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+@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
+
+@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
+
+Requires the presence of the libx264 headers and library during
+configuration. You need to explicitly configure the build with
+@code{--enable-libx264}.
+
+x264 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).
+
+The FFmpeg wrapper provides a mapping for most of them using global options
+that match those of the encoders and provides private options for the unique
+encoder options. Additionally an expert override is provided to directly pass
+a list of key=value tuples as accepted by x264_param_parse.
+
+@subsection Option Mapping
+
+The following options are supported by the x264 wrapper, the x264-equivalent
+options follow the FFmpeg ones.
+
+@multitable @columnfractions .2 .2
+@item b                 @tab bitrate
+FFmpeg @code{b} option is expressed in bits/s, x264 @code{bitrate} in kilobits/s.
+@item bf                @tab bframes
+Maximum number of B-frames.
+@item g                 @tab keyint
+Maximum GOP size.
+@item qmin              @tab qpmin
+@item qmax              @tab qpmax
+@item qdiff             @tab qpstep
+@item qblur             @tab qblur
+@item qcomp             @tab qcomp
+@item refs              @tab ref
+@item sc_threshold      @tab scenecut
+@item trellis           @tab trellis
+@item nr                @tab nr
+Noise reduction.
+@item me_range          @tab merange
+@item me_method         @tab me
+@item subq              @tab subme
+@item b_strategy        @tab b-adapt
+@item keyint_min        @tab keyint-min
+@item coder             @tab cabac
+Set coder to @code{ac} to use CABAC.
+@item cmp               @tab chroma-me
+Set to @code{chroma} to use chroma motion estimation.
+@item threads           @tab threads
+@item thread_type       @tab sliced_threads
+Set to @code{slice} to use sliced threading instead of frame threading.
+@item flags -cgop       @tab open-gop
+Set @code{-cgop} to use recovery points to close GOPs.
+@item rc_init_occupancy @tab vbv-init
+Initial buffer occupancy.
+@end multitable
+
+@subsection Private Options
+@table @option
+@item -preset @var{string}
+Set the encoding preset (cf. x264 --fullhelp).
+@item -tune @var{string}
+Tune the encoding params (cf. x264 --fullhelp).
+@item -profile @var{string}
+Set profile restrictions (cf. x264 --fullhelp).
+@item -fastfirstpass @var{integer}
+Use fast settings when encoding first pass.
+@item -crf @var{float}
+Select the quality for constant quality mode.
+@item -crf_max @var{float}
+In CRF mode, prevents VBV from lowering quality beyond this point.
+@item -qp @var{integer}
+Constant quantization parameter rate control method.
+@item -aq-mode @var{integer}
+AQ method
+
+Possible values:
+@table @samp
+@item none
+
+@item variance
+Variance AQ (complexity mask).
+@item autovariance
+Auto-variance AQ (experimental).
+@end table
+@item -aq-strength @var{float}
+AQ strength, reduces blocking and blurring in flat and textured areas.
+@item -psy @var{integer}
+Use psychovisual optimizations.
+@item -psy-rd @var{string}
+Strength of psychovisual optimization, in <psy-rd>:<psy-trellis> format.
+@item -rc-lookahead @var{integer}
+Number of frames to look ahead for frametype and ratecontrol.
+@item -weightb @var{integer}
+Weighted prediction for B-frames.
+@item -weightp @var{integer}
+Weighted prediction analysis method.
+
+Possible values:
+@table @samp
+@item none
+
+@item simple
+
+@item smart
+
+@end table
+@item -ssim @var{integer}
+Calculate and print SSIM stats.
+@item -intra-refresh @var{integer}
+Use Periodic Intra Refresh instead of IDR frames.
+@item -b-bias @var{integer}
+Influences how often B-frames are used.
+@item -b-pyramid @var{integer}
+Keep some B-frames as references.
+
+Possible values:
+@table @samp
+@item none
+
+@item strict
+Strictly hierarchical pyramid.
+@item normal
+Non-strict (not Blu-ray compatible).
+@end table
+@item -mixed-refs @var{integer}
+One reference per partition, as opposed to one reference per macroblock.
+@item -8x8dct @var{integer}
+High profile 8x8 transform.
+@item -fast-pskip @var{integer}
+@item -aud @var{integer}
+Use access unit delimiters.
+@item -mbtree @var{integer}
+Use macroblock tree ratecontrol.
+@item -deblock @var{string}
+Loop filter parameters, in <alpha:beta> form.
+@item -cplxblur @var{float}
+Reduce fluctuations in QP (before curve compression).
+@item -partitions @var{string}
+A comma-separated list of partitions to consider, possible values: p8x8, p4x4, b8x8, i8x8, i4x4, none, all.
+@item -direct-pred @var{integer}
+Direct MV prediction mode
+
+Possible values:
+@table @samp
+@item none
+
+@item spatial
+
+@item temporal
+
+@item auto
+
+@end table
+@item -slice-max-size @var{integer}
+Limit the size of each slice in bytes.
+@item -stats @var{string}
+Filename for 2 pass stats.
+@item -nal-hrd @var{integer}
+Signal HRD information (requires vbv-bufsize; cbr not allowed in .mp4).
+
+Possible values:
+@table @samp
+@item none
+
+@item vbr
+
+@item cbr
+
+@end table
+
+@item x264opts @var{options}
+Allow to set any x264 option, see @code{x264 --fullhelp} for a list.
+
+@var{options} 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
+
+For more information about libx264 and the supported options see:
+@url{http://www.videolan.org/developers/x264.html}
+
+@item -x264-params @var{string}
+Override the x264 configuration using a :-separated list of key=value parameters.
+@example
+-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
+@end example
+@end table
+
+Encoding avpresets for common usages are provided so they can be used with the
+general presets system (e.g. passing the @code{-pre} option).
+
+@c man end VIDEO ENCODERS