https://bugs.kde.org/show_bug.cgi?id=452121
Bug ID: 452121
Summary: Alpha channel missing in rendering
Product: kdenlive
Version: 21.12.3
Platform: Ubuntu Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Video Display & Export
Assignee: j...@kdenlive.org
Reporter: sebastian.guert...@gmx.de
Target Milestone: ---
Created attachment 147865
--> https://bugs.kde.org/attachment.cgi?id=147865&action=edit
Videoproject file used for performing tests.
Alpha channel missing in rendering, black pixels instead
***
Different behaviour in comparison to former version, here: 20.08.3.
STEPS TO REPRODUCE
Creating a simple short video with transparent alpha sections (file attached)
1. Put colour clip into project bin
2. Insert that clip in video track 2.
2. Add transform effect to that clip
3. Shrink clip to size 50%
Rendering "with alpha":
4. Render: Choose format: All formats "Video with alpha" tested.
OBSERVED RESULT
Works fine with version 20.08.3b (with formats VP8, VP9, MOV and custom prores
(f=mov acodec=pcm_s16le vcodec=prores_ks vprofile=4444 vendor=ap10
pix_fmt=yuva444p10le mlt_image_format=rgb24a qscale=%quality):
Results with 21.12.3 uniformly no alpha, just black pixels in the available
formats VP9, MOV, Ut; and in custom prores.
VP8 Crashes: "[libvpx @ 0x7fe6e0003740] Transparency encoding with auto_alt_ref
does not work Failed to copy encoder parameters to output video stream" (adding
auto-alt-ref=0 in the options prevents rendering from crashing but with same
result as other formats - no alpha)
SOFTWARE/OS VERSIONS
Ubuntu 20.04.4
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
MLT version 7.4.0
Difference to 20.08.3 where it works still properly: MLT-Version there is
6.23.0 (KDE Frameworks 5.74.0 and Qt 5.14.1 shouldn't be relevant).
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