2017-07-30, 22:28
I create M4A files by extracting audio stream from MP4 using ffmpeg and then muxing into M4A again with ffmpeg. I don't think there is any particular requirement on the stream codec -- mine generally are AAC. The M4A container uses exactly the same metadata tag structure (Apple proprietary but reverse-engineered) so whatever tags you have in MP4 work the same in M4A.
scott s.
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scott s.
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