The Internet carries a large variety of exciting multimedia applications. Three broad classes of multimedia applications:
streaming stored audio/video, streaming live audio/video, and real-time interactive audio/video.
Streaming Stored Audio and Video
In this class of applications, clients request on-demand compressed audio or video files that are stored on servers.
Stored audio files might contain audio from a professor's lecture. Stored video files might contain video of a professor's
lecture, full-length movies, prerecorded television shows, documentaries, video archives of historical events, cartoons, or
music video clips.
This class of applications has three key distinguishing features.
- Stored media - The multimedia content has been prerecorded and is stored at the server.
- Streaming - In a streaming stored audio/video applications, a client typically begins playout
of the audio/video a few seconds after it begins receiving the file froom the server. Streaming,
avoids having to sownload the entire file before beginning playout.
- Continuous playout - Once playout of the multimedia content begins, it should process according
to the original timing of the recording.
Streaming Live Audio and Video
This class of applications is similar to traditional braodcast radio and television, except that transmission takes place
over the Internet. These applications allow a user to receive a live radio or television transmission emitted from any
cormer of the world.
Since streaming live audio/video is not stored, a client cannot fast-forward through the media. With local storage
of received data, other interactive operations such as pausing and rewinding through live multimedia transmissions are possible
in some applications. Live, broadcast-like applications often havy many clients who are receiving the same audio/video
program. Distribution of live audio/video to many receivers can be efficiently accoomplished using the IP multicasting
technique. At the time of this writing, live audio/video distribution is more often accomplished through multiple separate
unicast streams. As with streaming stored multimedia, continuous playout is required, although the timing constraints
are less stringent that for real-time interactive applications.
Real-Time Interactive Audio and Video
This class of applications allows people to use audio/video to communicate with each other in real time. Real-time
interactive audio over the Internet is often referred to a Internet phone. Internet phone can potentially
provide private branch exchange (PBX), local, and long-distance telephone service at very low cost. It can also facilitate
the deployment of new services that are not easily supported by the traditional circuit-switched networks. With real-time
interactive video, also called video-conferencing, individuals communicate visually as well as orally. In a real-time
interactive audio/video application, a user can speak or move at any time.
