I think this is a repeat of 0001434.

I've been seeing this problem for ages (a year at least), but never managed to narrow down whether it was a bug in DCP-o-matic or something I was doing wrong. But I finally have a solid repro case, and it is a bug.

Symptoms:

With non-integer frame rate sources (e.g. 29.97 fps), once you have set a value for end trim, the preview window does not update properly.

1. Changing crop values is not reflected in preview. You have to step forward/backwards by a frame to see it updated.

2. If you change container from Flat to Scope after setting end trim, the preview window remains Flat ratio, and remains so no matter how much you skip around the timeline.

Steps to reproduce:

Problem 1:

• Create new DCP-o-matic project
• Add a video file with non-integer frame rate
• Set 'trim end' to 1 frame
• Set 'crop left' to 100
• Notice that there is no change in the preview
• Step forward 1 frame
• Notice preview now updates to reflect the crop

Problem 2:

• Create new DCP-o-matic project
• Add a video file with non-integer frame rate
• Set 'trim end' to 1 frame
• Change container from Flat to Scope
• Notice preview remains in Flat ratio

Weirdly, if you save the project and reopen it, the problem disappears.

Carl, this can be reproduced with the same source file I have sent you for 0001708.