Multimedia broadcasting on the Internet requires the use of specialized protocols to overcome the inconsistencies of data transfers. Delivery of the content requires the data to be received at specific times and in the proper sequential order to ensure a quality viewing / listening experience. Multimedia received late or out of order causes the stream to drop off or stutter.
Multimedia can be streamed or broadcast via the Internet using one of several protocols that can provide a quality Internet broadcast. The criteria for selecting the most suitable one is based on the type of software used for encoding and delivery of the multimedia content.
The following protocols are the most commonly used for multimedia streaming :
Shoutcast was developed by Justin Frankel and is a modification of HTTP, which is used to distribute web page data over the Internet. Shoutcast uses special meta tag data that is placed within HTTP communications headers. TCP is used to transport the data.
Icecast was developed by the Xiph open media organization and is a modification of HTTP, which is used to distribute web page data over the Internet. Icecast is similar to Shoutcast and uses special meta tag data that is placed within HTTP communications headers. TCP is used to transport the data.
HTTP ( Hyper Text Transport Protocol ) was developed by the Internet Engineering Task Force and provides a definitive architecture for data communications between a client and server. TCP is used to transport the data.
RTSP ( Real Time Streaming Protocol ) was developed by the Internet Engineering Task Force and functions similarly to HTTP. RTSP differs from regular HTTP content delivery by requiring a permanent data connection between clients that are exchanging data. RTSP uses a message ID to monitor each data connection between clients, so that no permanent TCP connection is required. RTSP also allows users to control the basic functions of a media server; such as starting, pausing or stopping the delivery of the content. TCP is used to transport the data.
RTP ( Real Time Transport Protocol ) was developed by the Internet Engineering Task Force. RTP provides identification and sequential ordering of data bits as well as monitoring the delivery of multimedia content. RTP is less susceptible to the loss of data being sent via computer networks, but it is very sensitive to data delay that can be caused by network irregularities. RTP does not provide the ability to guarantee content delivery. UDP is used to transport the data.
Real Data Transport (RDT) was developed by RealNetworks as a proprietary alternative to RTP. RDT is commonly used in conjunction with a control protocol such as RTSP. UDP is used to transport the data.
MMSH ( Microsoft Media Server ) was developed by Microsoft as a proprietary protocol that was used with the Windows Media Server. MMSH was replaced by RTSP, but is still used as a fall back alternative. Either TCP or UDP can be used to transport the multimedia data.
These are the data protocols that are used to deliver the packets of information over the Internet.
TCP ( Transport Control Protocol ) was developed by the Defense Advanced Research Projects Administration and is one of the primary methods for controlling data exchange over computer networks. TCP guarantees the reliability and order of data by requiring acknowledgment for receiving data from clients before more is sent. The use of TCP will result in a large communications overhead.
UDP ( User Datagram Protocol ) was developed by David Reed and is one of the primary methods for controlling data exchange over computer networks. UDP does not require the verification of data, which does not provide guaranteed delivery of the data or proper ordering of the data. This greatly reduces overall communications overhead. It provides a greater data delivery speed and is much more efficient.
Without the use of specialized protocols for multimedia content delivery, video and audio distribution would be very complicated and costly. The quality of the streamed content would be marginal and not well suited for continuous multimedia distribution.