[OpenSIPS-Devel] media proxy with sangoma

[Saúl Ibarra Corretgé]

Hi,

On 08/26/2010 04:31 PM, Richard Revels wrote:
> I was thinking the media relay would modify the SDP as per normal but set the trancoder IP/port as one side (user configurable?) of the audio stream rather than itself.  Then it would tell the transcoder to send to itself so the packets could be forwarded to the endpoints as usual.

Alright, putting the transcoder between the network and the relay could 
do. However...

>
> And now that I reread your email, having the connection tracking rules send and receive from the transcoder in the middle of the two sides of the media relay would be much nicer.  The SDP would still have the relay IP/ports advertised to each side.
>
> Good point about the whole SDP mangling thing.  I was thinking only of the case where you know, say, G-729 is available on one side and not the other.  You know you need transcoding so you send rtp through the transcoder and tell each side it is using what it wanted.  In reality the SDP has to be looked at from both ends and then a choice made to use the transcoder if nothing matches, and then modify the SDP for the far end to reflect what it is getting.  It would not be desired to send rtp streams through the transcoder if both sides were already supporting a given codec.
>

... lets assume the standard scenario: Alice calls Bob. Alice offers 
G711, G722 and G729. When the INVITE arrives at the proxy and *before* 
it goes out to Bob, MediaProxy module kicks in and mangles the SDP. At 
this point we don't know what Bob's answer will be, so what should we 
put in there, the transcoder IP and port or the relay?

We can only know this once Bob answers, but the it'd be too late to 
activate MediaProxy for Alice.

> I bet this gets a lot more complicated than I was picturing up until now.  :>
>

Feels like it ;-)

> However, I'm thinking there might be a demand for this so Sangoma may have a compelling reason to invest the work required for it.
>

In a B2BUA scenario this would make more sense, since you can start 
without the transcoder and if you detect it's needed, you could reINVITE 
both parties and put the transcoder in the middle. In a proxy scenario, 
OTOH, I find it utterly complicated.

Anyway, don't take my word for granted, there could be something obvious 
which I am overlooking here.


Regards,

-- 
Saúl Ibarra Corretgé
AG Projects