VDP313XY datasheet(14/76 Pages) MICRONAS

14 / 76 page

VDP 313xY

ADVANCE INFORMATION

Micronas

2.8. Video Sync Processing

Fig. 2–9 shows a block diagram of the front-end sync

processing. To extract the sync information from the

video signal, a linear phase lowpass filter eliminates all

noise and video contents above 1 MHz. The sync is

separated by a slicer; the sync phase is measured. A

variable window can be selected to improve the noise

immunity of the slicer. The phase comparator mea-

sures the falling edge of sync, as well as the integrated

sync pulse.

The sync phase error is filtered by a phase-locked loop

that is computed by the FP. All timing in the front-end is

derived from a counter that is part of this PLL, and it

thus counts synchronously to the video signal.

A separate hardware block measures the signal back

porch and also allows gathering the maximum/mini-

mum of the video signal. This information is processed

by the FP and used for gain control and clamping.

For vertical sync separation, the sliced video signal is

integrated. The FP uses the integrator value to derive

vertical sync and field information.

The information extracted by the video sync process-

ing is multiplexed onto the hardware front sync signal

(FSY) and is distributed to the rest of the video pro-

cessing system.

The data for the vertical deflection, the sawtooth, and

the East-West correction signal is calculated by the

VDP 313xY. The data is buffered in a FIFO and trans-

ferred to the back-end by a single wire interface.

Frequency and phase characteristics of the analog

video signal are derived from PLL1. The results are fed

to the scaler unit for data interpolation and orthogonal-

ization and to the clock synthesizer for line-locked

clock generation. Horizontal and vertical syncs are

latched with the line-locked clock.

Fig. 2–9: Sync separation block diagram

2.9. Macrovision detection

Video signals from Macrovision encoded VCR tapes

are decoded without loss of picture quality. However, it

might be necessary in some applications to detect the

presence of Macrovision encoded video signals. This

is possible by reading the Macrovision status register

(MCV_STATUS).

Macrovision encoded video signals typically have AGC

pulses and pseudo sync pulses added during VBI. The

amplitude of the AGC pulses is modulated in time. The

Macrovision detection logic measures the VBI lines

and compares the signal against thresholds.

The window in which the video lines are checked for

Macrovision pulses can be defined in terms of start

and stop line (e.g. 6-15 for NTSC).

frontend

timing

FIFO

clamping, colorkey, FIFO_write

PLL1

clock

synthesizer

syncs

video

input

lowpass

1MHz

syncslicer

horizontal

sync

separation

phase

comparator

lowpass

counter

front

sync

generator

clamp &

signal

meas.

vertical

sync

separation

Sawtooth

Parabola

Calculation

vertical

serial

data

vertical

E/W

sawtooth

clock

H/V syncs

front sync

skew

vblank

field

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