I have done some testing with the modified filter.
In RGB color space, autolevels works like it should, now.
Stretching the histogram to 0-255 is perfect.
I have tested it with VDubs levels filter, just to be sure.
The whites are a bit blown out both in YUY2 and in YV12 color space. The colors are much better in RGB color space, even if I convert back to YV12 afterwards.
I have disabled the scene change detection because this sometimes fails and then we have unwanted level changes in the middle of a scene. The filter works fine without the scene change detection. It needs a few frames (set with FilterRadius) to re-adjust at scene change, but that's not a problem for me. I have even tried FilterRadius=20 and this gives a very smooth levels adjustment.
Here are the test results, it is all transfered 8mm film.
Please notice the big difference in the red channel!
There might be some color shift, but I can live with that.
Fred.