How to use rtmpsrv/rtmpsuck correctly in Ubuntu 13.04

[StreamRecorder]

Here is how I use rtmpsrv/rtmpsuck

1. Added the rtmp user
2. Run the following in the terminal:
   

   sudo iptables -t nat -A OUTPUT -p tcp --dport 1935 -m owner \! --uid-owner rtmp -j REDIRECT
   sudo su rtmp
   rtmpsrv
   exit
   sudo iptables -t nat -D OUTPUT -p tcp --dport 1935 -m owner \! --uid-owner rtmp -j REDIRECT

The problem is that when I run the rtmpdump command, it finds the parameters, but I can't download using them because of an error. When I reboot my computer (Ubuntu 13.04 and 13.10), I can download the stream just fine. What am I doing wrong?

Another problem is that rtmpsuck makes my computer too slow (it almost freezes). Can it be caused by HD videos (h.264 1280x720 streaming videos from UStream)?