Video Image Controls

The following Chromotion components include user-accessible controls for adjustment and manipulation of video images.

ChromoColor for Gamma Adjustment

There are two basic issues to consider when attempting to produce a color image that will faithfully reproduce the correct data (color, hue, saturation, intensity) on a display. The first issue is to properly compensate for the inherent physical properties of the display hardware itself (Gamma Correction). The second is to produce a mechanism to deal with data streams that have been previously altered for a specific and different viewing environment (Gamma Adjustment).

Gamma Correction for Display

The displays that are everywhere - from CRTs, to DVI monitors, to LCD panels, to TVs, to HDTVs - are all inherently non-linear devices. The intensity of brightness reproduced at the screen of a display is not proportional to its applied voltage. Display intensity has a power-law response to applied voltage: intensity reproduced at the face of the display is approximately the applied voltage, raised to some fixed power. The numerical value of the exponent of this power function is known as gamma. Thus, some sort of gamma correction is required to achieve linearity of the voltage-to-intensity response curve. Gamma correction can be thought of as the process of applying an inverse power transfer function of 1/gamma to the intensity, thus compensating for this non-linearity and enabling a user to reproduce an accurate intensity for a certain display.

Gamma standardization is limited for flat panel (LCD and Plasma) displays; such as DVI monitors, LCD displays, some TV, and some HDTV monitors. Gamma settings will vary between panel sizes, types, and manufacturers. Therefore, trying to get good quality color images reproduced on flat panel displays is very difficult without some sort of gamma correction and/or adjustment. S3 Graphics' Chromotion implements gamma correction and gamma adjustment for full screen images through the use of a color look-up table (CLUT). The CLUT is loaded with a default gamma value to do the gamma correction. The user can adjust the gamma through the S3GammaPlus utility. S3 Graphics implements two sets of CLUTs, one for the primary display and one for the secondary display. This allows independent gamma correction/adjustment for the two independent displays; such as CRT and LCD or LCD and HDTV, etc.

S3Gamma Plus Utility Control Panel

TV and HDTV video images are usually viewed in a dim environment and are therefore encoded with that assumption using a particular gamma for a certain type of display. The viewing environments typical of computers are usually bright. When a video image is encoded according to a known TV video standard, it implicitly carries this assumption of a dim viewing environment; such as the living room in the evening, as well as the gamma for a certain type of display, TV. If the video image that is created for a dim viewing environment is transmitted and viewed in a bright viewing environment, then the video image may show excessive contrast. Gamma adjustment can be used to compensate for these different viewing environments.

Gamma Adjustment for Video

Chromotion allows gamma adjustment on a video window that is independent of the full screen graphics data for the display.

Because there are inherent gamma differences between graphics and video data, viewing video data with display gamma settings, usually is not appropriate. This is especially true when viewing windowed video using common computer applications.

S3Color Plus ChromoColor allows a user to adjust the brightness, contrast, hue and saturation of the display of video. Custom schemes can be created by the user and saved for re-use.

S3Color Plus ChromoColor Utility Control Panel

ChromoColor Tonal Adjustments

Tonal Adjustments controls allow user adjustment of the Y (Luma or brightness) range for video data provided in YUV, YCbCr, and YPbPr formats. Tonal Adjustment options will be available to users through the Advanced Button on the S3ColorPlus ChromoColor utility.

S3Color Plus ChromoColor Tonal Adjustments Dialog

Two slider bars are provided. The thumb on each slider will initially be set to the extreme edge of its range. The Black Point Enhancement slider will initialize to the left side with a value of 0 to represent black (the lack of brightness), while the White Point Enhancement slider will initialize with a value of 255 to represent full Luma (maximum brightness).

The slider thumbs are used to set threshold levels to limit the range of shadows (darks) and highlights(lights). For example, if the range is 0(dark) to 255(light), and the user sets the shadow threshold by moving the thumb to 35 and moves the highlight threshold to 210, then the range of available Luma will be adjusted to 35-210. All values below 35 will be treated as if they were 0 and all highlights brighter than 210 will be treated as if they were 255. Thus, the effective range of values is clipped. To avoid reduction in the contrast range of the picture, after black and white point adjustment, all pixels are remapped to the original range (that is, from 35-210 to 0-255). Adjusting black point or white point prior to the remapping will shift the center of the histogram to the left or right respectively.

The following examples illustrate the type of tonal and value adjustment possible with the S3 Graphics' Tonal Adjustmens controls for White and Black Point Enhancement.

Increasing white or decreasing black will lighten the overall luma of the image. Decreasing white or increasing black will darken the overall luma of an image. Black and White Point adjustments can be combined for a wide range of effects.

Original Image

White Point Enhancement Increased	Black Point Enhancement Decreased
White Point Enhancement Decreased	Black Point Enhancement Increased

The results of these manipulations are most noticeable in the shadows and highlights areas of the image. When the Black Point Enhancement value is decreased, shadows are lightened. Increasing the Black Point Enhancement darkens the shadows. Decreasing the White Point Enhancement lightens the highlights in the image, while increasing the White Point Enhancement darkens the highlights.

ArtisticLicense Effects

S3 Graphics' Chromotion ArtisticLicense filters offer the consumer access to high quality image enhancement effects for both motion and still images. Real-time image processing allows users to visualize their art work on a monitor and select a particular filter (or filters) best suited to their creative needs. ArtisticLicense filters give options to create a painterly or fine-arts looks as described below. ArtisticLicense Effects are controled using slider bars found in the S3Chromo utility.	Original Image
Sharpening Effect This effect focuses blurry images and improves clarity by increasing the contrast of adjacent pixels. This filter corrects blurring introduced during photographing or scanning. This effect is similar to the sharpening filters used in publishing and advertising where the need for sharp photographs is essential. Use this filter to re-focus images of high or sentimental value.	Image with Sharpening Effect
Soft Focus Effect This effect gives images a dreamy and glossy soft focus. Soft Focus produces a warm glow, softening details and diminishing noise and artifacts. It is ideal for creating romantic portraits, glamour photographs, and for giving images a warm and subtle glow to video images. It also gives DVD playback on LCD panels a filmlike appearance.	Image with Sharpening Effect
Embossed Effect This effect makes an image appear raised or stamped by converting its entire fill color to gray and tracing the edges with a color. The degree of embossing can be controlled through the S3Chromo utility slider.	Image with Sharpening Effect
Neon Edge Effect This effect identifies the edges of color in an image and adds a neon-like glow to them. As with the other filters, a Neon Edge slider bar is located within S3Chromo ArtisticLicense Effects utility, and allows to control of the amount of neon edge effect.	Image with Sharpening Effect

All ArtisticLicense Effects are accessible on the S3Chromo Utility ArtisticLicense Effects tab.

S3Chromo ArtisticLicense Effects Utility Tab