# FFmpeg Codecs Documentation

# Table of Contents

- 1 Description
- 2 Codec Options
- 3 Decoders
- 4 Video Decoders
  - 4.1 rawvideo
    - 4.1.1 Options
- 5 Audio Decoders
  - 5.1 ffwavesynth
- 6 Subtitles Decoders
  - 6.1 dvdsub
    - 6.1.1 Options
- 7 Encoders
- 8 Audio Encoders
  - 8.1 ac3 and ac3_fixed
    - 8.1.1 AC-3 Metadata
      - 8.1.1.1 Metadata Control Options
      - 8.1.1.2 Downmix Levels
      - 8.1.1.3 Audio Production Information
      - 8.1.1.4 Other Metadata Options
    - 8.1.2 Extended Bitstream Information
      - 8.1.2.1 Extended Bitstream Information - Part 1
      - 8.1.2.2 Extended Bitstream Information - Part 2
    - 8.1.3 Other AC-3 Encoding Options
    - 8.1.4 Floating-Point-Only AC-3 Encoding Options
- 9 Video Encoders
  - 9.1 libtheora
    - 9.1.1 Options
  - 9.2 libvpx
    - 9.2.1 Options
  - 9.3 libx264
    - 9.3.1 Options
- 10 See Also
- 11 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 unsensical 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.

  ‘`gmc`’

    Use gmc.

  ‘`mv0`’

    Always try a mb with mv=<0,0>.

  ‘`input_preserved`’
  ‘`pass1`’

    Use internal 2pass ratecontrol in first pass mode.

  ‘`pass2`’

    Use internal 2pass ratecontrol in second pass mode.

  ‘`gray`’

    Only decode/encode grayscale.

  ‘`emu_edge`’

    Do not draw edges.

  ‘`psnr`’

    Set error[?] variables during encoding.

  ‘`truncated`’
  ‘`naq`’

    Normalize adaptive quantization.

  ‘`ildct`’

    Use interlaced DCT.

  ‘`low_delay`’

    Force low delay.

  ‘`global_header`’

    Place global headers in extradata instead of every keyframe.

  ‘`bitexact`’

    Use only bitexact stuff (except (I)DCT).

  ‘`aic`’

    Apply H263 advanced intra coding / mpeg4 ac prediction.

  ‘`cbp`’

    Deprecated, use mpegvideo private options instead.

  ‘`qprd`’

    Deprecated, use mpegvideo private options instead.

  ‘`ilme`’

    Apply interlaced motion estimation.

  ‘`cgop`’

    Use closed gop.

‘`sub_id integer`’

  Deprecated, currently unused.

‘`me_method integer (encoding,video)`’

  Set motion estimation method.

  Possible values:

  ‘`zero`’

    zero motion estimation (fastest)

  ‘`full`’

    full motion estimation (slowest)

  ‘`epzs`’

    EPZS motion estimation (default)

  ‘`esa`’

    esa motion estimation (alias for full)

  ‘`tesa`’

    tesa motion estimation

  ‘`dia`’

    dia motion estimation (alias for epzs)

  ‘`log`’

    log motion estimation

  ‘`phods`’

    phods motion estimation

  ‘`x1`’

    X1 motion estimation

  ‘`hex`’

    hex motion estimation

  ‘`umh`’

    umh motion estimation

  ‘`iter`’

    iter motion estimation

‘`extradata_size integer`’

  Set extradata size.

‘`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/framerate and timestamp increments should be identically 1.

‘`g integer (encoding,video)`’

  Set the group of picture 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.

‘`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.

‘`b_qfactor float (encoding,video)`’

  Set qp factor between P and B frames.

‘`rc_strategy integer (encoding,video)`’

  Set ratecontrol method.

‘`b_strategy integer (encoding,video)`’

  Set strategy to choose between I/P/B-frames.

‘`ps integer (encoding,video)`’

  Set RTP payload size in bytes.

‘`mv_bits integer`’
‘`header_bits integer`’
‘`i_tex_bits integer`’
‘`p_tex_bits integer`’
‘`i_count integer`’
‘`p_count integer`’
‘`skip_count integer`’
‘`misc_bits integer`’
‘`frame_bits integer`’
‘`codec_tag integer`’
‘`bug flags (decoding,video)`’

  Workaround not auto detected encoder bugs.

  Possible values:

  ‘`autodetect`’
  ‘`old_msmpeg4`’

    some old lavc generated msmpeg4v3 files (no autodetection)

  ‘`xvid_ilace`’

    Xvid interlacing bug (autodetected if fourcc==XVIX)

  ‘`ump4`’

    (autodetected if fourcc==UMP4)

  ‘`no_padding`’

    padding bug (autodetected)

  ‘`amv`’
  ‘`ac_vlc`’

    illegal vlc bug (autodetected per fourcc)

  ‘`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

‘`lelim integer (encoding,video)`’

  Set single coefficient elimination threshold for luminance (negative values also consider DC coefficient).

