HD Sound uses a system called Coyopa, which is based on AAC coding using what Rupert Brun, head of technology at BBC Audio and Music, describes as "respectable bit-rates". Brun explains that Coyopa was the Mayan god who produced the sound of thunder and so "makes the impressive noises".
The format was originally called XHQ (Extra High Quality) but the name has been changed for the full launch. "We feel HD Sound will be meaningful to the audience without further explanation," comments Brun.
The BBC has been criticised for broadcasting classical music on DAB transmission of Radio 3 at 192kb/s, with the other national music networks going out at 128kb/s. Audiophiles and devotees of the classics feel this is not good enough quality, so HD Sound can be seen as the BBC beginning to rectify the situation.
Brun observes that "a strong case" can be made to say that the internet delivers the best quality of all the digital platforms used currently by the BBC. Right now HD Sound is available only on the web as streams of live programmes, although not for on-demand or listen again transmissions. It is also not available outside the UK at the moment. Brun explains that the internet audio feed comes from the signal path that carries signals to digital television, with no multi-band processing in the chain.
Electrifying the Electric Proms
HD Sound is now part of the Radio 3 website and will also be used for special events on the other BBC national radio networks, as with Elton John's performance at the Electric Proms on Radio 2. Among the highlights for the new service so far has been recordings of new Christmas carols, including work by British composer Sir John Tavener.
The standout so far for 2011 is the Mozart festival, celebrating all his works, from the piano concertos and strings quartets to the operas and symphonies. Roger Wright, controller of Radio 3, comments: "It's wonderful that Radio 3 listeners can now experience all our programmes in even better sound quality when listening online."
Tim Davie, director of BBC Audio and Music, adds: "We are excited to be driving innovation in the radio industry. I expect Radio 2 to be the first of an overall industry drive to keep improving the quality of audio for listeners."
Listeners on DAB and FM might feel short-changed by this but Rupert Brun says development is not stopping with the internet: "We received a lot of feedback about other platforms and I am committed to exploring ways to further improve the audio we deliver to our audience on all platforms."