As of TopView 6.30, VOIP configurations allow the specification of call codecs. This article explains what codecs are and why you might want to use a codec that is different from the defaults used by TopView.
What is a “codec”?
From Wikipedia’s definition of Audio Codec:
An audio codec is a codec (a device or computer program capable of encoding or decoding a digital data stream) that encodes or decodes audio
Why is this a VOIP configuration option?
Since TopView’s voice notifications utilize audio, codecs are used to encode and decode the notification message. Different VOIP providers can provide and support different audio codecs, and some of them play better on certain types of connections.
Most VOIP providers and endpoints within the same region support the same codecs.
If you notice poorer than expected audio quality over the call, you may find a different codec that will provide better quality.
TopView supports the following codecs:
| Name | Alt. name | Payload type | No. of channels | Rate (Hz) | Ratet (Hz) |
| PCMU (G.711) | PCMU | 0 | 1 | ITU-T G.711 PCM ยต-Law audio 64 kbit/s | 8000 |
| PCMA (G.711) | PCMA | 8 | 1 | ITU-T G.711 PCM A-Law audio 64 kbit/s | 8000 |
| G.722 | G722 | 9 | 1 | ITU-T G.722 audio 64 kbit/s. Usually the codec in use for TopView voice calls. It is of excellent quality. | 8000 |
| G.723 | G723 | 4 | 1 | Obsoleted codec superseded by G726 | 8000 |
| G.726-16 | G726 | 104 | 1 | ITU-T G.726 audio 16 kbit/s | 8000 |
| G.726-24 | G726 | 105 | 1 | ITU-T G.726 audio 24 kbit/s | 8000 |
| G.726-32 | G726 | 106 | 1 | ITU-T G.726 audio 32 kbit/s | 8000 |
| G.726-40 | G726 | 107 | 1 | ITU-T G.726 audio 40 kbit/s | 8000 |
| G.728 | G728 | 15 | 1 | ITU-T G.728 audio 16 kbit/s | 8000 |
| G.729 | G729 | 18 | 1 | ITU-T G.729 and G.729a audio 8 kbit/s; Annex B is implied unless the annexb=no parameter is used | 8000 |
| GSM | GSM | 3 | 1 | European GSM Full Rate audio 13 kbit/s (GSM 06.10) | 8000 |
| iLBC | iLBC | 98 | 1 | Internet low Bitrate Codec 13.33 or 15.2 kbit/s | 8000 |
| L16 (2 channel) | L16 | 10 | 2 | Linear PCM 16-bit stereo audio | 44100 |
| L16 | L16 | 11 | 1 | Linear PCM 16-bit audio | 44100 |
| opus | opus | 120 | 1 | Opus audio | 48000 |
| SPEEX-Narrow | SPEEX | 97 | 1 | Speex audio | 8000 |
| SPEEX-Wideband | SPEEX | 100 | 1 | Speex audio | 16000 |
| SPEEX-Dynamic | SPEEX | 108 | 1 | Speex audio | 32000 |