Texas Instruments TMS320C64x DSP manual 13 /2 Scaled Co-Sited Filtering

Video Input Filtering

Figure 3–13. 1/2 Scaled Co-Sited Filtering

a b c d e

YCbCr 4:2:2 co-sited input samples

1/2 scaled co-sited capture results

Luma (Y)	Chroma (Cb/Cr)
–sample	–samples

f g h i j k l

Y’h = (–3Ye+ 32Yg+ 70Yh+ 32Yi – 3Yk) / 128

Y’f = (–3Yc+ 32Ye+ 70Yf+ 32Yg – 3Yi) / 128 Cb’f = (–1Cbc+ 17Cbe+ 17Cbg – 1Cbi ) / 32

Cr’f = (–1Crc+ 17Cre+ 17Crg – 1Cri ) / 32

Figure 3–14. 1/2 Scaled Chrominance Resampled Filtering

a b c d e

YCbCr 4:2:2 co-sited input samples

1/2 scaled chroma-resampled capture results

Luma (Y)	Chroma (Cb/Cr)
–sample	–samples

f g h i j k l

Y’g = (–3Yd+ 32Yf + 70Yg + 32Yh –3Yj) / 128

Cb’f = (–1Cbc+ 17Cbe + 17Cbg – 1Cbi) / 32 Cr’f = (–1Crc+ 17Cre + 17Crg – 1Cri ) / 32

Note that because input scaling is limited to ½, true CIF horizontal resolution is not achieved if the full BT.656 horizontal line (720 pixels) is captured. A CIF size line can be captured by selecting a 704 pixel-sized window within the BT.656 line. This window size and location on the line are programmed using the VCXSTARTn and VCXSTOPn bits.

Note that when ½ scaling is selected, horizontal timing applies to the incoming data (before scaling). The VCTHRLD value applies to the data written into the FIFO after scaling.

3-28 Video Capture Port SPRU629