Attila Bakos

I can only do it sometime tomorrow. It's easy to test though. Shoot a color chart or something with reds, export a frame from Resolve, and do another export with ffmpeg like this: ffmpeg -i input.mov -vframes 1 output.tif Then compare output.tif with the frame coming from Resolve. If they look identical, the issue is fixed.

If we are lucky they fixed this issue:

That's actually a good advice, I watched some of Juan Melaras videos on repeat

I didn't watch all of it, but he doesn't seem to convert S-Gamut to Rec.709. I know that he has skills and a good reputation, but I always find it amateurish when people apply some contrast and forget about the gamut.

One of the files he uploaded is actually H.264.

Just tested it with similar settings and conditions, my unit doesn't have this issue.

Yes I only need to use a single CST node after the fix and then the Arri LogC to Rec709 LUT. The problem is concatenating, because the matrix fix works in a different domain. That is, it does not require a shaper to work with values outside the 0-1 range. In theory I could use a shaper to bring values into the 0-1 range and alter the matrix fix to work with these new values (if I can), then I could concatenate the matrix fix, the cst node, and the arri lut. There is a problem though, while Resolve can load a 3D LUT with a shaper included (which is basicly an 1D LUT), Premiere doesn't seem to support this. So again, I think it's not worth the effort that's required.

You mentioned that it happens in various bitrates, but does it happen in both H.264 and H.265?

I couldn't create an all-in-one LUT that addresses the values outside of the 0-1 range as well. If I ignore those values then creating a HLG to Arri 709 LUT with the correction included is no problem. However, I can't include anything in a technical pack that's not technically perfect. In theory you could apply the correction matrix via DCTL and in that same DCTL you could load the HLG to Arri 709 LUT. (I never used it but I read somewhere that DCTLs can load LUTs.) This could work but only for Resolve Studio users, so I don't think it's worth doing.

The matrix fix has to go first (it's not an RGB color space correction, doesn't require linear space). You can absolutely concatenate LUTs, I can even make LUTs from CST corrections, but they will work in the 0-1 floating point range, just like the one you can download from Arri LUT generator. The matrix fix however is a special LUT, it's input range is wider. The reason for that is that a wrong YCbCr->RGB conversion will result in values outside of this range and you need to fix them as well. One does not simply concatenate LUTs with different input ranges But I guess I can scale everything else to the range of the matrix fix. Will be an interesting experiment as soon as I have time.

If RCM alters the RGB values before the first node, then you can't use these LUTs with them. I don't use RCM, but to use these LUTs I would recommend Davinci YRGB mode, then the correction LUT in the first node, and then a CST node to simulate what you do in RCM. There is only a minor difference in the header of the file, the data is exactly the same. What you say is theoretically possible if the math for HLG to Alexa 709 conversion is known.

I removed the free fix, and created a package with more options, including DCTLs: http://colorizer.net/index.php?op=technical On the bottom of the page you'll still find an option to fix these issues for free using FFMPEG. I can include more stuff in the package if any of you have suggestions.

Just keep in mind that you can't fix a bad yuv to rgb conversion with cst. So if you know the math, create a dctl that undoes the 709 matrix and applies the 601 matrix. You can also create one for hlg that undoes the 709 matrix and applies the 2020 matrix. I think I'll create a package with all the possible fixes for this issue, in lut and dctl format, and I might ask a few dollars for it.

Sometimes I feel stupid that I give away stuff like this for free..

I understand your issue but I honestly don't know what's causing it, OSX is unknown territory for me. What kind of matrix do you need?