Originally Posted by alluringreality
I can only comment on my AMD card. Screen capture or the color cop progam can pull RGB values. The video and desktop will report as full-range, and that's the way the expansion setting has to be to stay in line with the 0-255 desktop. When the pixel format is set to the limited range it's clear that the pulled RGB values are not what's actually being output, and things are being put in the 16-235 range.
I just tested, and Windows Media Player acts as if the full-range is being scaled back to the limited range, which means BTB and WTW are gone. I'm not sure what the DVD player I tried is doing, but the BTB and WTW are flashing. I would have to do a brightness comparison to guess and didn't have time.
Interesting, thanks. The only way I can get desktop output of 16-235 and demonstrate a Video Levels round trip is by setting my Nvidia GT430 "Digital Color Format", AKA Pixel Format, to YCbCr444, which I don't do, as RGB works better with my TV per Spears and Munsil 2nd ed Color Space Evaluation pattern as played on my Sony S5100, and WMC and XBMC calibrate consistently with each other and the BD player when Nvidia is left at the default RGB. With Pixel Format RGB, the video card outputs 0-255, and Video Levels is in principle just passthrough. Further, I have no evidence that it isn't just passthrough in reality. I haven't measured any discrepancies between the BD player and WMC/XBMC, I haven't observed gradient anomalies in one that aren't present in the others, BTB and WTW are fully present and behave as they should when they would have been destroyed in the first leg of this hypothetical levels round trip, etc. The only way I can demonstrate a levels round trip is by using YCbCr444, which compresses all output to 16-235. So I stand by everything I've said about Nvidia cards, as long as one is using the default RGB instead of YCbCr444.
Here's a summary of what I just tried with Windows Media Center (WMC) and Windows Media Player (WMP) in Windows 8.1 x64:
AVS HD 709 Black Clipping played on Panasonic ST60 set to Video Levels, that is, "HDMI/DVI RGB Range" set to "Standard (16-235)"; Nvidia Control Panel at its defaults
Nvidia GT430 "Digital Color Format", AKA Pixel Format, set to RGB, the default, which is what I use
Video Levels output; the bars contain the pixel values they are labeled with. Pattern appears as it should, and BTB is revealed by turning up Brightness on the TV. This is what I would call "passthrough". This is what I use.
PC Levels output; the bars < 17 contain 0, 17 contains 1, and so forth. Black is crushed, and BTB has been eliminated. Brightness has to be cranked hugely on the TV to make bars 17 and above flash. This is just simple expansion of Video to PC Levels which would require the TV to be configured to PC Levels for correct viewing.
Nvidia Pixel Format set to YCbCr444, which I don't use, but otherwise the Nvidia Control Panel is at its defaults:
PC Levels output; the bars < 17 contain 0, 17 contains 1, and so forth. BTB has been eliminated, but bars 17 and above are flashing at my normal Brightness setting. Clearly, the video card is compressing to Video Levels after the PC Levels images are buffered and available to screenshots. This seems to be a "levels round trip", and it applies to all output, video and desktop, making it all "work" when the TV is set to Video Levels. That said, if you want video and desktop consistency, it would be better to use PC Levels for everything if possible, so at least the desktop would be passthrough.
Just like WMC here. (Note the difference between this and WMP-RGB. Both legs of the round trip are completed here.)
OK, that's it for the Pixel Format experiment. As for the Video section of the Nvidia Control Panel, where you can set the Video Dynamic Range to Limited or Full, it has no effect on the desktop, and I don't think it can contribute to a levels round trip. In any case, I leave the entire Video section at "With the video player settings" and get the results I've described in previous messages.