Question 1

Is the audio copied straight from the MP4 or re-encoded?

Accepted Answer

It's re-encoded as AAC at the bitrate you choose. If the MP4's audio is already AAC, pick the same or a higher bitrate and the difference won't be audible.

Question 2

Isn't an M4A just an MP4 without the video?

Accepted Answer

Pretty much. Both use the MPEG-4 container, and the .m4a extension tells players the file holds audio only. That's why the Music app, iPhones and podcast apps treat it as a song instead of a video.

Question 3

Should I pick M4A or MP3?

Accepted Answer

M4A if the file is going to Apple devices or apps, or if you want a smaller file at the same quality. MP3 if it has to play on older players, car stereos or software that only accepts MP3.

Question 4

Can I just rename the .mp4 to .m4a?

Accepted Answer

Sometimes it plays, but the file still contains the whole video track, so it stays just as large, and some apps reject it. Converting writes a real audio-only file.

Question 5

How big will the M4A be?

Accepted Answer

About 1.4 MB per minute at 192 kbps, or about 0.96 MB per minute at 128 kbps. A 10-minute video gives a 10 to 15 MB audio file.

Question 6

Does the video leave my device?

Accepted Answer

No. The MP4 is read and the audio is encoded in your browser. Nothing is uploaded.

MP4 to M4A Converter

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