The following script extracts all audio streams from files in current directory
ls |parallel "ffmpeg -i {} 2>&1 |\
sed -n 's/.*Stream \#\(.\+\)\:\(.\+\)\: Audio\: \([a-zA-Z0-9]\+\).*$/-map \1:\2 -c copy \"{.}.\1\2.\3\"/p' |\
xargs -n5 ffmpeg -i {} "
