Well, we can confirm that what you described is indeed weird, but so far we haven’t been able to reproduce the problem. We tried running the composition for several minutes on two different computers.
If I convert to a H264 movie then all is well. This might point to a movie issue(?)
Vuo would be using its FFmpeg player for the H.265 movie. For the H.264 movie, depending on the specifics of the movie file, Vuo could be using either the FFmpeg player or the macOS AV Foundation player. If it’s using a different player for the two movies, that could partly explain the difference.
BUT, if I change the “missingcolour” value in the shader (which isn’t used to display the frames) to say (0.0,0.0,0.0,0.01), or (1.0,0.0,0.0,0.0) then it works fine.
The fact that the downstream Shadertoy node can somehow affect the movie image suggests either a macOS OpenGL driver bug or some sort of race condition in Vuo’s use of OpenGL.
Perhaps the problem only happens with certain GPUs?
Since you’ve found a workaround, and since we’ll be converting Vuo’s graphics from OpenGL to Metal in Vuo 2.5.0, we’re thinking it would be better not to take a detour to fix this bug, unless new information comes in indicating that the problem is not specific to OpenGL.
I guess my question is, what different might be happening between the two resolutions in how reverse playback can occur?
Hard to say without seeing the movie files. Would you be able to provide examples? It might also help to see the ffmpeg commands used to generate the movies.
Why are the line feeds in my post being ignored?
We’ve moved to the new forum platform since your last comment, so the answer has changed somewhat. Both the old and the new platform allow Markdown formatting. In strict Markdown, if you have a paragraph followed by a numbered list or vice versa, you have to put a blank line in between. The new platform’s Markdown parser is a little more relaxed, but check the preview of your post to see if you need to add blank lines.