[Asterisk-video] How to test Video conference with Asterisk

[tran quoc tuan]

Hi all,
I'm newbie in Asterisk, but I want to test a application conference
with Asterisk.
I have chosen the app_conference to test. I have installed Asterisk
1.6.2 from source code in Ubuntu 9.10 and installed patch for
app_conference. I have used client softphone : PortGo, X-lite, Ekiga,
Next I have tested my system. But I only create successfully a
conference with audio. And wiith video, I have only seen the video
local from webcam, I didn't see the video from other participants.  I
think that the problem is Asterisk or app_conference, because I can do
a video call from 2 user Ekiga,

Anyone has tested successfully with Video conference ? Could you help
me to implement this app for conference ?
Thank in advance for all helps!

Best regards,
T.Q.Tuan