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multicast relay and packet loss

Greetings

I've setup a relay to take an announced unicast from QTB on OSX 10.2.3 to DSS 4.1.2 running on a Solaris 8 box which then multicasts the streams. This will eventually be used to relay to other sites via similar relays.

The relay is working but am getting way too much packet loss. QT (v 6/6.1) clients when tuned in to the multicast reports 2-4% ave, 10-15% max packet loss and poor video quality.

However if I use QTB to send direct to the same multicast address/ports I get zero packet loss and good quality.
Also if I use QT client to rtsp in to the DSS (unicast) I also get zero packet loss and good quality.

So the problem seems to be only when I'm relaying unicast to multicast.

I'm using MPEG4 video/audio, all computers are on the same 100 Mb switched LAN (at the moment for testing).

The above packet losses are for a stream with max bit rates around 300 kbps. I've also tried 1 Mbps and the packet loss increases to 5-15% ave, 15-40 % max.

The DSS CPU load reports at around 2% at 0.3 Mbps and ~4% at 1 Mbps. There is virtually zero additional load on the relay machine from other processes during my testing. There are no problems with port configurations on the computers and switches e.g. duplex mismatches.

Side-by-side QT clients (1 OSX, one XP) show identical packet loss patterns.

Any help appreciated.
regards
warren

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Warren Jones http://homepage.mac.com/warrenj/
Perth, Western Australia
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