path: root/doc/encoders.texi

@chapter Encoders
@c man begin 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 @code{--enable-lib} option. You can list all
available encoders using the configure option @code{--list-encoders}.

You can disable all the encoders with the configure option
@code{--disable-encoders} and selectively enable / disable single encoders
with the options @code{--enable-encoder=@var{ENCODER}} /
@code{--disable-encoder=@var{ENCODER}}.

The option @code{-codecs} of the ff* tools will display the list of
enabled encoders.

@c man end ENCODERS

@chapter Audio Encoders
@c man begin AUDIO ENCODERS

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

@section 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 @var{ac3} encoder uses floating-point math, while the @var{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 @var{ac3_fixed} encoder is not the
default codec for any of the output formats, so it must be specified explicitly
using the option @code{-acodec ac3_fixed} in order to use it.

@subsection 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.
@itemize
@item @uref{http://www.atsc.org/cms/standards/a_52-2010.pdf,A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard}
@item @uref{http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf,A/54 - Guide to the Use of the ATSC Digital Television Standard}
@item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf,Dolby Metadata Guide}
@item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf,Dolby Digital Professional Encoding Guidelines}
@end itemize

@subsubsection Metadata Control Options

@table @option

@item -per_frame_metadata @var{boolean}
Allow Per-Frame Metadata. Specifies if the encoder should check for changing
metadata for each frame.
@table @option
@item 0
The metadata values set at initialization will be used for every frame in the
stream. (default)
@item 1
Metadata values can be changed before encoding each frame.
@end table

@end table

@subsubsection Downmix Levels

@table @option

@item -center_mixlev @var{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:
@table @option
@item 0.707
Apply -3dB gain
@item 0.595
Apply -4.5dB gain (default)
@item 0.500
Apply -6dB gain
@end table

@item -surround_mixlev @var{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:
@table @option
@item 0.707
Apply -3dB gain
@item 0.500
Apply -6dB gain (default)
@item 0.000
Silence Surround Channel(s)
@end table

@end table

@subsubsection 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.

@table @option

@item -mixing_level @var{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 @code{room_type} option is not the default value, the @code{mixing_level}
option must not be -1.

@item -room_type @var{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 @code{mixing_level}
option and the @code{room_type} option have the default values.
@table @option
@item 0
@itemx notindicated
Not Indicated (default)
@item 1
@itemx large
Large Room
@item 2
@itemx small
Small Room
@end table

@end table

@subsubsection Other Metadata Options

@table @option

@item -copyright @var{boolean}
Copyright Indicator. Specifies whether a copyright exists for this audio.
@table @option
@item 0
@itemx off
No Copyright Exists (default)
@item 1
@itemx on
Copyright Exists
@end table

@item -dialnorm @var{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.

@item -dsur_mode @var{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 @b{NOT} mean the encoder will actually
apply Dolby Surround processing.
@table @option
@item 0
@itemx notindicated
Not Indicated (default)
@item 1
@itemx off
Not Dolby Surround Encoded
@item 2
@itemx on
Dolby Surround Encoded
@end table

@item -original @var{boolean}
Original Bit Stream Indicator. Specifies whether this audio is from the
original source and not a copy.
@table @option
@item 0
@itemx off
Not Original Source
@item 1
@itemx on
Original Source (default)
@end table

@end table

@subsection 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 @code{center_mixlev}
and @code{surround_mixlev} options if it supports the Alternate Bit Stream
Syntax.

@subsubsection Extended Bitstream Information - Part 1

@table @option

@item -dmix_mode @var{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.
@table @option
@item 0
@itemx notindicated
Not Indicated (default)
@item 1
@itemx ltrt
Lt/Rt Downmix Preferred
@item 2
@itemx loro
Lo/Ro Downmix Preferred
@end table

@item -ltrt_cmixlev @var{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.
@table @option
@item 1.414
Apply +3dB gain
@item 1.189
Apply +1.5dB gain
@item 1.000
Apply 0dB gain
@item 0.841
Apply -1.5dB gain
@item 0.707
Apply -3.0dB gain
@item 0.595
Apply -4.5dB gain (default)
@item 0.500
Apply -6.0dB gain
@item 0.000
Silence Center Channel
@end table

