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Compression problem: banding in graduated areas

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Shelly Sheilds
Compression problem: banding in graduated areas
on Dec 22, 2008 at 1:38:15 pm

Hi,
Can anyone help? Im working in Motion and FCP and getting posterised effects when I apply codecs to my output files. Any codec applied with compression greater than Animation results in colour banding in the graduated areas, of which there are a lot. Im working Broadcast HD1080i50, 1920x1080. Ive tried a number of alternatives Apple ProRez HDV (at 1440x0180) etc and I just get varying degrees of the same problem....The only solution seems to be to work uncompressed, which results in slow performance (even on my top spec MacPro with 18gb of ram and NVIDIA GeForce 8800 GT and AJA Kona LHe) I have to take this project into FCP to add 4-5 layers and create a loop movie.

I have tried exporting via Compressor but I still get the problem.

My ultimate concern is that the client wants this with the H.264 codec applied which gives me the banding again!

If anyone can offer any advice I would be very grateful.


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Daniel Low
Re: Compression problem: banding in graduated areas
on Dec 22, 2008 at 6:57:49 pm

Could you post a screenshot of the problem, just so I'm sure what it is?




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Please post back saying what solved your problem. It could help others, and saying 'thanks' is free!


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Shelly Sheilds
Re: Compression problem: banding in graduated areas
on Dec 23, 2008 at 1:19:38 pm

Here is a screen grab to show extent of the problem







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Daniel Low
Re: Compression problem: banding in graduated areas
on Dec 23, 2008 at 4:14:14 pm

I'd need to see a grab of the source before being 100% sure but I believe you are seeing the effects of colour sub-sampling i.e. going from a 4:4:4 codec like Animation to one of the others which could be 4:2:0, 4:2:1 or 4:2:2.

Different applications will perform the colour-space conversion in different ways. I've not done any side-by-side test for a while but I'd hazzard a guess that After Effects, or Shake might do the best job.

H.264 can be 4:4:4, 4:2:2 or 4:2:0, it all depends on which H.264 codec, profile and level you'll be using. Quicktime h.264 is 4:2:0 IIRC

http://en.wikipedia.org/wiki/H.264




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Please post back saying what solved your problem. It could help others, and saying 'thanks' is free!


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Shelly Sheilds
Re: Compression problem: banding in graduated areas
on Dec 28, 2008 at 6:44:48 pm

Thanks Daniel,

Im not very knowledgeable on compression techniques but if I understand you I have to keep to 4:4:4 to stop the banding that I experiencing. Now how do I do that? I dont seem to have any options for changing settings on H264 other than compressor Quality, Data rates Frames and Encode quality. No mention of 4:4:4 etc. Does this mean I have to buy a Quicktime codec set to 4:4:4?

Thanks again for you advice



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Daniel Low
Re: Compression problem: banding in graduated areas
on Dec 28, 2008 at 11:08:29 pm

There's not really much you can do about it.

While it's possible to buy software that will allow you to encode H.264 at 4:4:4, it's unlikely that a: that's what the client wants, and b: that anything available freely will play it back.

The bottom line is the banding you are seeing is very slight in comparison to what other types of compression are going to do to really screw up your picture.

Even the best quality commercial DVDs show far, far worse banding than what you are experiencing.




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Please post back saying what solved your problem. It could help others, and saying 'thanks' is free!


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