479 lines
14 KiB
Plaintext
479 lines
14 KiB
Plaintext
@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 On
|
|
@item 2
|
|
@itemx off
|
|
Dolby Surround EX Off
|
|
@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 On
|
|
@item 2
|
|
@itemx off
|
|
Dolby Headphone Off
|
|
@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 libx264
|
|
|
|
H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 format supported through
|
|
libx264.
|
|
|
|
Requires the presence of the libx64 headers and library during
|
|
configuration. You need to explicitely configure the build with
|
|
@code{--enable-libx264}.
|
|
|
|
@subsection Options
|
|
|
|
@table @option
|
|
|
|
@item preset @var{preset_name}
|
|
Set the encoding preset.
|
|
|
|
@item tune @var{tune_name}
|
|
Tune the encoding params.
|
|
Deprecated in favor of @var{x264_opts}
|
|
|
|
@item fastfirstpass @var{bool}
|
|
Use fast settings when encoding first pass, default value is 1.
|
|
Deprecated in favor of @var{x264_opts}.
|
|
|
|
@item profile @var{profile_name}
|
|
Set profile restrictions.
|
|
Deprecated in favor of @var{x264_opts}.
|
|
|
|
@item level @var{level}
|
|
Specify level (as defined by Annex A).
|
|
Deprecated in favor of @var{x264_opts}.
|
|
|
|
@item passlogfile @var{filename}
|
|
Specify filename for 2 pass stats.
|
|
Deprecated in favor of @var{x264_opts}.
|
|
|
|
@item wpredp @var{wpred_type}
|
|
Specify Weighted prediction for P-frames.
|
|
Deprecated in favor of @var{x264_opts}.
|
|
|
|
@item x264opts @var{options}
|
|
Allow to set any x264 option, see x264 manual for a list.
|
|
|
|
@var{options} is a list of @var{key}=@var{value} couples separated by
|
|
":".
|
|
@end table
|
|
|
|
For example to specify libx264 encoding options with @file{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}
|
|
|
|
@c man end VIDEO ENCODERS
|