VDP3108B datasheet(12/72 Pages) MICRONAS

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VDP 31xxB

PRELIMINARY DATA SHEET

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cross-color components, as well as cross-luminance.

The loss of vertical resolution in the luminance channel

is compensated by adding the vertical detail signal with

removed color information.

Chroma

Notch

filter

Chroma

Process.

CVBS

1 H

Delay

CVBS

Chroma

Process.

Notch

filter

Chroma

Process.

Luma

a) conventional

b) S-VHS

d) comb filter

Fig. 2–7: NTSC color decoding options

C C

r b

C C

r b

C C

r b

Notch

filter

1 H

Delay

Chroma

Process.

CVBS

c) compensated

C C

r b

Chroma

Notch

filter

1 H

Delay

Chroma

Process.

CVBS

Chroma

Process.

Luma

1 H

Delay

a) conventional

b) S-VHS

Fig. 2–8: PAL color decoding options

C C

r b

C C

r b

MUX

Notch

filter

1 H

Delay

Chroma

Process.

CVBS

Fig. 2–9: SECAM color decoding

C C

r b

2.3.8. Luminance Notch Filter

If a composite video signal is applied, the color informa-

tion is suppressed by a programmable notch filter. The

position of the filter center frequency depends on the

subcarrier frequency for PAL/NTSC. For SECAM, the

notch is directly controlled by the chroma carrier fre-

quency. This considerably reduces the cross-lumi-

nance. The frequency responses for all three systems

are shown in Fig. 2–10.

PAL/NTSC notch filter

MHz

–10

–20

–30

–40

MHz

–10

–20

–30

–40

Fig. 2–10: Frequency responses of the luma

notch filter for PAL, NTSC, and SECAM

SECAM notch filter

2.3.9. Skew Filtering

The system clock is free-running and not locked to the

TV line frequency. Therefore, the ADC sampling pattern

is not orthogonal. The decoded YCrCb signals are con-

verted to an orthogonal sampling raster by the skew fil-

ters, which are part of the scaler block.

The skew filters allow the application of a group delay to

the input signals without introducing waveform or fre-

quency response distortion.

The amount of phase shift of this filter is controlled by the

horizontal PLL1. The accuracy of the filters is 1/32

clocks for luminance and 1/4 clocks for chroma. Thus

the 4:2:2 YCrCb data is in an orthogonal pixel format

even in the case of nonstandard input signals such as

VCR.

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