Trouble with an mp4 (OK in VLC, OK in Gem, not OK in Jitter)

I'm having trouble with jit.movie vs mp4s assembled from separate image files.

I had, in the past, downloaded some abstract animations (as GIF) and separated those into a series of jpgs.

I had thought that in Jitter it would be easier to pack them into a video file and use jit.movie. So I ffmpeg-ed them, and I have a video that plays correctly in VLC (and which displays most of the frames correctly in Pure Data / Gem with pix_film).

However in jit.movie, I get garbage -- at left is a pwindow, at right, a Gem window.

I'm wondering, then, if there are known restrictions about video encoders, or recommendations for encoders that are more likely to work. ffmpeg libx264 in this context is a problem (although I tried with a different video encoded by ffmpeg libx264, and it was fine)... I'm not sure where to start troubleshooting when the video looks OK in other software but not Jitter.

As a workaround, I suppose I can Uzi and load the jpg files into a jit.matrixset -- a bit more logic than I wanted to get into with the students, but should work...? (Edit: Got the loading part right... I always forget the "bang" after "importmovie" lol.)

hjh