TW2837 datasheet(21/232 Pages) RENESAS

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TW2837

FN7742 Rev. 1.00

Page 21 of 232

August 28, 2012

FIGURE 6 CHROMINANCE LOW-PASS FILTER CURVES

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, TW2837 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

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 TW2837 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 TW2837 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.

Med

High

CBW=0

CBW=3

CBW=1

CBW=2

x 10

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

Frequency (Hertz)

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