Datasheet

SAV EAV

Unscaled

Scaled

TVP5154A

www.ti.com

SLES214C–DECEMBER 2007–REVISED SEPTEMBER 2010

8 Scaler Configuration

8.1 Overview

The TVP5154A contains four independent scalers, one for each video decoder channel. Each scaler is

able to filter and scale both horizontally and vertically to different ratios.

Horizontally, a 7-tap poly-phase filter is used to ensure optimal scaling performance and can be

configured to scale to any output size below the input resolution, in decrements of two pixels. Vertically a

running average filter is used to filter vertically and can be configured to scale to any output size below the

input resolution.

When scaling horizontally, the output pixels are packed together to allow continuous reading of the pixels.

AVID should be configured so that it qualifies the active pixels, allowing the receiving back end to ignore

nonactive pixels. When scaling vertically, inactive lines are not removed from the output since there is no

internal frame memory. The receiving back end must use AVID to qualify active lines/pixels. AVID can be

configured to be either active or inactive during invalid output lines.

Due to the fact that vertical scaling is performed on a field basis, it is possible that the vertical resolution

will be reduced due to filtering across lines within the field, rather than adjacent lines in the frame. Aliasing

will not occur, but the output image will appear soft vertically. If the desired scaling ration is 0.5, this can

be achieved by simply ignoring every other field. This maintains sharpness, but may introduce aliasing

artifacts.

8.2 Horizontal Scaling

8.2.1 Registers

The horizontal scaler uses a 32-phase polymorphic filter. Excellent performance can be achieved by using

the set of coefficients programmed into the 5154 for all scaling ratios.

It is necessary to program the input and output scaling control registers (3AB and 3AD).

Figure 8-1 shows how data is packed horizontally when scaled.

Figure 8-1. Unscaled and Scaled Pixel Data Alignment

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