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DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

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480i NTSC<br />

composite video 42<br />

Although this book is mainly concerned with digital<br />

video, the installed base of hundreds of millions of units<br />

of analog video equipment cannot be ignored. Furthermore,<br />

composite 4f SC digital video – including video<br />

recorded in the D-2 and D-3 formats – is essentially just<br />

digitized analog video. To understand 4f SC equipment,<br />

you must understand conventional analog NTSC video.<br />

This chapter details the technical parameters of<br />

composite 480i video. I discuss subcarrier, composite<br />

chroma, composite analog NTSC, and the S-video-525<br />

interface. I assume that you have read the Introduction<br />

to composite NTSC and PAL, on page 103; additionally,<br />

I assume you are familiar with the sync structure and<br />

R’G’B’ coding described in 480i component video, on<br />

page 499. Before explaining the signal flow, I will introduce<br />

subcarrier and burst.<br />

Subcarrier<br />

Synchronous with the scanning raster is a pair of continuous-wave<br />

subcarriers having 2271 ⁄2 cycles per total<br />

raster line: a sine wave (referred to as subcarrier) whose<br />

zero-crossing is coincident ±10° with 0H, and a cosine<br />

wave in quadrature (equivalent to a sine wave at<br />

a phase advance of 90°). Delay of the subcarrier’s zerocrossing<br />

with respect to the 0H datum, measured in<br />

degrees of subcarrier, is known as subcarrier to horizontal<br />

(SCH) phase, or if greater than 10°, SCH error.<br />

Derived color subcarrier frequency is 315 ⁄88 MHz<br />

±10 ppm, or about 3.58 MHz. Subcarrier drift should<br />

511

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