@item -ltrt_surmixlev @var{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.
@table @option
@item 0.841
Apply -1.5dB gain
@item 0.707
Apply -3.0dB gain
@item 0.595
Apply -4.5dB gain
@item 0.500
Apply -6.0dB gain (default)
@item 0.000
Silence Surround Channel(s)
@end table

@item -loro_cmixlev @var{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.
@table @option
@item 1.414
Apply +3dB gain
@item 1.189
Apply +1.5dB gain
@item 1.000
Apply 0dB gain
@item 0.841
Apply -1.5dB gain
@item 0.707
Apply -3.0dB gain
@item 0.595
Apply -4.5dB gain (default)
@item 0.500
Apply -6.0dB gain
@item 0.000
Silence Center Channel
@end table

@item -loro_surmixlev @var{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.
@table @option
@item 0.841
Apply -1.5dB gain
@item 0.707
Apply -3.0dB gain
@item 0.595
Apply -4.5dB gain
@item 0.500
Apply -6.0dB gain (default)
@item 0.000
Silence Surround Channel(s)
@end table

@end table

@subsubsection Extended Bitstream Information - Part 2

@table @option

@item -dsurex_mode @var{mode}
Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX
(7.1 matrixed to 5.1). Using this option does @b{NOT} mean the encoder will actually
apply Dolby Surround EX processing.
@table @option
@item 0
@itemx notindicated
Not Indicated (default)
@item 1
@itemx on
Dolby Surround EX Off
@item 2
@itemx off
Dolby Surround EX On
@end table

@item -dheadphone_mode @var{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 @b{NOT} mean the encoder will actually apply Dolby Headphone
processing.
@table @option
@item 0
@itemx notindicated
Not Indicated (default)
@item 1
@itemx on
Dolby Headphone Off
@item 2
@itemx off
Dolby Headphone On
@end table

@item -ad_conv_type @var{type}
A/D Converter Type. Indicates whether the audio has passed through HDCD A/D
conversion.
@table @option
@item 0
@itemx standard
Standard A/D Converter (default)
@item 1
@itemx hdcd
HDCD A/D Converter
@end table

@end table

@subsection Other AC-3 Encoding Options

@table @option

@item -stereo_rematrixing @var{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.

@end table

@subsection 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.

@table @option

@item -channel_coupling @var{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.
@table @option
@item -1
@itemx auto
Selected by Encoder (default)
@item 0
@itemx off
Disable Channel Coupling
@item 1
@itemx on
Enable Channel Coupling
@end table

@item -cpl_start_band @var{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 @var{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.
@table @option
@item -1
@itemx auto
Selected by Encoder (default)
@end table

@end table

@section 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
@code{--enable-libmp3lame}.

@subsection Option Mapping

The following options are supported by the libmp3lame wrapper,
the LAME-equivalent options follow the FFmpeg ones.

@multitable @columnfractions .2 .2
@item FFmpeg            @tab LAME
@item b                 @tab b
Set bitrate expressed in bits/s, LAME @code{bitrate} is expressed in
kilobits/s.
@item q                 @tab V
Set quality setting for VBR.
@item compression_level @tab q
Set algorithm quality. Valid arguments are integers in the 0-9 range.
@item reservoir         @tab N.A.
Enable use of bit reservoir. LAME has this enabled by default.
@item joint_stereo      @tab -m j
Enable the encoder to use (on a frame by frame basis) either L/R
stereo or mid/side stereo.
@end multitable

@section 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
@code{--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 @option{strict} to @samp{unofficial} or
lower.

@subsection Options

@table @option

@item b
Set bitrate in bits per second. Only the following bitrates are supported,
otherwise libavcodec will round to the nearest valid bitrate.

@table @option
@item 4750
@item 5150
@item 5900
@item 6700
@item 7400
@item 7950
@item 10200
@item 12200
@end table

@item dtx
Allow discontinuous transmission (generate comfort noise) when set to 1. The
default value is 0 (disabled).

