I had roughly fifty video files across four different folders that I wanted to extract the audio from. You can use ffmpeg to pull the audio out of a single video file, but I didn’t want to type in a slightly different ffmpeg command fifty times.
Write a Node.js script that loops over all the files in a directory and runs the correct ffmpeg command to attempt to extract the audio from each file. And, of course, spend more time writing the script than it would have taken to just manually run the command dozens of times.
You can grab the script from GitHub. It was a fun learning experience. When you run the ffmpeg command, you need to make sure that the file extension for the audio file matches the format that’s actually in the movie file. This is kind of a drag. It would be nice if ffmpeg was smart enough to extract whatever audio was in the video, in whatever format it was in. It’s entirely possible it is that smart, I’m just not smart enough to know how to make it do what I want. At any rate, my script allows you to pass in an argument to set what format the audio is in.
Oh, all you care about is the ffmpeg command that’ll pull the existing audio out of a video file? No problem:
ffmpeg -i input-video.avi -vn -acodec copy output-audio.mp3