MPEG-4 Video (Apple)
Convert DRM-free M4V video to MP4, WebM, or GIF directly in your browser — no upload, no server, no quality loss for remuxing. FileDex uses FFmpeg WebAssembly to process Apple's video container locally on your device.
Your files never leave your device
Common questions
Can I convert DRM-protected M4V to MP4?
No. FairPlay-encrypted M4V files from the iTunes Store cannot be converted by FileDex or any standard tool — the media data is AES-encrypted and playback requires Apple's DRM authorization. Only DRM-free M4V files (personal recordings, DRM-free purchases) can be converted.
Is M4V the same as MP4?
Structurally, yes. Both use the ISO Base Media File Format (BMFF). The only differences are the file extension, the ftyp major brand identifier, and the optional presence of Apple FairPlay DRM in M4V. DRM-free M4V files can be renamed to .mp4 and will play identically.
How do I convert M4V to MP4 in my browser?
Drop your DRM-free M4V file into FileDex above and select MP4 as the output format. FileDex remuxes the file locally — copying the H.264/AAC streams into an MP4 container with zero quality loss and no file upload.
Why won't my M4V file play on Android or Windows?
The device likely does not recognize the .m4v extension. If the file is not DRM-protected, simply renaming it to .mp4 often solves the problem. For a proper conversion, use FileDex to remux to MP4 with the moov atom relocated for fast playback start.
What makes .M4V special
iTunes video files carry the .m4v extension, a format Apple adopted to distinguish its media store content from generic MP4 files. The distinction is almost entirely commercial, not technical. M4V is structurally identical to MP4 — same ISOBMFF atoms, same box hierarchy, same codec support. Apple adds an iTunes DRM layer (FairPlay) and changes the file extension so that only iTunes/Apple TV can decrypt and play the protected content. Unprotected M4V files (from HandBrake exports or iTunes Plus purchases) are byte-for-byte compatible with any MP4 player. Rename the extension, and they play everywhere.
Continue reading — full technical deep dive
ISOBMFF structure parity
M4V uses the same ISO Base Media File Format as MP4. The file starts with an ftyp box declaring compatible brands — typically M4V as the major brand with isom and mp42 as compatible brands. The moov box contains track metadata, mdat holds compressed media data, and optional udta boxes carry iTunes-specific metadata.
The internal atom tree is identical:
| Atom | Function | M4V vs MP4 |
|---|---|---|
ftyp |
File type declaration | Major brand M4V vs isom or mp42 |
moov |
Movie metadata, track headers | Identical structure |
mdat |
Compressed A/V data | Identical (or FairPlay-encrypted) |
udta/meta/ilst |
iTunes metadata tags | M4V uses extended iTunes tag set |
sinf |
DRM protection info | Present only in FairPlay-protected files |
FairPlay DRM mechanism
When an M4V file is purchased from the iTunes Store with DRM, Apple wraps each video sample in AES-128 encryption. The sinf atom inside the track's sample description contains the FairPlay scheme information: a frma box with the original codec FourCC, a schm box identifying the encryption scheme, and a schi box with scheme-specific parameters. The decryption key is tied to the user's Apple ID and the authorized device's hardware identity.
FairPlay-protected M4V files play only in iTunes (Windows/macOS), Apple TV app, and iOS/iPadOS devices signed into the purchasing Apple ID. They do not play in VLC, mpv, or any non-Apple player. Since 2009, iTunes Plus music has been DRM-free (AAC in M4A), but most purchased movies and TV shows still carry FairPlay protection.
iTunes metadata extensions
M4V files support an extensive metadata tag set within the ilst atom under moov/udta/meta. Beyond standard MP4 tags (title, artist, album, year), M4V includes:
stik— media type (Movie, TV Show, Music Video)tves/tvsn— TV episode and season numberstvsh— TV show namepurd— purchase datecovr— cover artwork (JPEG or PNG, often 600x600 or larger)desc/ldes— short and long descriptionshdvd— HD flag (0 = SD, 1 = 720p, 2 = 1080p)
These tags power iTunes library sorting, Apple TV browsing, and Spotlight search on macOS.
Codec and quality tiers
Apple encodes iTunes Store video in H.264 (Main or High Profile) for HD content and H.265 (HEVC) for 4K HDR titles. Typical bitrates:
- SD (480p): 1.5–2.5 Mbit/s H.264, 128 kbit/s AAC stereo
- HD (1080p): 5–8 Mbit/s H.264, 160 kbit/s AAC stereo or Dolby Digital 5.1
- 4K HDR: 15–25 Mbit/s HEVC Main 10, Dolby Atmos (E-AC-3 JOC) or AAC
A 2-hour 1080p movie typically occupies 4–6 GB. 4K HDR versions range from 10–20 GB.
