I'm experimenting with mixing two Quicktime movie files as textures in OpenGL. I've gotten it to work starting from OneSadCookie's excellent QTValuePak (thank you, OSC!), but my app crashes frequently.

I see this problem more with large movies and ones that use codecs that are more CPU-intensive. I can also trigger a crash by causing spikes in processor workload from other apps, messing around with exposé for a minute is a sure way. Movie playback will generally get gradually out of sync as my app doesn't get enough cycles, and finally crash with a SIGBUS error. If I keep it well-fed with cycles, though, it'll generally be stable.

Now, I understand that this type of error comes from trying to address a memory resource that, for some reason, is unavailable or nonexistant. The backtrace after such a crash always points to some function in Quicktime. e.g:


So I'm thinking that it might be one of the OpenGL-calls (glTexSubImage2D specifically) conflicting with what QT is doing in MoviesTask, as they use some of the same pointers.

That's why I'm asking all you QT-gurus out there

- if that indeed could be the problem, and
- what can be done about it.

Specifically, is there a simple function to ask QT if it's done with decompressing? I'd rather drop a few frames than crash every five minutes..

This is of course all assuming that you can understand my question at all. I'll gladly provide more info if needed.

Thanks & goodnight (5 AM overhere)

Have you looked at Apple's sample code showing QT movie texturing?