Fix for apparent CLAHE failure

[sirnicholasevan]

After a system update (Gentoo Linux), my Vapoursynth script breaks when piped to ffmpeg as the clahe->apply() function is called. I thought it might be a result of a Python update or some API change. It turns out that OpenCV dumps INFO log information to stderr/stdout by default. This also happens when running CLAHE using Python. The fix is dead simple. Add this line to any shell script before running Vapoursynth:

export OPENCV_LOG_LEVEL=OFF

I hope this helps anyone with the same issue.