VDP3108 datasheet(9/61 Pages) MICRONAS

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ADVANCE INFORMATION

VDP 3108

MICRONAS INTERMETALL

MHz

0.01

0.1

1.0

–1

–2

–3

–4

–5

–6

–7

–8

–9

–10

–11

Fig. 2–6: Frequency response of SECAM

deemphasis

2.2.5. Burst Detection

In the PAL/NTSC-system the burst is the reference for

the color signal. The phase and magnitude outputs of

the CORDIC are gated with the color key and used for

controlling the phase-lock-loop (APC) of the demodula-

tor and the automatic color control (ACC) in PAL/NTSC.

The ACC has a control range of +30 ... –6 dB.

For SECAM decoding, the frequency of the burst is mea-

sured. Thus, the current chroma carrier frequency can

be identified and is used to control the SECAM proces-

sing. The burst measurements also control the color kill-

er operation; they can be used for automatic standard

detection as well.

2.2.6. Color Killer Operation

The color killer uses the burst–phase, –frequency mea-

surement to identify a PAL/NTSC or SECAM color sig-

nal. For PAL/NTSC the color is switched off (killed) as

long as the color subcarrier PLL is not locked. For SE-

CAM the killer is controlled by the toggle of the burst fre-

quency. The burst amplitude measurement is used to

switch–off the color if the burst amplitude is below a pro-

grammable threshold. Thus color will be killed for very

noisy signals. The color amplitude killer has a program-

mable hysteresis.

2.2.7. Delay Line / Comb Filter

The color decoder uses one fully integrated delay line.

Only active video is stored.

The delay line application depends on the color stan-

dard:

NTSC:

combfilter or color compensation

PAL:

color compensation

SECAM:

crossover-switch

In the NTSC compensated mode, Fig. 2–7 c), the color

signal is averaged for two adjacent lines. Thus cross–

color distortion and chroma noise is reduced. In the

NTSC combfilter mode, Fig. 2–7 d), the delay line is in

the composite signal path, thus allowing reduction of

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

MUX

Chroma

Process.

Luma

Notch–

filter

1 H

Delay

Chroma

Process.

CVBS

1 H

Delay

a) conventional

b) S-VHS

Fig. 2–8: PAL color decoding options

Fig. 2–9: SECAM color decoding

C C

r b

C C

r b

C C

r b

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