264 encoder use CAVLC instead of CABAC.
9.23.3 Common Options
Following options are used by all qsv encoders.
- async_depth
Specifies how many asynchronous operations an application performs before the application explicitly synchronizes the result. If zero, the value is not specified.
- preset
This option itemizes a range of choices from veryfast (best speed) to veryslow (best quality).
- ‘veryfast’
- ‘faster’
- ‘fast’
- ‘medium’
- ‘slow’
- ‘slower’
- ‘veryslow’
- forced_idr
Forcing I frames as IDR frames.
- low_power
For encoders set this flag to ON to reduce power consumption and GPU usage.
9.23.4 Runtime Options
Following options can be used durning qsv encoding.
- global_quality
- i_quant_factor
- i_quant_offset
- b_quant_factor
- b_quant_offset
Supported in h264_qsv and hevc_qsv. Change these value to reset qsv codec’s qp configuration.
- max_frame_size
Supported in h264_qsv and hevc_qsv. Change this value to reset qsv codec’s MaxFrameSize configuration.
- gop_size
Change this value to reset qsv codec’s gop configuration.
- int_ref_type
- int_ref_cycle_size
- int_ref_qp_delta
- int_ref_cycle_dist
Supported in h264_qsv and hevc_qsv. Change these value to reset qsv codec’s Intra Refresh configuration.
- qmax
- qmin
- max_qp_i
- min_qp_i
- max_qp_p
- min_qp_p
- max_qp_b
- min_qp_b
Supported in h264_qsv. Change these value to reset qsv codec’s max/min qp configuration.
- low_delay_brc
Supported in h264_qsv and hevc_qsv. Change this value to reset qsv codec’s low_delay_brc configuration.
9.23.5 H264 options
These options are used by h264_qsv
- extbrc
Extended bitrate control.
- recovery_point_sei
Set this flag to insert the recovery point SEI message at the beginning of every intra refresh cycle.
- rdo
Enable rate distortion optimization.
- max_frame_size
Maximum encoded frame size in bytes.
- max_frame_size_i
Maximum encoded frame size for I frames in bytes. If this value is set as larger than zero, then for I frames the value set by max_frame_size is ignored.
- max_frame_size_p
Maximum encoded frame size for P frames in bytes. If this value is set as larger than zero, then for P frames the value set by max_frame_size is ignored.
- max_slice_size
Maximum encoded slice size in bytes.
- bitrate_limit
Toggle bitrate limitations. Modifies bitrate to be in the range imposed by the QSV encoder. Setting this flag off may lead to violation of HRD conformance. Mind that specifying bitrate below the QSV encoder range might significantly affect quality. If on this option takes effect in non CQP modes: if bitrate is not in the range imposed by the QSV encoder, it will be changed to be in the range.
- mbbrc
Setting this flag enables macroblock level bitrate control that generally improves subjective visual quality. Enabling this flag may have negative impact on performance and objective visual quality metric.
- low_delay_brc
Setting this flag turns on or off LowDelayBRC feautre in qsv plugin, which provides more accurate bitrate control to minimize the variance of bitstream size frame by frame. Value: -1-default 0-off 1-on
- adaptive_i
This flag controls insertion of I frames by the QSV encoder. Turn ON this flag to allow changing of frame type from P and B to I.
- adaptive_b
This flag controls changing of frame type from B to P.
- p_strategy
Enable P-pyramid: 0-default 1-simple 2-pyramid(bf need to be set to 0).
- b_strategy
This option controls usage of B frames as reference.
- dblk_idc
This option disable deblocking. It has value in range 0~2.
- cavlc
If set, CAVLC is used; if unset, CABAC is used for encoding.
- vcm
Video conferencing mode, please see ratecontrol method.
- idr_interval
Distance (in I-frames) between IDR frames.
- pic_timing_sei
Insert picture timing SEI with pic_struct_syntax element.
- single_sei_nal_unit
Put all the SEI messages into one NALU.
- max_dec_frame_buffering
Maximum number of frames buffered in the DPB.
- look_ahead
Use VBR algorithm with look ahead.
