Color banding on HDV footage

[Morten Gjerstad]

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?

[David Newman]

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.

[David Newman]

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.

[Morten Gjerstad]

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?

[David Newman]

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.

[Dave Campbell]

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

[David Newman]

Dave,

Yes, for issues of color quality, eliminating banding and 1920x1080 resolution support, you will get better quality with Prospect HD.

[Morten Gjerstad]

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.

[David Newman]

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.

[Morten Gjerstad]

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?

[David Newman]

Wasting time with that operator.