Hi, I formulated my self wrongly, I meant sending multiple voice frames per RTP packet (ptime > 20 ms) The RTP/UDP/IP overhead is ~16 kbit/s for a single frame/pkt so for a low bit rate codec that is ~25 kbit/s and few GPRS links have that. Secondly latency is totally random from low ~50 ms to really high could be seconds in worse case. This at least our experience. BR/Olle -----Original Message----- From: Klaus Darilion [mailto:klaus.mailinglists@xxxxxxxxx] Sent: den 24 mars 2010 18:13 To: pjsip list Cc: Olle Frimanson Subject: Re: Debugging RTP packets sending Hi Olle! Am 24.03.2010 17:53, schrieb Olle Frimanson: > The I'm just querious how you should get PJSIP work on GPRS, all the > test we have done shows this is very hard in rel conditions even if you > send multiple packets per frame, especially on the uplink. Sending multiple packets can be counter productive. The GPRS devices I tested with did have a huge sending buffer, and GPRS has retransmissions on layer2. So, packet loss on the mobile link is really rare - also with bad connectivity. By sending packets twice you need double bandwidth and if the needed bandwidth is not available, due to the device's sending buffer the delay increases. I once did lots of T.38 faxing over GPRS. Everybody told us that we have an unreliable link thus we have to enable T.38 redundancy - but that was the totally wrong approach (as described above). Yes, GPRS is slow, but GPRS is rather reliable. Thus, once we turned-off T.38 redundancy we were able to fax over GPRS. regards Klaus No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.791 / Virus Database: 271.1.1/2763 - Release Date: 03/23/10 20:33:00
