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DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

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Main audio<br />

program,<br />

(monophonic)<br />

Frequency range<br />

a Deviation of sum not to exceed 50 kHz.<br />

b Professional channel can be used for either voice or data.<br />

Table 48.2 BTSC audio subchannel summary<br />

like FM radio: A suppressed-carrier AM subcarrier<br />

carries the L-R difference component (precoded with<br />

dbx-TV noise reduction, which involves proprietary<br />

frequency-selective compression). A secondary audio<br />

program (SAP) channel is typically used for a second<br />

language; this is also subject to dbx compression.<br />

A low-bandwidth “professional” channel is also<br />

provided, to allow voice or data communication for<br />

engineering and operational purposes. The signal<br />

composition is summarized in Table 48.2 below.<br />

Audio processing<br />

or preemphasis<br />

Subcarrier<br />

frequency<br />

Subcarrier<br />

type<br />

Subcarrier<br />

deviation<br />

(kHz)<br />

L+R 50 Hz … 15 kHz 75 µs 25. a<br />

Pilot f H 5<br />

Stereo subchannel L-R 50 Hz … 15 kHz<br />

Secondary audio<br />

program (SAP)<br />

Professional<br />

channel (not for<br />

consumer use) b {<br />

dbx-TV<br />

compression<br />

B,G,H,I/PAL (PAL)<br />

A diverse collection of RF parameters are used for 576i<br />

broadcast, denoted by systems B, G, H, I (and others).<br />

The notation 576i should be used unless bandwidth<br />

and RF properties are being discussed.<br />

Systems B, G, H, and I PAL all have 576i scanning and<br />

a video bandwidth ranging to 6 MHz. Australia and<br />

Europe (excluding France) use B,G,H/PAL; the U.K. uses<br />

I /PAL. The systems differ in their video bandwidths,<br />

channel spacing, and sound subcarrier frequencies;<br />

a summary is provided in Table 48.4, on page 578.<br />

574 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES<br />

2f H<br />

AM<br />

DSB- SC<br />

50 Hz … 10 kHz<br />

dbx-TV<br />

compression<br />

5fH FM 15<br />

voice 50 Hz … 3.5 kHz 150 µs 6.5f data 50 Hz … 1.5 kHz none<br />

H<br />

6.5fH FM<br />

FSK<br />

3<br />

3<br />

25. a<br />

Total 73

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