bash - Execute "ffmpeg" command in a loop

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Answer 1

Use the -nostdin flag to disable interactive mode,

ffmpeg -nostdin -i "$f" -ab 320k -ac 2 "${f%.*}.mp3"

or have ffmpeg read its input from the controlling terminal instead of stdin.

ffmpeg -i "$f" -ab 320k -ac 2 "${f%.*}.mp3" </dev/tty

See the -stdin/-nostdin flags in the ffmpeg documentation