I am trying to establish a video call with with UCMA 2.0. But, I always end up with establishing an audio call.
I found that default value of the DefaultMediaType property of the AudioVideoCall is MediaType.Audio.
Sample code is:
_call = new AudioVideoCall (_conversation);
_call.DefaultMediaType = MediaType.Video;
call.BeginEstablish(_yourSipUri, null , CallEstablishCompleted, _call);
Do you guys know the right way to establish a video call between users with UCMA 2.0 and OCS 2007 R2?
UCMA doesn't support this, for a number of reasons. The primary being that there isn't anything UCMA can do with the video stream. Unlike text and audio, UCMA cannot do any recognition against video and it cannot generate any video.
UCMA can recognize what you speak or type, and it can generate text or audio (using Text-to-Speech) responses. Video is very different, it cannot recognize images and it couldn't generate any video responses. While the technology exists to do these things, they are far beyond the scope of what UCMA can handle.
Another important thing to remember is that not all callers have video support, and even fewer have a camera with the quality required to do recognition. Video is still very expensive to work with (both computationally and in bandwidth). I expect you won't see support for it until systems like Kinect (with high-quality cameras and built in recognition capabilities) become commonplace.
You didn't mention what the goal of this was so I'll make a small assumption that you're looking for a way to initiate a video call between two parties programmatically. If this is the case, what you really want here is the Communicator 2007 (of Lync 2010) SDK. This is an SDK for automating the communicator client itself.
Communication 2007 SDK: http://www.microsoft.com/download/en/details.aspx?id=10176
Lync 2010 SDK: http://www.microsoft.com/download/en/details.aspx?id=18898