ADV7180WBSTZ datasheet(32/120 Pages) AD

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ADV7180

Data Sheet

Rev. G | Page 32 of 120

An automatic mode is provided that allows the ADV7180 to

evaluate the quality of the incoming video signal and select the

filter responses in accordance with the signal quality and video

standard. YFSM, WYSFMOVR, and WYSFM allow the user to

manually override the automatic decisions in part or in full.

The luma shaping filter has three control registers.

•

YSFM[4:0] allows the user to manually select a shaping

filter mode (applied to all video signals) or to enable an

automatic selection (depending on video quality and video

standard).

•

WYSFMOVR allows the user to manually override the

WYSFM decision.

•

WYSFM[4:0] allows the user to select a different shaping

filter mode for good quality composite (CVBS), component

(YPrPb), and SVHS (Y/C) input signals.

In automatic mode, the system preserves the maximum possible

bandwidth for good CVBS sources (because they can be successfully

combed) as well as for luma components of YPrPb and Y/C

sources (because they need not be combed). For poor quality

signals, the system selects from a set of proprietary shaping

filter responses that complements comb filter operation to

reduce visual artifacts.

The decisions of the control logic are shown in Figure 21.

YSFM[4:0], Y Shaping Filter Mode, Address 0x17[4:0]

The Y shaping filter mode bits allow the user to select from a

wide range of low-pass and notch filters. When switched in

automatic mode, the filter selection is based on other register

selections, such as detected video standard, as well as properties

extracted from the incoming video itself, such as quality and

time base stability. The automatic selection always selects the

widest possible bandwidth for the video input encountered.

The Y-shaping filter mode operates as follows:

•

If the YSFM settings specify a filter (that is, YSFM is set to

values other than 00000 or 00001), the chosen filter is

applied to all video, regardless of its quality.

•

In automatic selection mode, the notch filters are only used

for bad quality video signals. For all other video signals,

wideband filters are used.

WYSFMOVR, Wideband Y Shaping Filter Override,

Address 0x18[7]

Setting the WYSFMOVR bit enables the use of the WYSFM[4:0]

settings for good quality video signals. For more information on

luma shaping filters, see the Y Shaping Filter section and the

flowchart shown in Figure 21.

When WYSFMOVR is 0, the shaping filter for good quality

video signals is selected automatically.

Setting WYSFMOVR to 1 (default) enables manual override via

WYSFM[4:0].

AUTO SELECT LUMA

SHAPING FILTER TO

COMPLEMENT COMB

SET YSFM

YSFM IN AUTO MODE?

00000 OR 00001

VIDEO

QUALITY

BAD

GOOD

SELECT WIDEBAND

FILTER AS PER

WYSFM[4:0]

SELECT AUTOMATIC

WIDEBAND FILTER

WYSFMOVR

USE YSFM SELECTED

FILTER REGARDLESS OF

VIDEO QUALITY

YES

Figure 21. YSFM and WYSFM Control Flowchart

ADV7180WBSTZ Datasheet(PDF) 32 Page - Analog Devices

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