Hands on: Tune in to internet radio

There’s plenty of interest in digital radio at the moment.

The BBC is heavily promoting the DAB digital radio platform, a move supported by the Government, which eventually wants to switch off the analogue transmitters and flog off the bandwidth that this will free up - although unlike analogue TV transmissions, which end in 2012, switch-off of the FM transmitters isn’t likely to happen until around 2020.

However, the DAB standard that broadcasters use in the UK is based on old technology and its combination of an ancient MP2 audio compression system and low bit-rate transmissions means that audio quality has suffered.

Stations generally sound OK when listened to on small kitchen radios, but hook up a digital receiver to a decent hifi and the weaknesses become readily apparent. The other issue is that although DAB offers plenty of stations, the variety is controlled by the regulators, who decide who gets a licence.

Radio online
If you want to immerse yourself in the world of digital radio, it’s best to go in search of it on the internet.

There are thousands of stations available on the web, with an astonishing breadth of content ranging from Caribbean talk radio to stations covering the latest happenings on the London indie rock scene (see attached PDF).

And while some broadcast at low bit rates, other stations use advanced audio codecs and bit rates good enough to deliver CD or near-CD quality. Of course, there are several different technologies used to stream internet radio.

The most popular is currently the Shoutcast format. When you click on a Shoutcast stream it first sends a .pls file to your PC containing a URL to which the media player connects to play the stream.

The stream itself is encoded using MP3 compression. Because Shoutcast uses MP3, it’s compatible with a broad range of software and hardware players.

The disadvantage is that radio stations typically use bit rates of 128Kbits/sec or lower and the MP3 format doesn’t produce wonderful sound quality at these rates.

Real Audio is another popular format used by radio stations. In fact, it was once the most popular way of streaming audio over the internet, as it was especially good when working at low bit rates suitable for use with analogue modem links.

However, Real Audio has lost a lot of ground over the years and the format is nowhere near as popular as it once was. Nevertheless, it’s still important in the UK as the BBC uses it for most of its radio programming.