networking problem...losing packets...looking for ideas

[Chuck Crisler]

I am using GStreamer 0.10.30 (please, no comments) to send an H264 RTP
stream. This starts from a GStreamer RTSP server and the architecture is a
bit strange. There is an app that receives MP2T packets from the network
and writes them to the loopback interface after decrypting them. I have an
app that receives those MP2T packets and transmuxes them to RTP, also
writing the packets to the loopback interface. The RTSP server pipeline
reads from the loopback interface and writes to eth1. The problem is that I
seem to be losing RTP packets on the loopback interface. I believe this to
be true because I added a log message in gstrtph264pay.c to log the RTP
sequence number of each packet that is pushed and I compared that list of
sequence numbers to a packet capture. The logged RTP sequence numbers
monotonically increase but the packet capture sequence numbers show gaps.
Needless to say, the remote display is bad, which confirms that packets are
missing.

There is one important point to note. There are a lot of MP2T packets. The
average frame is 10-12 K bytes. MP2T packets have 188 bytes. The loopback
interface is quite busy.

IFCONFIG doesn't display any dropped packets or errors for the loopback
interface. The default txqueuelen for that interface is 0. I changed it to
1000 but that didn't make any difference. I added a call to usleep(500)
(500 microseconds) between packets (not frames) and that didn't make any
difference.

This system is running on a server that runs several LXC containers, so it
is virtualized. I don't know anything about the effect that has on the
loopback interface performance.

I am out of ideas. Can anyone make any suggestions?

Thank you,
Chuck Crisler
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