‘`celim integer (encoding,video)`’

  Set single coefficient elimination threshold for chrominance (negative values also consider dc coefficient)

‘`strict integer (decoding/encoding,audio,video)`’

  Specify how strictly to follow the standards.

  Possible values:

  ‘`very`’

    strictly conform to a 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

‘`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

  ‘`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`’
‘`mpeg_quant integer (encoding,video)`’

  Use MPEG quantizers instead of H.263.

‘`qsquish float (encoding,video)`’

  How to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function).

‘`rc_qmod_amp float (encoding,video)`’

  Set experimental quantizer modulation.

‘`rc_qmod_freq integer (encoding,video)`’

  Set experimental quantizer modulation.

‘`rc_override_count integer`’
‘`rc_eq string (encoding,video)`’

  Set rate control equation. When computing the expression, besides the standard functions defined in the section ’Expression Evaluation’, the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.

‘`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).

‘`rc_buf_aggressivity float (encoding,video)`’

  Currently useless.

‘`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.

‘`rc_init_cplx float (encoding,video)`’

  Set initial complexity for 1-pass encoding.

‘`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`’
  ‘`libmpeg2mmx`’
  ‘`mmi`’
  ‘`arm`’
  ‘`altivec`’
  ‘`sh4`’
  ‘`simplearm`’
  ‘`simplearmv5te`’
  ‘`simplearmv6`’
  ‘`simpleneon`’
  ‘`simplealpha`’
  ‘`h264`’
  ‘`vp3`’
  ‘`ipp`’
  ‘`xvidmmx`’
  ‘`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

‘`bits_per_coded_sample integer`’
‘`pred integer (encoding,video)`’

  Set prediction method.

  Possible values:

  ‘`left`’
  ‘`plane`’
  ‘`median`’
‘`aspect rational number (encoding,video)`’

  Set sample aspect ratio.

‘`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)

  ‘`mv`’

    motion vector

  ‘`dct_coeff`’
  ‘`skip`’
  ‘`startcode`’
  ‘`pts`’
  ‘`er`’

    error recognition

  ‘`mmco`’

    memory management control operations (H.264)

  ‘`bugs`’
  ‘`vis_qp`’

    visualize quantization parameter (QP), lower QP are tinted greener

  ‘`vis_mb_type`’

    visualize block types

  ‘`buffers`’

    picture buffer allocations

  ‘`thread_ops`’

    threading operations

‘`vismv integer (decoding,video)`’

  Visualize motion vectors (MVs).

  Possible values:

  ‘`pf`’

    forward predicted MVs of P-frames

  ‘`bf`’

    forward predicted MVs of B-frames

  ‘`bb`’

    backward predicted MVs of B-frames

‘`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.

‘`last_pred integer (encoding,video)`’

  Set amount of motion predictors from the previous frame.

‘`preme integer (encoding,video)`’

  Set pre motion estimation.

‘`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.

‘`dtg_active_format integer`’
‘`me_range integer (encoding,video)`’

  Set limit motion vectors range (1023 for DivX player).

‘`ibias integer (encoding,video)`’

  Set intra quant bias.

‘`pbias integer (encoding,video)`’

  Set inter quant bias.

‘`color_table_id integer`’
‘`global_quality integer (encoding,audio,video)`’
‘`coder integer (encoding,video)`’

  Possible values:

  ‘`vlc`’

    variable length coder / huffman coder

  ‘`ac`’

    arithmetic coder

  ‘`raw`’

    raw (no encoding)

  ‘`rle`’

    run-length coder

  ‘`deflate`’

    deflate-based coder

‘`context integer (encoding,video)`’

  Set context model.

‘`slice_flags integer`’
‘`xvmc_acceleration 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

‘`stream_codec_tag integer`’
‘`sc_threshold integer (encoding,video)`’

  Set scene change threshold.

‘`lmin integer (encoding,video)`’

  Set min lagrange factor (VBR).

‘`lmax integer (encoding,video)`’

  Set max lagrange factor (VBR).

‘`nr integer (encoding,video)`’

  Set noise reduction.

‘`rc_init_occupancy integer (encoding,video)`’

  Set number of bits which should be loaded into the rc buffer before decoding starts.

‘`inter_threshold integer (encoding,video)`’
‘`flags2 flags (decoding/encoding,audio,video)`’

  Possible values:

  ‘`fast`’

    allow non spec compliant speedup tricks

  ‘`sgop`’

    Deprecated, use mpegvideo private options instead

  ‘`noout`’

    skip bitstream encoding

  ‘`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

  ‘`skiprd`’

    Deprecated, use mpegvideo private options instead

‘`error integer (encoding,video)`’
‘`qns integer (encoding,video)`’

  Deprecated, use mpegvideo private options instead.

