Poor Results From Uncompressed Quicktime 10 Bit 4:2:2 Codec

[user_deleted]

I'm having problems with Apple's Uncompressed 10 bit codec. A number of tests have shown substantial shifts in chroma and black levels when converting to .iff and then back to Quicktime (using Shake). Same tests using Blackmagic's DV10 codec yielded much better results.

Codec Test Breakdown (Step-by-Step):

1. Capture HD footage using Uncompressed 10 bit codec in FCP
2. Render Uncompressed 10 bit Quicktime into .iff sequence in Shake
3. Render .iff sequence back into Uncompressed 10 bit Quicktime in Shake
4. Visually inspect new quicktime against original footage using HD monitor
5. Noticeable shift in black levels/chroma

Any idea as to why this codec holds up so poorly?

[user_deleted]

At the conversion there is certain a gamma problem. Try to import the QT file directly to Shake.

[user_deleted]

What you're seeing is the 10bit to 8bit shift. IFF is suposed to allow 16 bits per layer, true but that's only within RGB colour space, not YUV. so when you go from 10 bit YUV to RGB, your purest white becomes 236 and your black becomes 16 (they get mapped to 255 and 0 respectively). Hence the jump in colour.

[user_deleted]

I'm having a similar problem, and wonder if it's related:

• File in an 8 bit uncompressed quicktime to shake
• File out in the same format

I compared the input and output just to see if going thru shake introduced any change, and found that shake is clamping down any luminance values greater than 100. There are some areas of the source footage that are a little hot, but I like the look, and the clamped footage coming back in looks a little unnatural. Nothing I've tried in shake has any effect.

Any ideas on how to prevent shake from doing that?

[user_deleted]

QUOTE(GlennJ @ 02/03/07, 04:38 AM) [snapback]258805[/snapback]
- File in an 8 bit uncompressed quicktime to shake
- File out in the same format

I compared the input and output just to see if going thru shake introduced any change, and found that shake is clamping down any luminance values greater than 100. There are some areas of the source footage that are a little hot, but I like the look, and the clamped footage coming back in looks a little unnatural. Nothing I've tried in shake has any effect.

Any ideas on how to prevent shake from doing that?

this has been discussed quite a bit both on the forum and the list and gavin from the shake team confirmed that there is nothing you can do about it because quicktime handles the conversion (and clamping) on the filein, so shake has no way to acess the superwhite values.

one workaround i used is to use a color corrector in fcp, then export, and reverse the color correction in shake or later in fcp.

++ christoph ++