[PATCH 1/1] Extend and clarify documentation for -ac ffmpeg option.

[Stefano Sabatini]

Fix roundup issue #2061.
---
 doc/ffmpeg-doc.texi |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/doc/ffmpeg-doc.texi b/doc/ffmpeg-doc.texi
index a4330cf..4a61de1 100644
--- a/doc/ffmpeg-doc.texi
+++ b/doc/ffmpeg-doc.texi
@@ -510,7 +510,9 @@ 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 number of
+channels in the last audio stream of the input.
 @item -an
 Disable audio recording.
 @item -acodec @var{codec}
-- 
1.7.0.4


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