[Asterisk-Users] G729 codec

[Adam Hart]

Ivan Meic (Vox Mundi) wrote:
>>Actually G.729A is a reduced complexity version, and G.729B is a version 
>>with silence suppression. The data rate while sending voice is exactly 
>>the same, although the quality of G.729B should be a little higher. 
>>However the average rate for B can be lower if the silence suppression 
>>is used. Right now Asterisk doesn't make use of that silence 
>>suppression, so it makes not difference.
> 
> 
> Steve,
> 
> Any Cisco gateway support two G.729 variants.
> They call them g729r8 and g729br8.
> So I guess that Cisco never implemented a reduced complexity version ?
> Also as far as I understand there are 3 G.729 variants generaly used.
> The first version (G.729), Annex A and Annex B.
> Are they all compatible with each others ?
> 
> Ivan

Actually, I believe Cisco uses G.729A, as they use TI chips.

The difference between G.729 and G.729A is Annex A spends less time 
looking for the optimal representation of the voice. G.729 and G.729A 
are completely compatible. Annex B adds silence suppression. I believe 
you need to support and negotiate annex B on both ends if you want to 
use it. I'm against silence suppression but that's just me. Annex C is 
the floating point version and obviously completely compatiable as well

-Adam