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