Reference Video Clips for Video Compression Testing?

Hi Folks,

Are there any raw video clips (YUV 4:2:2, preferably)
that are known stressors on video encoders (e.g., MPEG-4 ASP,
H.264, etc.)? Is there a standard set of clips used for
verification of video codecs?

--Randy

Folks, I was hoping someone here can address this question. Please help
if
you can. I hate trying to pick something for my testing based on my own
ignorance of the subject.  Any help would be appreciated.

--Randy