[FFmpeg-cvslog] doc: add decoders.texi

[John Stebbins]

ffmpeg | branch: master | John Stebbins <stebbins at jetheaddev.com> | Sun Jan 26 14:49:10 2014 +0000| [a17ab0e46a9fec7c31cc1be363828184c6ecebf7] | committer: Tim Walker

doc: add decoders.texi

Only documents ac3 decoder options at this point.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a17ab0e46a9fec7c31cc1be363828184c6ecebf7
---

 doc/avconv.texi   |    1 +
 doc/avplay.texi   |    1 +
 doc/decoders.texi |   56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/doc/avconv.texi b/doc/avconv.texi
index 972d13f..7ef415f 100644
--- a/doc/avconv.texi
+++ b/doc/avconv.texi
@@ -1120,6 +1120,7 @@ avconv -i src.ext -lmax 21*QP2LAMBDA dst.ext
 @c man end EXAMPLES
 
 @include eval.texi
+ at include decoders.texi
 @include encoders.texi
 @include demuxers.texi
 @include muxers.texi
diff --git a/doc/avplay.texi b/doc/avplay.texi
index 50142ab..4d9af5f 100644
--- a/doc/avplay.texi
+++ b/doc/avplay.texi
@@ -155,6 +155,7 @@ Seek to percentage in file corresponding to fraction of width.
 @c man end
 
 @include eval.texi
+ at include decoders.texi
 @include demuxers.texi
 @include muxers.texi
 @include indevs.texi
diff --git a/doc/decoders.texi b/doc/decoders.texi
new file mode 100644
index 0000000..c3573a6
--- /dev/null
+++ b/doc/decoders.texi
@@ -0,0 +1,56 @@
+ at chapter Decoders
+ at 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
+ at code{--disable-decoders} and selectively enable / disable single decoders
+with the options @code{--enable-decoder=@var{DECODER}} /
+ at code{--disable-decoder=@var{DECODER}}.
+
+The option @code{-decoders} of the av* tools will display the list of
+enabled decoders.
+
+ at c man end DECODERS
+
+ at chapter Audio Decoders
+ at c man begin AUDIO DECODERS
+
+A description of some of the currently available audio decoders
+follows.
+
+ at 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).
+
+ at subsubsection AC-3 Decoder Options
+
+ at table @option
+
+ at 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:
+ at table @option
+ at item drc_scale == 0
+DRC disabled. Produces full range audio.
+ at item 0 < drc_scale <= 1
+DRC enabled.  Applies a fraction of the stream DRC value.
+Audio reproduction is between full range and full compression.
+ at item drc_scale > 1
+DRC enabled. Applies drc_scale asymmetrically.
+Loud sounds are fully compressed.  Soft sounds are enhanced.
+ at end table
+
+ at end table
+
+ at c man end AUDIO DECODERS