- look_ahead_depth
Depth of look ahead in number frames.
- look_ahead_downsampling
Downscaling factor for the frames saved for the lookahead analysis.
- ‘unknown’
- ‘auto’
- ‘off’
- ‘2x’
- ‘4x’
- int_ref_type
Specifies intra refresh type. The major goal of intra refresh is improvement of error resilience without significant impact on encoded bitstream size caused by I frames. The SDK encoder achieves this by encoding part of each frame in refresh cycle using intra MBs. none means no refresh. vertical means vertical refresh, by column of MBs. horizontal means horizontal refresh, by rows of MBs. slice means horizontal refresh by slices without overlapping. In case of slice, in_ref_cycle_size is ignored. To enable intra refresh, B frame should be set to 0.
- int_ref_cycle_size
Specifies number of pictures within refresh cycle starting from 2. 0 and 1 are invalid values.
- int_ref_qp_delta
Specifies QP difference for inserted intra MBs. This is signed value in [-51, 51] range if target encoding bit-depth for luma samples is 8 and this range is [-63, 63] for 10 bit-depth or [-75, 75] for 12 bit-depth respectively.
- int_ref_cycle_dist
Distance between the beginnings of the intra-refresh cycles in frames.
- profile
- ‘unknown’
- ‘baseline’
- ‘main’
- ‘high’
- a53cc
Use A53 Closed Captions (if available).
- aud
Insert the Access Unit Delimiter NAL.
- mfmode
Multi-Frame Mode.
- ‘off’
- ‘auto’
- repeat_pps
Repeat pps for every frame.
- max_qp_i
Maximum video quantizer scale for I frame.
- min_qp_i
Minimum video quantizer scale for I frame.
- max_qp_p
Maximum video quantizer scale for P frame.
- min_qp_p
Minimum video quantizer scale for P frame.
- max_qp_b
Maximum video quantizer scale for B frame.
- min_qp_b
Minimum video quantizer scale for B frame.
- scenario
Provides a hint to encoder about the scenario for the encoding session.
- ‘unknown’
- ‘displayremoting’
- ‘videoconference’
- ‘archive’
- ‘livestreaming’
- ‘cameracapture’
- ‘videosurveillance’
- ‘gamestreaming’
- ‘remotegaming’
- avbr_accuracy
Accuracy of the AVBR ratecontrol (unit of tenth of percent).
- avbr_convergence
Convergence of the AVBR ratecontrol (unit of 100 frames)
The parameters avbr_accuracy and avbr_convergence are for the average variable bitrate control (AVBR) algorithm. The algorithm focuses on overall encoding quality while meeting the specified bitrate, target_bitrate, within the accuracy range avbr_accuracy, after a avbr_Convergence period. This method does not follow HRD and the instant bitrate is not capped or padded.
9.23.6 HEVC Options
These options are used by hevc_qsv
- extbrc
Extended bitrate control.
- recovery_point_sei
Set this flag to insert the recovery point SEI message at the beginning of every intra refresh cycle.
- rdo
Enable rate distortion optimization.
- max_frame_size
Maximum encoded frame size in bytes.
- max_frame_size_i
Maximum encoded frame size for I frames in bytes. If this value is set as larger than zero, then for I frames the value set by max_frame_size is ignored.
- max_frame_size_p
Maximum encoded frame size for P frames in bytes. If this value is set as larger than zero, then for P frames the value set by max_frame_size is ignored.
- max_slice_size
Maximum encoded slice size in bytes.
- mbbrc
Setting this flag enables macroblock level bitrate control that generally improves subjective visual quality. Enabling this flag may have negative impact on performance and objective visual quality metric.
- low_delay_brc
Setting this flag turns on or off LowDelayBRC feautre in qsv plugin, which provides more accurate bitrate control to minimize the variance of bitstream size frame by frame. Value: -1-default 0-off 1-on
- adaptive_i
This flag controls insertion of I frames by the QSV encoder. Turn ON this flag to allow changing of frame type from P and B to I.
- adaptive_b
This flag controls changing of frame type from B to P.
