AMR Audio
| Format | AMR Audio |
|---|---|
| Short name | AMR |
| Category | media |
| Platforms | Windows, macOS, Linux, iOS, Android, QNX |
| Crush support | Supported (MediaParser) |
| Status | Reviewed |
| Last reviewed | 2026-10-04 |
Forensic relevance
Adaptive Multi-Rate speech codec standardised by 3GPP for GSM/UMTS networks. Two variants: AMR-NB (Narrowband, 4.75-12.2 kbps, 8 kHz sampling) and AMR-WB (Wideband/HD Voice, 6.6-23.85 kbps, 16 kHz, also known as G.722.2). Identified by ASCII magic: '#!AMR\n' (NB) or '#!AMR-WB\n' (WB). Used as the default voice recording format on older Android devices, in MMS attachments, and embedded in 3GP containers. AMR codec artefacts survive transcoding to WAV/PCM — quantization patterns in the waveform can identify mobile phone origin and detect splicing forgeries even after decompression. No native embedded timestamps — recording time inferred from filesystem metadata or messaging app databases. Replaced by AAC and Opus on modern devices but common in older acquisitions.
Signatures
| Offset | Hex | ASCII (non-printable as .) | Description |
|---|---|---|---|
| offset 0 (0x0) | 23 21 41 4D 52 0A | #!AMR. | AMR-NB file magic ('#!AMR\n') |
| offset 0 (0x0) | 23 21 41 4D 52 2D 57 42 0A | #!AMR-WB. | AMR-WB file magic ('#!AMR-WB\n') |
| offset 0 (0x0) | 23 21 41 4D 52 5F 4D 43 31 2E 30 0A | #!AMR_MC1.0. | AMR-NB multichannel file magic ('#!AMR_MC1.0\n') |
| offset 0 (0x0) | 23 21 41 4D 52 2D 57 42 5F 4D 43 31 2E 30 0A | #!AMR-WB_MC1.0. | AMR-WB multichannel file magic ('#!AMR-WB_MC1.0\n') |
Known extensions
.amr, .awb
References
- AMR/AMR-WB storage format (RFC 4867, section 5) https://www.rfc-editor.org/rfc/rfc4867.html
- AMR codec specification (3GPP TS 26.071) https://www.3gpp.org/ftp/Specs/archive/26_series/26.071/
- Adaptive Multi-Rate audio codec (Wikipedia) https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec
- Identification of AMR decompressed audio (Luo, Yang, Huang — Digital Signal Processing 2015) https://www.sciencedirect.com/science/article/abs/pii/S1051200414003200
Cite this entry
Crush Format Reference, “AMR Audio”. https://kalink0.github.io/crush-forensics/formats/amr/ — source: crush/data/build_formats_db.py at commit 640a2a9928f4e36a976b89901512a8dce824d093, built 2026-10-21 06:46:19 UTC.
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