Avical's DVE user-level video calibration tutorialIntroduction
DVE (Digital Video Essentials) begins with an introduction on basic video and splits off into different sections that one navigates through using their DVD player's remote. At Avical, we suggest viewing the entire disc as it includes many sections that will further troubleshoot video and audio systems beyond the scope of this article. For those wanting an even deeper explanation behind each pattern's intended use, Joe Kane Productions has provided test pattern descriptions available on their website
.Understanding a DVD player's navigational options and DVE's menu structure.
DVDs come with two different menu systems. The first (upper menu) is usually accessed via a "Top Menu" or "Title" button on a player's remote. The second (lower menu) is simply called the Menu and is accessed using the "Menu" button. It acts as a sub menu to the Title/Top menu system. The trick to DVE is knowing the exact locations of a few key test patterns and how to get to them quickly. For example, on most Sony DVD players, pressing the "Display" button will bring up a page that allows the title and chapter number to be entered. Since DVE comes with an index that lists the program in a Title/Chapter format, it is much easier to know the specific location associated with each pattern. But as a heads up, every pattern in this article is found in Title 12. Perform adjustments in a light controlled environment.
A quality image cannot be attained in a room that doesn't have total light control. If this cannot be achieved during the day, the adjustments ought to be made during the evening with the lights off. A rear mounted Cinema Quest Ideal-lume
bias light would be an exception.Preparing the DVD player for calibration.
Whenever possible, the DVD player's video output should be connected directly to the display. Doing so will lessen the chance of potentially degrading the signal by having it go through unnecessary circuitry. There will likely be a number of different connectivity options. In order of grade, these may include composite (1 RCA), S-video, component (3 RCA), DVI, and HDMI.
The DVD player will also need to be adjusted within its own setup menu to ensure that it is outputting properly. This can get tricky as every make/model can have different controls. But in general, if the TV's screen is oblong (1.78:1), the "16x9" or "Widescreen" option should be chosen. If it has the older squarish shape (1.33:1), the "4x3" or "Normal" option should be selected. If there is a black-level control and the composite or S-video output is being used, place it in the 7.5 IRE position. If component is being used, place it in the "0" IRE position. On newer players with digital video outputs (DVI, HDMI), there is often one more adjustment for black-level consisting of a Normal or Enhanced mode. These modes differentiate between video based systems (16-235) and computer based systems (0-255). For most applications, this should be set to the "Normal" mode. As stated earlier, some players may offer additional controls such as brightness, contrast, color, tint, gamma, etc. Generally speaking, these should be left untouched although there are a few players that need further adjusting within these extended setup menus to output properly. Please refer to the player's owner's manual for additional setup configurations.Preparing the display for calibration.
The display should be "neutralized" prior to running DVE as well. This entails turning off all controls such as "Iris", "SVM", "Black Extension", etc., putting the user-menu controls at 50% or down the middle, choosing a viewing mode that has the least amount of edge enhancement (often titled Movie, Cinema or Pro) and placing the TV within a color temperature that will be closer to the SMPTE D6500 color temperature reference standard (often titled Warm, Low, NTSC, etc.). However, keep in mind that no two displays will come out of the factory looking exactly the same. Consequently, while putting one in the "Warm" color temperature may bring it closer to the desired 6500K region, on another display of the same make and model, the Warm color temperature might be higher or lower than 6500k. This is where having an instrument like the Photo Research PR650 Minolta CS200 comes in handy as they will reveal with incredible accuracy where the grayscale lies.Step 1: Brightness
The first two items adjusted on a display are the brightness and contrast. While these two controls are interactive, brightness primarily impacts the lower end of the grayscale (blacks) and contrast the top end (whites). It is also important to note that they will influence the grayscale somewhat and therefore any color information placed over it.Navigate to Title 12, Chapter 2, DVE PLUGE w/Gray Scale
This pattern's function is to assess/adjust the brightness level on all types of displays and the contrast on a CRT. It consists of a background at video black and symmetrical PLUGE on both the left and right side of the log gray scale (four vertically aligned rectangles in the middle of the screen).
The log gray scale can be used to inspect the neutrality or lack thereof of the grayscale. A bluish tint is usually indicative of a grayscale that is higher (cooler) than D6500. A reddish tint is usually indicative of a grayscale that is lower (warmer) than D6500. A greenish tint, on the other hand, can be warmer or cooler than D6500 and is usually the least desirable as most people are more sensitive to its inaccuracies than a grayscale that leans towards blue or red.This section of the PLUGE pattern can be used as a guide in selecting a color temperature preset that is closest to D6500.
The background of this pattern represents "black" while the three vertical strips at either side represent 4% below black, 4% above black, and 2% above black. Ideally, one should only be able to see the 4% and 2% above black strips.Navigate to Title 12, Chapter 3, DVE PLUGE w/White
The previous PLUGE pattern represented a low average picture level (APL) whereas this one represents a high APL. Toggle between these two patterns to arrive at the most accurate brightness setting.We have found that on many CRT displays, one will have to compromise by adjusting the brightness so that only the 4% above black is visible within this pattern. Otherwise, the blacks may look too washed out.Those with CRT displays should adjust the brightness control and set it to where the 4% below black strip has disappeared while the 4% above strips are still viewable using T.12/CH2 & CH3.