- p_strategy
Enable P-pyramid: 0-default 1-simple 2-pyramid(bf need to be set to 0).
- b_strategy
This option controls usage of B frames as reference.
- dblk_idc
This option disable deblocking. It has value in range 0~2.
- idr_interval
Distance (in I-frames) between IDR frames.
- ‘begin_only’
Output an IDR-frame only at the beginning of the stream.
- load_plugin
A user plugin to load in an internal session.
- ‘none’
- ‘hevc_sw’
- ‘hevc_hw’
- load_plugins
A :-separate list of hexadecimal plugin UIDs to load in an internal session.
- look_ahead_depth
Depth of look ahead in number frames, available when extbrc option is enabled.
- profile
Set the encoding profile (scc requires libmfx >= 1.32).
- ‘unknown’
- ‘main’
- ‘main10’
- ‘mainsp’
- ‘rext’
- ‘scc’
- gpb
1: GPB (generalized P/B frame)
0: regular P frame.
- tile_cols
Number of columns for tiled encoding.
- tile_rows
Number of rows for tiled encoding.
- aud
Insert the Access Unit Delimiter NAL.
- pic_timing_sei
Insert picture timing SEI with pic_struct_syntax element.
- transform_skip
Turn this option ON to enable transformskip. It is supported on platform equal or newer than ICL.
- int_ref_type
Specifies intra refresh type. The major goal of intra refresh is improvement of error resilience without significant impact on encoded bitstream size caused by I frames. The SDK encoder achieves this by encoding part of each frame in refresh cycle using intra MBs. none means no refresh. vertical means vertical refresh, by column of MBs. horizontal means horizontal refresh, by rows of MBs. slice means horizontal refresh by slices without overlapping. In case of slice, in_ref_cycle_size is ignored. To enable intra refresh, B frame should be set to 0.
- int_ref_cycle_size
Specifies number of pictures within refresh cycle starting from 2. 0 and 1 are invalid values.
- int_ref_qp_delta
Specifies QP difference for inserted intra MBs. This is signed value in [-51, 51] range if target encoding bit-depth for luma samples is 8 and this range is [-63, 63] for 10 bit-depth or [-75, 75] for 12 bit-depth respectively.
- int_ref_cycle_dist
Distance between the beginnings of the intra-refresh cycles in frames.
- max_qp_i
Maximum video quantizer scale for I frame.
- min_qp_i
Minimum video quantizer scale for I frame.
- max_qp_p
Maximum video quantizer scale for P frame.
- min_qp_p
Minimum video quantizer scale for P frame.
- max_qp_b
Maximum video quantizer scale for B frame.
- min_qp_b
Minimum video quantizer scale for B frame.
- scenario
Provides a hint to encoder about the scenario for the encoding session.
- ‘unknown’
- ‘displayremoting’
- ‘videoconference’
- ‘archive’
- ‘livestreaming’
- ‘cameracapture’
- ‘videosurveillance’
- ‘gamestreaming’
- ‘remotegaming’
- avbr_accuracy
Accuracy of the AVBR ratecontrol (unit of tenth of percent).
- avbr_convergence
Convergence of the AVBR ratecontrol (unit of 100 frames)
The parameters avbr_accuracy and avbr_convergence are for the average variable bitrate control (AVBR) algorithm. The algorithm focuses on overall encoding quality while meeting the specified bitrate, target_bitrate, within the accuracy range avbr_accuracy, after a avbr_Convergence period. This method does not follow HRD and the instant bitrate is not capped or padded.
9.23.7 MPEG2 Options
These options are used by mpeg2_qsv
- profile
- ‘unknown’
- ‘simple’
- ‘main’
- ‘high’
9.23.8 VP9 Options
These options are used by vp9_qsv
- profile
- ‘unknown’
- ‘profile0’
- ‘profile1’
- ‘profile2’
- ‘profile3’
- tile_cols
Number of columns for tiled encoding (requires libmfx >= 1.29).
- tile_rows
Number of rows for tiled encoding (requires libmfx >= 1.29).
