Audio format
The GSM format
GSM is phone-quality speech from telephone systems and voicemail. The GSM full-rate codec was defined for the first digital mobile networks around 1990; phone systems still record in it.
When to use GSM
Convert GSM voicemail and call recordings to MP3 or WAV to play or transcribe them.
It is best for voicemail and PBX recordings, and it opens on VLC, SoX and phone system software.
How to open it: VLC and Audacity (via FFmpeg) open GSM files.
| Full name | GSM 06.10 Audio |
|---|---|
| Extensions | .gsm |
| MIME type | audio/x-gsm |
| Introduced | 1990 |
| Compression | Lossy |
| Typical quality | 13 kbps, 8 kHz |
| Support | Specialist format |
| Typical size | About 100 KB a minute |
Good at
- Very small speech files
Not so good at
- 8 kHz telephone quality
- Few players open it
The common mistake
Raw GSM files have no header, so tools must be told the sample rate; converting them to WAV makes them open anywhere.
Questions
What is a GSM file?
GSM (GSM 06.10 Audio) is phone-quality speech from telephone systems and voicemail. The GSM full-rate codec was defined for the first digital mobile networks around 1990; phone systems still record in it.
How do I open a GSM file?
VLC and Audacity (via FFmpeg) open GSM files.