Live Video Conferencing and Broadcasting - Some Requirements

Live video streaming requires more resources than streaming archived video files. That makes video conferencing or broadcasting more expensive than other types of streaming.

The main difference between live video streaming and VOD (video on demand) is that a streaming server MUST be used for live broadcasts or conferences. VOD can sometimes be hosted on a regular HTTP server if the demand for the video is not too high, but the nature of live video streaming requires the use of a specialized streaming server.

It is true that JAVA applications hosted on HTTP servers can be used for live video, but the video stream is quite slow compared to using a dedicated streaming server. Think one frame per second for JAVA as opposed to 15 - 25 frames per second for live webcasting or conferencing.

Video streaming requires that the video material be encoded. Encoding compresses the original material and saves it in a particular streaming format. Encoding for VOD can be done on any desktop computer because it is a non-realtime process. For live webcasts or webconferences, however, encoding must be done on the fly before the video signal can be sent out over the Internet. This requires the use of a dedicated computer that is connected directly to the video camera. Encoders can usually accept inputs from several video cameras at the same time.

Because the speed of data transmission is critical (especially for webconferencing) digital video cameras must be used. There can be no analog to digital conversion process which would delay the webcast signal.

VOD streaming is accomplished by setting up a communication channel between two computers – the server and the viewer's computer. This makes the streaming video accessible to anyone at any time.

Webcasts are different. They are also available to anyone with a computer, but only at one specified time. Since thousands of people could be watching a webcast, setting up individual data streams between each computer and the central server could overwhelm the server.

So instead of setting up individual streaming channels, webcasts are transmitted with a protocol known as multicast. This allows a limited number of video streams to be watched by a potentially unlimited number of viewers.

Multicasting can also be used for web conferencing when a large number of participants in various locations are involved. In this case, each participant is delivering a multicast data stream while receiving several multicast streams from the other participants. This is a cost-effective method of allowing many people in widely separated locations to participate in a web conference.

Web conferencing can present new challenges, however, depending on the complexity of the setup. If each participant is at an individual computer, a simple webcam and microphone is sufficient. However, sometimes web conferences will consist of several groups of participants, each gathered in a large conference room. This kind of setup requires more planning and there should be technicians on hand to deal with the details of setting up and maintaining data connections.