9.24 snow
9.24.1 Options
- iterative_dia_size
dia size for the iterative motion estimation
9.25 VAAPI encoders
Wrappers for hardware encoders accessible via VAAPI.
These encoders only accept input in VAAPI hardware surfaces. If you have input in software frames, use the hwupload filter to upload them to the GPU.
The following standard libavcodec options are used:
- g / gop_size
- bf / max_b_frames
- profile
If not set, this will be determined automatically from the format of the input frames and the profiles supported by the driver.
- level
- b / bit_rate
- maxrate / rc_max_rate
- bufsize / rc_buffer_size
- rc_init_occupancy / rc_initial_buffer_occupancy
- compression_level
Speed / quality tradeoff: higher values are faster / worse quality.
- q / global_quality
Size / quality tradeoff: higher values are smaller / worse quality.
- qmin
- qmax
- i_qfactor / i_quant_factor
- i_qoffset / i_quant_offset
- b_qfactor / b_quant_factor
- b_qoffset / b_quant_offset
- slices
All encoders support the following options:
- low_power
Some drivers/platforms offer a second encoder for some codecs intended to use less power than the default encoder; setting this option will attempt to use that encoder. Note that it may support a reduced feature set, so some other options may not be available in this mode.
- idr_interval
Set the number of normal intra frames between full-refresh (IDR) frames in open-GOP mode. The intra frames are still IRAPs, but will not include global headers and may have non-decodable leading pictures.
- b_depth
Set the B-frame reference depth. When set to one (the default), all B-frames will refer only to P- or I-frames. When set to greater values multiple layers of B-frames will be present, frames in each layer only referring to frames in higher layers.
- async_depth
Maximum processing parallelism. Increase this to improve single channel performance. This option doesn’t work if driver doesn’t implement vaSyncBuffer function. Please make sure there are enough hw_frames allocated if a large number of async_depth is used.
- max_frame_size
Set the allowed max size in bytes for each frame. If the frame size exceeds the limitation, encoder will adjust the QP value to control the frame size. Invalid in CQP rate control mode.
- rc_mode
Set the rate control mode to use. A given driver may only support a subset of modes.
Possible modes:
- auto
Choose the mode automatically based on driver support and the other options. This is the default.
- CQP
Constant-quality.
- CBR
Constant-bitrate.
- VBR
Variable-bitrate.
- ICQ
Intelligent constant-quality.
- QVBR
Quality-defined variable-bitrate.
- AVBR
Average variable bitrate.
Each encoder also has its own specific options:
- h264_vaapi
profile sets the value of profile_idc and the constraint_set*_flags. level sets the value of level_idc.
- coder
Set entropy encoder (default is cabac). Possible values:
- ‘ac’
- ‘cabac’
Use CABAC.
- ‘vlc’
- ‘cavlc’
Use CAVLC.
- aud
Include access unit delimiters in the stream (not included by default).
- sei
Set SEI message types to include. Some combination of the following values:
- ‘identifier’
Include a user_data_unregistered message containing information about the encoder.
- ‘timing’
Include picture timing parameters (buffering_period and pic_timing messages).
- ‘recovery_point’
Include recovery points where appropriate (recovery_point messages).
- hevc_vaapi
profile and level set the values of general_profile_idc and general_level_idc respectively.
- aud
Include access unit delimiters in the stream (not included by default).
- tier
Set general_tier_flag. This may affect the level chosen for the stream if it is not explicitly specified.
- sei
Set SEI message types to include. Some combination of the following values:
- ‘hdr’
Include HDR metadata if the input frames have it (mastering_display_colour_volume and content_light_level messages).
- tiles
Set the number of tiles to encode the input video with, as columns x rows. Larger numbers allow greater parallelism in both encoding and decoding, but may decrease coding efficiency.
- mjpeg_vaapi
Only baseline DCT encoding is supported. The encoder always uses the standard quantisation and huffman tables - global_quality scales the standard quantisation table (range 1-100).
For YUV, 4:2:0, 4:2:2 and 4:4:4 subsampling modes are supported. RGB is also supported, and will create an RGB JPEG.
- jfif
Include JFIF header in each frame (not included by default).
