Any way to get a thumbnail image from live stream?

I have been attempting to retrieve a thumbnail image from a live RTSP stream in Evostream using FFMPEG but have had no success. Although I do not have much experience using FFMPEG, I have tried many different command line arguments, such as the ones here http://superuser.com/questions/663928/f … 264-stream and here: http://stackoverflow.com/questions/1131 … ith-ffmpeg But always get the error: cannot allocate temp picture, check pix_fmt. Has anyone been able to successfully pull a thumbnail image from a live RTSP stream on Evostream, and if so, could you share an example of how you accomplished this? Thanks! Joshua