When to convert M4V
If your M4V files are DRM-free (HandBrake output, screen recordings, or DRM-stripped purchases), conversion to MP4 is a simple remux — no re-encoding, no quality loss, just changing container metadata. This broadens playback compatibility to Android, Windows, smart TVs, and web browsers. DRM-protected files cannot be converted without decryption, which FileDex does not perform.
FileDex handles DRM-free M4V to MP4, MKV, or WebM conversion directly in the browser, preserving the original video and audio bitstreams when the target container supports the source codecs.
.M4V compared to alternatives
| Formats | Criteria | Winner |
|---|---|---|
| .M4V vs .MP4 | Compatibility MP4 is the universal video container supported by all browsers, devices, and platforms. M4V is functionally identical but some non-Apple players reject the .m4v extension. Renaming or remuxing to .mp4 solves this with no quality change. | MP4 wins |
| .M4V vs .MKV | Container flexibility MKV (Matroska) supports virtually any codec, multiple subtitle tracks, chapter markers, and attachments. M4V is limited to codecs within the ISO BMFF specification and Apple's DRM layer. | MKV wins |
| .M4V vs .WEBM | Open licensing WebM uses royalty-free VP9/AV1 codecs. M4V typically contains H.264/H.265 which carry patent licensing obligations in some jurisdictions, plus optional FairPlay DRM locks content to Apple devices. | WEBM wins |
Convert .M4V to...
Technical reference
- MIME Type
video/x-m4v- Magic Bytes
00 00 00 xx 66 74 79 70ftyp box, same structure as MP4.- Developer
- Apple Inc.
- Year Introduced
- 2001
- Open Standard
- No
ftyp box, same structure as MP4.
Binary Structure
M4V uses the ISO Base Media File Format (BMFF), identical to MP4 at the container level. The file is a sequence of atoms (also called boxes), each starting with a 4-byte big-endian size and 4-byte type identifier. The file begins with an ftyp atom at offset 0: the first 4 bytes are the atom size (typically 00 00 00 18 for 24 bytes), followed by 66 74 79 70 (ftyp), then a 4-byte major brand (M4V or mp42), 4-byte minor version, and compatible brands list. The moov atom contains the movie header (mvhd), track headers (trak), and media data references. Each track has a stbl (sample table) atom with stts (time-to-sample), stsc (sample-to-chunk), stsz (sample sizes), and stco/co64 (chunk offsets). The mdat atom holds the actual encoded video and audio bitstream data. DRM-protected M4V files include sinf atoms with FairPlay encryption metadata inside each trak.
| Offset | Length | Field | Example | Description |
|---|---|---|---|---|
0x00 | 4 bytes | Atom Size | 00 00 00 18 (24 bytes) | Big-endian size of the ftyp atom including the size and type fields themselves. |
0x04 | 4 bytes | Atom Type | 66 74 79 70 (ftyp) | File Type atom — identifies the container format and compatible brands. |
0x08 | 4 bytes | Major Brand | 4D 34 56 20 (M4V ) or 6D 70 34 32 (mp42) | Primary format identifier. M4V indicates Apple's iTunes video variant. mp42 indicates generic MPEG-4 Part 14. |
0x0C | 4 bytes | Minor Version | 00 00 00 00 | Version of the major brand specification. Typically zero for consumer M4V files. |
0x10 | variable | Compatible Brands | 69 73 6F 6D 4D 34 56 20 | List of compatible format brands (isom, M4V, mp41, etc.). Each brand is 4 bytes. |
varies | variable | moov Atom | 6D 6F 6F 76 (moov) | Movie metadata container: track layouts, codec parameters, sample tables, and timing information. |
varies | variable | mdat Atom | 6D 64 61 74 (mdat) | Media data container holding the actual H.264/H.265 video and AAC/AC-3 audio bitstreams. |
Attack Vectors
- Malformed ftyp or moov atoms with crafted size fields can trigger integer overflow in ISO BMFF parsers that allocate memory based on declared atom sizes without ceiling checks
- Deeply nested atom structures can cause stack overflow in recursive atom parsers
- Crafted stbl (sample table) entries with extreme sample counts or offsets can cause out-of-bounds reads in decoders
Mitigation: FileDex processes M4V files locally using FFmpeg WASM in a sandboxed browser environment. No data is sent to external servers.