Alpha compositing fails when the bottom clip is introduced first.
@bens
Submitted by bens Assigned to bens @bens
Description
If I do the following:
- Drag transparent clip to the top video track on the timeline
- Drag opaque clip to the second video track
then alpha compositing in the preview window works as expected. However, if I instead do:
- Drag opaque clip to the second video track
- Drag transparent clip to the top video track above it
(i.e. reverse the order of these two steps)
then compositing does not work as expected. Instead, the alpha channel of the transparent clip is ignored, so that all I can see in the preview window is the non-alpha values of the transparent clip.
This behavior is not accompanied by a traceback.
The behavior is highly reproducible with my particular test set, which weighs 4.5 GB and consists of a transparent raw AYUV MKV (4:4:4) and an opaque HuffYUV-AVI (4:2:2). However, it is not reproducible with all files; tests with PNG images did not show the problem.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=634951