Convert MP4 to M4A
Settings
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Settings appear after you choose a file.
Got an MP4 where only the sound matters, such as a recorded talk or a music clip? Save it as an M4A audio file. It carries no picture and plays on iPhones, iPads, and Macs.
MP4 or M4A?
Keep MP4 when
- You still need the picture. An M4A holds only the sound.
Pick M4A when
- You want only the sound of a video, as a small audio file.
- The sound goes to a player or app that takes M4A.
About MP4 and M4A
MP4
The most widely used video format. It plays on most phones, computers and platforms, and is the usual way video is shared.
M4A
AAC audio that plays in iTunes and Apple Music. Common for songs and voice recordings.
Questions
Does the sound change?
Not with the copy line, which keeps AAC sound as it is. The other lines and Audacity encode the sound again, and AAC to AAC loses a little.
What does the copy line do?
It puts the sound in an M4A without encoding it again, so nothing is lost. It works only when the sound in the MP4 is AAC; ffprobe clip.mp4 shows the codec. For any other sound, use the lines that encode it.
Which bitrate should I pick?
The commands aim for 192 kbps, a common middle ground between size and sound. Change -b:a 192k to 128k for a smaller file or 256k for more detail; for afconvert, change -b 192000 to 128000 or 256000.
What happens to the video?
It is left out. The M4A holds only the sound of the MP4, and the Terminal lines drop the picture with -vn.
Do the title and artist stay?
With the FFmpeg lines, yes: FFmpeg carries tags such as the title across to the M4A. afconvert leaves them out.