Dissolve transition in images over a video have a weird transparency effect

Mostly of my videos have images over a video. I’m using the dissolve transition to make them appear (10 or 30 frames duration). Until the v19.01.27 I have not problems, but after that version, the transition have transparency and the video beneath can be seen.

The only solution is put the images in differents tracks and apply a fade in and out to the superior, but this dupplicate the time of the process and make the project more ram consuming.
I want to use the update version of Shotcut, but with this little problem I go on with the obsolete version.

Any advice to avoid this problem? How can I make this transition works as before?

1 Like

It was changed to fix a bug when transitioning between images with differing alpha channels. The only solution is workarounds. Another workaround is to make a background with the desired shape and place that in a track under the transition.

I notice that this happens with PNG images (with alpha channel).
It does not happen with jpeg (without alpha channel), so this could be a solution to your problem.

Thanks a lot to both of you for the answers. I will try with the multiple tracks or with the old version. The change to jpg it’s gonna be a mess (a lot ot images in a lot of projects) and I tried others programs that don’t have this problem, but I prefer the timeline, transitions process and others features of Shotcut.

To better understand the fixed issue in versions older than 19.01 create a transition between two text clips A and B on a track above video.

Due to incorrect alpha compositing, A does not fade out and B fades in from black when not requested. Here is how it looks in the current version

1 Like

Does it help if you add a filter to your images to make the alpha channel opaque? For example, you can add Alpha Channel Adjust with threshold mode and set the amount to 100%:

I did not try this for your specific situation. Might be worth a try.

1 Like

Making the images opaque defeats his goal because you can see in the screen shots the image is a rectangle with rounded corners. The problem does not occur with opaque images.

I already tried the alpha adjust and didn’t work.
It only makes that the transparent zones of the image be white and occult the video in the background.

I rounded the corners of two images and saved as PNG to preserve transparency in those corners (as in your example).
I created a standard Dissolve transition, dragging one clip to the other. Then I add an Alpha Channel filter: Adjust - Threshold - 40%.
You can see how well it works.
Without the filter, the light rays of the video are seen underneath the transition. With the filter activated, this transparency disappears.
I hope this helps to solve your problem.
This is what @Brian indicated but without Invert and with a different amount value.

1 Like

@ejmillan Thanks, that solution works, but I will need to put the filter in every transition. It’s the Threshold option that make the magic, I can put a 0% and this filter works… Time to try that with others images because this error happens with all PNG images, with or without transparency. With images that covers all the video happened the same.

In your case, it works with 0% because in both images there is a black background. I tried with transparent images of non-rectangular shapes and the threshold has to be adjusted.
In my case, there are two images with different color backgrounds so in my case the value 40% does the “magic”.

Then that will be a problem, every transition will need to be adjusted. The other solution, differents tracks and fade-in/out will be easier.

I am sorry I cannot be of more help.
Best regards.

1 Like

This topic was automatically closed after 90 days. New replies are no longer allowed.