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Old November 23rd, 2005, 02:05 PM   #1
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Color banding on HDV footage

I'm using the FX1 with Aspect HD.
I'm experiencing problems with color banding on my footage, especially on heavy gradients after color correcting. I've tried adding noise/grain to mask it, but it's still a big problem.

Does anyone know if I'll benefit from using a 10-bit workflow in Prospect HD? Does the 16-bit project setting in After Effects help at all, considering my footage is originally 8-bit?
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Old November 23rd, 2005, 02:41 PM   #2
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The main point of a 10-bit workflow is it solve color banding issues. Source footage being 8-bit is not the issue, after all most compressed sources are 8-bit (HDCAM, DVCPRO_HD, etc.) yet professional post-production is often processed in 10-bit. Even if you are mastering to 8-bit (e.g. back to HDCAM) and 10-bit intermediate allows you to dither to a very high quality 8-bit. Using 16-bit AE will help as long as you keep your data deep until you renderout, if you render to an 8-bit codec you can dither by adding 0.4% noise. This only works if you are working with deeper data, i.e. adding noise to an 8-bit image that has banding will only give you noisy bands.

Here how it works:
If a have a luma gradient from 0 to 255 (8-bit source), that I want to darken to 0 to 63, an 8-bit system will only give you 64 levels, whereas a 10-bit system will still have the original 256 levels (no information was lost -- although they are darker -- as required by the example.)
8.bit outputs shows bands 0,0,0,0,1,1,1,1,2,2,2,2,....63,63,63,63
10-bit (normalize to 8bit values) 0,0.25,0.5,0.75,1,1.25,...62.5,62.75,63
If I add noise between 0-0.99 (one LSB - less significant bit - of noise or 0.4% noise)

8.bit output is still 0,0,0,0,1,1,1,1,2,2,2,2,....63,63,63,63 (bands still there)
10-bit output (truncated to 8-bit) 0,1,0,1,2,2,3,2,3,3,4...
So the 8-bit from 10-bit is safely dithered to remove the color bands. The noise level is low. To hide banding in an 8-bit system requires so much noise that you are losing the signal.

Prospect HD does all its interim processing at 16-bits per channel, and renders to a 10-bit codec.
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Old November 23rd, 2005, 02:43 PM   #3
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One of there days I want to produce a page will real-world examples so it is clear to everyone why 10-bits are cool.
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Old November 23rd, 2005, 02:54 PM   #4
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Thanks David!
That really set things straight. Only problem is I can't afford Prospect HD at this point, is there anything I can do with Aspect HD to help with this issue?
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Old November 23rd, 2005, 03:48 PM   #5
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The only work around is to color correct in After Effect Pro, and dither 16-bit data like I suggested. If you don't have AE Pro it almost the cost of an upgrade to Prospect HD Edit.
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Old November 24th, 2005, 01:23 PM   #6
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David, if one upgrades from Aspect HD to Prospect HD, using PPro 1.5, will one get better quality on the final output project? I am using dual xeons 3.6 2M l2 cache at the moment.

If so, if you could send me a PM about upgrade cost since I paid the 1000 for aspect HD.

Thanks

Dave
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Old November 24th, 2005, 01:55 PM   #7
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Dave,

Yes, for issues of color quality, eliminating banding and 1920x1080 resolution support, you will get better quality with Prospect HD.
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Old November 25th, 2005, 08:31 AM   #8
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David, do you know if using 4:1:1 deartifacting in Magic Bullet will help with the banding at all? Also is it possible to download a trial version of Prospect HD? I couldn't find anything on your site.
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Old November 25th, 2005, 12:06 PM   #9
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4:1:1 deartifacting is not a banding issue, rather it addresses the blockiness introduced by the low chroma resolution of DV. CineForm already deartifacts 4:2:0 HDV with a 4:2:2 upconvertion.

Trial versions of Prospect HD Edit/Ingest are no available on the web site, because we would get 1000+ downloads a week (as we do with Aspect HD.) There does need to be some customer education on Prospect HD and 10-bit before we open it up. If you are seriously interested in PHD for you production needs, please email us so we can make rangement to get you a trial.
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Old November 25th, 2005, 12:31 PM   #10
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So if Aspect HD converts 4:2:0 to 4:2:2 am I wasting my time using the deartifacting tool in Magic Bullet or should I set it to 4:2:2?
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Old November 25th, 2005, 12:41 PM   #11
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Wasting time with that operator.
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