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IDProjectCategoryView StatusDate SubmittedLast Update
0001485KdenliveTransitionspublic2010-03-07 08:232012-09-26 02:23
Assigned To 
Platform32 bit intelOSopenSuseOS Version11.3
Product Version0.7.7 
Target VersionFixed in Version 
Summary0001485: Image Alpha Transparency does not work as expected
DescriptionImage Alpha Transparency does not work as expected

Track 1 - png or svg image with alpha transparency
Track 2 - nothing
Track 3 - clip (video or image)

Image on track 1 has to have a composite transition to display its alpha transparency. This is wrong wrong wrong. Kdenlive should natively use the alpha transparency of the image.

And apply that over all of the clips below it, not just the immediate clip below.

In the above track description, the alpha transparency does not work because there is no clip in the track immediately below.

Alpha transparency should be applied to all tracks just as in any standard graphical program such as Gimp, Photoshop, Inkscape does with layers, allowing all layers below to show through.

This makes persistent titling (a title that spans many clips) extremely painful to implement and just plain impractical.

At the moment, I will have to resort to rendering the whole clip and then creating a new project to apply the title over the whole of the clip.
Steps To ReproduceTrack 1 - png or svg image with alpha transparency
Track 2 - nothing
Track 3 - clip (video or image)
TagsNo tags attached.
Build/Install MethodDistribution package
Attached Files

- Relationships
duplicate of 0001500new SVG Does Not Render Propely 
has duplicate 0001456new no anti-aliasing of transparent title clips without compositing 
related to 0001713assignedddennedy Font antialiasing only with background color? 

-  Notes
ttill (developer)
2010-03-07 09:56

To apply the composite transition to a track other than the one below you have to choose a track for the transition to apply on (can be found in the upper right corner of the transition tab).
But for sure it is not ideal that way.
LeHomard (developer)
2010-03-08 10:57

The composite transition is really just an ugly hack. Having a simple option to activate it(maybe directly in the clip's right click menu) would make life so much easier.
This would simply take into account the alpha channel (from pictures and videos) and apply the compositing to all tracks.

Combine that with clip positionning (perhaps simply a keyframable "position" effect) and you would get quite nice compositing possibilities.

I've started to look into the Kdenlive code, but this is a really advanced feature and I doubt I'll get anywhere anytime soon.

To my mind this is maybe THE most important new feature Kdenlive could get. (Well that and having audio fade-out and volume effect work together...)
neoarttec (reporter)
2010-03-10 03:57

ttil, that is not a viable option. I have a title with alpha transparency the I want to float above multiple clips as the time line progresses, so applying the alpha to just one track will not serfice.

I agree with LeHomard, it is one of THE most important features Kdenlive shoud get.

Until then, I'm going to have to render the whole project, then create a new one with the rendered clip and overlay my titles there.
neoarttec (reporter)
2010-05-02 09:47

Actually, I've discovered I can import other kdenlive project files into the current one. This allows me to composite the layering of alpha transparencies I want. Which proves it is not a deficiency in MLT but Kdenlive.

Its a work around that has give me a new interesting workflow. what would be also great to see now, is the ability to expand, collapse or edit these imported projects.
jpsantos (reporter)
2012-09-26 02:23

I need to add something to this that is a HUGE problem for me.

Currently anything with alpha transparency is not 100% transparent. It leaves a kinda "green" color that is extremely visible on light backgrounds to it. I do an intro outro to some vidoes with multiple tracks of PNG files (I've tried the same with SVG but the problem persists!), with the multiple composites the green is much much more pronounced. I was using OpenShot to generate these before, but OpenShot is currently in a state of complete uselessness at the moment if you try to run it in a system with the latest kdenlive & mlt libraries installed, and up until recently it didn't display this. Now it seems to do the same thing - which leads me to believe this might be something going on in MLT, but you guys will have to tell me.

I'm happy using composites, but having this GREEN layer is a dealbreaker and I don't have an alternative in which to animate these intros/outros at the moment, and frankly it should just work here without adding that nasty green.

- Issue History
Date Modified Username Field Change
2010-03-07 08:23 neoarttec New Issue
2010-03-07 09:56 ttill Note Added: 0004791
2010-03-08 10:57 LeHomard Note Added: 0004796
2010-03-10 03:57 neoarttec Note Added: 0004801
2010-05-01 08:44 ddennedy Relationship added duplicate of 0001500
2010-05-01 08:49 ddennedy Relationship added has duplicate 0001456
2010-05-02 09:47 neoarttec Note Added: 0005099
2010-07-29 20:17 Granjow Relationship added related to 0001713
2012-09-26 02:23 jpsantos Note Added: 0008397

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