On an LCD, D-ILA, and DLP display, this process is slightly different in that many of these do not have gamma curves similar to a CRT which cause the below/above black strips to appear/disappear. For these displays, it is necessary to look for where black is being "crushed" or lost. If one stands close to the screen and raises the brightness, they will notice that there is some "noise" in the black background. Conversely, as the brightness is brought back down, the noise eventually goes away.Those with digital displays should adjust the brightness control until they can clearly see the noise in the background, and then lower it again until the noise disappears but where the 2% above black strips are still visible.Step 2: Contrast
On a CRT, you may use the PLUGE pattern to set contrast.Those with CRT displays should raise the contrast control while carefully viewing the top box (peak white) until it starts to bloom (become larger than the other boxes), or when it starts to turn yellow in comparison to the boxes below it. When this occurs, back off the contrast so that it is no longer clipping.Contrast and brightness are interactive so make sure to recheck the brightness once you have adjusted contrast and vice versa.
If one is using a digital display, setting contrast is slightly different. For these, we recommend a different pattern.Navigate to Title 12, Chapter 14, "Reverse Gray Ramps & Steps"
This pattern may be used to assess/adjust brightness, contrast, bit depth, and gamma. Here we will describe its use in setting contrast properly on a digital display.
Notice the top and bottom portions of this pattern which consists of a gray ramp. The twenty-two steps extend from 5% below black to 5% above white with the ramps extending to the limits of the digital video system. Markers, which appear as three vertical dots, are placed at video black, 50% and 100%.
Unlike an analog CRT, digital displays do not go into blooming. Hence the reason why a PLUGE pattern cannot be used to adjust contrast on an LCD, D-ILA, and DLP. On these displays, any video information must be below the clip point level. If the contrast is turned too high, chances are that part of the video signal will be pushed into clipping and whatever detail is in that portion will be lost. The contrast control must be turned down so that the bars towards the brighter sections of the ramp (top left or bottom right) are clearly delineated from one another.Those with digital displays should run the contrast control up to see if the steps start to blend together. The proper position for contrast is below the point of clipping, i.e. when each bar is distinguishable and/or uniform in color.On some displays, turning the contrast down will not pull the video out of the clip. This is often an indication that the DVD player is running into its own digital clip. If so, go back to the player's setup menu and turn down its contrast by one click. This will usually eliminate the clip. If not, lower the contrast by another click and so on until every bar is clearly visible. In some cases, the two lightest bars will remain blended together no matter how much the contrast is lowered. In such cases, revert the player to its factory contrast setting.Step 3: Color and Tint
As with the brightness and contrast, the color and tint controls are interactive.Navigate to Title 12, Chapter 6, "Color Bars w/Gray Reference"
For calibrating composite or S-Video, observe the blue channel (blue, magenta, and cyan squares) while viewing through the blue portion of the filter that came with DVE (the red, yellow, and green squares will be masked).Adjust the color control (amplitude) so that the two outer blue squares appear close in shade with one another. This may alter the shade of the magenta and cyan squares which will need to be adjusted using the tint/hue control (phase) so that they appear as close in shade with one another as well. There may be a bit of going back and forth before favorable results are achieved.
For component video, the same observations apply except that the tint will control color balance instead of decoder phase. Tint is not normally available in component video.While this procedure will work for the majority of displays, there are a few that require an ISF technician to achieve the desired results. For example, the current Samsung DLP RPTVs utilize a color coordinate adjustment mode known as "CCA" which color corrects the primary and secondary colors to system specifications. It does this by adding red and green to blue, thus negating the results when using a color filter. As such, it can only be adjusted properly by temporarily disabling the CCA option within the service menu.Step 4: Sharpness
The last adjustment in the typical consumer menu is the sharpness control.Navigate to Title 12, Chapter 17, "1.33 Overscan Pattern"
The Overscan pattern shows how much picture information is being displayed. This pattern may also be used to assess different aspects of a system's performance. Here we will describe its use in setting the sharpness control.
When the sharpness is set too high, it introduces noise as well as "ringing" on the edges of objects. Most people are used to this excessive edge enhancement and sometimes feel that a display looks too "soft" when it is turned down. It is therefore important for one to give themselves a period of time to acclimate to a less "edgy" picture once sharpness is lowered.To set the sharpness, raise and lower the control while observing the image transitions between the gray and black areas of the picture. If halos or artificial edges start becoming apparent, the sharpness is set too high. Simply lower it until the edges are clean without any artificial edge enhancement.On some displays, bringing the sharpness control all the way down may adversely affect image resolution. If when lowering the sharpness control the overscan pattern suddenly looks fuzzy from one click to the next, set it back to the position right before the major change. This can be the case with certain DVD players that have a sharpness control in their setup menu as well.Conclusion
As mentioned earlier, there are many more patterns than the ones that we described that can assist in evaluating and setting up other aspects of a video (and audio) system. We just touched upon the critical patterns needed for a quick and easy user-level video calibration. Again, we suggest going through the entire disc to gain an even deeper understanding of how a home theater audio/video system works.