TW2866C datasheet(16/143 Pages) RENESAS

16 / 143 page

TW2866C

FN8253 Rev. 0.00

Page 16 of 143

February 3, 2012

ACC (AUTOMATIC COLOR GAIN CONTROL)

The Automatic Chroma Gain Control (ACC) compensates for reduced amplitudes caused by high-frequency

loss in video signal. In the NTSC/PAL standard, the color reference signal is the burst on the back porch. It

is measured to control the chroma output gain. The range of ACC control is –6db to +24db.

Chrominance Processing

CHROMINANCE GAIN, OFFSET AND HUE ADJUSTMENT

When decoding NTSC signals, TW2866 can adjust the hue of the chroma signal. The hue is defined as a

phase shift of the subcarrier with respect to the burst. This phase shift of NTSC decoding can be

programmed through a control register. For the PAL standard, the PAL delay line is provided to

compensate any hue error; therefore, there is no hue adjustment available. The color saturation can be

adjusted by changing the gain of Cb and Cr signals for all NTSC, PAL and SECAM formats. The Cb and Cr

gain can be adjusted independently for flexibility.

CTI (COLOR TRANSIENT IMPROVEMENT)

The TW2866 provides the Color Transient Improvement function to further enhance the image quality. The

CTI enhance the color edge transient without any overshoot or under-shoot.

Luminance Processing

The TW2866 adjusts brightness by adding a programmable value (in register BRIGHTNESS) to the Y signal.

It adjusts the picture contrast by changing the gain (in register CONTRAST) of the Y signal.

The TW2866 also provide programmable peaking function to further enhance the video sharpness. The

peaking control has built-in coring function to prevent enhancement of noise.

Figure 6 shows the characteristics of the peaking filter for four different gain modes and different center

frequencies.

FIGURE 6. THE CHARACTERISTIC OF LUMINANCE PEAKING FILTER

x 10

Frequency (Hertz)

TW2866C Datasheet(PDF) 16 Page - Renesas Technology Corp