problems in parsing RTSP stream which uses VC-1 codec

hello every one,

      I have to parse I-frame in the RTSP stream which uses VC-1 codec.

ffmpeg has open source code. I tried to print the information about the RTSP
stream which uses VC-1 codec using ffmpeg -i rtsp://ipaddress/rtspstreamname

I get the following error message "Error while parsing header" This stream
works well with VLC player.

IF ANYBODY HAS IDEA FOR MY PROBLEM THEN PLEASE LET ME KNOW.

*(For testing*
I had downloaded the whole RTSP stream using NET transport tool. And I
checked the video which is now in my local HDD and was in RTSP server, could
be able to print all its information using ffmpeg -i localHDD/videofile .
Also I could be able to separate the I-frames into another video file.
So the video file which is in the server has no problem. )

Regards,
Arang