[Asterisk-Users] ADPCM - vs - G.726

[Steve Underwood]

Whisker, Peter wrote:

>I have been looking at the medium-rate codecs in Asterisk - ADPCM and
>G.726. Both of these are adaptive PCM codecs - the G.726 one is a little
>more expensive in processing power, however both are 32k bit-rate.
>
>I am experiencing problems using G.726 where the audio level is high. It
>produces loud clicks as if clipping. For quiet audio however, it seems
>fine.
>
>ADPCM (Digilogic VOX?) seems to be better in this respect without the
>clicks but has slight artifacts audible.
>
>Anybody had the same problems with G.726? I can't find any comparisons
>out there between the two codecs - does anyone have a link?
>
>Thanks
>Peter
>  
>
If it does strange things at high volume the G.726 codec is buggy.

G.726 has a number of bells and whistles, such that DTMF and some lower 
speed modems will pass through OK, and so tandem operation does not 
become progressively worse. The OKI/Dialogic ADPCM doesn't have these, 
and as a result cause far less CPU loading. However, for typical speech 
only use they should offer comparable quality.

Regards,
Steve