‘`threads integer (decoding/encoding,video)`’

  Possible values:

  ‘`auto`’

    detect a good number of threads

‘`me_threshold integer (encoding,video)`’

  Set motion estimation threshold.

‘`mb_threshold integer (encoding,video)`’

  Set macroblock threshold.

‘`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)`’

  Possible values:

  ‘`unknown`’
  ‘`aac_main`’
  ‘`aac_low`’
  ‘`aac_ssr`’
  ‘`aac_ltp`’
  ‘`aac_he`’
  ‘`aac_he_v2`’
  ‘`aac_ld`’
  ‘`aac_eld`’
  ‘`dts`’
  ‘`dts_es`’
  ‘`dts_96_24`’
  ‘`dts_hd_hra`’
  ‘`dts_hd_ma`’
‘`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.

‘`skip_threshold integer (encoding,video)`’

  Set frame skip threshold.

‘`skip_factor integer (encoding,video)`’

  Set frame skip factor.

‘`skip_exp integer (encoding,video)`’

  Set frame skip exponent.

‘`skipcmp integer (encoding,video)`’

  Set frame skip 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`’
‘`border_mask float (encoding,video)`’

  Increase the quantizer for macroblocks close to borders.

‘`mblmin integer (encoding,video)`’

  Set min macroblock lagrange factor (VBR).

‘`mblmax integer (encoding,video)`’

  Set max macroblock lagrange factor (VBR).

‘`mepc integer (encoding,video)`’

  Set motion estimation bitrate penalty compensation (1.0 = 256).

‘`skip_loop_filter integer (decoding,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`skip_idct integer (decoding,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`skip_frame integer (decoding,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`bidir_refine integer (encoding,video)`’

  Refine the two motion vectors used in bidirectional macroblocks.

‘`brd_scale integer (encoding,video)`’

  Downscale frames for dynamic B-frame decision.

‘`keyint_min integer (encoding,video)`’

  Set minimum interval between IDR-frames.

‘`refs integer (encoding,video)`’

  Set reference frames to consider for motion compensation.

‘`chromaoffset integer (encoding,video)`’

  Set chroma qp offset from luma.

‘`trellis integer (encoding,audio,video)`’

  Set rate-distortion optimal quantization.

‘`sc_factor integer (encoding,video)`’

  Set value multiplied by qscale for each frame and added to scene_change_score.

‘`mv0_threshold integer (encoding,video)`’
‘`b_sensitivity integer (encoding,video)`’

  Adjust sensitivity of b_frame_strategy 1.

‘`compression_level integer (encoding,audio,video)`’
‘`min_prediction_order integer (encoding,audio)`’
‘`max_prediction_order integer (encoding,audio)`’
‘`timecode_frame_start integer (encoding,video)`’

  Set GOP timecode frame start number, in non drop frame format.

‘`request_channels integer (decoding,audio)`’

  Set desired number of audio channels.

‘`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)`’
‘`color_trc integer (decoding/encoding,video)`’
‘`colorspace integer (decoding/encoding,video)`’
‘`color_range integer (decoding/encoding,video)`’
‘`chroma_sample_location integer (decoding/encoding,video)`’
‘`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 multithreading type.

  Possible values:

  ‘`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`’

# 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 `-codecs` 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 rawvideo

Raw video decoder.

This decoder decodes rawvideo streams.

### 4.1.1 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

# 5 Audio Decoders

## 5.1 ffwavesynth

Internal wave synthetizer.

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.

# 6 Subtitles Decoders

## 6.1 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.

### 6.1.1 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 comas, for example `0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b`.

# 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 `-codecs` 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 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 floating-point encoder will generally produce better quality audio for a given bitrate. 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.

### 8.1.1 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

#### 8.1.1.1 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.

#### 8.1.1.2 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)

#### 8.1.1.3 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, the `mixing_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 the `room_type` option have the default values.

  ‘`0`’
  ‘`notindicated`’

    Not Indicated (default)

  ‘`1`’
  ‘`large`’

    Large Room

  ‘`2`’
  ‘`small`’

    Small Room

#### 8.1.1.4 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)

### 8.1.2 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.

#### 8.1.2.1 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)

#### 8.1.2.2 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

### 8.1.3 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.

### 8.1.4 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)

# 9 Video Encoders

A description of some of the currently available video encoders follows.

## 9.1 libtheora

Theora format supported through libtheora.

Requires the presence of the libtheora headers and library during configuration. You need to explicitly configure the build with `--enable-libtheora`.

