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AMR
What is an AMR file?
The voice recording format from older phones. Speech only, tiny files, poor music quality.
What AMR is
AMR is a codec: the encoding itself rather than the box it travels in. It is used for phones.
The extension is .amr, and the full name is Adaptive Multi-Rate Audio. Both matter less than what the file can hold, which is what the rest of this page is about.
Where AMR came from
3GPP published it in 1999.
A format that has been readable for that long is a format worth trusting with something you want back in ten years.
The specification is public
Anyone can implement it without asking permission or paying a licence, which is why it turns up in so many programs and why files written twenty years ago still open.
It is a legacy format
It still opens everywhere and is still written by older tools, but nothing new is being built around it. Convert what you mean to keep, and do not choose it for something starting today.
Detail is traded for size
AMR discards detail to stay small, and what it discards does not come back. That is the right trade for something being looked at and the wrong one for something being edited: each re-save takes another bite.
How many audio channels
Up to 1. Two covers stereo and is what almost everything is; more than two is surround, and it is the part most likely to be folded down when converting to a format that does not define it.
What opens AMR
VLC and FFmpeg 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
No browser reads it.
That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.
It is a delivery format
AMR 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.
What goes wrong with it
The recurring complaints: support outside its home ground is uneven.
None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.
The facts, in one place
| Extension | .amr |
|---|---|
| Media type | audio/amr |
| Published by | 3GPP |
| First published | 1999 |