Como funcionam os canais extra no HD

Porque só existe nos EUA, porque é uma realidade completamente nova, porque ler é uma coisa, ouvir, outra, tenho tido muita curiosidade em perceber como funcionam os canais de audio oferecidos pela tecnologia digital (HD).

Na Forbes desta semana um artigo faz vários relatos interessantes. Entre eles, este:

"Local broadcasters can deliver up to three program feeds that, depending on how they divvy up the bandwidth, can sound like decent MP3s or pretty good phone calls. The first channel usually duplicates the conventional analog station. Others, when they exist, differ wildly.

In Seattle, where I test this stuff, public radio station KUOW's second digital channel (also available on the Web) shifts some of its regular programming to different hours and adds extra shows. A third channel delivers the BBC World Service, heavily compressed to conserve bandwidth, but listenable.

On the commercial side of the dial, two Seattle FM stations use secondary HD channels to simulcast sister AM talk stations--with wildly better audio. A third station's main HD channel puts country song titles and artists on the radio's screen and displays weather forecasts during ads; the secondary channel offers commercial-free "classic country." And when I tuned to the secondary channel of an in-your-face rap station during the holidays, I stumbled upon a surprisingly low-key commercial-free mix of hip Christmas music. "

fonte: "Radio Goes HD", Forbes
Stephen Manes, 01.09.06, 12:00 AM ET