@end table

@section libtwolame

TwoLAME MP2 encoder wrapper.

Requires the presence of the libtwolame headers and library during
configuration. You need to explicitly configure the build with
@code{--enable-libtwolame}.

@subsection Options Mapping

The following options are supported by the libtwolame wrapper. The
TwoLAME-equivalent options follow the FFmpeg ones and are in
parentheses.

@table @option
@item b
(b) Set bitrate in bits/s. Note that FFmpeg @code{b} option is
expressed in bits/s, twolame @code{b} in kilobits/s. The default
value is 128k.

@item q
(V) Set quality for experimental VBR support. Maximum value range is
from -50 to 50, useful range is from -10 to 10.

@item mode
(mode) Set MPEG mode. Possible values:

@table @samp
@item auto
Choose mode automatically based on the input. This is the default.
@item stereo
Stereo
@item joint_stereo
Joint stereo
@item dual_channel
Dual channel
@item mono
Mono
@end table

@item 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.

@item energy_levels
(energy) Enable energy levels extensions when set to 1. The default
value is 0 (disabled).

@item error_protection
(protect) Enable CRC error protection when set to 1. The default value
is 0 (disabled).

@item copyright
(copyright) Set MPEG audio copyright flag when set to 1. The default
value is 0 (disabled).

@item original
(original) Set MPEG audio original flag when set to 1. The default
value is 0 (disabled).

@end table

@section libvo-aacenc

VisualOn AAC encoder.

Requires the presence of the libvo-aacenc headers and library during
configuration. You need to explicitly configure the build with
@code{--enable-libvo-aacenc --enable-version3}.

@subsection Options

The VisualOn AAC encoder only support encoding AAC-LC and up to 2
channels. It is also CBR-only. It is considered to be worse than the
native experimental FFmpeg AAC encoder.

@table @option

@item b
Bitrate.

@end table

@section 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
@code{--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 @option{strict} to
@samp{unofficial} or lower.

@subsection Options

@table @option

@item b
Set bitrate in bits/s. Only the following bitrates are supported, otherwise
libavcodec will round to the nearest valid bitrate.

@table @samp
@item 6600
@item 8850
@item 12650
@item 14250
@item 15850
@item 18250
@item 19850
@item 23050
@item 23850
@end table

@item dtx
Allow discontinuous transmission (generate comfort noise) when set to 1. The
default value is 0 (disabled).

@end table

@section 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
@code{--enable-libopus}.

@subsection Option Mapping

Most libopus options are modeled after the @command{opusenc} utility from
opus-tools. The following is an option mapping chart describing options
supported by the libopus wrapper, and their @command{opusenc}-equivalent
in parentheses.

@table @option

@item b (@emph{bitrate})
Set the bit rate in bits/s.  FFmpeg's @option{b} option is
expressed in bits/s, while @command{opusenc}'s @option{bitrate} in
kilobits/s.

@item vbr (@emph{vbr}, @emph{hard-cbr}, and @emph{cvbr})
Set VBR mode. The FFmpeg @option{vbr} option has the following
valid arguments, with the their @command{opusenc} equivalent options
in parentheses:

@table @samp
@item off (@emph{hard-cbr})
Use constant bit rate encoding.

@item on (@emph{vbr})
Use variable bit rate encoding (the default).

@item constrained (@emph{cvbr})
Use constrained variable bit rate encoding.
@end table

@item compression_level (@emph{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.

@item frame_duration (@emph{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 of FFmpeg is 10ms, but is 20ms in @command{opusenc}.

@item packet_loss (@emph{expect-loss})
Set expected packet loss percentage. The default is 0.

@item application (N.A.)
Set intended application type. Valid options are listed below:

@table @samp
@item voip
Favor improved speech intelligibility.
@item audio
Favor faithfulness to the input (the default).
@item lowdelay
Restrict to only the lowest delay modes.
@end table

@item 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).

@end table

@section libwavpack

A wrapper providing WavPack encoding through libwavpack.

