Great work, @Paul2! 
Did you make the whole filter yourself?
I was testing this and here are some initial thoughts.
- The default settings for the filter should be something else with Frequency being higher. The default right now doesn’t show any effect happening immediately after choosing the filter.
- There is an error when the default buttons for Block and Shift are hit. If you change the values and hit default then it both will go to .5000. But if you hit them again then they go to .4991 and .4993 respectively.
- When you hover the mouse over where the number values are shown and move the center mouse wheel the numbers move in increments of .1000. I think it would be better if they move at increments of .0010 or .0100.
- Would the parameters be better if they were represented in percentages? So instead of the highest being 1.0000 it would be 100.00%?
- I’m wondering if there could be either a modification to the Block parameter or an additional control made that would allow to break up the blocks that appear into smaller blocks kinda like this:
- I wonder if the parameter for Color can be modified. Something like where 100% would be the default colors of the original video and if you go higher than 100% then the effect that is the same as is right now but if you go below 100% then the colors would desaturate. Desaturation could help achieve the classic VHS glitch that is usually seen in effects like this.
- This filter currently suffers from Bug #10 on my V19.02.28 Bug Report.
Also, can this filter be keyframeable at all?
Thanks for making this and sharing it, @Paul2!