I know about avisynth being 8bit- wish for more :) I know that your file is 10bit 4:2:2 (just converted form 16bit RGB), but once exported through BM 4:4:4 codec all spikes are gone- gradient is smooth. Based on you explanation, I assume that when codec is capable of 4:4:4 there won't be spikes or there will be much less. This seams to be true- any 4:4:4 codec smooths spikes during my tests. Any 4:2:2 kept them or make even more. The only problem was with HQX codec (oficially 4:2:2), but it also removes spikes- so maybe it's internally 4:4:4. This was my question- are removed spikes prove that codec is 4:4:4? With full range you have 255 levels with YUV 220- not? Thx, Andrew