3Com MSR 30, MSR 50 Relationship between algorithms and bandwidth, Codec Bandwidth Voice quality

2560 CHAPTER 173: VOIP CONFIGURATION COMMANDS

g729r8: G.729 (the voice compression technology using conjugate algebraic-code-excited linear-prediction), requiring a bandwidth of 8 kbps.

Description Use the compression command to configure the voice compression method and the preference level.

Use the undo compression command to restore the default value.

By default, the codec with the first priority is g729r8, that with the second priority is g711alaw, that with the third priority is g711ulaw, and that with the fourth priority is g723r53.

g711alaw and g711ulaw provide high-quality voice transmission, while requiring greater bandwidth.

g723r53 and g723r63 provide silence suppression technology and comfortable noise, the relatively higher speed output is based on multi-pulse multi-quantitative level technology and provides relatively higher voice quality to certain extent, and the relatively lower speed output is based on the Algebraic-Code-Excited Linear-Prediction technology and provides greater flexibility for application.

The voice quality provided by g729r8 and g729a is similar to the ADPCM of 32 kbps, having the quality of a toll, and also featuring low bandwidth, lesser event delay and medium processing complexity, hence it has a wide field of application.

Table 664 describes the relationship between codec algorithms and bandwidth.

Table 664 Relationship between algorithms and bandwidth

Codec	Bandwidth	Voice quality
G.711 (A-law and µ-law)	64 kbps (without compression)	Best
G.726	16, 24, 32, 40 kbps	Good
G.729	8 kbps	Good
G.723 r63	6.3 kbps	Fair
G.723 r53	5.3 kbps	Fair

Actual network bandwidth is related to packet assembly interval and network structure. The longer the packet assembly interval is, the closer the network bandwidth is to the media stream bandwidth. More headers consume more bandwidth. Longer packet assembly interval results in longer fixed coding latency.

The following tables show the relevant packet assembly parameters without IPHC compression, including packet assembly interval, bytes coded in a time unit, and network bandwidth, etc. Thus, you can choose a suitable codec algorithm according to idle and busy status of the line and network situations more conveniently.