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64
x64
For the example shown in Figure 31-4, the horizontal skip count is set to 15 pixels and the vertical skip
count is set to 15 rows. This distributes the forty-eight (8
over the full resolution image. The horizontal and vertical counts are not required to be identical, however
for 4:3 ratio images, these counts are the same.
31.6.3 Auto Focus
The sum of absolute difference (SOAD) hardware runs parallel with the color summation hardware,
however it only generates one value per statistic block based on green pixel values. The absolute difference
is computed on each pair of green pixels in a row without any overlap. For the example frame in
×
Figure 31-4 (218
216), there would be 72 absolute differences computed and summed per line. In the
×
content of the 36
36 statistic block shown in Figure 31-3, there would be 9 absolute differences in each
×
line of 36 pixels and 9
31.6.4 Packing of Statistic Data
All of the statistic data, the red, green (sum of all the green pixels), blue, and the focus data, are in a 16-bit
data format.
The data is packed into the 32 bits of the FIFO in the following sequence:
•
(Red, Green, 1st block for big endian) or (Green, Red, 1st block for little endian) 32-bit data.
•
(Blue, Focus, 1st block for big endian) or (Focus, Blue, 1st block for little endian) 32-bit data.
•
(Red, Green, 2nd block for big endian) or (Green, Red, 2nd block for little endian) 32-bit data.
•
(Blue, Focus, 2nd block for big endian) or (Focus, Blue, 2nd block for little endian) 32-bit data.
When a DMA operation is used to transfer the data to the RAM, the statistic data is placed in the RAM
regardless if it is big endian (set the BIG_ENDIAN bit for correct data transfer) or little endian mode
(default) as follows:
MOTOROLA
640 pixels = (64 + 16) x 8
Figure 31-4. Full Resolution Statistic Example
36 = 324 differences summed together for each 36
CMOS Sensor Interface Module
Statistic Data Generation
16 row gap
64
x64
×
×
6) statistic blocks (64
×
36 block of pixels.
16 row gap
64 pixels each) evenly
31-15
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