Internet radio technology

Streaming

One of the most common ways to distribute internet radio is via streaming technology using a lossy audio codec. The MP3 codec is most popular, followed by Ogg Vorbis, Windows Media Audio, and RealAudio; use of HE-AAC (sometimes called aacPlus) is gaining in popularity. The bits are "streamed" over a TCP/IP connection, then reassembled and played within about 2 seconds. Therefore, streaming radio has about a two-second lag time.

There are three major components to an audio stream:

1. Audio stream source.
2. Audio stream repeater (server).
3. Audio stream playback.

Creating a stream

There are many methods for creating the audio stream source. Those more technologically savvy may opt for the SHOUTcast service, which utilizes Winamp and the SHOUTcast DSP plugin to deliver MP3 audio at higher bitrates. Other methods include open source technologies such as Streamcast, stream-db, IceS, and MuSE, and patent-free data formats such as Ogg Vorbis. Using open source stream source tools allows for interesting web interface possibilities like phpStreamcast.

Two of the most popular internet radio networks are Live365 and SHOUTcast. Open source alternatives include Icecast and Xiph.org, which include Ogg Vorbis streamings (that can be played by Winamp and Zinf). Collectively, these internet radio servers list thousands of Internet radio stations covering an ever-expanding variety of genres. The purpose of the server is to repeat the stream source to the audio playback software.

Types of radio that stream

Sites that aggregate links of Internet radio broadcasts enable listeners to find internet broadcasts by genre, language, or location. If looking for traditional radio that streams online, you can use RadioTime. It also aggregates radio station schedule information, popular radio show topics, and access to radio personalities that offer podcasts. The Radeo Internet player includes a database with more than 500,000 broadcast, webcast, and podcast streams; search; and a player.

What you need to listen

Some sort of audio playback software or hardware, that is capable of reading HTTP data streams, is needed to listen to streaming MP3 audio. Some popular software players are Winamp for Windows, iTunes for Macintosh and Microsoft Windows, and XMMS on Unix/Linux. Listening to internet radio through stand-alone hardware devices has not been very popular in the past, due to the limited number of devices on the market, though the availability of such devices and their consumer popularity is expected to increase significantly during 2006. Here is a list of commercially available Internet radio devices. Many of these are limited in which audio codecs they can use and consequently the variety of internet radio stations they are compatible with although the number of codecs being used today is becoming somewhat limited due to the inevitable commercial process.

Audio quality

There is a tradeoff between audio quality and audience size. Stations that encode their streams at a lower bitrate have lower audio quality, but they are more accessible to listeners with a dialup connection, and they can serve more simultaneous users on a given upstream pipe.

User ratings

There are also a small number of web radio programs that allow users to rate the songs they are listening to. This allows a user's music listening choices to be correlated against those of others, as with the programs iRATE radio, Last.fm, and Radio Paradise.

You can also rate traditional radio stations and radio programs that stream at a site like RadioTime.

Portalcasting

Portalcasting is a full featured broadcasting service transmitted via the Internet. Portalcasting stations broadcast more visual content and sensory gratification for the listener than typical internet radio stations. The music is high definition and the site supports the station with active time displays of current song, requests, dedication, games and other visual supporting content. Portalcasters provide services via internet sites, cable tv systems and wireless providers.

Podcasting

Audio and video programmes resembling those of radio and TV can also now be distributed by podcasting which can be published by various means including RSS feed and P2P clients.