[asterisk-dev] IAX Voice Framing

Manivasagam Sivaraman smvasagam2000 at gmail.com
Fri Feb 5 16:54:47 CST 2010


Tilghman thanks for your quick reply. This is a test project for some
research purpose only. I'm aware of the increased latency involved in this
method. Could you please provide some pointer to hook up the multiple frame
in an IAX audio packet ? I could not follow the some of the code in chan_iax
as I'm pretty new to this code. If there are any short cut method like using
an existin function in the core code like frame.c, it will be very helpful.

Thanks in advance.
I appreciate your inputs.
smv

On Fri, Feb 5, 2010 at 1:58 PM, Tilghman Lesher <tlesher at digium.com> wrote:

>  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 ?
>
> 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.
>
> --
> Tilghman Lesher
> Digium, Inc. | Senior Software Developer
> twitter: Corydon76 | IRC: Corydon76-dig (Freenode)
> Check us out at: www.digium.com & www.asterisk.org
>
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