This introductory guide explains how to pull audio tracks out of video files using free software.
I learned how to "rip" audio from movie files because I digitized some VCR tapes into MPEG-4 (.mp4) video files and wanted to listen to some of them as audio-only tracks on my Android device. This overview page and its two companion pages explain information you may want to know if you need something similar.
FFmpeg can produce an exact copy of the audio track, however it runs from the command-line which may be off-putting to some. Audacity is graphical audio-editing software so it's much more user friendly. Audacity offers some flexible options when an exact copy isn't necessarily what you want. The workflow is simple:
- Open the video file (
File -> Open...).
- Optionally edit the track.
- Export the audio file (
File -> Export...).
Extract with FFmpeg vs. Convert with Audacity
- The quality level and file size you're willing to tolerate
- Whether or not the audio track is encoded in the audio format you prefer
- Whether or not you want to edit the audio stream
- How comfortable you are using command-line commands
Reason to Extract With FFmpeg
Extracting the audio with FFmpeg is accomplished by copying the file (or a portion of it) and stripping video and subtitle streams, resulting in an audio stream in the output copy.
The main reason to extract with FFmpeg is because you get an exact copy of the audio stream that was inside the video file. There's no resampling loss because there's no recompression.
You can extract a specified portion of the audio stream, but that's about the extent of editing you would do with FFmpeg.
Reasons to Convert With Audacity
Converting the audio track using Audacity brings the audio track into the program as a waveform you can edit. Doing it this way provides plentiful options for improvement. Some possibilities are:
- Convert the audio's encoding to another format.
- Compress to a smaller file size.
- Delete portions of the audio.
- Adjust the balance of a stereo track.
- Convert a stereo track to a monaural one.
- Adjust the track so it plays back at the correct volume.
Transcoding with Audacity
Transcoding the audio means converting it from one format (say, AAC or MP3) to another audio format (say, MP3, Ogg Vorbis, or FLAC). You're also transcoding if you keep the original audio format but increase compression to achieve a smaller file size.
MP3, AAC, and Ogg are "lossy" formats. When you transcode to a lossy format there will be some quality loss from recompression. Often, however, this quality loss is negligible or at least acceptable.
WAV and FLAC are lossless formats that can sound exactly like the original, but with a much larger file size.
Transcoding is easy. You simply open the video file and export an audio file.
Editing with Audacity
Audacity is a powerful audio editor and there are countless way you can change an audio track with it. Here are some common ways you can improve your ripped track before you export it.
Improve with Practice
There's no substitute for practice when you're learning to optimize audio files. If you have some good headphones and/or high-quality speakers, consider listening with them when you're determining what compression level to use.
If you're like me you'll want to keep your source files available a while and not delete them. Chances are you'll want to re-encode some of your early attempts, especially if file size is important to you.