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Video Processor Module (Continued)

6.2.2.2

Horizontal Downscaler with 4-Tap Filtering

The Video Processor implements up to 8:1 horizontal

downscaling with 4-tap filtering for horizontal interpolation.

Filtering is performed on video data input to the Video Pro-

cessor. This data is fed to the filter and then to the down-

scaler. There is a bypass path for both filtering and

downscaling logic. If this bypass is enabled, video data is

written directly into the line buffers. (See Figure 6-8.)

Filtering

There are four 4-bit coefficients which can have pro-

grammed values of 0 to 15. The filter coefficients can be

programmed via the Video Downscaler Coefficient register

(F4BAR0+Memory Offset 40h) to increase picture quality.

Horizontal Downscaler

The Video Processor supports horizontal downscaling. The

downscaler can be implemented in the Video Processor to

shrink the video window by a factor of up to 8:1, in 1-pixel

increments. The downscaler factor (m) is programmed in

the Video Downscaler Control register (F4BAR0+Memory

Offset 3Ch[4:1]). If bit 0 of this register is set to 0, the down-

scaler logic is bypassed.

The horizontal downscaler supports downscaling of video

data input format YUV 4:2:2 only.

The downscaler supports up to 29 downscaler factors.

There are two types of factors:

• Type A is (1/m+1). One pixel is retained, and m pixels

are dropped. This enables downscaling factors of 1/16,

1/15, 1/14, 1/13, 1/12, 1/11, 1/10, 1/9,1/8, 1/7, 1/6, 1/5,

1/4, 1/3, and 1/2.

• Type B is (m/m+1). m pixels are retained, and one pixel

is dropped. This enables downscaling factors of 2/3, 3/4,

4/5, 5/6, 6/7, 7/8, 8/9, 9/10, 10/11, 11/12, 12/13, 13/14,

14/15, and 15/16.

Bit

the

Video

Downscaler

Control

(F4BAR0+Memory Offset 3Ch) selects the type of down-

scalingfactortobe used.

Note:

There is no vertical downscaling in the Video Pro-

cessor.

Figure 6-8. Horizontal Downscaler Block Diagram

Bypass

4-Tap

Horizontal

4x4

Downscale

Video

Input

Filtering

Coefficients

Downscaler

Factors

To Line

Buffers

SC2200 Datasheet(PDF) 324 Page - National Semiconductor (TI)

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