[Ekiga-list] Receiving SIP RTP before media description [was ekiga answers with delay ...?]

[Craig Southeren]

On Mon, 27 Nov 2006 10:42:01 +0100
Damien Sandras <dsandras at seconix.com> wrote:

..deleted

> Well, let's forget about that and summarize the results of that
> discussion. There are actually right now 2 problems in OPAL :
> 
> 1: Establishing the media streams after having sent or received the ACK
> takes between 1 or 2 seconds during which the media stream is lost.

This seems to be only a problem on Linux. I'm not seeing this problem on
Windows.

What is OPAL during the 1 or 2 seconds? Is this how long it takes to
open the sound device on Linux? I'll need more information before I can
work out how to fix the problem

> 2: If OPAL sends an INVITE with 3 codecs in a given order, and that
> Asterisk supports the 3 same codecs but with a different priority order,
> it will send the 200 OK with those 3 codecs in the order it prefers.
> OPAL will then choose the codec it prefers and send the media with that
> codec. It could happen that Asterisk uses another codec from the list,
> ie a codec for which OPAL is not ready to receive a stream.
> 
> e.g. :
> INVITE PCMU, iLBC, PCMA
> 200 OK iLBC, PCMA, PCMU
> 
> OPAL will send the stream using iLBC.
> Asterisk could decide to send the stream using PCMU.
> However OPAL expects iLBC...

Replying to an INVITE with more than one codec has a very specific
meaning, and OPAL does not support these semantics. Fortunately, very
few devices seem to do this.

   Craig

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 Craig Southeren          Post Increment – VoIP Consulting and Software
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