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M4V
What is an M4V file?
Apple's MP4 variant. Identical in practice unless the file carries copy protection.
What M4V is
M4V is a container: a wrapper that holds streams encoded by something else. It is used for handing a finished file over and phones.
The extension is .m4v, and the full name is iTunes Video. Both matter less than what the file can hold, which is what the rest of this page is about.
Where M4V came from
Apple published it in 2005.
Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.
The specification is published, but by its owner
It is written down and implementable, though the vendor decides what the next version looks like. In practice that is enough for the file to keep opening; it is not enough to be sure of it.
M4V is a box, and the codec is what is in it
It usually holds H.264, HEVC and AAC. This is the distinction behind most "why will this not play" questions: two files with the same extension can contain entirely different encodings, and a player that refuses one may be perfectly happy with the other.
It also explains why changing container is often fast and lossless while changing codec is neither. Moving the same stream into a different box rewrites the box; re-encoding rewrites the picture.
What else it can carry
M4V can hold several audio tracks and subtitle tracks.
That matters mostly when converting: whatever the target cannot hold is dropped, usually without a warning.
What it does to protect itself
M4V carries optional encryption.
An encrypted file has to be unlocked before anything can convert it, here or anywhere else — a password is not something a converter can work around, and one that claimed to could not be trusted with the file either.
What opens M4V
QuickTime Player, VLC and iTunes read it, and so do most programs of the same kind.
If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.
Opening it in a browser
Only some browsers read it.
Where support is uneven, serving a second format alongside it is the usual answer — the browser takes the one it understands and nobody is left out.
It is a delivery format
M4V is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.
The facts, in one place
| Extension | .m4v |
|---|---|
| Media type | video/x-m4v |
| Published by | Apple |
| First published | 2005 |