This is a nasty problem, because it slowed down my editing during an IC
When I import a 1280x720 full length MJPEG encode of a movie (for proxy editing) into Adobe Premiere Pro CS5. Premiere Pro interprets the .avi as black still image.
When I import this sucker via AVS-script, I get a video with the proper duration, but everything is black.
MJPEG should work, because I also made short test clips and they worked as they should. Months ago I also used it with 1080p files in a project with CS5 and everything worked fine. Those files were 2 feature length movie encodes.
First I had MJPEG 3 on my system, but I upgraded to MJPEG 4. Same problem.