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doc/encoders: document the libfdk-aac wrapper
Partially based on the https://trac.ffmpeg.org/wiki/AACEncodingGuide guide.
This commit is contained in:
Stefano Sabatini
parent
4fdec65eb3
commit
d339e03fc3
@ -38,8 +38,8 @@ As this encoder is experimental, unexpected behavior may exist from time to
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time. For a more stable AAC encoder, see @ref{libvo-aacenc}. However, be warned
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that it has a worse quality reported by some users.
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@c Comment this out until somebody writes the respective documentation.
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@c See also @ref{libfaac}, @ref{libaacplus}, and @ref{libfdk-aac-enc}.
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@c todo @ref{libfaac}, @ref{libaacplus}
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See also @ref{libfdk-aac-enc,,the libfdk_aac section}.
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@subsection Options
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@ -494,6 +494,171 @@ Selected by Encoder (default)
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@end table
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@anchor{libfdk-aac-enc}
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@section libfdk_aac
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libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.
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The libfdk-aac library is based on the Fraunhofer FDK AAC code from
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the Android project.
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Requires the presence of the libfdk-aac headers and library during
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configuration. You need to explicitly configure the build with
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@code{--enable-libfdk-aac}. The library is also incompatible with GPL,
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so if you allow the use of GPL, you should configure with
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@code{--enable-gpl --enable-nonfree --enable-libfdk-aac}.
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This encoder is considered to be of higher quality with respect to
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both @ref{aacenc,,the native experimental FFmpeg AAC encoder} and
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libfaac.
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For more information see the fdk-aac project at
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@url{http://sourceforge.net/p/opencore-amr/fdk-aac/}.
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@subsection Options
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The following options are mapped on the shared FFmpeg codec options.
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@table @option
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@item b
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Set bit rate in bits/s. If the bitrate is not explicitly specified, it
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is automatically set to a suitable value depending on the selected
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profile.
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In case VBR mode is enabled the option is ignored.
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@item ar
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Set audio sampling rate (in Hz).
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@item channels
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Set the number of audio channels.
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@item flags +qscale
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Enable fixed quality, VBR (Variable Bit Rate) mode.
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Note that VBR is implicitely enabled when the @option{vbr} value is
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positive.
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@item cutoff
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Set cutoff frequency. If not specified (or explicitly set to 0) it
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will use a value automatically computed by the library. Default value
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is 0.
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@item profile
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Set audio profile.
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The following profiles are recognized:
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@table @samp
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@item aac_low
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Low Complexity AAC (LC)
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@item aac_he
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High Efficiency AAC (HE-AAC)
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@item aac_he_v2
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High Efficiency AAC version 2 (HE-AACv2)
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@item aac_ld
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Low Delay AAC (LD)
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@item aac_eld
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Enhanced Low Delay AAC (ELD)
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@end table
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If not specified it is set to @samp{aac_low}.
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@end table
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The following are private options of the libfdk_aac encoder.
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@table @option
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@item afterburner
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Enable afterburner feature if set to 1, disabled if set to 0. This
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improves the quality but also the required processing power.
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Default value is 1.
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@item eld_sbr
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Enable SBR (Spectral Band Replication) for ELD if set to 1, disabled
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if set to 0.
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Default value is 0.
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@item signaling
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Set SBR/PS signaling style.
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It can assume one of the following values:
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@table @samp
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@item default
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choose signaling implicitly (explicit hierarchical by default,
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implicit if global header is disabled)
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@item implicit
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implicit backwards compatible signaling
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@item explicit_sbr
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explicit SBR, implicit PS signaling
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@item explicit_hierarchical
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explicit hierarchical signaling
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@end table
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Default value is @samp{default}.
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@item latm
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Output LATM/LOAS encapsulated data if set to 1, disabled if set to 0.
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Default value is 0.
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@item header_period
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Set StreamMuxConfig and PCE repetition period (in frames) for sending
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in-band configuration buffers within LATM/LOAS transport layer.
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Must be a 16-bits non-negative integer.
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Default value is 0.
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@item vbr
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Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty
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good) and 5 is highest quality. A value of 0 will disable VBR mode,
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and CBR (Constant Bit Rate) mode is enabled.
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Currently only the @samp{aac_low} profile supports VBR mode.
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VBR modes 1-5 correspond to roughly the following average bit rate:
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@table @samp
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@item 1
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32 kbps/channel
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@item 2
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40 kbps/channel
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@item 3
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48-56 kbps/channel
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@item 4
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64 kbps/channel
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@item 5
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about 80-96 kbps/channel
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@end table
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Default value is 0.
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@end table
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@section Examples
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@itemize
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@item
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Use @command{ffmpeg} to convert an audio file to VBR AAC in an M4A (MP4)
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container:
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@example
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ffmpeg -i input.wav -codec:a libfdk_aac -vbr 3 output.m4a
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@end example
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@item
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Use @command{ffmpeg} to convert an audio file to CBR 64k kbps AAC, using the
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High-Efficiency AAC profile:
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@example
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ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
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@end example
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@end itemize
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@anchor{libmp3lame}
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@section libmp3lame
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