[asterisk-dev] queries regarding SDP implementation for multiple bit rates for g.722 codec.

[Steve Underwood]

Kevin P. Fleming wrote:
> lalit kumar wrote:
>
>   
>> As we know that g.722 supports 48,56 and 64 kbps.
>>     
>
> Sort of... It supports using 8kbps or 16kbps of the stream as a data
> channel. The stream is always 64kbps, but may contain fewer bits of
> audio data.
>
>   
>> Query-1: à I want to negotiate g.722 codec with multiple bitrates 64
>> 56,and 48. Then what would be SDP attributes value in Sip invite.
>>     
>
> RFC3551 makes no accommodation for the various G.722 audio/data channel
> modes. I do not see (in a quick Google search) where using these modes
> has ever been specified over RTP, or to be signaled in SDP.
>
>   
>> Query-3 à On network what flavor of G.722 codec is better from 64, 56
>> and 48 kbps?
>>     
>
> It makes no difference because the media stream is always 64kbps. The
> only reason to use the other modes is if you want to transmit a data
> channel between the endpoints as part of the media stream.
>   
On a packet network, the 48k and 56k options for G.722 make no sense 
whatsoever. They were modes purely for ISDN networks, and they never 
caught on.

Steve