MPEG-4 Video (Apple)

Apple Is the Registration Authority — and Apple Ignores It

The MP4 Registration Authority — the registry where every legal MP4 brand label is filed, administered by Apple itself — has exactly one M4V entry. Search the public list for M4V: one row, registered with the description MPEG-4 protected audio+video. Now search the file(1) magic database — the rule list every macOS and Linux system uses to identify file types, shipped with every Unix-like operating system since the 1980s. Three rows: M4V for Apple iTunes Video, M4VH for Apple TV's M4V variant, and M4VP for Apple iPhone's M4V variant. Two of three brand labels Apple has shipped on M4V files since 2006 do not exist in Apple's own registry. Apple wrote the registry. Apple administers the registry. Apple has shipped two brand labels — one on every Apple TV, one on every iPhone — without ever filing them. The file(1) project caught the brands by reverse-engineering actual files from Apple devices; the canonical registry never received a submission. Identifying an M4V file in 2026 still requires consulting both lists. The brand is supposed to mean protected. That's what Apple's own registry says. Open an actual M4V file and check whether it's protected: the brand will lie to you.

The Brand Says Protected. Most Files Aren't.

Open a music video bought from iTunes Store in 2008. Open a HandBrake export from 2024 with the Apple TV preset. Both files are .m4v. Both have M4V at offset 8 — the four-byte string registered with the description MPEG-4 protected audio+video. The brand says encrypted on both files. Now open the codec table inside each file — the part that names the video and audio compression. The 2008 iTunes file says encv, the codec label MP4 uses to mark a video or audio track as encrypted. Real FairPlay protection — Apple's video DRM, the encryption Apple uses to control playback of iTunes Store purchases. The 2024 HandBrake file says avc1, the codec label for unencrypted H.264 video. No DRM. No encryption. The same brand label outside the file. The brand was meant to mean encrypted. The byte format the world ships says encrypted on both files. The actual files are protected on one and unprotected on the other — the brand cannot tell them apart. FairPlay protection lives in the codec entry inside the file, not in the four-byte label outside it. The HandBrake file, the Final Cut Pro render, the QuickTime screen recording — they all carry the M4V brand without ever touching FairPlay. Which is why the workaround everyone has used since 2006 actually works — and why Apple's own software is the only thing that notices.

Why the Rename Trick Works (And Why Only Apple Notices)

A user on a 2009 Windows XP machine has just bought a music video from iTunes Store. The download finishes. Double-click the .m4v file. Windows Media Player opens, looks at the file extension, decides it doesn't know what .m4v is, and refuses to play. The user right-clicks the file, picks Rename, types .mp4. Double-clicks again. Windows Media Player opens, looks at the new extension, decides it knows MP4, reads the file, finds the H.264 video and AAC audio inside, and plays. The bytes never changed. The codec never changed. Not a single byte of the file moved. Windows Media Player dispatches on the file extension; the moment the extension changes, it recognizes the file. The file was always playable; it was just labeled wrong for the player asking. iTunes on the same machine works in the opposite direction: iTunes opens the file, reads the four bytes at offset 8, sees M4V , and treats the file as iTunes Store property. The extension does not matter to iTunes. It reads the brand. Apple is the only software in the world that does. Every other player on every other operating system reads the box hierarchy and ignores the four-byte label entirely. Rename to .mp4, the file plays. The brand is still M4V . Apple's apps would still notice. Nothing else does.