Command Reference Guide

3Com Router 5000 Family and Router 6000 Family compression ● 39
Command Reference
Specifies G.726 Annex A coding. It uses ADPCM,
requiring the bandwidth of 32 kbps.
g726r40
Specifies G.726 Annex A coding. It uses ADPCM,
requiring the bandwidth of 40 kbps.
Default By default, g729r8 coding mode is set.
Example Configure to select g723r53 compression method first, then to select the g729r8
compression method.
[Router-voice-dial-entity1] compression 1st-level g723r53
[Router-voice-dial-entity1] compression 2nd-level g729r8
View This command can be used in the following views:
■ Voice Entity view
Description g711alaw and g711ulaw coding provide high-quality voice transmission, while
requiring greater bandwidth.
g726r16, g726r24, g726r32, and g726r40 are widely adopted now for voice coding.
They use the ADPCM technology and provide multiple bandwidth options.
g723r53 and g723r63 coding provide silence suppression technology and comfort
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 the g729r8 and g729a coding 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.
The following table describes the relation between codec algorithms and bandwidth.
Usually, 8000 Hz is adopted to collect voice samples. The bandwidth without
compression is 64 kbps, and it is compressed using the ITU-T G series codec
algorithms. The table also shows the compression ratio.
Table 1 Relation between algorithms and bandwidth
Codec algorithm 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
G.711 (A-law and
µ-law)
64 kbps (without
compression)
Best