Convert M4V to MP3 - extract audio
M4V is Apple's MP4 profile - same file format under a different filename convention (see MP4 vs MOV for the wider Apple-vs-MP4 container story). Audio is always AAC. Wave discards the video track and re-encodes the AAC to a portable MP3 through libmp3lame.
What actually changes
M4V and MP4 share the ISO base media file format; the difference is entirely in the ftyp box (M4V uses `M4V ` where MP4 uses `mp42` or `isom`) and Apple's convention of using the .m4v extension for its own video downloads. Audio is always AAC - iTunes-purchased content, HandBrake rips of DVDs and Blu-rays, Final Cut Pro exports, iMovie exports, Apple Photos exports of Live Photos, and every screen recording from macOS Screenshot all write AAC into the .m4v file.
Because AAC and MP3 are different codecs, the extract is always a re-encode. Wave decodes the AAC track in your browser through the wasm engine's AAC decoder, then re-encodes to MP3 at 192 kbps through libmp3lame. Video is discarded entirely - Wave never decodes a single video frame - so the extract runs in a fraction of the time a full file conversion would take. An hour-long M4V typically produces an 85 MB MP3 in under 30 seconds on modern hardware.
M4V arrived with iTunes 4.5 in April 2004 to carry the DRM-protected music videos Apple started selling that year, and by iTunes 6 (2005) it was the extension of choice for every video Apple's store sold. The convention stuck: Final Cut Pro, iMovie, QuickTime Player, and macOS Screenshot all default their video exports to .m4v when the container is MP4 and the presumed audience is Apple. On the ripping side, HandBrake's "iPhone" and "Apple TV" preset chains write .m4v because the AAC-in-MP4 combination those presets produce is the same as Apple's own encoding conventions.
The DRM caveat only applies to a narrow window of files: iTunes movie and TV purchases from before 2009 (when FairPlay was applied to video), and rentals through the iTunes Store today. Wave detects the FairPlay flag during inspect and stops with a clear message - no browser-side tool can decrypt FairPlay-protected content. Music from the iTunes Store has been DRM-free since 2009 (as iTunes Plus AAC), and every self-authored .m4v (Final Cut export, HandBrake rip of your own DVD, screen recording) is unencrypted.
Three steps.
-
01
Step 1
Drop the .m4v file onto the card.
-
02
Step 2
Pick MP3 as the output format.
-
03
Step 3
Convert. Save the MP3.
Answers, specifically.
Is my iTunes-purchased .m4v protected?
Music videos and movie/TV purchases from before 2009 usually carry FairPlay DRM. iTunes Store music has been DRM-free since 2009 (labelled iTunes Plus AAC). Wave detects DRM during inspect and stops with a message before any conversion runs.
What if the .m4v has DRM?
Wave can't decrypt FairPlay-protected content. No browser-side tool can - Apple's DRM keys are held in the device secure enclave. For DRM-protected content, playback in the Apple TV app on your own device is the only supported path.
How does 192 kbps MP3 compare to the AAC source?
On any consumer playback gear, indistinguishable. AAC is more efficient bit-for-bit at very low bitrates, but at 192 kbps MP3 the difference falls below the audible threshold for music, speech, and film audio.
Can I extract from a Final Cut Pro .m4v export?
Yes. Final Cut Pro's Apple ProRes exports usually land in .mov, but the H.264 export chain writes .m4v with AAC audio at 192 or 256 kbps stereo. Wave decodes the AAC and re-encodes to MP3 with essentially no audible difference.
iMovie exports?
Same behaviour. iMovie's "Share to File" writes .m4v with AAC audio; Wave extracts it into MP3 the same way.
What about macOS screen recording?
Screen recordings from macOS Screenshot (Command-Shift-5) are .mov containers by default, but the "Save as..." dialog offers .m4v with H.264 + AAC. Wave handles both extensions.
Multiple audio tracks - alternate languages, director commentary?
Wave extracts the default-flagged track. HandBrake rips with commentary as a second track will yield the primary language. Multi-track extraction is on the roadmap.
Does the file name of the movie or song carry over?
Basic ID3 tags (title, artist if the source .m4v has metadata) are written to the MP3. Album art doesn't transfer through the current pipeline - use a tag editor if you need the artwork.