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command line audio stream selection?
I have an mxf file from a canon camcorder. It contains 1 video stream and 2 audio streams corresponding to left and right channel. My video editor (an old version of premiere) cannot read this file, so I have to demux it into video and audio files. I have no problem with the video and first audio stream.
To extract the 2nd audio channel, I can do
ffmpeg -i input.mxf -map 0:2 -acodec copy out2.wav
I also read that you can put stream specifier on the option, so i tried
ffmpeg -i input.mxf -codec:a:2 copy out2.wav
This doesn’t work. I get the first audio stream. What am I misunderstanding?
I’m trying to understand ffmpeg better because I have more advance operations in mind (e.g. re-package the mxf file into a file that premiere cs4 can read). -
1 Reply
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Hi Peter,
MXF files are great because of the wealth of information that they can pack in to the metadata to describe the essence it carries however as a result there are a myriad of different ways of carrying audio in MXF files which will impact what is the appropriate mapping for you to output to extract the files you need.
I would recommend that you post the information you get from the source file by just running the -i command and pasting the results here for us to take a full look at.
The -map option is usually enough to allocate the mapping of your output into files, streams and channels (in that order).
e.g. 0:1:0:0:1:0
:::::tip – A regular gotcha for anybody dealing with numbers in this output is to remember that the first item whether it is a file, stream or channel will start from ‘0’
-Chris Oram
https://antiversal.com
Technology, Design and Development for Moving Image Creators
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