[wesk05]

Now that nVIDIA has provided the recovery image download for 7.0.1 update, I updated one of my Shields that has an open bootloader. I did a quick testing of the new gamut mapping API in Android Oreo. It is different from SE 6.3 update especially at 100% saturation levels. The mapped values all seem to lie within Rec. 709 boundaries (In SE 6.3, the 100% points were close to BT.2020 boundaries). With that said, I got some mixed results. While the theoretically calculated CIE 1931 points were very close to the reference Rec.709 points, the results were different when checked on a CIE scope. CIE scope display showed a desaturated image with 7.0.1 update. The desaturation is very obvious in the frame grab. 

CIE 1931 Chromaticity Chart



Pink diamond: reference Rec.709, Filled circle: Shield Experience 6.3 update, Filled square: Shield Experience 7.0.1 update. Black triangles represent the boundaries for BT.709 and BT.2020 gamuts (smaller one is BT.709).

The tests were done on two different Shield Android TVs, one with 6.3 update and the other with the 7.0.1 update. The test patterns were classic color checker and 100% saturation/stimulus test pattern of primaries and secondaries. The test patterns were played in the latest Kodi Leia alpha build. Shield's output was set to 4K 23.976Hz 12-bit Rec.2020. The code values of the output signal were read of a HDMI analyzer. XYZ and xy calculations were based on ITU-R BT.2020 and BT.709 recommendations.

EDIT 6/17/18
I have removed the CIE scope captures that I posted earlier because I suspect something weird going on with the waveform monitor when the primaries are set to BT.2020.

At this time, I am just going to go ahead and say that the new colorspace API does a good job rendering BT.709 gamut to BT.2020 gamut. It is doing an "absolute" or "saturation" rendering. This is as good as it can get! 

By making this bold statement, I hope I won't have to eat my hat.