[asterisk-dev] H324M Gateway

[Sergio García Murillo]

Steve Underwood wrote:
> Sergio García Murillo wrote:
>> 
>> Would it be just framing the gsm amr stream in covered by the
>> transcoded license? 
>> I don't know much of gsm framing, if it's fixed length or if you have
>> to do a more in deep analisys of the stream to construct the rtp
>> packet (as it would be the case of h263). 
>> 
>> 
> Do you mean analysing what comes from the handset? If so, then yes,
> the AMR bit stream between the base station and handset is very
> speech oriented, with lots of error correction on things like the
> MSBs of the frame energy, and almost no error correction for the
> LSBs.    

No, I mean that if we are able to establish a video call what we are going to get in asterisk from
the audio channel is a bit stream, and we will have to convert somehow into an rtp packet.
If the gsm arm has a fixed length framing, then we just have to count bits, pack them and fit it in an rtp packet.
If the gsm needs some special framing depending on the internal structure of the stream (as it's the case of h263), you need to do some parsing (but not decoding) of the stream to know where are the frame boundaries.

Sergio
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