Gradient Export, Which Codec?

cribble · Post by **cribble** » Sun Apr 08, 2007 1:47 pm

Hello everyone.

I've been doing some test animations recently, and i've found that whenever i export a scene with a subtle, but long gradient, the codec destroys it and makes the colours clump together in blocks, and creates a soft line that divides the colours apart.

I was wondering, what Quicktime codec is best for exporting scene's with a lot of colour data, such as a gradient?

I can not provide any examples at present, sorry.

Thanks

slowtiger · Post by **slowtiger** » Sun Apr 08, 2007 4:17 pm

Best choice: no compression. This would be "Animation"codec in highest quality setting, or even a sequence of PNGs. But because of the big file size this is only suitable for stuff which goes into still another program.

Any other codec will destroy your nice gradient more or less visibly.

Hiddicop · Post by **Hiddicop** » Sun Apr 08, 2007 6:06 pm

As far as I know, Sorenson 3 is lossless, so this would produce a much smaller file than having no compression at all.

slowtiger · Post by **slowtiger** » Mon Apr 09, 2007 10:12 am

Sorry, Sörensen is definitely not lossless - otherwise it coudn't reduce file size.

jahnocli · Post by **jahnocli** » Mon Apr 09, 2007 11:50 am

One thing does not necessarily follow from the other -- the GIF format is lossless, and those files are small -- so is RLE encoding, and I'm sure there are other examples...

Manu · Post by **Manu** » Mon Apr 09, 2007 1:21 pm

In Quicktime, "animation" at full quality is supposed to be lossless (=RLE)

cribble · Post by **cribble** » Mon Apr 09, 2007 3:48 pm

Hello, thanks for everyones responses. I did some tests for you guys to look at.

Here's a simple mock up scene (mov 348kb)

Codec used:
Animation
Million Colours+
Full quality

And here's a still that is directly from a render (png).

Now i'm being picky here, but can anyone see what I'm talking about. As the gradient slides off towards the planet you can see... well... the colours blocking up. My only concern is that when i make this into a DVD'd final product, will the gradient quality look this bad (can't burn a dvd right now)?

I also read somewhere that the ratio for the animation codec on full quality is like having a 1:1 compression almost. So the problem isn't the codec, i've got a feeling it's the AS's gradient abilities.

Genete · Post by **Genete** » Mon Apr 09, 2007 4:21 pm

I supouse you're talking about hte gradient of the black space from left to right (more or less).
I see the mov more ore less the same as the png. Yes, there are strips of gradient (thick strips) I think like you that it is a AS problem of gradient not the codec. PNG have the same effect (very small but it is). If you elevate the bright of the monitor you will see the gradient effect. I think it would happen in same situations on other programs. Try to do with another program and see what happen.

Genete

slowtiger · Post by **slowtiger** » Tue Apr 10, 2007 9:34 am

The problem you have is known as "banding" in printing industry for decades now, and it happens always when you have to spread a short colour range over a long screen distance. What you see is the borders between the single values of the 3 8-bit colour channels. As long as you don't increase the resolution (to 10 or 12 bit), there's no way to get rid of them.

In printing there's some tricks to deal with that. The most common is to apply some kind of noise over the gradient so the values will get a bit stirred and don't form a line anymore. Unfortunately this will not work in video files since they still average the image in small sqares of 8x8 pixels, no matter which codec is used.

For your style the solution can be simpler: don't use gradients. If you absolutely must, restrict them to short screen distances. Your style has flat colours everywhere, so just stick to that and everything will be fine.