https://bugs.kde.org/show_bug.cgi?id=428794
Bug ID: 428794
Summary: fatal error on pixelize effect when the block size
becomes negative due to smooth interpolation
Product: kdenlive
Version: 20.08.2
Platform: Appimage
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Effects & Transitions
Assignee: vpi...@kde.org
Reporter: pierre.ner...@free.fr
Target Milestone: ---
SUMMARY
I start with adding a "Pixelize" effect to a clip. Then I add 4 control points
to drive the blocksizes X and Y. The problem appears with at least 4 points,
not with 3. I put 64 as block sizes for the first and the last, and zero to
both middle points. Then I choose Smooth interpolation for all. Kdenlive exits
immediately when playing the clip around the second point.
I think there is lacking some clamping of the blocksize in the effect. Due to
the smooth interpolation, the block size surely becomes negative, and the
pixelize effect throws an exception.
I would check the Pixelize effect source code, and add something to clamp any
negative block size value to zero, or clamp the value between the min and max
of the interface. Maybe the same problem could affect other effects? (I hope
no)
STEPS TO REPRODUCE
1. Add "Pixelize" effect to a clip
2. Add 4 control points, all with smooth interpolation, the two outer will have
64 as block sizes, and the two inner point have zero as block sizes.
3. Play the clip.
OBSERVED RESULT
Kdenlive quits abruptly when it is the time of the second point, after having
correctly played the effect with decreasing block sizes.
EXPECTED RESULT
Kdenlive should play the whole clip without exiting, and cope with any
accidental negative block size due to smooth interpolation.
SOFTWARE/OS VERSIONS
Windows:
macOS:
Linux/KDE Plasma:
(available in About System)
KDE Plasma Version:
KDE Frameworks Version:
Qt Version:
ADDITIONAL INFORMATION
To go around the problem, I added other control points with linear
interpolation. So it is not severe. Many thanks for your work (I say this for
every bug I report, but I think it every minute I use Kdenlive).
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