We'd like to open the discussion of video quality by pointing out there were a large number of players that didn't convert Y Cr Cb to RGB properly at the HDMI output. This is a general problem in the HD consumer industry and is detailed in the tutorial sections of HD Basics. The errors we're seeing are improper color decoding of Y Cr Cb to RGB and not providing video levels for the RGB output. We expected differences in the video performance of individual players beyond the Y Cr Cb to RGB issues, but were surprised where the largest difference occurred.
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Our biggest surprise was none of the Blu-ray players tested could properly handle 720p playback in conjunctions with a Java script in the menu system. Considering the wildly different experiences we've had with various Blu-ray players at 720p we believe the majority of their manufacturers are not testing for that HD rate. Some of the problems were minor, as in not being able to play 720p/24 as 720p/24 or 1080p/24. Keep in mind Blu-ray is the original 24 Hz format. At least one player down converts 720p to 480p instead of up converting it to the 1080p set as the desired output rate. When returning to the menu system the player only displayed a 480p section of the menu. Only the top left corner of the menu shows up on screen. When we set the player for a 720p output it would play the 720p material as 720p but the 24 frame material was converted to 60 frames and only a section of the menu showed up on screen when we went back to the menu. We should mention the player could play 720p properly prior to the latest software upgrade. In this case the capability of the player went backwards with the upgrade. Once again, we don't think enough manufacturers are fully testing their players. In contrast the majority of HD DVD players convert the 720p/24 to 1080p/24. Here's the most unexpected change in functionality we found in a particular player related to playing the 720p section of the program. The amount of delay time in menu navigation goes up by at a factor of at least four times once you start a 720p video section. The slower rate of menu operation remains even if you go back to 1080p content. The only way to reset the interaction time is to start the disc over again. Pressing the “Top Menu” key will do that for you.
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You may know that in a Y Cr Cb signal the bandwidth of Cr Cb is half that of the Y channel. We were therefore initially surprised to find ringing in the chroma where there wasn't any in the Y signal. You can see the ringing in transitions in the color bars, or at least in the green/cyan transition. How can you build a clean Y channel, which has twice the bandwidth of a color channel and still get the color channels wrong? Our best guess is the circuit is taking 4:2:0 that is on the disc and processing it up to 4:4:4, then converting it back down to 4:2:2 for the Y Cr Cb output. We've not seen anywhere near this kind of a problem in HD DVD players, but then there are a larger number of manufacturers building Blu-ray players.
