# Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones. — file signature 23 21 41 4D 52 at offset 0

For Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones., hex signature is 23 21 41 4D 52; offset is 0; extension is amr, verified against its source on 2026-09-22.

- **Hex signature:** 23 21 41 4D 52 _(verified: appears in the quote below)_
- **Offset:** 0 _(verified: appears in the quote below)_
- **Extension:** amr _(verified: appears in the quote below)_
- **Format:** Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones. _(verified: appears in the quote below)_

## What the source says

> 23 21 41 4D 52 | #!AMR | 0 | amr | Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones. |

## Source

- https://en.wikipedia.org/wiki/List_of_file_signatures

Last verified: 2026-09-22. Review by: 2027-09-22.
Part of [File format magic numbers](https://referencesource.org/file-format-signatures/).