- huffman
Include standard huffman tables (on by default). Turning this off will save a few hundred bytes in each output frame, but may lose compatibility with some JPEG decoders which don’t fully handle MJPEG.
- mpeg2_vaapi
profile and level set the value of profile_and_level_indication.
- vp8_vaapi
B-frames are not supported.
global_quality sets the q_idx used for non-key frames (range 0-127).
- loop_filter_level
- loop_filter_sharpness
Manually set the loop filter parameters.
- vp9_vaapi
global_quality sets the q_idx used for P-frames (range 0-255).
- loop_filter_level
- loop_filter_sharpness
Manually set the loop filter parameters.
B-frames are supported, but the output stream is always in encode order rather than display order. If B-frames are enabled, it may be necessary to use the vp9_raw_reorder bitstream filter to modify the output stream to display frames in the correct order.
Only normal frames are produced - the vp9_superframe bitstream filter may be required to produce a stream usable with all decoders.
9.26 vbn
Vizrt Binary Image encoder.
This format is used by the broadcast vendor Vizrt for quick texture streaming. Advanced features of the format such as LZW compression of texture data or generation of mipmaps are not supported.
9.26.1 Options
- format string
Sets the texture compression used by the VBN file. Can be dxt1, dxt5 or raw. Default is dxt5.
9.27 vc2
SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed at professional broadcasting but since it supports yuv420, yuv422 and yuv444 at 8 (limited range or full range), 10 or 12 bits, this makes it suitable for other tasks which require low overhead and low compression (like screen recording).
9.27.1 Options
- b
Sets target video bitrate. Usually that’s around 1:6 of the uncompressed video bitrate (e.g. for 1920x1080 50fps yuv422p10 that’s around 400Mbps). Higher values (close to the uncompressed bitrate) turn on lossless compression mode.
- field_order
Enables field coding when set (e.g. to tt - top field first) for interlaced inputs. Should increase compression with interlaced content as it splits the fields and encodes each separately.
- wavelet_depth
Sets the total amount of wavelet transforms to apply, between 1 and 5 (default). Lower values reduce compression and quality. Less capable decoders may not be able to handle values of wavelet_depth over 3.
- wavelet_type
Sets the transform type. Currently only 5_3 (LeGall) and 9_7 (Deslauriers-Dubuc) are implemented, with 9_7 being the one with better compression and thus is the default.
- slice_width
- slice_height
Sets the slice size for each slice. Larger values result in better compression. For compatibility with other more limited decoders use slice_width of 32 and slice_height of 8.
- tolerance
Sets the undershoot tolerance of the rate control system in percent. This is to prevent an expensive search from being run.
- qm
Sets the quantization matrix preset to use by default or when wavelet_depth is set to 5
- - default Uses the default quantization matrix from the specifications, extended with values for the fifth level. This provides a good balance between keeping detail and omitting artifacts.
- - flat Use a completely zeroed out quantization matrix. This increases PSNR but might reduce perception. Use in bogus benchmarks.
- - color Reduces detail but attempts to preserve color at extremely low bitrates.
10 Subtitles Encoders
10.1 dvdsub
This codec encodes the bitmap subtitle format that is used in DVDs. Typically they are stored in VOBSUB file pairs (*.idx + *.sub), and they can also be used in Matroska files.
10.1.1 Options
- palette
Specify the global palette used by the bitmaps.
The format for this option is a string containing 16 24-bits hexadecimal numbers (without 0x prefix) separated by commas, for example
0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b
.- even_rows_fix
When set to 1, enable a work-around that makes the number of pixel rows even in all subtitles. This fixes a problem with some players that cut off the bottom row if the number is odd. The work-around just adds a fully transparent row if needed. The overhead is low, typically one byte per subtitle on average.
By default, this work-around is disabled.
11 See Also
ffmpeg, ffplay, ffprobe, libavcodec
12 Authors
The FFmpeg developers.
For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
git log
in the FFmpeg source directory, or browsing the
online repository at http://source.ffmpeg.org.
Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.
This document was generated on September 24, 2022 using makeinfo.