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Re: [Linphone-developers] oddities with Linphone's handling of USB camer

From: Simon Morlat
Subject: Re: [Linphone-developers] oddities with Linphone's handling of USB camera / microphone
Date: Sun, 19 Jul 2009 15:34:33 +0200
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> Setting the remote linphone's MTU to 1200 worked like a charm.  Thanks
> for the precise solution!
> Is this a bug that should be formally documented somewhere?  (Or
> fixed, if the fix is "obvious"?)
I don't remeber since I fixed a bug around packet segmentation since version 
3.0.0 (we are at 3.1.2 right now).
Linphone uses a well known algorithm called "mtu discovery" to discover the 
mtu to reach the other end. You can see related traces in the log. This relies 
on the fact that the routers can send back an ICMP packet in case of mtu 
exceeded. If for some reason this ICMP packet is not sent, or not received 
(because of a firewall that drops it for example), then the algorithm cannot 
work. It's not 100% reliable unfortunately. The detection might also be done 
correctly, but for a wrong ip address (thanks to firewalls).
It works at my home (i have a dsl router that limits at 1460 instead of 1500).
It seems that, in your case, your home linphone detects properly the mtu, but 
not the remote one.
A safer solution surely exists to solve this problem magically, but for now 
documenting this in the FAQ should be enough !


> > From what I see it is unrelated with the fact of using the webcam's
> > microphone or not.
> Yes, so it seems.  I will have to play around with the webcam and get
> back to you on that.  However, a solution to this other problem is a
> big help for me.
> Thanks.
>                               Jim

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