Only lossless mode using 32-bit integer samples is supported currently.
The @option{compression_level} option can be used to control speed vs.
compression tradeoff, with the values mapped to libwavpack as follows:

@table @option

@item 0
Fast mode - corresponding to the wavpack @option{-f} option.

@item 1
Normal (default) settings.

@item 2
High quality - corresponding to the wavpack @option{-h} option.

@item 3
Very high quality - corresponding to the wavpack @option{-hh} option.

@item 4-8
Same as 3, but with extra processing enabled - corresponding to the wavpack
@option{-x} option. I.e. 4 is the same as @option{-x2} and 8 is the same as
@option{-x6}.

@end table

@c man end AUDIO ENCODERS

@chapter Video Encoders
@c man begin VIDEO ENCODERS

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

@section 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
@code{--enable-libtheora}.

@subsection Options

The following global options are mapped to internal libtheora options
which affect the quality and the bitrate of the encoded stream.

@table @option
@item b
Set the video bitrate, only works if the @code{qscale} flag in
@option{flags} is not enabled.

@item flags
Used to enable constant quality mode encoding through the
@option{qscale} flag, and to enable the @code{pass1} and @code{pass2}
modes.

@item g
Set the GOP size.

@item global_quality
Set the global quality in lambda units, only works if the
@code{qscale} flag in @option{flags} is enabled. The value is clipped
in the [0 - 10*@code{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
@command{ffmpeg}:
@example
ffmpeg -i INPUT -flags:v qscale -global_quality:v "10*QP2LAMBDA" -codec:v libtheora OUTPUT.ogg
@end example
@end table

@section 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 @code{--enable-libvpx}.

@subsection Options

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

@table @option

@item threads
g_threads

@item profile
g_profile

@item vb
rc_target_bitrate

@item g
kf_max_dist

@item keyint_min
kf_min_dist

@item qmin
rc_min_quantizer

@item qmax
rc_max_quantizer

@item bufsize, vb
rc_buf_sz
@code{(bufsize * 1000 / vb)}

rc_buf_optimal_sz
@code{(bufsize * 1000 / vb * 5 / 6)}

@item rc_init_occupancy, vb
rc_buf_initial_sz
@code{(rc_init_occupancy * 1000 / vb)}

@item rc_buffer_aggressivity
rc_undershoot_pct

@item skip_threshold
rc_dropframe_thresh

@item qcomp
rc_2pass_vbr_bias_pct

@item maxrate, vb
rc_2pass_vbr_maxsection_pct
@code{(maxrate * 100 / vb)}

@item minrate, vb
rc_2pass_vbr_minsection_pct
@code{(minrate * 100 / vb)}

@item minrate, maxrate, vb
@code{VPX_CBR}
@code{(minrate == maxrate == vb)}

@item crf
@code{VPX_CQ}, @code{VP8E_SET_CQ_LEVEL}

@item quality
@table @option
@item @var{best}
@code{VPX_DL_BEST_QUALITY}
@item @var{good}
@code{VPX_DL_GOOD_QUALITY}
@item @var{realtime}
@code{VPX_DL_REALTIME}
@end table

@item speed
@code{VP8E_SET_CPUUSED}

@item nr
@code{VP8E_SET_NOISE_SENSITIVITY}

@item mb_threshold
@code{VP8E_SET_STATIC_THRESHOLD}

@item slices
@code{VP8E_SET_TOKEN_PARTITIONS}

@item max-intra-rate
@code{VP8E_SET_MAX_INTRA_BITRATE_PCT}

@item force_key_frames
@code{VPX_EFLAG_FORCE_KF}

@item Alternate reference frame related
@table @option
@item vp8flags altref
@code{VP8E_SET_ENABLEAUTOALTREF}
@item @var{arnr_max_frames}
@code{VP8E_SET_ARNR_MAXFRAMES}
@item @var{arnr_type}
@code{VP8E_SET_ARNR_TYPE}
@item @var{arnr_strength}
@code{VP8E_SET_ARNR_STRENGTH}
@item @var{rc_lookahead}
g_lag_in_frames
@end table

@item vp8flags error_resilient
g_error_resilient

@end table

For more information about libvpx see:
@url{http://www.webmproject.org/}

@section libx264

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
@code{--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 @option{x264opts} and @option{x264-params}
private options allows to pass a list of key=value tuples as accepted
by the libx264 @code{x264_param_parse} function.

