Quicktime Color Space

[Rafael Amador]

Hi Dan,
In video, it doesn’t makes sense an only RGB codec.
I had a look to Wikipedia, and there is nothing that brings to think that JPEG-2000 works in RGB.

https://en.wikipedia.org/wiki/JPEG_2000

rafael

http://www.nagavideo.com

[Walter Soyka]

JPEG2000 supports multiple color spaces, including YUV (specified as sRGB-YCC, with 4:2:2 or 4:4:4 chroma subsampling), XYZ, and RGB color spaces. See https://jpeg.org/public/DCINEMA-v2.pdf for more.

I think that which color spaces are available depends on which parts of the JPEG2000 standard the encoder complies with.

As noted in the Wikipedia article, JPEG2000 is capable of completely reversible RGB-component transformations.

I’ve only done a little work with JPEG2000, so any clarifications or corrections are appreciated.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events

[Dan Charrington]

Thanks for the insight guys.

I’m brought back to my original question now: is there a way to determine the colorspace information of a JPEG 2000 quicktime file attained from an unknown source? (Via FCP, plug-ins or other means).

–

Dan Charrington
Supervisor, Non-Linear Technologies

MIJO
635 Queen St E. Toronto, ON
416-964-7539

[Rafael Amador]

[Walter Soyka] “As noted in the Wikipedia article, JPEG2000 is capable of completely reversible RGB-component transformations. “
Hi Walter’
This what Wikipedia writes:

Color components transformation
Initially, images have to be transformed from the RGB color space to another color space, leading to three components that are handled separately. There are two possible choices:
– Irreversible Color Transform (ICT) uses the well known YCBCR color space. It is called “irreversible” because it has to be implemented in floating or fix-point and causes round-off errors.

– Reversible Color Transform (RCT) uses a modified YUV color space that does not introduce quantization errors, so it is fully reversible. Proper implementation of the RCT requires that numbers are rounded as specified that cannot be expressed exactly in matrix form. The transformation is”:

I don’t see the RGB color space.
Cheers,
rafael

http://www.nagavideo.com

[Rafael Amador]

Not sure if there is a way to determine that unless the file contains some metadata.
I have here a little application (VideoSpec), that have no problem telling you the color space of the XDCAM or H264. Nothing to guess with those formats; however with a Prores file its shows no info on the color space.
Rafael

http://www.nagavideo.com

[Walter Soyka]

Unfortunately, I don’t know how to answer Dan’s question; I was just trying to point out that the question is valid, because JPEG2000 supports multiple color spaces. Dan, beyond the question of color space, the question of chroma subsampling will also be valid. If the file is component, it could be 4:2:2 or 4:4:4.

[Rafael Amador] “I don’t see the RGB color space.”

I didn’t see it in the Wikipedia article, either — but I think the Wikipedia article is incomplete. The Wikipedia article on DCI describes JPEG2000 compression with an XYZ color space. If you look at p. 11 of the PDF I linked to earlier, (https://jpeg.org/public/DCINEMA-v2.pdf) you’ll see other color spaces mentioned. Some of the color space may only availabe in extensions of the JPEG2000 standard and not in the baseline standard.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events

[Rafael Amador]

Hi Walter,
I’ve found another pdf (JPEG2000 for Digital Cinema
by Ali Bilgin and Michael W. Marcellin. Sorry can’t copy the link)
Talks again about XYZ. I never heard about that.
In general i’m very lost about codecs, but tis kind of posts make me Google and some times I learn something.
It seems that this codec still being developed and, as you point, is possible that some of his profiles can support RGB. But the truth is that what I’ve read it doesn’t let this any clear.
Anyway, here is 1 AM. Time to close.
Cheers,
rafael
PS: Russell Larson may know about this. He is mastering DCI stuff.

http://www.nagavideo.com