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Re: [Linphone-users] high latency network and linphone


From: Jan de Kruyf
Subject: Re: [Linphone-users] high latency network and linphone
Date: Tue, 21 Aug 2012 20:22:58 +0200

Hello Ray,
thanks an awful lot for coming back to me. Next weekend I will certainly do some playing about.
Problem is, as you might have guessed, that I know next to nothing about this technology.
But we live and learn.

Regards,

Jan.


On Tue, Aug 21, 2012 at 8:07 PM, MJ Ray <address@hidden> wrote:
Jan de Kruyf <address@hidden>
> However, I am hardly able to use it, when the latency on the network
> is bad (like now)
> Even in stretches where there is no yellow or red warning avbout the
> line quality, nearly all sound packets are dropped.
>
> At the same time Skype performs without a hitch on the same line and
> at the same time of day!
>
> I have attaches a copy of the log, for 1 call, to illustrate the problem.

Thanks for the log.  I've left the bits I found interesting below.

The line quality warnings aren't perfect.  Also, you can probably
assume Skype is doing whatever the code decides is best for Skype,
rather than what you're telling it to do, and that it's using some
pretty aggressive codec which might be secret or licensed
restrictively.  Linphone's not going to do much except what you tell
it and prefers freely-improvable codecs.

Firstly, it looks like whatever you're calling supports only PCMU,
PCMA, GSM and telephone-event.  None of those are great, but you
probably want to use GSM if you're having bandwidth problems.
Sadly, you seem to be using PCMU.  Sounds good but high bandwidth.
Disable that and PCMA and see if things improve.

Secondly, linphone says "Audio bandwidth for this call is 80".
Do you really have a sustained 80 (I think kbps)?  If not, set
a lower quality limit in the settings or configuration file.

Finally, there's a warning about alsa not supporting the period size.
I doubt that's a serious problem but it probably doesn't help make
it sound good when it does work.  I'm not sure but it might suggest
a hardware problem or deficiency.

Interesting log snippets only below:

> linphone-message : Received message:
> SIP/2.0 200 OK
[...]
> m=audio 35350 RTP/AVP 0 8 3 101
> a=rtpmap:0 PCMU/8000
> a=rtpmap:8 PCMA/8000
> a=rtpmap:3 GSM/8000
> a=rtpmap:101 telephone-event/8000


> linphone-message : Call 0x8944f40: moving from state LinphoneCallOutgoingProgress to LinphoneCallConnected
> linphone-message : Audio bandwidth for this call is 80
> linphone-message : Payload's bitrate is 80000
> linphone-message : Setting audio encoder network bitrate to 80000
> linphone-message : MSUlawEnc: got ptime=20

> linphone-warning : alsa_set_params: The period size 256 is not supported by your hardware.
>  ==> Using 170 instead.


--
MJ Ray (slef), member of www.software.coop, a for-more-than-profit co-op.
http://koha-community.org supporter, web and library systems developer.
In My Opinion Only: see http://mjr.towers.org.uk/email.html
Available for hire (including development) at http://www.software.coop/

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