[asterisk-dev] IAX Voice Framing

[Steve Edwards]

> On Friday 05 February 2010 13:31:16 Manivasagam Sivaraman wrote:

>> I'm trying to pack 3 or 4 audio voice frames into one IAX audio packet 
>> and send it out. The receiving end will also be the same asterisk that 
>> would expect the 3 or 4 voice frame in one IAX audio packet. Before 
>> touching the code I want to know if this is feasible. I'm new to 
>> asterisk and I want to have a heads up before I begin. Please let me 
>> know if there will be some risk involved in this. I see a function in 
>> frame.h that allows framing of multiple voice frames in one RTP packet 
>> for instance in sip and h323 channels. However no such function is used 
>> in chan_iax2.c file. Could you please expalin why ? Why iax channel is 
>> coded a bit different ?

On Fri, 5 Feb 2010, Tilghman Lesher wrote:

> Clearly, because the IAX channel does not use RTP.  This is a feature, 
> which helps IAX to more cleanly go through NATs, and it may work in 
> places where SIP does not, such as double and triple NAT situations.
>
> I really don't understand why you'd want to pack multiple frames into a 
> single packet.  That increases latency, which for a real time protocol 
> is rather bad.

If the goal is to reduce the Ethernet and IP packet overhead, then maybe 
"IAX trunking" is what you are looking for. I think this only packs 
packets from multiple calls, not packets from the same call.

-- 
Thanks in advance,
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Steve Edwards       sedwards at sedwards.com      Voice: +1-760-468-3867 PST
Newline                                              Fax: +1-760-731-3000