AL128 View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

AL128

Plug and Play VGA to NTSC/PAL Converter

Unspecified 

AL128

6.5 Flicker Filter

The AL128 chip performs 5 line flicker filtering to reduce the flicker due to interlaced display of high

contrast lines. Eight levels of flicker reduction, as well as sharpness adjustment, are provided to

control the picture quality.

Proprietary dynamic filtering (SmartFilter™ ) is applied to retain the original PC video resolution and

sharpness while removing the flickering effect. The hardware intelligently detects which parts of the

screen are natural picture and which are text whose clarity needs to be retained. One out of 45

different filters is selected and applied dynamically for each single pixel based on the statistics of its

surrounding pixels. The criteria of which filter to choose from is based on a model derived from the

ensemble of psychophysical experiments based on human eye responses to the flicker of different

picture types.

6.6 Overscan/Underscan Control

Televisions normally overscan, meaning that the border of the picture is outside the visible area of

the TV screen. To program the AL128 from Overscan to Underscan, reduce the horizontal display

width and vertical display height, and increase the H-display delta and V-display delta. For

underscan to overscan, reverse the process. The capture-related registers may need to be

programmed for optimization.

The AL128 linearly scales the input picture into the visible part of a TV’s screen. Digital filtering

techniques are applied to remove the scaling artifacts.

6.7 Pan and Position Control

The panning feature selects the portion of the graphic picture to be displayed on the TV screen.

When in zoom mode, the visible screen can be progressively panned to any area of the virtual screen.

To pan the display, change the values of H-pan delta (Reg. #21h, #26h) and V-pan delta (Reg. #22h,

2Ch). To pan in zoom mode, #2Bh and #2Ch may also need to be programmed.

Position control is used to center the video on the TV screen. To position the display, change the

values of H-display delta (Reg. #52h) and V-display delta (Reg. #51h).

6.8 Zoom Feature

AL128 performs 2x zoom in both horizontal and vertical directions. This can be used with panning,

or activated by jumping to any given quadrant via use of the push buttons or software.

April 2, 1999

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