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Compression and Color Stepping

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jason agar
Compression and Color Stepping
on Jan 6, 2009 at 5:16:43 pm

I'm in the final stages of work on a Music video and noticed that at each stage of compression, color stepping starts to build (pic below).

The light is added using after effects. The project is set to 32 bit (float) with no noticeable stepping. The animation export is also as high as that codec can get with some subtle stepping, but still a problem.

The H264 is on Automatic, but even if I increase the bit rate, it still has some serious stepping. When I watch compressed movies on Quicktime they don't seem to do what my footage is doing.

Is there something else I need to think about while color correcting? Should I be using other software for web compression? When I go to do the final export for TV, what would the most space efficient method be?




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Daniel Low
Re: Compression and Color Stepping
on Jan 6, 2009 at 5:52:28 pm

Looks like bad Colour subsampling along with lossy compression:

http://forums.creativecow.net/readpost/20/861130



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Daniel Low
Re: Compression and Color Stepping
on Jan 6, 2009 at 5:59:54 pm

What's happening is that you are coming from uncompressed 32bit 4:4:4 to 24bit 4:2:2 (or 4:2:0). You'll get better results using something like compressor or Episode to do your final encoding.

Even the best titles can't get round the colour banding problem without dithering.

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Jason Agar
Re: Compression and Color Stepping
on Jan 6, 2009 at 6:12:23 pm

Thanks for the info. I'll give them a try and maybe throw is some dithering to hide the bands.



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