DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

ATSC A/53, Digital Television
Standard.
Image
Progressive/Interlace,
Image
format ‡Frame rate (Hz) aspect ratio Sampling
1920×1080 p 24, 30
16:9 Square
i 30
1280×720 p 24, 30, 60 16:9 Square
704×480 p 24, 30, 60
4:3 Nonsquare
i 30
p 24, 30, 60 16:9 Nonsquare
i 30
640×480 p 24, 30, 60
4:3 Square
i 30
‡Frame rates modified by the ratio 1000 ⁄ 1001 – that is, frame
rates of 23.976 Hz, 29.97 Hz, and 59.94 Hz – are
permitted.
Table 13.1 ATSC A/53 Table 3 defines the so-called 18 formats – including 12 SDTV formats – for
digital television in the U.S. I find the layout of ATSC’s Table 3 to be hopelessly contorted, so
I rearranged it. ATSC specifies 704 S AL for several SDTV formats, instead of Rec. 601’s 720 S AL; see
page 325. ATSC standard A/53 doesn’t accommodate 25 Hz and 50 Hz frame rates, but A/63 does.
In addition to the 1 Mpx (progressive) and 2 Mpx
(interlaced) systems, several SDTV scanning systems and
several additional frame rates and were included in the
ultimate ATSC standards for U.S. digital television
(DTV). Table 13.1 above summarizes the “18 formats”
that are found in Table 3 of the ATSC’s A/53 standard.
Figure 13.2 sketched the 1920×1080 image format for
frame rates of 30 Hz and 60 Hz. This image format can
be carried at frame rates of 24 Hz and 25 Hz, using the
standard 74.25 MHz sample rate. Figure 13.3 at the top
of the facing page sketches raster structures for 24 Hz
and 25 Hz systems; Table 13.2 overleaf summarizes the
scanning parameters.
To carry a 1920×1080 image at a frame rate of 25 Hz,
two approaches have been standardized. One approach
is standardized in SMPTE 274M: 1125 total lines are
retained, and S TL is increased to 2640. This yields the
1080p25 format, using an 1125/25 raster. Scanning can
be either progressive or interlaced; with progressive
scanning, the signal is usually interfaced using the
114 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES