October 14, 2002

Replayed Dumped Video

Chema got back to me and informed me that vic actually listens for RTP streams on even ports only, and the RTCP stream should show up on the odd ports. This is probably mentioned somewhere in RFC 1889 but all I knew was that the RTP and RTCP port numbers were right next to each other. So I was able to use 'netstat -f inet' to figure out exactly which even numbered port vic was listening on for the RTP stream.

Once I got that figured out, I was able to get the receiving vic to acknowledge my recast RTP packets without sending the RTCP stream. However, my recast program was sending them back out way too fast for vic to display the frames; all it would show is the gray thumbnail. So I calculated the frame delay by taking the difference between RTP packet timestamps and reversing the formula used to generate the timestamps to get a delay time in microseconds.

With RTP packets going out to the correct UDP port and delayed to match the original send pattern as best as possible (as the timestamps are approximations themselves), the receiving vic plays back the recorded frames perfectly. Looks like this part of the project is complete. All I need now is the VQM Software.

Posted by josuah at October 14, 2002 11:24 PM UTC+00:00

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