The x264 project website is at
@url{http://www.videolan.org/developers/x264.html}.

@subsection Options

The following options are supported by the libx264 wrapper. The
@command{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
@ref{codec-options,,the Codec Options chapter}.

To get a more accurate and extensive documentation of the libx264
options, invoke the command @command{x264 --full-help} or consult
the libx264 documentation.

@table @option
@item b (@emph{bitrate})
Set bitrate in bits/s. Note that FFmpeg's @option{b} option is
expressed in bits/s, while @command{x264}'s @option{bitrate} is in
kilobits/s.

@item bf (@emph{bframes})

@item g (@emph{keyint})

@item qmax (@emph{qpmax})

@item qmin (@emph{qpmin})

@item qdiff (@emph{qpstep})

@item qblur (@emph{qblur})

@item qcomp (@emph{qcomp})

@item refs (@emph{ref})

@item sc_threshold (@emph{scenecut})

@item trellis (@emph{trellis})

@item nr  (@emph{nr})

@item me_range (@emph{merange})

@item me_method (@emph{me})
Set motion estimation method. Possible values in the decreasing order
of speed:

@table @samp
@item dia (@emph{dia})
@item epzs (@emph{dia})
Diamond search with radius 1 (fastest). @samp{epzs} is an alias for
@samp{dia}.
@item hex (@emph{hex})
Hexagonal search with radius 2.
@item umh (@emph{umh})
Uneven multi-hexagon search.
@item esa (@emph{esa})
Exhaustive search.
@item tesa (@emph{tesa})
Hadamard exhaustive search (slowest).
@end table

@item subq (@emph{subme})

@item b_strategy (@emph{b-adapt})

@item keyint_min (@emph{min-keyint})

@item coder
Set entropy encoder. Possible values:

@table @samp
@item ac
Enable CABAC.

@item vlc
Enable CAVLC and disable CABAC. It generates the same effect as
@command{x264}'s @option{--no-cabac} option.
@end table

@item cmp
Set full pixel motion estimation comparation algorithm. Possible values:

@table @samp
@item chroma
Enable chroma in motion estimation.

@item sad
Ignore chroma in motion estimation. It generates the same effect as
@command{x264}'s @option{--no-chroma-me} option.
@end table

@item threads (@emph{threads})

@item thread_type
Set multithreading technique. Possible values:

@table @samp
@item slice
Slice-based multithreading. It generates the same effect as
@command{x264}'s @option{--sliced-threads} option.
@item frame
Frame-based multithreading.
@end table

@item flags
Set encoding flags. It can be used to disable closed GOP and enable
open GOP by setting it to @code{-cgop}. The result is similar to
the behavior of @command{x264}'s @option{--open-gop} option.

@item rc_init_occupancy (@emph{vbv-init})

@item preset (@emph{preset})
Set the encoding preset.

@item tune (@emph{tune})
Set tuning of the encoding params.

@item profile (@emph{profile})
Set profile restrictions.

@item fastfirstpass
Enable fast settings when encoding first pass, when set to 1. When set
to 0, it has the same effect of @command{x264}'s
@option{--slow-firstpass} option.

@item crf (@emph{crf})
Set the quality for constant quality mode.

@item crf_max (@emph{crf-max})
In CRF mode, prevents VBV from lowering quality beyond this point.

@item qp (@emph{qp})
Set constant quantization rate control method parameter.

@item aq-mode (@emph{aq-mode})
Set AQ method. Possible values:

@table @samp
@item none (@emph{0})
Disabled.

@item variance (@emph{1})
Variance AQ (complexity mask).

@item autovariance (@emph{2})
Auto-variance AQ (experimental).
@end table

@item aq-strength (@emph{aq-strength})
Set AQ strength, reduce blocking and blurring in flat and textured areas.

