[FFmpeg-user] Audio Stream Mapping issue

Tim Nicholson tim.nicholson at bbc.co.uk
Tue Nov 15 16:34:36 CET 2011

On 15/11/11 10:14, Carl Eugen Hoyos wrote:
> HI!
> Tim Nicholson<tim.nicholson<at>  bbc.co.uk>  writes:
>> According to http://ffmpeg.org/ffmpeg.html#Main-options
>> "ffmpeg -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
>> encodes all video streams with libx264 and copies all audio streams"
>> However I have an mxf file with 1 video and 4 audio streams I am trying
>> to rewrap as a mov where I seem unable to get more than a single audio
>> stream copied.
>> I have tried the following command lines:-
>> ffmpeg -i in.mxf -vcodec copy -acodec copy tim2.mov
>> ffmpeg -i in.mxf -vcodec copy -acodec copy -ac 4 tim2.mov
>> ffmpeg -i in.mxf -vcodec copy -c:a copy tim2.mov
>> ffmpeg -i in.mxf -vcodec copy -c:a:0 copy -c:a:1 copy -c:a:2 copy -c:a:3
>> copy  tim2.mov
>> fmpeg -i in.mxf -vcodec copy -ac 4 -c:a:0 copy -c:a:1 copy -c:a:2 copy
>> -c:a:3 copy  tim2.mov
> Afaict, all command lines you list omit "-map 0" meaning you ask ffmpeg NOT to
> map all streams into the output file (but exactly one video and one audio
> stream).
> Or do I miss something?

You miss the documentation that states that the default mapping is:-
"For video, this means the highest resolution, for audio the highest 
channel count" which says to me that one video of the highest resolution 
is mapped and all audio (The highest count).

If this is not what it means then the documentation is ambiguous. since 
for subtitles it specifically says "the first subtitle stream", and in 
my tests as above it is the first audio as well.


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