That’s really interesting, Glenn. To your original question, I don’t have a problem with The Incredibles render I did, which is around 150,000 frames. I did the Lego Movie too, which runs just as smooth. According to my debug output, they run at approximately 24fps. As I’m sure you know, my script above outputs filmstrip BMPs that are 2000 frames long, so I’m confused why your “few hundred frames” movie created multiple files. The very reason for the filmstrips is to keep the system from having to open new files for each frame. The whole Incredibles movie is only 78 BMP files, and switching files doesn’t appear to cause slowdown.
I would be curious if you experienced the same problem with a freshly formatted microSD card.
Nonetheless, your solution sounds like it creates much higher frame rate playback. I’m very curious what your file format looks like, and why it’s so much faster. BMPs practically mirror the frame buffer byte-for-byte.