@item psy
Use psychovisual optimizations when set to 1. When set to 0, it has the
same effect as @command{x264}'s @option{--no-psy} option.

@item psy-rd  (@emph{psy-rd})
Set strength of psychovisual optimization, in
@var{psy-rd}:@var{psy-trellis} format.

@item rc-lookahead (@emph{rc-lookahead})
Set number of frames to look ahead for frametype and ratecontrol.

@item weightb
Enable weighted prediction for B-frames when set to 1. When set to 0,
it has the same effect as @command{x264}'s @option{--no-weightb} option.

@item weightp (@emph{weightp})
Set weighted prediction method for P-frames. Possible values:

@table @samp
@item none (@emph{0})
Disabled
@item simple (@emph{1})
Enable only weighted refs
@item smart (@emph{2})
Enable both weighted refs and duplicates
@end table

@item ssim (@emph{ssim})
Enable calculation and printing SSIM stats after the encoding.

@item intra-refresh (@emph{intra-refresh})
Enable the use of Periodic Intra Refresh instead of IDR frames when set
to 1.

@item b-bias (@emph{b-bias})
Set the influence on how often B-frames are used.

@item b-pyramid (@emph{b-pyramid})
Set method for keeping of some B-frames as references. Possible values:

@table @samp
@item none (@emph{none})
Disabled.
@item strict (@emph{strict})
Strictly hierarchical pyramid.
@item normal (@emph{normal})
Non-strict (not Blu-ray compatible).
@end table

@item 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 @command{x264}'s @option{--no-mixed-refs} option.

@item 8x8dct
Enable adaptive spatial transform (high profile 8x8 transform)
when set to 1. When set to 0, it has the same effect as
@command{x264}'s @option{--no-8x8dct} option.

@item fast-pskip
Enable early SKIP detection on P-frames when set to 1. When set
to 0, it has the same effect as @command{x264}'s
@option{--no-fast-pskip} option.

@item aud (@emph{aud})
Enable use of access unit delimiters when set to 1.

@item mbtree
Enable use macroblock tree ratecontrol when set to 1. When set
to 0, it has the same effect as @command{x264}'s
@option{--no-mbtree} option.

@item deblock (@emph{deblock})
Set loop filter parameters, in @var{alpha}:@var{beta} form.

@item cplxblur (@emph{cplxblur})
Set fluctuations reduction in QP (before curve compression).

@item partitions (@emph{partitions})
Set partitions to consider as a comma-separated list of. Possible
values in the list:

@table @samp
@item p8x8
8x8 P-frame partition.
@item p4x4
4x4 P-frame partition.
@item b8x8
4x4 B-frame partition.
@item i8x8
8x8 I-frame partition.
@item i4x4
4x4 I-frame partition.
(Enabling @samp{p4x4} requires @samp{p8x8} to be enabled. Enabling
@samp{i8x8} requires adaptive spatial transform (@option{8x8dct}
option) to be enabled.)
@item none (@emph{none})
Do not consider any partitions.
@item all (@emph{all})
Consider every partition.
@end table

@item direct-pred (@emph{direct})
Set direct MV prediction mode. Possible values:

@table @samp
@item none (@emph{none})
Disable MV prediction.
@item spatial (@emph{spatial})
Enable spatial predicting.
@item temporal (@emph{temporal})
Enable temporal predicting.
@item auto (@emph{auto})
Automatically decided.
@end table

@item slice-max-size (@emph{slice-max-size})
Set the limit of the size of each slice in bytes. If not specified
but RTP payload size (@option{ps}) is specified, that is used.

@item stats (@emph{stats})
Set the file name for multi-pass stats.

@item nal-hrd (@emph{nal-hrd})
Set signal HRD information (requires @option{vbv-bufsize} to be set).
Possible values:

@table @samp
@item none (@emph{none})
Disable HRD information signaling.
@item vbr (@emph{vbr})
Variable bit rate.
@item cbr (@emph{cbr})
Constant bit rate (not allowed in MP4 container).
@end table

@item x264opts (N.A.)
Set any x264 option, see @command{x264 --fullhelp} for a list.

