ADV7183ABST datasheet(29/104 Pages) AD

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ADV7183A

Rev. A | Page 29 of 104

An automatic mode is provided. Here, the ADV7183A evaluates

the quality of the incoming video signal and selects 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 (dependent 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 CVBS, component (YPrPb),

and S-VHS (YC) input signals.

In automatic mode, the system preserves the maximum possible

bandwidth for good CVBS sources (since they can successfully

be combed) as well as for luma components of YPrPb and YC

sources, since 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 in order

to reduce visual artifacts.

The decisions of the control logic are shown in Figure 11.

YSFM[4:0] Y Shaping Filter Mode (SDP), 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 is selected based on other register

selections (e.g., detected video standard) as well as properties

extracted from the incoming video itself (e.g., quality, time base

stability). The automatic selection always picks the widest

possible bandwidth for the video input encountered.

•

If the YSFM settings specify a filter (i.e., 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 (SDP),

Address 0x18,[7]

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

settings for good quality video signals. For more information,

refer to the general discussion of the luma shaping filters in the

Y Shaping Filter section and the flowchart shown in Figure 11.

Table 59.

WYSFMOVR

Description

Automatic selection of shaping filter for good

quality video signals.

Enable manual override via WYSFM[4:0].

*Default value.

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 FOR

GOOD AND BAD VIDEO

YES

Figure 11. YSFM and WYSFM Control Flowchart

ADV7183ABST Datasheet(PDF) 29 Page - Analog Devices

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