### 9.1.1 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, only works if the `qscale` flag in ‘`flags`’ is not enabled.

‘`flags`’

  Used to enable constant quality mode encoding through the ‘`qscale`’ flag, and to enable the `pass1` and `pass2` modes.

‘`g`’

  Set the GOP size.

‘`global_quality`’

  Set the global quality in lambda units, only works if the `qscale` flag in ‘`flags`’ is enabled. The value is clipped in the [0 - 10*`FF_QP2LAMBDA`] range, and then multiplied for 6.3 to get a value in the native libtheora range [0-63]. A higher value corresponds to a higher quality.

  For example, to set maximum constant quality encoding with `ffmpeg`:

      ffmpeg -i INPUT -flags:v qscale -global_quality:v "10*QP2LAMBDA" -codec:v libtheora OUTPUT.ogg

## 9.2 libvpx

VP8 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`.

### 9.2.1 Options

Mapping from FFmpeg to libvpx options with conversion notes in parentheses.

‘`threads`’

  g_threads

‘`profile`’

  g_profile

‘`vb`’

  rc_target_bitrate

‘`g`’

  kf_max_dist

‘`keyint_min`’

  kf_min_dist

‘`qmin`’

  rc_min_quantizer

‘`qmax`’

  rc_max_quantizer

‘`bufsize, vb`’

  rc_buf_sz `(bufsize * 1000 / vb)`

  rc_buf_optimal_sz `(bufsize * 1000 / vb * 5 / 6)`

‘`rc_init_occupancy, vb`’

  rc_buf_initial_sz `(rc_init_occupancy * 1000 / vb)`

‘`rc_buffer_aggressivity`’

  rc_undershoot_pct

‘`skip_threshold`’

  rc_dropframe_thresh

‘`qcomp`’

  rc_2pass_vbr_bias_pct

‘`maxrate, vb`’

  rc_2pass_vbr_maxsection_pct `(maxrate * 100 / vb)`

‘`minrate, vb`’

  rc_2pass_vbr_minsection_pct `(minrate * 100 / vb)`

‘`minrate, maxrate, vb`’

  `VPX_CBR` `(minrate == maxrate == vb)`

‘`crf`’

  `VPX_CQ`, `VP8E_SET_CQ_LEVEL`

‘`quality`’
  ‘`best`’

    `VPX_DL_BEST_QUALITY`

  ‘`good`’

    `VPX_DL_GOOD_QUALITY`

  ‘`realtime`’

    `VPX_DL_REALTIME`

‘`speed`’

  `VP8E_SET_CPUUSED`

‘`nr`’

  `VP8E_SET_NOISE_SENSITIVITY`

‘`mb_threshold`’

  `VP8E_SET_STATIC_THRESHOLD`

‘`slices`’

  `VP8E_SET_TOKEN_PARTITIONS`

‘`max-intra-rate`’

  `VP8E_SET_MAX_INTRA_BITRATE_PCT`

‘`force_key_frames`’

  `VPX_EFLAG_FORCE_KF`

‘`Alternate reference frame related`’
  ‘`vp8flags altref`’

    `VP8E_SET_ENABLEAUTOALTREF`

  ‘`arnr_max_frames`’

    `VP8E_SET_ARNR_MAXFRAMES`

  ‘`arnr_type`’

    `VP8E_SET_ARNR_TYPE`

  ‘`arnr_strength`’

    `VP8E_SET_ARNR_STRENGTH`

  ‘`rc_lookahead`’

    g_lag_in_frames

‘`vp8flags error_resilient`’

  g_error_resilient

For more information about libvpx see: http://www.webmproject.org/

## 9.3 libx264

H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 format supported through libx264.

Requires the presence of the libx264 headers and library during configuration. You need to explicitly configure the build with `--enable-libx264`.

### 9.3.1 Options

‘`preset preset_name`’

  Set the encoding preset.

‘`tune tune_name`’

  Tune the encoding params.

‘`fastfirstpass bool`’

  Use fast settings when encoding first pass, default value is 1.

‘`profile profile_name`’

  Set profile restrictions.

‘`level level`’

  Specify level (as defined by Annex A). Deprecated in favor of x264opts.

‘`passlogfile filename`’

  Specify filename for 2 pass stats. Deprecated in favor of x264opts (see stats libx264 option).

‘`wpredp wpred_type`’

  Specify Weighted prediction for P-frames. Deprecated in favor of x264opts (see weightp libx264 option).

‘`x264opts options`’

  Allow to set any x264 option, see `x264 --fullhelp` for a list.

  options 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 -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv

For more information about libx264 and the supported options see: http://www.videolan.org/developers/x264.html

# 10 See Also

ffmpeg, ffplay, ffprobe, ffserver, libavcodec

# 11 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.