The unsharp filter is completely broken. First of all, there are 2 of all parameters (e.g., av.luma_msize_x AND av.lx). Second, if you try to set av.lx big (like 17) the whole program crashes. Third, often the effect won't show up in the project monitor until you tweak them back and forth a few times. Fourth, the effect won't get applied during render, not even if it shows up in the project monitor.
When it crashes it writes this to the console: [filt @ 0x7faea3a2cb40] luma or chroma matrix size too big [filter avfilter.unsharp] Cannot init filter: Invalid argument Segmentation fault
If the crash is reproducible, please add the backtrace. For more information, please see https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
Created attachment 111534 [details] segfault stack dump
The segfault stack dump is using kdenlive 18.03.70 and mlt 6.7.0 where these problems still occurs.
“unsharp” seems to be the "movit.unsharp_mask" effect which is blacklisted. I see in Kdenlive 18.08.2 Windows version no effect as well. See bug Bug 399911
I get the error: [filter avfilter.unsharp] Cannot init scale filter: Invalid argument
With version 20.12 the effects get an update. Please try with the current Kdenlive AppImage version 20.12.2 https://download.kde.org/stable/kdenlive/20.12/linux/
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This bug has been in NEEDSINFO status with no change for at least 30 days. The bug is now closed as RESOLVED > WORKSFORME due to lack of needed information. For more information about our bug triaging procedures please read the wiki located here: https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging Thank you for helping us make KDE software even better for everyone!