4 Encoders are configured elements in FFmpeg which allow the encoding of
7 When you configure your FFmpeg build, all the supported native encoders
8 are enabled by default. Encoders requiring an external library must be enabled
9 manually via the corresponding @code{--enable-lib} option. You can list all
10 available encoders using the configure option @code{--list-encoders}.
12 You can disable all the encoders with the configure option
13 @code{--disable-encoders} and selectively enable / disable single encoders
14 with the options @code{--enable-encoder=@var{ENCODER}} /
15 @code{--disable-encoder=@var{ENCODER}}.
17 The option @code{-codecs} of the ff* tools will display the list of
22 @chapter Audio Encoders
23 @c man begin AUDIO ENCODERS
25 A description of some of the currently available audio encoders
28 @section ac3 and ac3_fixed
32 These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as
33 the undocumented RealAudio 3 (a.k.a. dnet).
35 The @var{ac3} encoder uses floating-point math, while the @var{ac3_fixed}
36 encoder only uses fixed-point integer math. This does not mean that one is
37 always faster, just that one or the other may be better suited to a
38 particular system. The floating-point encoder will generally produce better
39 quality audio for a given bitrate. The @var{ac3_fixed} encoder is not the
40 default codec for any of the output formats, so it must be specified explicitly
41 using the option @code{-acodec ac3_fixed} in order to use it.
43 @subsection AC-3 Metadata
45 The AC-3 metadata options are used to set parameters that describe the audio,
46 but in most cases do not affect the audio encoding itself. Some of the options
47 do directly affect or influence the decoding and playback of the resulting
48 bitstream, while others are just for informational purposes. A few of the
49 options will add bits to the output stream that could otherwise be used for
50 audio data, and will thus affect the quality of the output. Those will be
51 indicated accordingly with a note in the option list below.
53 These parameters are described in detail in several publicly-available
56 @item @uref{http://www.atsc.org/cms/standards/a_52-2010.pdf,A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard}
57 @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}
58 @item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf,Dolby Metadata Guide}
59 @item @uref{http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf,Dolby Digital Professional Encoding Guidelines}
62 @subsubsection Metadata Control Options
66 @item -per_frame_metadata @var{boolean}
67 Allow Per-Frame Metadata. Specifies if the encoder should check for changing
68 metadata for each frame.
71 The metadata values set at initialization will be used for every frame in the
74 Metadata values can be changed before encoding each frame.
79 @subsubsection Downmix Levels
83 @item -center_mixlev @var{level}
84 Center Mix Level. The amount of gain the decoder should apply to the center
85 channel when downmixing to stereo. This field will only be written to the
86 bitstream if a center channel is present. The value is specified as a scale
87 factor. There are 3 valid values:
92 Apply -4.5dB gain (default)
97 @item -surround_mixlev @var{level}
98 Surround Mix Level. The amount of gain the decoder should apply to the surround
99 channel(s) when downmixing to stereo. This field will only be written to the
100 bitstream if one or more surround channels are present. The value is specified
101 as a scale factor. There are 3 valid values:
106 Apply -6dB gain (default)
108 Silence Surround Channel(s)
113 @subsubsection Audio Production Information
114 Audio Production Information is optional information describing the mixing
115 environment. Either none or both of the fields are written to the bitstream.
119 @item -mixing_level @var{number}
120 Mixing Level. Specifies peak sound pressure level (SPL) in the production
121 environment when the mix was mastered. Valid values are 80 to 111, or -1 for
122 unknown or not indicated. The default value is -1, but that value cannot be
123 used if the Audio Production Information is written to the bitstream. Therefore,
124 if the @code{room_type} option is not the default value, the @code{mixing_level}
125 option must not be -1.
127 @item -room_type @var{type}
128 Room Type. Describes the equalization used during the final mixing session at
129 the studio or on the dubbing stage. A large room is a dubbing stage with the
130 industry standard X-curve equalization; a small room has flat equalization.
131 This field will not be written to the bitstream if both the @code{mixing_level}
132 option and the @code{room_type} option have the default values.
