Extract audio from a video: M4A, MP3 or WAV?
To extract the audio from a video you rarely need to convert anything. The video already has a finished sound track inside it, and saving that track is a copy, as long as you pick the right format.
What is inside a video file
An MP4 or MOV file is a container. Inside it are separate tracks: one of video, one of sound, sometimes more. The sound track in a phone recording is almost always AAC, a compressed audio format, at somewhere between 128 and 256 kbps.
Because the tracks are separate, the sound can be lifted out without touching it. Put that AAC track in a container of its own and you have an M4A file. Nothing has been decoded or compressed again, so it is identical to what was in the video.
The three formats
| M4A | MP3 | WAV | |
|---|---|---|---|
| What it holds | AAC audio | MP3 audio | Uncompressed audio |
| From a phone video | A direct copy | Needs re-compressing | Needs decoding |
| Quality compared with the video | Identical | Slightly lower | Identical |
| Size per minute | 1 to 2 MB | 1 to 2 MB | About 10 MB in stereo |
| Plays on | Current phones and computers | Nearly everything, including very old players | Nearly everything |
Why converting to MP3 loses quality
AAC and MP3 are both lossy formats. Each one saves space by removing sound the ear is unlikely to notice, and each has its own idea of what that is. Converting AAC to MP3 means decoding sound that has already had detail removed, then removing a different set of detail. The result is a copy of a copy, and it is never better than what you started with.
MP3 is the older of the two and needs a higher bitrate to reach the same quality. Its one advantage is age: a car stereo or music player from fifteen years ago will play MP3 and may not play M4A. If you are not feeding a device like that, M4A is the better file.
When WAV makes sense
A WAV file stores sound uncompressed, so it is large. Stereo sound at 44,100 samples per second and 16 bits is 1,411 kbps, which comes to about 10.6 MB per minute. At 48,000 samples per second, which many phones use for video, it is about 11.5 MB per minute.
A WAV made from a phone video is not higher quality than the M4A. It is the same AAC sound, decoded. What you gain is convenience for editing: audio and video editors work with uncompressed sound internally, so a WAV opens instantly and can be cut and saved repeatedly without another round of compression. Use WAV when the sound is going into an editor. Use M4A for everything else.
Doing it
- Open the video to audio tool and choose your video.
- Pick M4A, or WAV if the sound is going into an editing app.
- To save only part of it, type the From and To times.
- Press Save audio.
Leave these alone
- Sample rate. Converting between 44,100 and 48,000 gains nothing you can hear.
- Channels. Turning mono into stereo doubles a WAV's size and adds no sound.
- Bitrate. Saving 128 kbps sound at 320 kbps makes a bigger file with the same quality. Detail that was removed cannot be put back.
Whose sound is it?
Taking the audio out of a video does not change who owns it. Your own recordings are yours to use: voice notes, interviews you conducted, your band's rehearsal, a talk you gave. Music playing in the background of your video still belongs to whoever made it, and a song saved from someone else's video is still their song. If you plan to publish the audio, make sure it is yours or that you have permission.
Converters for this
More guides
- Video sizes for Reels, Shorts and TikTokThe one export setting that works for all three apps, and the length limits that differ.
- Bitrate, resolution and file size: how they fit togetherThe sums behind video file size, and how to work back from a size limit.
- How to get a video under 16 MB for WhatsAppCompress it yourself or send it as a document, and what 16 MB allows at each length.