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Video Processor Module (Continued)

6.2.2.3

Line Buffers

After the data has been optionally horizontally downscaled

thevideo data is stored ina3-linebuffer. Each lineis360

DWORDs, which means a line width of up to 720 pixels can

be stored. This buffer supports two functions. First, the

clock domain of the video data changes from the GX1

module’s video clock to the GX1 module’s graphics clock.

This clock domain change is required because the video

data and graphics data can only be mixed/blended in the

same clock domain. The second function the line buffer

performs is to provide the necessary look ahead and look

behind data in the vertical direction for the vertical

upscaler. There is no direct program control of the line

buffer.

6.2.2.4

Formatter

Video data in YUV 4:2:2 or YUV 4:2:0 format is converted

to YUV 4:4:4 format. RGB data is not translated. There is

no direct program control of the Formatter.

6.2.2.5

2-Tap Vertical and Horizontal Upscalers

After the video data has been buffered, the upscaling algo-

rithm can be applied. The Video Processor employs a Digi-

tal Differential Analyzer-style (DDA) algorithm for both

horizontal and vertical upscaling. The scaling parameters

are

programmed

via

the

Video

Upscale

(F4BAR0+Memory Offset 10h). The scalers support up to

8x factors for both horizontal and vertical scaling. The

scaled video pixel stream is then passed through bi-linear

interpolating filters (2-tap, 8-phase) to smooth the output

video, significantly enhancing the quality of the displayed

image.

The X and Y Upscaler uses the DDA and linear interpolat-

ing filter to calculate (via interpolation) the values of the pix-

els to be generated. The interpolation formula uses Ai,j,

Ai,j+1,Ai+1,j,and Ai+1,j+1 values to calculate the value of

intermediate points. The actual location of calculated

points is determined by the DDA algorithm.

The location of each intermediate point is one of eight

phases between the original pixels (see Figure 6-9).

Figure 6-9. Linear Interpolation Calculation

Ai,j+1

Ai+1,j+1

Ai+1,j

Ai,j

Notes:

xand y are 0- 7

()8y

–

------------A

i1 j

()y

---

()8y

–

------------A

i1 j1

()y

---

()8x

–

------------b

()x

---

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