136 Not Indicated (default)
147 @subsubsection Other Metadata Options
151 @item -copyright @var{boolean}
152 Copyright Indicator. Specifies whether a copyright exists for this audio.
156 No Copyright Exists (default)
162 @item -dialnorm @var{value}
163 Dialogue Normalization. Indicates how far the average dialogue level of the
164 program is below digital 100% full scale (0 dBFS). This parameter determines a
165 level shift during audio reproduction that sets the average volume of the
166 dialogue to a preset level. The goal is to match volume level between program
167 sources. A value of -31dB will result in no volume level change, relative to
168 the source volume, during audio reproduction. Valid values are whole numbers in
169 the range -31 to -1, with -31 being the default.
171 @item -dsur_mode @var{mode}
172 Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround
173 (Pro Logic). This field will only be written to the bitstream if the audio
174 stream is stereo. Using this option does @b{NOT} mean the encoder will actually
175 apply Dolby Surround processing.
179 Not Indicated (default)
182 Not Dolby Surround Encoded
185 Dolby Surround Encoded
188 @item -original @var{boolean}
189 Original Bit Stream Indicator. Specifies whether this audio is from the
190 original source and not a copy.
197 Original Source (default)
202 @subsection Extended Bitstream Information
203 The extended bitstream options are part of the Alternate Bit Stream Syntax as
204 specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts.
205 If any one parameter in a group is specified, all values in that group will be
206 written to the bitstream. Default values are used for those that are written
207 but have not been specified. If the mixing levels are written, the decoder
208 will use these values instead of the ones specified in the @code{center_mixlev}
209 and @code{surround_mixlev} options if it supports the Alternate Bit Stream
212 @subsubsection Extended Bitstream Information - Part 1
216 @item -dmix_mode @var{mode}
217 Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt
218 (Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.
222 Not Indicated (default)
225 Lt/Rt Downmix Preferred
228 Lo/Ro Downmix Preferred
231 @item -ltrt_cmixlev @var{level}
232 Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the
233 center channel when downmixing to stereo in Lt/Rt mode.
246 Apply -4.5dB gain (default)
250 Silence Center Channel
253 @item -ltrt_surmixlev @var{level}
254 Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the
255 surround channel(s) when downmixing to stereo in Lt/Rt mode.
264 Apply -6.0dB gain (default)
266 Silence Surround Channel(s)
269 @item -loro_cmixlev @var{level}
270 Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the
271 center channel when downmixing to stereo in Lo/Ro mode.
284 Apply -4.5dB gain (default)
288 Silence Center Channel
291 @item -loro_surmixlev @var{level}
292 Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the
293 surround channel(s) when downmixing to stereo in Lo/Ro mode.
302 Apply -6.0dB gain (default)
304 Silence Surround Channel(s)
309 @subsubsection Extended Bitstream Information - Part 2
313 @item -dsurex_mode @var{mode}
314 Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX
315 (7.1 matrixed to 5.1). Using this option does @b{NOT} mean the encoder will actually
316 apply Dolby Surround EX processing.
320 Not Indicated (default)
326 Dolby Surround EX Off
329 @item -dheadphone_mode @var{mode}
330 Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone
331 encoding (multi-channel matrixed to 2.0 for use with headphones). Using this
332 option does @b{NOT} mean the encoder will actually apply Dolby Headphone
337 Not Indicated (default)
346 @item -ad_conv_type @var{type}
347 A/D Converter Type. Indicates whether the audio has passed through HDCD A/D
352 Standard A/D Converter (default)
360 @subsection Other AC-3 Encoding Options
364 @item -stereo_rematrixing @var{boolean}
365 Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This
366 is an optional AC-3 feature that increases quality by selectively encoding
367 the left/right channels as mid/side. This option is enabled by default, and it
368 is highly recommended that it be left as enabled except for testing purposes.
372 @subsection Floating-Point-Only AC-3 Encoding Options
374 These options are only valid for the floating-point encoder and do not exist
375 for the fixed-point encoder due to the corresponding features not being
376 implemented in fixed-point.
380 @item -channel_coupling @var{boolean}
381 Enables/Disables use of channel coupling, which is an optional AC-3 feature
382 that increases quality by combining high frequency information from multiple
383 channels into a single channel. The per-channel high frequency information is
384 sent with less accuracy in both the frequency and time domains. This allows
385 more bits to be used for lower frequencies while preserving enough information
386 to reconstruct the high frequencies. This option is enabled by default for the
387 floating-point encoder and should generally be left as enabled except for
388 testing purposes or to increase encoding speed.
