[Tamas.Toth.ebola]

I work in broadcast video areas - so I deal less in opinion and more in international standards 

I'm glad to hear a person who know the relevant theoretical background as profession. What I currently investigate is just how real life experience could broke any not strictly handled industrial standard.

HDR content can exist in both wide Rec 2020 and narrow Rec 709 gamut...

This is exactly what I wrote about still images. Basically all images which have more then 8 bit luminance resolution in the file itself defined as HDR images independently from their targeted color gamut and also independently from their target real word luminance. Sadly as wrote in this case there is no real word luminance defined as any type of standard so at the end there could be simply such 10 bit images what have no real high dynamic range in their content and also no have wide color gamut informations _(I mean referenced to the source of the image)_.

- though in consumer video pretty much all HDR content is Rec 2020.

And here we are. Seems in consumer practice HDR content is that content what use more then 10 bit resolution to store luminance values and have wide color gamut (perhaps P3 in HDR10 and BT.2020 in Dolby Vision but you know it better). So technically one 10 bit and originally BT.2020 targeted file in theory is a HDR file. On SDR display devices these files need DCR (it's type is irrelevant). And at this point we did not talked about the tone curve to store those color*luminance values properly aligned to real world luminances. Just got the facts that the file 10 bit and it's color values need to targeted to BT.2020 RGB primaries. And here I directly not go further as from this point the viewing environment also such important that the file content itself (and the display device). For proper dynamic range we should define one exact viewing environment and use a display device what can really reach some required luminance results, etc. I think (and you now) Dolby Vision and HDR10 as standards contain these type of regulations. But we from the aspect of Kodi sadly not yet arrived here.

Of course how you already wrote these metadatas are vital for the fine final result but the original problem was not exactly that with some files the colors are off or the dynamic range seems thin or tight. The problem is that seems there are situations where Kodi maybe not properly handled the content of the file or worse can not decode/render them. But I was inaccurate as with HW decoding this should be not the problem of Kodi but GCGTV itself.

If we always could get fluid 4k HEVC playback the whole investigation would not have started. So all the informations what you wrote is important. Important for a fine result. But I think now we are not 'there' yet. If Dolby Vision uses special tone curve to store the data and we decode those data without that proper tone curve of course we could get wrong colors. No problem (of course this is a problem, but not yet). But for example seems that Dolby Vision files are perfectly works while HDR10 files not. HDR10 files simply kill my Kodi on GCGTV. On desktop they are perfect on SDR display device also with working Kodi's tonemap function. So our problems not really those problems what you wrote. At least not yet. You know lot more informations about the video standards as me, especially as I'm knowing almost nothing about them just generic knowledge about A/V technic.

As I wrote I really do not expect frozen Kodi with any type of 4k HEVC files (just because their HDR types) as their metadata content should really not modulate the ability of the playback (the 'wrong colors' is another aspect...). Of course in the practice there could be problems and as we see there are problems.

In short. In theory we should get fluid playback performance from all 4k HEVC files with working HW or SW tonemap (or any other type of DRC) on SDR display devices. The real visual result (what you wrote about as basic technical background) would be just the next step.

Anyway thanks for your written details as I'm really glad to read them as my soft hobby...