Bug 456830

Summary:	Mix Clips compositions transition applies to lower layers
Product:	[Applications] kdenlive	Reporter:	Mihai Vasiliu <mihai.vasiliu.93>
Component:	Video Effects & Transitions	Assignee:	Jean-Baptiste Mardelle <jb>
Status:	VERIFIED FIXED
Severity:	normal	CC:	fritzibaby, mihai.vasiliu.93
Priority:	NOR	Flags:	mihai.vasiliu.93: low_hanging+ fritzibaby: timeline_corruption+
Version First Reported In:	22.04.3
Target Milestone:	---
Platform:	Microsoft Windows
OS:	Microsoft Windows
Latest Commit:	https://invent.kde.org/multimedia/kdenlive/-/commit/d1178a66be64026c5e8b24f70b19d33a8684875c	Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	project and files to reproduce issue Workaround with the desired behaviour

Description Mihai Vasiliu 2022-07-17 17:10:01 UTC

SUMMARY
When having at least 2 video tracks and using the Mix Clips transition between two clips from the same upper video track, the effect applies to the lower video track as well.


STEPS TO REPRODUCE
1.  Add a color clip on V1 track
2.  Add two pictures/images on V2 track one after the other (the V1 track must be visible on the background)
3.  Use Mix Clips to create a transition between the two.
4.  Play the video and see that the color clip on V1 track also reacts to the transition instead of staying unchanged.

OBSERVED RESULT
The color clip on track V1 gets darker as the transition occurs and then it pops up again when transition ends.

EXPECTED RESULT
The color clip should not be affected by the transition. The transitions should only dissolve the two image clips from track V2.

ADDITIONAL NOTES:
The same applies if I use normal legacy compositions between tracks V2 and V3, which is not desired.

SOFTWARE/OS VERSIONS
Windows: Windows 11

Comment 1 Mihai Vasiliu 2022-07-26 10:51:08 UTC

Created attachment 150920 [details]
project and files to reproduce issue

Comment 2 emohr 2022-11-11 18:46:23 UTC

Thanks for your report!
I can confirm this behavior following your steps. Something with track composition is wrong.

Comment 3 Mihai Vasiliu 2023-04-10 07:24:53 UTC

For anyone having the same issue or interested in fixing the bug, I have found a workaround:
If you add an Alpha Operations effect to both images that are meant to use the MixClips effect, the desired transition is now possible without the black bars.
Check out the workaround attachment.
So the issue is definitely with the alpha and must be addressed in the MixClips effect itself.

Comment 4 Mihai Vasiliu 2023-04-10 07:25:24 UTC

Created attachment 157986 [details]
Workaround with the desired behaviour

Comment 5 Mihai Vasiliu 2023-04-11 13:02:07 UTC

After finding out the the Alpha operations effect makes it work right, I tested out using png files with transparency instead of jpg files for the pictures. In this case the issue is no longer seen.

It doesn't matter what is the size of the png file, it is only important to have an alpha layer.
So, the fix for this issue should be something like, when using MixClips, it should automatically treat the images with a transparency layer even if the images do not have one.

Comment 6 Mihai Vasiliu 2023-04-17 11:24:47 UTC

Shotcut is already working on this.
We may need to port the changes from there.
See https://github.com/mltframework/shotcut/commit/6e5c57ef9edb06951cf972c4b5e1575f84265657

Comment 7 Mihai Vasiliu 2023-04-18 08:04:15 UTC

The commit in the MLT framework is this one: https://github.com/mltframework/mlt/commit/85d669e573d33ea7a786337a198e1c03620a1294

Comment 8 Mihai Vasiliu 2023-07-04 09:17:37 UTC

Anyone available to help porting the changes indicated from the Shotcut commit? I am not familiar with the Kdenlive codebase/repo.

Comment 9 Jean-Baptiste Mardelle 2023-07-13 06:32:01 UTC

 Thanks a lot for your report and investigation. This will be fixed in git master and for the upcoming 23.08.0 version

Comment 10 Jean-Baptiste Mardelle 2023-07-13 06:33:07 UTC

Git commit d1178a66be64026c5e8b24f70b19d33a8684875c by Jean-Baptiste Mardelle.
Committed on 13/07/2023 at 06:30.
Pushed by mardelle into branch 'master'.

Ensure luma transition considers padding as transparent

M  +6    -0    data/transitions/dissolve.xml
M  +3    -0    data/transitions/luma.xml

https://invent.kde.org/multimedia/kdenlive/-/commit/d1178a66be64026c5e8b24f70b19d33a8684875c

Comment 11 Mihai Vasiliu 2023-07-14 07:37:02 UTC

Thanks for your time to commit this fix! I really appreciate it and can start working again on my projects without any workarounds.

Confirmed fixed in nightly version 23.07.70 (rev. d2b889602)