[Asterisk-Users] G729 codec

[Steve Underwood]

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.
>  
>
Those are versions with different bit packing. Cisco started using G.729 
before the packing order was standardised. They guessed it wrong. They 
had to change. :-)

>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 ?
>  
>
There are Annexes up to I. The earlier versions are fixed point, reduced 
complexity fixed point and floating point at 8kbps. These are all 
compatible. Later annexes add (if memory serves me correctly) silence 
suppression, assistance for packet loss concealment (some people say 
G.729 includes PLC. It doesn't. What it includes is some features to 
reduce how badly PLC works with it), the standard for bit packing, and 
additional bit rates of 6.4kbps and 11.8kbps.

Regards,
Steve