On 4/9/10 3:00 PM, Blaise Gassend wrote: > I wonder if the following is happening: > > 1. You are saturating your network connection. > 2. The packet size on the TCP connection carrying your camera data is > maxing out. > 3. Because you now have mostly large packets, your probability of a > packet error increases. > 4. Your adapter realizes that you have a lot of errors and decreases the > data rate. (Can you confirm where you are getting the data rate from?) > > Things you might want to play with are the fragmentation threshold > (fragment large packets so that they get through), the RTS/CTS threshold > (use RTS/CTS to clear the channel for those large packets). > I'll play around with this and see what happens. > You might also want to use tcpdump to confirm that your packets are > indeed large. > The man file isn't particularly useful for figuring out how what the output means, so here is a few lines: 15:04:57.045705 IP toil.robots.cse.wustl.edu.53552 > 192.168.1.115.49680: . 931064:932512(1448) ack 1 win 108 15:04:57.045710 IP 192.168.1.115.49680 > toil.robots.cse.wustl.edu.53552: . ack 931064 win 33304 15:04:57.045711 IP 192.168.1.1.http > 192.168.1.115.49706: P 1:351(350) ack 597 win 6556 15:04:57.045777 IP 192.168.1.115.49680 > toil.robots.cse.wustl.edu.53552: . ack 933960 win 33304 15:04:57.045809 IP 192.168.1.115.49706 > 192.168.1.1.http: . ack 351 win 33129 > Have you tried using compressed image transports? > I've tried with raw, compressed and theora, all with the same results > On Fri, 2010-04-09 at 14:34 -0500, Dan Lazewatsky wrote: > >> Hi all - >> This isn't strictly a ROS question, but I was hoping people here would >> have some thoughts. I'm grabbing video off a webcam on my robot and >> using image transport to stream it to another computer on the same >> wireless network. I'm having a problem where shortly after I start >> subscribing to messages, my network latency skyrockets (like 1000ms+ >> ping times for computers on the same network, and bit rate on the >> robot's wifi connection goes down to 1Mb/s from 54Mb/s). I had fixed >> this problem a while ago by letting the router choose which channel to >> use, but the problem came back and I haven't had any luck fixing it. >> It's not a signal strength issue - iwconfig shows a link quality of >> 90/100 or better. Any suggestions as to what might be going on would be >> much appreciated. >> >> (I'm using a WRT54GS with DD-WRT) >> >> Thanks, >> -Dan >> _______________________________________________ >> ros-users mailing list >> ros-users@code.ros.org >> https://code.ros.org/mailman/listinfo/ros-users >> > > _______________________________________________ > ros-users mailing list > ros-users@code.ros.org > https://code.ros.org/mailman/listinfo/ros-users >