Please try with the export defaults (Reset) instead of your custom.
Please try with parallel processing turned off.
A quick answer: as your suggestion, now It works (!!!) Later I will tell you which of the two setting generate the problem. Thx !
I made other tests. I summarize test done with converted input video :
custom export + parallel on = bad (we knew it)
no custom export + parallel off = good
custom export + parallel off= good
custom export + parallel on = bad (to be sure)
I made also tests with the original project where the input video is not-converted:
custom export + parallel on = bad (we knew it)
custom export + parallel off = good
I seems that the problem is not related to the input video (in fact Shotcut didn’t ask me to convert it when I imported It in playlist) but the parallel processing.
This makes perfect logical sense.
With a Constant Frame Rate (let’s use PAL 25 fps for example) the parallel threads are all looking at the same “truth” about time; a constant series of frames 40 ms apart.
But with Variable Frame Rate, perhaps three threads have seen that the “time truth” is “40 ms between frames”, but the fourth thread, having seen two frames 80 ms apart, is working from the “truth” of “there is 80 ms between frames”. So the algorithms become applied differently by the different threads, and the result would be as you have seen.
I do not think variable vs constant frame rate applies here because OP has converted the file - and converted files are always constant frame rate. But the premise of everything else you stated still stands. The filter relies on some cached state from the previous frame. If parallel threads work out of order, that could cause the cached state to be unexpected.
I will bookmark this to take a look later.
I missed that.
On further thought…
Cached by whom from what source? If time is being remapped, are we seeing a discrepancy between cached-before-remap and cached-after-remap, or something like that?
My tests had me arrive at a different conclusion. For me Parallel Processing is only an issue when a specific kind of video is used and the Convert To Friendly option is not used on it. For me that’s videos from youtube.
Here is a video demo I did using the Bruno Mars music video “Leave The Door Open” directly from the 4K youtube upload that we were using in the last thread for Time Remap here. The first clip and second clip are exactly the same in terms of the section that it is slowed down and both exports used Parallel Processing. But only the second video shows this flash at exactly 29sec19ms:
The difference is that the first export in the demo used a converted to edit friendly sub-clip whereas the second did not convert a sub-clip so it’s the youtube video as is allowed by Shotcut to use Time Remap on and it’s on that one that the above flash appears. Not in the demo but I can confirm is that if I turn Parallel Processing off then the second export without the converted to edit friendly sub-clip does not produce a flash in the clip.
Perhaps there is yet another category of video file that should get the “Convert to Friendly” popup.
Or perhaps only if Time Remap is selected on it.
I got a good result with Parallel Processing when I converted the youtube video to edit friendly. That’s the first example in my demo video.
Yes, I confirm: with or without Edit Friendly, with parallel processing turned off I got the good result.
I spent some time trying to reproduce this issue using the bruno mars clip. I have not been able to create the problem, but I do not know if I am creating your same scenario. Some questions:
- When the problem occurs, what is the frequency? Is it once per video or multiple times?
- If you export the same project twice, does the problem always occur at exactly the same time? Or is it random?
- Can you share the xml file from an export that created the problem (right click on an export job and save)?
Try again but make sure the Image Mode is set to Blend. Then export it once with Parallel Processing on and once with it off. What are your results?
@brian, did you get to try the above? I’m bringing it up again to see if it can get fixed in time for this month’s release.
I have not successfully reproduced the issue. Can you privately provide me a package that reproduces the problem?
- MLT project
- Referenced media
- Export job XML
@shotcut, I want to ask you if this is the kind of bug that could be fixed for the upcoming release. I haven’t supplied Brian what he’s asking for yet but I want to know first if I do it soon and he could fix it then if that fix could be included in the release that’s coming up. It is an export bug so I imagine so but I want to just confirm.
It would depend on the nature of the fix. If the fix is simple and low risk, then it can be included. If the fix is complex and risky, then it would wait for the next release and more testing since we already have a work-around.
@DRM have you had a chance to provide a test project? It would be great if I could reproduce this to fix it. Thanks!
Good news. Another users has reproduced this issue and submitted a fix for the 21.08 release: