The data is usually there, just inaccessible.
Install faad2 via Homebrew ( brew install faad2 ) and try converting the raw file, adjusting the sample rate if necessary. 01 90 Proof.m4a
Once you have a working file, use ffmpeg to re-encode it into a stable format: ffmpeg -i newfile.m4a -c:a aac output.m4a . Prevention: How to Save Files Forever The data is usually there, just inaccessible