Strange inconsistency between shotcut preview and generated video

Strange… Please have a look on first image I’ve attached in this thread (when reporting bug). Just please be sure that you watch it full size as it’s very big image. This line is not visible despite high zoom. Also when exporting frame to png it was not visible.

But more tricky and interesting why it’s added and if it’s possible to modify somehow algorithm to make it not to appear? Sure I don’t think about my single case but this case my suggested that sometimes some strange artefacts might be added at the corners of the image which is not sth expected by user.

Perhaps you can take a screenshot using the MLT you posted in that zip file.

It’s hard to tell what’s going on in your original posted screenshot. You have at least 1 filter on the Output, at least 1 filter on all tracks, and more tracks that are not visible.

When it comes about initial (big) project: 1 filter on Output it’s only sound filter. Filters on tracks are sharpen filters only. Also other tracks are not important as they are either empty either contain only transparent images (generated from shotcut) (at least in this place). Moreover also this small mlt project which I prepared for you, which is so simple, also has this problem. And the screenshot from mlt project (from zip file) is exactly the same as first screenshoot in this thread when it comes about video preview. There is no this additional line above. I’m attaching the screenshoot from it but I have bad impression that you don’t trust me and what I write and I have to prove everything with screenshoots… :frowning:

When I made my comparison screenshots I always zoomed in 100% in the Shotcut Viewer to give a good common view that anyone would be able to see.

How far are you zoomed in with your screenshot?

Here I am zoomed in at 100% in the Shotcut preview window.

And this is not zoomed in. Here, I do not see the second line. And I wouldn’t because of the zoom level in the player. Not enough room for pixels in such a small space. Zoom Fit is the default.

Not at all. I’m just trying to get some baseline to effectively compare that anyone could easily perform to duplicate the issue.

At this point, I have no idea how to help further.
Feel free to use the image I fixed in your project if you wish to. :smiley:

I zoomed shotcut preview to different values. 100%, 300%, 400% and the line is still not visible. I exported frame to png and also zoomed in in graphical software to different values and there is no this line…

Do you know if upscaling algorithm is embedded in shotcut code or is any linux available library used? However it might be not just pure upscaling but also something also which has impact…

From your MLT file at 1:00

100% zoom in Gimp

Ok man, I understand that you have different situation than me. But even if we keep this case why you can see this and me not as not solved, the question is also why this line appears and it shouldn’t.

Sorry the fact that you are attaching more screenshoots doesn’t change anything here. It’s the question if someone could analyse algorithms to determine the reason. Sure it’s not the most crucial bug in shotcut but it seems that something is wrong here.

It appears because of the use of the invert filter against your image. The line has always been there, it’s more visible with filter usage.

This is the reason why I chose to use Gimp to change the scaling and fix flaws with the image.

This viewing the original image in Gimp. The line is a part of the image.

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Please have look on the GIMP screenshoot of the original image (the only operation is invert and then zoom). I can’t see this line.

Are you sure that in GIMP you analysed the input png image and not keyframe generated from shotcut?

You are showing it in your screenshot. It’s 2px border.

Yes. Also showing a 2px white border. 800% view zoom. I moved the image away from the side/top so you can easier see where the edge of the image is.

No man, that’s not this border. It’s simply background. And this should be black thus not visible. Please analyse this once again. The part you show it’s background as also the part inside this frame. And you have only ONE frame here. While in the output from shotcut you have TWO frames.

When you invert an image, background will become the forground.

Well perhaps I should be more precise to write additionally which image I mean etc.

However @TimLau please make me a favour and please download this zipped shotcut project, please open NARCYZ-270-lepsza-jakosc_PRZED_KOMBINACJAMI_Z_WIDOCZNA_LINIA.png file and please check if it has single border or double border :stuck_out_tongue:

I downloaded your zip file an rendered the project (default profile)

I don’t see the double line in my render

Did you use the same export parameters like mine (in particular Lanczos algorithm)?

I just used the default one in shotcut. if it work then every thing is good in my book

You should properly cleanup the source picture, it is really crappy quality.
You can invert it and make it real black and white (or black and green) in gimp
It is a waste of resource to use so many filters to get what you want, because you source image is really crappy quality, much better to clean it up and use shotcut to do the animation.

Ok it might be good in your book but it’s not in other’s book.

I wrote precisely all the export parameters. And those parameters in combinations of filters causes that some additional artefact appear on the image.

If I should to clean the image or not, it’s another story and let me allow to keep it as it is. There is few pixels empty space between the borders of the image and something which is painted as the border in the image thus it shouldn’t have any impact on “creating” this additional line. Moreover other graphical programs doesn’t have any problems with interpolation of this picture, including GIMP. The quality of image doesn’t have any influence for this bug or not so let’s keep the main subject.

So there is sth wrong here definitely and for me that’s not the question of the discussion. We might for sure discuss what priority error is that and probably it’s low priority as there have to be special circumstances to “create” this additional line (in practice those errors make visible problems probably very seldom). However on the other hand, if something is working wrong here, that it might also cause some artefacts in other situations. Also including some things which are hardly noticeable like bad impact on sharpening.

Sorry, I don’t know what is ur role in shotcut project. And I’m not going anyone to “force” to correct the bugs I’m proposing. I’m only wondering how many people decided to stop using shotcut because of many probably small bugs but taking into consideration their number that caused them to move to sth else. My patience is close to the limits. And I’m deeply surprised that such a good project at first glance is loosing so many points just because of high number of bugs.

I am just a normal user like you, but I don’t experience all the strange “bugs” you are seeing
It is the result that matters, but if you work bad source files it need a lot of filters to try to clean things up, it is much easier to cleanup your source files. less work and a better result, no need to make it harder for yourself

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I also wonder that. But there will never be a way to find out. It is interesting (and sometimes frustrating) see how different users can have such different experiences. One user reports that Shotcut crashes all the time. Another user reports that it never crashes for them. One user reports that Shotcut has poor performance on their high-end machine. Another user reports that Shotcut has good performance on their low-end machine. I can only contribute these inconsistencies to the infinite varieties of ways that Shotcut is being used - and the infinite variety of different computer configurations that it is being used on. I do not think that Shotcut will ever be able to work perfectly for all uses on all computer configurations. I just hope that some people find it useful.


consider not all persons agree on anything.

My experience with Shotcut is the USER (myself included) are the limitation / problem / complaints like your experience.

Shotcut is better than great - learn how to use it’s amazingly vast functionality - then critique.

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