Streaming audio is the transmission of compressed audio files that are transmitted as audio streams over IP networks. The transmission takes place in a store-and-forward process with intermediate storage as live streaming or time-delayed. The audio data is digitized and compressed before transmission and temporarily stored in the streaming server. The data stream, which is divided into data packets, can be played back on the receiving side.
Streaming is determined by the audio file format and by the streaming method. There are several popular file formats, which differ by the compression method, compression rate and thus playback quality. The most popular are MP3, mp3pro, Audio Code Number 3( AC-3), Adaptive Transform Acoustic Coding( ATRAC), TwinVQ, Ogg Vorbis, Advanced Audio Coding( AAC) and aacPlus. Some of these are better suited for voice transmission, others for audio and music transmission.
The streaming methods are defined by the transmission protocols. Besides some proprietary protocols and industry standards, several standardization bodies such as the International Telecommunication Union( ITU) or the Internet Engineering Task Force( IETF) have developed standards that support streaming and real-time representations. Protocols developed by the IETF include the Realtime Transport Protocol( RTP) and the Realtime Streaming Protocol( RTSP); from the International Telecommunication Union (ITU), the H Recommendations H.323.
Streaming audio is used for Internet radio, web conferencing, and music downloads, and can be played back with stream-enabled players and music players.