How to calculate the required PPI Clock when interfacing a Video device to Blackfin?
The PPI clock calculation depends on several factors while you are interfacing a Video device. It depends on:
1. Number of Frames/second
2. Number of Pixels/line
3. Number of Lines/Frame
4. Number of bytes/Pixel
Fro example if you take a NTSC Frame of a ITU 656 video, the PPI Clock can be calculated as follows:
For ITU 656 NTSC:
Number of Frames/second = 30
Number of Pixels/line = 858
Number of Lines/Frame = 525
Number of bytes/Pixel = 2 (one byte for luma and one for chroma)
PPI_CLK = (No. of pixels per Line * No. of lines per frame * No. of frames per second) * Number of bytes/Pixel
PPI_CLK = (858 * 525 * 29.97) *2 ~= 27 MHz.
PPI_CLK = (864 * 625 * 25) *2 = 27 MHz.
Same way you can calculate for different video devices based on the configuration you have selected.
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