Bug 428794

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).