In the VoIP world, codecs are used to encode voice for transmission across IP networks.
Codecs for VoIP use are also referred to as vocoders, for "voice encoders".
Codecs generally provide a compression capability to save network bandwidth. Some codecs also support silence suppression, where silence is not encoded or transmitted.
| Codec | Algorithm | Bit Rate (Kbps) | Comments |
|---|---|---|---|
| ITU G.711 | PCM (Pulse Code Modulation) | 64 | G.711 with mu-law used in North America and Japan, while G.711 with A-law used in the rest of the world. |
| ITU G.722 | SBADPCM (Sub-Band Adaptive Differential Pulse Code Modulation) | 48, 56 and 64 | |
| ITU G.723 | Multi-rate Coder | 5.3 and 6.4 | |
| ITU G.726 | ADPCM (Adaptive Differential Pulse Code Modulation) | 16, 24, 32, and 40 | |
| ITU G.727 | Variable-Rate ADPCM | 16-40 | |
| ITU G.728 | LD-CELP (Low-Delay Code Excited Linear Prediction) | 16 | |
| ITU G.729 | CS-ACELP (Conjugate Structure Algebraic-Code Excited Linear Prediction) | 8 | |
| ILBC | Internet Low Bitrate Codec | 13.33 and 15.20 | |
| Speex | CELP (Code Excited Linear Prediction) | 2.15-44.2 | Part of the GNU Project and available under the Xiph.org variant of the BSD license |
| GSM - Full Rate | RPE-LTP (Regular Pulse Excitation Long-Term Prediction) | 13 | |
| GSM - Enhanced Full Rate | ACELP (Algebraic Code Excited Linear Prediction) | 12.2 | |
| GSM - Half Rate | CELP-VSELP (Code Excited Linear Prediction - Vector Sum Excited Linear Prediction) | 11.4 | |
| DoD FS-1016 | CELP (Code Excited Linear Prediction) | 4.8 |
