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DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

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SMPTE 296M, 1280 × 720 Progressive<br />

Image Sample Structure –<br />

Analog and Digital Representation<br />

and Analog Interface.<br />

24<br />

1. 001<br />

30<br />

1. 001<br />

60<br />

1. 001<br />

≈<br />

≈<br />

≈<br />

23. 976<br />

29. 97<br />

59. 94<br />

1280×720 HDTV 46<br />

This chapter details the scanning, timing, and sync<br />

structure of 1280×720 video, also called 720p. The<br />

scanning and timing information in this chapter applies<br />

to all variants of 720p video, both analog and digital.<br />

Scanning<br />

720p video represents stationary or moving twodimensional<br />

images sampled temporally at a constant<br />

rate of 24 ⁄1.001, 24, 25, 30 ⁄1.001, 30, 50, 60 ⁄1.001, or 60<br />

frames per second. The sampling rate is 74.25 MHz<br />

(modified by the ratio 1000 ⁄1001 in 720p59.94,<br />

720p29.97, and 720p23.976). All of these systems<br />

have 750 total lines (LT). The number of samples per<br />

total line (STL ) is adapted to achieve the desired frame<br />

rate.<br />

Table 46.1 below summarizes the scanning parameters.<br />

System fS (MHz) STL 720p60 74.25 1650<br />

720p59.94 74.25 ⁄1.001 1650<br />

720p50 74.25 1980<br />

720p30 74.25 3300<br />

720p29.97 74.25 ⁄1.001 3300<br />

720p25 74.25 3960<br />

720p24 74.25 4125<br />

720p23.976 74.25 ⁄1.001 4125<br />

Table 46.1 720p scanning parameters are summarized.<br />

547

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