Quote:
Originally Posted by chros
1. Data
Picture data is stored as bt.2020 (???) 10bit 4:2:0, or just or DCI-P3 in a bt.2020 container (???), resulting in a washed out picture.
- Wait, what????! Washed out picture?
- so, how does a true red become some greyish color when it's stored?
- I thought we have a truly increased color space compared to bt.709. Is it similar cheating as with those old anamorphic DVDs?  |
Its stored as BT.2020, 10-bit 4:2:0. The actually used colorspace could be smaller, and usually is in fact DCI-P3 for now. The HDR metadata tells you this.
The more important part about HDR however is that its stored using a different transfer function (ie. how to convert it to RGB), called PQ (Perceptual Quantizer, standardized as SMPTE ST 2084), and if you use the wrong one it looks washed out - for example, if a renderer doesn't support HDR, or the info has gone missing.
There is no "cheating", it just looks washed out when its being mis-interpreted by the renderer. You can't look at a YCbCr image without some sort of processing, and if you do that processing wrong, it won't make much sense.
Quote:
Originally Posted by chros
How does the static HDR10 metadata look like?
- is it stored in the beginning of the hevc video data?
- is it just couple of properties (bytes) about the mastering attributes and picture levels and "that's it"?
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The HDR10 metadata is stored with every HEVC CVS (coded video sequence, what most people call "GOP"), so its repeated regularly in the bitstream. In a file format like MPEG-TS, as used on Blu-ray, this is important, because there are no global headers at the beginning of the file, or anything like that.
It doesn't contain a whole lot. It contains the color volume (ie. it specifies that the mastering was done in DCI-P3, for example), the white point, and the min/max luminance of the mastering display.
Quote:
Originally Posted by chros
2. Processing
Splitter and decoder pass data to renderer (MadVR) for further processing:
- that probably happens in the "limited washed out pictures" world
- then either passthrough or HDR processing happens (for SD displays)
-- what does bt.2020 -> DCI-P3 means in OSD?
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As explained above, there is no "washed out picture"
The data is passed as untouched YCbCr to madVR, which then converts it to RGB. Either for pass-through, or conversion to SDR.
BT.2020 -> DCI-P3 means that its using a BT.2020 container with DCI-P3 color volume, as described above.