Argument is a list of @var{key}=@var{value} couples separated by
":". In @var{filter} and @var{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 @command{ffmpeg}:
@example
ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
@end example

@item x264-params (N.A.)
Override the x264 configuration using a :-separated list of key=value
parameters.

This option is functionally the same as the @option{x264opts}, but is
duplicated for compability with the Libav fork.

For example to specify libx264 encoding options with @command{ffmpeg}:
@example
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
@end example
@end table

Encoding ffpresets for common usages are provided so they can be used with the
general presets system (e.g. passing the @option{pre} option).

@section 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
@code{--enable-libxvid --enable-gpl}.

The native @code{mpeg4} encoder supports the MPEG-4 Part 2 format, so
users can encode to this format without this library.

@subsection 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 @ref{codec-options,,the Codec
Options chapter} for their documentation. The other shared options
which are not listed have no effect for the libxvid encoder.

@table @option
@item b

@item g

@item qmin

@item qmax

@item mpeg_quant

@item threads

@item bf

@item b_qfactor

@item b_qoffset

@item flags
Set specific encoding flags. Possible values:

@table @samp

@item mv4
Use four motion vector by macroblock.

@item aic
Enable high quality AC prediction.

@item gray
Only encode grayscale.

@item gmc
Enable the use of global motion compensation (GMC).

@item qpel
Enable quarter-pixel motion compensation.

@item cgop
Enable closed GOP.

@item global_header
Place global headers in extradata instead of every keyframe.

@end table

@item trellis

@item me_method
Set motion estimation method. Possible values in decreasing order of
speed and increasing order of quality:

@table @samp
@item zero
Use no motion estimation (default).

@item phods
@item x1
@item log
Enable advanced diamond zonal search for 16x16 blocks and half-pixel
refinement for 16x16 blocks. @samp{x1} and @samp{log} are aliases for
@samp{phods}.

@item 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.

@item full
Enable all of the things described above, plus extended 16x16 and 8x8
blocks search.
@end table

@item mbd
Set macroblock decision algorithm. Possible values in the increasing
order of quality:

@table @samp
@item simple
Use macroblock comparing function algorithm (default).

@item bits
Enable rate distortion-based half pixel and quarter pixel refinement for
16x16 blocks.

@item 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.
@end table

@end table

@section png

PNG image encoder.

@subsection Private options

@table @option
@item dpi @var{integer}
Set physical density of pixels, in dots per inch, unset by default
@item dpm @var{integer}
Set physical density of pixels, in dots per meter, unset by default
@end table

@section ProRes

Apple ProRes encoder.

FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder.
The used encoder can be choosen with the @code{-vcodec} option.

@subsection Private Options for prores-ks

@table @option
@item profile @var{integer}
Select the ProRes profile to encode
@table @samp
@item proxy
@item lt
@item standard
@item hq
@item 4444
@end table

@item quant_mat @var{integer}
Select quantization matrix.
@table @samp
@item auto
@item default
@item proxy
@item lt
@item standard
@item hq
@end table
If set to @var{auto}, the matrix matching the profile will be picked.
If not set, the matrix providing the highest quality, @var{default}, will be
picked.

@item bits_per_mb @var{integer}
How many bits to allot for coding one macroblock. Different profiles use
between 200 and 2400 bits per macroblock, the maximum is 8000.

@item mbs_per_slice @var{integer}
Number of macroblocks in each slice (1-8); the default value (8)
should be good in almost all situations.

@item vendor @var{string}
Override the 4-byte vendor ID.
A custom vendor ID like @var{apl0} would claim the stream was produced by
the Apple encoder.

@item alpha_bits @var{integer}
Specify number of bits for alpha component.
Possible values are @var{0}, @var{8} and @var{16}.
Use @var{0} to disable alpha plane coding.

@end table

@subsection Speed considerations

In the default mode of operation the encoder has to honor frame constraints
(i.e. not produc 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 @option{bits_per_mb} limit will improve the speed.

For the fastest encoding speed set the @option{qscale} parameter (4 is the
recommended value) and do not set a size constraint.

@c man end VIDEO ENCODERS