The Secrets Blu-ray Player HDMI Benchmark - Part I


What We Will Report

Now that we know the issues that exist, how are we going to report on them to our readership? A Spears and Munsil Blu-ray test disc has a set of test patterns that let us evaluate the color conversion of players, either in RGB or YCbCr color spaces. Using a Quantum Data HDMI Analyzer, we can read these values directly and compare them to those that were encoded on the disc. 

There is no guessing based on visual observation, but instead we have the actual data to report on. We will look at multiple intensities of the primary colors (R, G, B) or the YCbCr components (Y, Cb, Cr) and compare those to their reference values. We will look at 0%, 25%, 50%, 75% and 100% amplitude levels for each to see how they compare.

Finally, we will take these values and compute the Delta Error, or dE, for these conversions using the CIE 1994 formula. If you have looked at a display review, the dE is the difference between what the color should be and what the color actually is. With a display, a dE of less than 1 implies a non-visible difference, and this is what you aim for with a display calibration. A value of over 10 is high, and the color errors are noticeable by a viewer. In most cases, you would see a dE less than 3 from a player, which isn't visible, so why would this be important?

Almost any display that you purchase will have a dE for all colors, even after calibration. You might be able to reduce that value with calibration, but it will still be present. If you are introducing a certain amount of dE from your source component as well, then it is going to be far harder to get those values below the visible threshold of 3 than if your source had a dE of 0. Additionally, you are going to want to use a source with a dE as close to 0 as possible to calibrate a display, since otherwise you will be applying the correction for that error to every component connected to your display, introducing it into devices that didn't have the error.

So, your ideal source will have output values that match the reference values on the disc, a dE of 0, and support all available color spaces: 4:2:2, 4:4:4, RGB and Source Direct. Players that don't support all these modes, or introduce errors, will no longer be able to be fully recommended by us, as it would be impossible to guarantee that they would work in a different system correctly.