MCK pbxgateway Administrator's Manual page 260

Appendix B
Selecting the Proper Voice Compression
The best voice quality is achieved by using the ADPCM 32 compression.
The maximum quality comes at the expense of the highest utilized bandwidth.
The largest voice compression is achieved by using G.729A. If you are using
this algorithm, you will save on bandwidth and still achieve voice quality that
is regarded as near toll. If absolute conversation quality is your focus and
bandwidth is no object, you probably want to select ADPCM 32. If
bandwidth is a priority you will employ G.729A.
If you are using different compression algorithms for each individual user
(port), use the following formula to establish your aggregate data bandwidth
needs.
A B C D
x 16 + x 32 + x 40 =
A: number of G.729A
B: number of ADPCM 24
C: number of ADPCM 32
D: Total Bandwidth
Divide this bandwidth by either 64 or 56, in order to establish the correct
number of DS0 channels to be used.
Example: If your DS0s on your CSU/DSUs are set up for 56Kbps, use 56 and
if they are set up for 64Kbps DS0s, use 64.
B-4
Issue 2.1 December 1999