The Dctdnoiz effect under the Misc effects in Kdenlive is very unstable and crashes the program. All one needs to do is to select some values for av.sigma and av.s then quickly select some random values with the mouse on av.overlap (click about 5 or 6 times quickly to select values between 1 and 12 or so). This will crash Kdenlive 17.04.01 running on Linux Mint.
Please try with the actual Kdenlive AppImage version 18.08.3 Run the Appimage from the terminal (press CTRL + ALT + T). Move to the AppImage folder and run the .AppImage: ./Kdenlive*.AppImage
The effect Dctdnoiz was black listed due to instability. We close this bug. If it still appears in the latest version, please feel free to re-open it and update the affected version number.