[Serusers] Video quality !!

Hello list !! Now everything seems to start working. I am using ser 0.8.14, radius for authenticating and accounting and mediaproxy for proxy audio and video sessions between my network and outside or between different subnetworks inside my general network. Now the problem is that video quality (I am using Windows Messenger) is really really BAD. Audio is almost perfect but video is really slow and pixelized. All media traffic (RTP, UDP, H263) go thru my ser proxy but I don't understand why is so bad because ser does not touch these packets, just forward them, isn't it ?. I dont think is a question of my network bandwidth because is a local area network with some acls.... Does anyone have a similar problem ? Is there any way of knowing how much bandwidth needs the video session ? Is there a minimun speed and memory for my server for this scenario ? Thanks in advance: Kiko