asterisk users - Mar 2006 - ADPCM - vs - G.726

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


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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