Internet radio (aka e-Radio) is an audio broadcasting service transmitted via the Internet. Broadcasting on the Internet is usually referred to as webcasting since it is not transmitted broadly through wireless means but is delivered over the World Wide Web. The term "e-Radio" suggests a streaming medium that presents listeners with a continuous stream of audio to which they have no control much like traditional broadcast media. It is not synonymous with podcasting which involves downloading. Nor does e-Radio suggest "on-demand" file serving. Many Internet "radio stations" are associated with a corresponding traditional "terrestrial" radio station or radio network. Internet-only radio stations are usually independent of such associations.

Internet radio "stations" are usually accessible from anywhere in the world—for example, to listen to an Australian station from Europe or America. This makes it a popular service for expatriates and for listeners with interests not adequately served by local radio stations (such as progressive rock, anime themed music, classical music, 24-hour stand up comedy, and others). Some Internet radio services offer news, sports, talkback, and various genres of music—everything that is on the radio station being simulcast over the internet with a netcast stream.


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 format 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" (transported) over the network in TCP or UDP packets, then reassembled and played within about 2-10 seconds, depending on server characteristics. This delay is referred to as 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 include Ogg Vorbis streamings that can be P2P clients.