AMD Geode LX 800@0.9W - Manual (Page 392)

392 AMD Geode™ LX Processors Data Book
Video Processor 33234H
6.7.2.3 Horizontal Downscaling
The Video Processor module supports horizontal down-
scaling (see Figure 6-25). The downscaler can be imple-
mented in the Video Processor module to shrink the video
window by a factor of up to 8:1, in one-pixel increments.
The Downscaler Factor Select (m) is programmed in the
Video Downscaler Control register (VP Memory Offset
078h[4:1]). If bit 0 (DCF) of this register is set to 0, the
downscaler logic is bypassed.
Note: Horizontal downscaling is supported in 4:2:2 YUV
video format only, not 4:2:0 YUV or 5:6:5 RGB.
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 1/8, 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.
Bit 6 of the Video Downscaler Control register (VP Memory
Offset 078h) selects the type of downscaling factor to be
used.
Note: There is no vertical downscaling in the Video Pro-
cessor module.
Figure 6-25. Downscaler Block Diagram
Bypass
4-Tap Horizontal
4x8 Downscale
Filtering
Coefficients
Downscaler
Factors
To line
buffers
Video
Input