[Standards-JIG] Re: [Psi-devel] Re: Implementing voice conversations in PSI

Cesar Martinez Izquierdo listas at ono.com
Sat May 14 16:46:07 UTC 2005


El Sábado 14 Mayo 2005 11:03, Nolan Eakins escribió:
> Do look at TINS. It's a JEP and will most likely be what other clients
> implement unless something better is found. I don't have the knowledge
> to know if there is anything better, but I looked through some of the
> SDP and RTSP(?) RFCs and was surprised by whats in there. They would
> definitely be worth exploring.

My project at university is about studying the different ways to implement 
videoconference in Jabber.
I've found that the best approach is to negotiate a SIP connection in a 
similar way as you negotiate a file transfer, and then just use SIP protocol 
to perform the conversation. (Of course, this is only my personal opinion).

The main problems of TINS are:
- the client developers are not very enthusiastic with it (and thus they are 
not implementing it)
- TINS makes mainly the same as SIP+SDP, but it uses some XPPP commands + SDP.
While this makes TINS more XMPP-friendly, it breaks compatibility with SIP, 
which means that you can't use existing SIP libraries (so more expensive 
implementation), you can't phone directly to Voip providers (which are mostly 
using SIP) and it doesn't offer a clear advantage over the SIP+SDP approach.

For finishing my project, now I need a proof-of-concept implementation, and I 
will not use TINS (because I've concluded that the other approach is better).

Now, let's speak about PSI.

We can define some steps:

- First of all I will create the proof-of-concept implementation for my 
project at university. I'm quite in a hurry, so maybe I will not care about 
the interface and maybe I even use an external application for perform the 
actual phone call. I'm understanding the PSI code quite fast, so I think I 
will have something working really soon (but it will not be suitable for 
official PSI, for sure).

- After this, we can discuss in which way we prefer to have voip in PSI, 
either with TINS or developing further the code I did in the previous step.
Note that I'm not against TINS, despite I'm not using it for my project. If we 
conclude that we prefer TINS in PSI, I'd be happy to work on it.
We can also discuss about how the interface should look.
And then we can finish the voip implementation. I think we can reuse some SIP 
(or SDP if we implement TINS) libraries, but we'll see.

But I repeat that I'm currently in a hurry about my project, so I'd prefer to 
don't spend too much time now discussing about this implementation. In some 
week I will show you what I did, and then I'll have time to properly discuss 
about the better implementation in PSI.

(By the way, you metioned SDP and RTSP. SDP + RTP are what both SIP and TINS 
use to negotiate and preform the conversations, as far as I know.
And I didn't know about RTSP, I'll have a look).

Regards,

  César



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