one way video capture only while both side sending streaming

[frankcch]

Hi,

I have two windows XP/PCs, both have 2.7 GHz CPU, one PC1 with ip 192.168.2.101, and another PC2 with 192.168.2.102. Both PC1 and PC2 set up to capture RTP streaming and send RTP streaming in both direction. But only one PC can capture the video streaming.
The other PC cannot capture streaming.

PC1 (192.168.2.101) <---------RTP-------> PC2 (192.168.2.102)
capture streaming <------- RTP ----- send streaming
send streaming --------- RTP -------> capture straming

Here are the set up
PC1 (192.168.2.101) set up
vlc --rtp-caching=300 rtp://@:1234
vlc dshow:// --sout #transcode{vcodec=h264,vb=800,fps=5,scale=1,acodec=none}:rtp{dst=192.168.2.102,port=1234,mux=ts}"

PC1 (192.168.2.102) set up
vlc --rtp-caching=300 rtp://@:1234
vlc dshow:// --sout #transcode{vcodec=h264,vb=800,fps=5,scale=1,acodec=none}:rtp{dst=192.168.2.101,port=1234,mux=ts}"


Problem: most of time only can capture one way video only and it take 10-20 seconds to capture the video, the other side without out video.

For example,
Both PC1 and PC2 are set up to capture and send streaming.
PC1 takes 10 seconds to capture video sending from PC2, and PC2 cannot see the video sending from PC1.
If PC2 stop sending streaming, then PC2 is able to capture video which sending from PC1,
If PC2 start to sending the streaming again, then most of time has only one PC can capture the video.

Both PC1 and PC2 CPU rate around 60% only, and I can see the both PC1 and PC2 do send and receive packets from sniffer, without lost any packets. But one one PC can capture the video.
I tried different vb, fps, and caching, but problem is still there. I am wondering where the CAPTURE is not running (or not activated) while sending streaming. The video capture is there if stop sending streaming.