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doc: add decoders.texi 

Only documents ac3 decoder options at this point.
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John Stebbins 2014-01-26 14:49:10 +00:00 committed by Tim Walker
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doc/avconv.texi
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@c man end EXAMPLES
@include eval.texi
@include decoders.texi
@include encoders.texi
@include demuxers.texi
@include muxers.texi

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doc/avplay.texi
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@ -155,6 +155,7 @@ Seek to percentage in file corresponding to fraction of width.
@c man end
@include eval.texi
@include decoders.texi
@include demuxers.texi
@include muxers.texi
@include indevs.texi

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@chapter Decoders
@c man begin DECODERS
Decoders are configured elements in Libav which allow the decoding of
multimedia streams.
When you configure your Libav build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding @code{--enable-lib} option. You can list all
available decoders using the configure option @code{--list-decoders}.
You can disable all the decoders with the configure option
@code{--disable-decoders} and selectively enable / disable single decoders
with the options @code{--enable-decoder=@var{DECODER}} /
@code{--disable-decoder=@var{DECODER}}.
The option @code{-decoders} of the av* tools will display the list of
enabled decoders.
@c man end DECODERS
@chapter Audio Decoders
@c man begin AUDIO DECODERS
A description of some of the currently available audio decoders
follows.
@section ac3
AC-3 audio decoder.
This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
@subsubsection AC-3 Decoder Options
@table @option
@item -drc_scale @var{value}
Dynamic Range Scale Factor. The factor to apply to dynamic range values
from the AC-3 stream. This factor is applied exponentially.
There are 3 notable scale factor ranges:
@table @option
@item drc_scale == 0
DRC disabled. Produces full range audio.
@item 0 < drc_scale <= 1
DRC enabled. Applies a fraction of the stream DRC value.
Audio reproduction is between full range and full compression.
@item drc_scale > 1
DRC enabled. Applies drc_scale asymmetrically.
Loud sounds are fully compressed. Soft sounds are enhanced.
@end table
@end table
@c man end AUDIO DECODERS