392 Selected by Encoder (default)
395 Disable Channel Coupling
398 Enable Channel Coupling
401 @item -cpl_start_band @var{number}
402 Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a
403 value higher than the bandwidth is used, it will be reduced to 1 less than the
404 coupling end band. If @var{auto} is used, the start band will be determined by
405 the encoder based on the bit rate, sample rate, and channel layout. This option
406 has no effect if channel coupling is disabled.
410 Selected by Encoder (default)
415 @c man end AUDIO ENCODERS
417 @chapter Video Encoders
418 @c man begin VIDEO ENCODERS
420 A description of some of the currently available video encoders
425 VP8 format supported through libvpx.
427 Requires the presence of the libvpx headers and library during configuration.
428 You need to explicitly configure the build with @code{--enable-libvpx}.
432 Mapping from FFmpeg to libvpx options with conversion notes in parentheses.
459 @code{(bufsize * 1000 / vb)}
462 @code{(bufsize * 1000 / vb * 5 / 6)}
464 @item rc_init_occupancy, vb
466 @code{(rc_init_occupancy * 1000 / vb)}
468 @item rc_buffer_aggressivity
475 rc_2pass_vbr_bias_pct
478 rc_2pass_vbr_maxsection_pct
479 @code{(maxrate * 100 / vb)}
482 rc_2pass_vbr_minsection_pct
483 @code{(minrate * 100 / vb)}
485 @item minrate, maxrate, vb
487 @code{(minrate == maxrate == vb)}
490 @code{VPX_CQ}, @code{VP8E_SET_CQ_LEVEL}
495 @code{VPX_DL_BEST_QUALITY}
497 @code{VPX_DL_GOOD_QUALITY}
499 @code{VPX_DL_REALTIME}
503 @code{VP8E_SET_CPUUSED}
506 @code{VP8E_SET_NOISE_SENSITIVITY}
509 @code{VP8E_SET_STATIC_THRESHOLD}
512 @code{VP8E_SET_TOKEN_PARTITIONS}
514 @item Alternate reference frame related
516 @item vp8flags altref
517 @code{VP8E_SET_ENABLEAUTOALTREF}
518 @item @var{arnr_max_frames}
519 @code{VP8E_SET_ARNR_MAXFRAMES}
520 @item @var{arnr_type}
521 @code{VP8E_SET_ARNR_TYPE}
522 @item @var{arnr_strength}
523 @code{VP8E_SET_ARNR_STRENGTH}
524 @item @var{rc_lookahead}
528 @item vp8flags error_resilient
533 For more information about libvpx see:
534 @url{http://www.webmproject.org/}
538 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 format supported through
541 Requires the presence of the libx264 headers and library during
542 configuration. You need to explicitly configure the build with
543 @code{--enable-libx264}.
549 @item preset @var{preset_name}
550 Set the encoding preset.
552 @item tune @var{tune_name}
553 Tune the encoding params.
554 Deprecated in favor of @var{x264_opts}
556 @item fastfirstpass @var{bool}
557 Use fast settings when encoding first pass, default value is 1.
558 Deprecated in favor of @var{x264_opts}.
560 @item profile @var{profile_name}
561 Set profile restrictions.
562 Deprecated in favor of @var{x264_opts}.
564 @item level @var{level}
565 Specify level (as defined by Annex A).
566 Deprecated in favor of @var{x264_opts}.
568 @item passlogfile @var{filename}
569 Specify filename for 2 pass stats.
570 Deprecated in favor of @var{x264_opts}.
572 @item wpredp @var{wpred_type}
573 Specify Weighted prediction for P-frames.
574 Deprecated in favor of @var{x264_opts}.
576 @item x264opts @var{options}
577 Allow to set any x264 option, see x264 manual for a list.
579 @var{options} is a list of @var{key}=@var{value} couples separated by
583 For example to specify libx264 encoding options with @file{ffmpeg}:
585 ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
588 For more information about libx264 and the supported options see:
589 @url{http://www.videolan.org/developers/x264.html}
591 @c man end VIDEO ENCODERS