[FFmpeg-devel] [PATCH] Clearer wording of audio channel maping limitations

Tim Nicholson nichot20 at yahoo.com
Wed Dec 21 16:32:54 CET 2011

> Since I and others have been caught out by the channel mapping limitations and the documentation
> is not clear about those limitations with regard to  stream mapping from a single file. I offer the attached patch
> in the hope it clarifies things.

Oops, sorry about the mime type. Trying to avoid my work generic disclaimer and use a web mail system, and now I have no control over the attachment type...:(

I hope putting it inline works better.


From 2ce04ac3c8fccda673cc08eed94cb57990161f69 Mon Sep 17 00:00:00 2001
From: Tim Nicholson <tim.nicholson at bbc.co.uk>
Date: Wed, 21 Dec 2011 15:11:04 +0000
Subject: [PATCH] Clearer explanation of audio channel mapping restrictions

 doc/ffmpeg.texi |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index 553d759..ace4b29 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -825,9 +825,10 @@ The following example split the channels of a stereo input into streams:
 ffmpeg -i stereo.wav -map 0:0 -map 0:0 -map_channel 0.0.0:0.0 -map_channel 0.0.1:0.1 -y out.ogg
 @end example
-Note that "-map_channel" is currently limited to the scope of one input for
-each output; you can't for example use it to pick multiple input audio files
-and mix them into one single output.
+Note that "-map_channel" is currently limited to the scope of one input stream for
+each output stream; you can't, for example, use it to pick multiple input audio channels
+contained in different streams (from the same or different files) and mix them into one single
+output stream in order to turn two separate mono streams into a single stereo stream.
 @item -map_metadata[:@var{metadata_type}][:@var{index}] @var{infile}[:@var{metadata_type}][:@var{index}] (@emph{output,per-metadata})
 Set metadata information of the next output file from @var{infile}. Note that

More information about the ffmpeg-devel mailing list