SC2200 NSC [National Semiconductor], SC2200 Datasheet - Page 324

• Manufacturer Part Number: SC2200
• Description: Thin Client On a Chip
• Manufacturer: NSC [National Semiconductor]

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Video Processor Module
6.2.2.2
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.
Horizontal Downscaler with 4-Tap Filtering
Video
Input
Figure 6-8. Horizontal Downscaler Block Diagram
(Continued)
Coefficients
Filtering
4-Tap
4x4
324
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
• Type B is (m/m+1). m pixels are retained, and one pixel
Bit
(F4BAR0+Memory Offset 3Ch) selects the type of down-
scaling factor to be used.
Note:
Downscaler
Downscale
Horizontal
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.
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.
Bypass
Factors
6
There is no vertical downscaling in the Video Pro-
cessor.
of
the
Video
Downscaler
To Line
Buffers
Control
Revision 3.0
register