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How to convert an MP4 to WAV on a Mac

· 6 min read

Converting an MP4 to WAV on a Mac means pulling the soundtrack out of the video and storing it uncompressed. You can do it with tools already on the Mac (QuickTime Player to extract the audio, then Terminal or the Music app to turn it into WAV) or in one step with a converter. Keep the sample rate the video already uses, choose 16-bit, and expect the WAV to be many times larger than the soundtrack was inside the MP4.

Why WAV, and what it will not do

WAV is the format audio software expects. Audio editors, samplers and DJ software read it without fuss, many transcription and captioning services ask for it, and anyone editing a soundtrack is better off working in WAV and compressing once at the end than stacking one lossy save on top of another.

What WAV will not do is improve the sound. The audio in an MP4 is almost always AAC, a lossy format that threw away detail when the video was made. Converting to WAV decodes what is left and stores it without any further loss, which is exactly what you want for editing. It cannot bring back what the AAC encoder discarded.

The built-in route: QuickTime Player and Terminal

This takes two steps: QuickTime extracts the audio, and a command that ships with macOS writes the WAV.

  1. Open the MP4 in QuickTime Player.
  2. If you only need part of it, choose Edit, Trim, drag the yellow handles around the section you want, and click Trim.
  3. Choose File, Export As, Audio Only, and save. QuickTime writes the soundtrack as an M4A file.
  4. Open Terminal (in Applications, Utilities) and type the following, replacing the names with your own. You can drag the M4A onto the Terminal window to fill in its path.
afconvert -f WAVE -d LEI16 "Interview.m4a" "Interview.wav"

-f WAVE asks for a WAV file and -d LEI16 asks for standard 16-bit samples. The sample rate and the number of channels carry over from the source unless you say otherwise.

If a service wants something specific, add it. For example, some speech recognition tools ask for 16 kHz mono:

afconvert -f WAVE -d LEI16@16000 -c 1 "Interview.m4a" "Interview.wav"

If QuickTime Player will not open the MP4 at all, this route ends at step one. That usually means the video or audio inside uses a codec QuickTime does not support, which container vs codec explains.

The other built-in route: the Music app

If you would rather avoid Terminal, the Music app can finish the job after step 3 above.

  1. In Music, choose Music, Settings (Preferences on older versions of macOS), click Files, then Import Settings.
  2. Set Import Using to WAV Encoder. Leave Setting on Automatic to keep the source’s sample rate, and click OK.
  3. Choose File, Import, and select the M4A that QuickTime exported.
  4. Select it in the library and choose File, Convert, Create WAV Version.
  5. Control-click the new copy and choose Show in Finder.

The WAV and the M4A both stay in your Music library until you delete them there.

The one-step route: Manatee

Manatee converts the MP4 straight to WAV without the intermediate M4A. Drag the video onto its menu bar icon or into its window, or Control-click it in Finder and choose Services, then “Fix with Manatee”. Pick Convert, then WAV. The WAV is written next to the MP4, which is left exactly as it was.

It handles a stack of files the same way, and the window shows each job’s progress. It also accepts MOV, MKV, WEBM, AVI and many other video formats, so the same steps work if the soundtrack you need is not in an MP4. Everything happens on the Mac, with no uploads, which matters if the video is a recorded interview or a meeting. It is free for 24 hours with every feature, then $9 once.

Manatee is not an audio editor. If you only want a section, trim the video in QuickTime Player first, or cut the WAV afterward in your audio software.

Sample rate and bit depth

Two numbers describe a WAV, and the right answer for both is usually “match the source”.

  • Sample rate. Video soundtracks are usually 48 kHz; music CDs use 44.1 kHz. Keeping the rate the MP4 already has avoids a resampling step that gains nothing. Change it only when the destination asks for a particular rate.
  • Bit depth. 16-bit is plenty for audio that started out as AAC. 24-bit is useful when recording or mixing, but on a decoded AAC track it only makes a bigger file.

Why the WAV is so big

Uncompressed audio is simple arithmetic. At 48 kHz, 16-bit, in stereo, each second takes 48,000 samples times 2 bytes times 2 channels: 192,000 bytes. That is about 11.5 MB a minute, or close to 700 MB for an hour. The AAC soundtrack in a typical MP4, at 128 kbps, takes under 1 MB a minute.

The classic WAV format also has a ceiling. Its size field cannot describe a file larger than 4 GB, which at those settings is a little over six hours of stereo audio. For anything longer, split the recording or use mono, which halves the size.

To send a WAV to someone without the bulk, convert it to FLAC, which is lossless and usually much smaller, or to M4A or MP3 if the recipient only needs to listen. Zipping a WAV saves far less than converting it to FLAC does.

Questions

Is MP4 to WAV the same as MP4 to MP3? Both extract the soundtrack. WAV keeps the decoded audio as it is; MP3 compresses it again, which is smaller but costs a little more quality each time. Converting MP4 to MP3 covers that route.

WAV or AIFF? Both are uncompressed and sound identical. AIFF is Apple’s and works everywhere on a Mac. WAV is accepted by more software and services on every platform, so it is the safer choice when the file is leaving your Mac.

The MP4 is damaged and will not play. Can I still get the audio? Sometimes. If part of the file is readable, the sound in that part can often be recovered. Getting the audio out of a video that will not play walks through what to try.