[SCM] libav/experimental: Extend and clarify documentation for -ac ffmpeg option.

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit e1f4dd6d41f2ef8cd6db444a3b70946d7a1e29a9
Author: Stefano Sabatini <stefano.sabatini-lala at poste.it>
Date:   Wed Aug 11 14:49:41 2010 +0000

    Extend and clarify documentation for -ac ffmpeg option.
    
    Fix roundup issue #2061.
    
    Originally committed as revision 24772 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/doc/ffmpeg-doc.texi b/doc/ffmpeg-doc.texi
index ccf06b5..71bed9b 100644
--- a/doc/ffmpeg-doc.texi
+++ b/doc/ffmpeg-doc.texi
@@ -510,7 +510,10 @@ Set the audio bitrate in bit/s (default = 64k).
 @item -aq @var{q}
 Set the audio quality (codec-specific, VBR).
 @item -ac @var{channels}
-Set the number of audio channels (default = 1).
+Set the number of audio channels. For input streams it is set by
+default to 1, for output streams it is set by default to the same
+number of audio channels in input. If the input file has audio streams
+with different channel count, the behaviour is undefined.
 @item -an
 Disable audio recording.
 @item -acodec @var{codec}

-- 
Libav/FFmpeg packaging