Step by Step: Extended Setup for Advanced User's - Color Space, De-Interlacer and Combination Tests

The following adjustments are aimed at advanced users. Here we'll be investigating the color proficiency of displays, particularly with HDTV movies in mind; the quality of video processing and finally the resolution of full HD compatible displays. All test pictures referred to on this page can be found in the third submenu "System Evaluation" in the 1080p section of the DVE High Definition DVD.

The disk provides both test pictures and movie scenes, and all pictures are two-fold since there are different standards for color space. One is for SDTV, which complies with the ITU-R BT 601 standard, and other is for HDTV, which is in accordance with the ITU-R BT 709 standard. These standards use a different calculation base for the determination of RGB and YUV values, which is why their color values differ enormously in places.

With the help of the test disk, one can easily determine the standard used by the set for color decoding. The first test picture is the already familiar color bars on a 75 percent gray saturated background. In "Blue Only" mode (if the set supports it) or with the aid of a blue color filter, HDTV displays and original picture material should conform to the correct 709-standard with the blue, magenta and cyan color components blending in with the background. Then follows the restaurant scene, which is well-known from older test DVDs and has been remastered for HD. Striking differences are immediately apparent on the calibrated set - particularly the green (bottle) and skin tones. The third test picture with graduated gray tones shows that gray tones are not affected by the color matrix in use.

By contrast, the fourth color bar test picture highlights dramatically how the screen colors alter if the calculation base is incorrect. Even the minutest of deviations in the blue channel cause the green, cyan, magenta and red components of the color spectrum to be greatly falsified. The problem that does exist though is that even if the color space is recognized as being incorrect, an adjustment is often just not possible (refer to boxes.)

The images from cameraman Allen Daviau clearly show the differences in color calculation for green, cyan, magenta and red in the divided screen with SDTV (601) left and HDTV (709) right.

Visualization of the color space setup with the help of the "75% Color Bars 601/709" test picture, which is the fourth test picture in the "System Evaluation" section of the DVE High Definition DVD:

The color space test picture with its colored bars for SDTV (601) in the upper portion and HDTV (709) in the lower portion.

The SDTV decoding according to 601 is discernable with the blue filter or in "Blue Only" mode.

For many years now, an improved color matrix has been in existence with superior algorithms for HDTV production. Known as the ITU-R BT 709 standard, it defines how camera pictures, shot in the RGB color space, are captured and converted for use as a master on Blu-ray disk or the space-saving YUV format on HD DVD. Then, in accordance with this standard, the video processing of projectors and flat-screen televisions must accurately and correctly convert the YUV formatted material back to RGB, since all image representation is performed according to the RGB principle.

The operation becomes somewhat more complex with scaled-up SDTV material as is the case, for example, when an HDTV player plays PAL DVD content in the 1080p format. The display, despite the HDTV transmission, should actually activate its usual BT 601 color matrix for PAL. When converting from YUV to RGB, HDTV players must conform to the relevant 601 or 709 standards - depending on the nature of the material that is to be played back. However, manufacturers are not very dependable in their interpretation. If a player can be set for the RGB color space, then ideally it should convert normal DVDs according to the 601 standard. As soon as an HD DVD or Blu-ray disk is inserted in the drive, then the player should convert the colors to RGB according to the applicable 709 standard. The benefits of this procedure are that older displays will also be able to reproduce color correctly.

Unfortunately, not all HDTV players have the possibility to manually set the RGB color space. If the player has "HDMI Handshake" enabling equipment to communicate with each other, then modern players and displays will anyway prefer the YUV color space. It is for exactly this reason that color space is an increasingly significant setting in the display menu. If the color space is not automatically distinguishable, which, as discussed, is not always the case, then experienced users can manually set the color space between "709" for HDTV material and "601" for PAL video. If the source material is incorrectly color decoded, then outputting the content in YCbCr format (digital YUV) will help. However, only a few projectors offer this level of decoding possibility.

The test picture shown (below) controls the geometry and has, in addition, pairs of lines to check whether the display is capable of accomplishing the full vertical and horizontal resolution. The saturation of the color channels is set to 50%, and the various graduated gray tones, integrated "Pluge" and fonts give a rapid overview of many of the screen's parameters.

The universal test picture number 13 "Raster Quick Ref", which is located under "Test & Calibration", is ideal for gaining an instant overview of the major picture parameters.

The "Vertical Multiburst" test picture shows vertical lines at different resolutions. Its purpose is to detect scaling artifacts, and tests whether the 1080i de-interlacer is capable of presenting flicker-free imagery along the full (100%) vertical axis. If not, then either the line pairs are replaced by black or white areas or the image flickers greatly.

The "Vertical Multiburst" test picture number 19 found in the section "Test & Calibration" is used to check the vertical resolution.

As depicted in the enlarged clipping (below), the test picture is comprised of brush strokes, in progressively finer resolution, positioned in all four picture corners. Only a display without overscan can reproduce this effect pixel perfectly. Moreover, the finest vertical line pairs should also be progressively presented, and if they flicker then the display is not operating in 1080i mode.

This enlarged clipping shows the potential full HD displays should be capable of, namely the exact and pixel perfect presentation of the detailed line pattern.