Convert audio to M4A
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Worked example
M4A is the natural target when the source audio came out of an MP4, because it is the same codec in a different wrapper.
| Extension | .m4a |
|---|---|
| MIME type | audio/mp4 |
| Playback | Plays everywhere |
| From MP4 without re-encoding | No |
| Audio codec | aac |
The equivalent command
ffmpeg -i holiday-clip.mp4 -vn -c:a aac -b:a 192k -movflags +faststart -threads 1 -y out-holiday-clip.m4aThis is exactly what runs in the browser. Copy it to run the same job locally on a file too large for a tab.
Why it matters
The audio inside almost every MP4 is AAC, and M4A is AAC in its own container. Extracting to M4A can therefore copy the stream out untouched with no second round of lossy compression — whereas extracting the same audio to MP3 re-encodes it and loses a little more. When the goal is to get the soundtrack out of a video, this is usually the right format.