TORREVIEJA.com - Interactive website of the city of Torrevieja, in Alicante, Spain.: Video Streaming Nitty Gritty

Video Streaming Nitty Gritty
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Redacción  on 05 May, 2008 10:17:00
 
All downloads work by dividing the original file into small 'packets' which are
encoded with their destination and their order in the data stream. This last
bit is important – packets can arrive in any sequence, but thanks to their
unique ID, they can be reassembled in the correct order.
The Internet is a vast array of pathways that carry millions of bits of data
every second. In order for that data to reach its destination as quickly as
possible, every pathway is open to every data packet. One packet may go via
Bombay, another via Tokyo, but they all end up at their correct destination.
Video Streaming
Video streaming follows the same basic principle of breaking data into packets.
Instead of waiting for all the data to arrive, however, a streaming video can be
watched as it is downloading. This allows the end-user to see the video almost
immediately after clicking the 'View' button, whereas if the entire video file
had to be downloaded there could be a delay of several minutes or even hours.
Video streaming is possible thanks to a set of streaming protocols. Unlike
protocols designed for other types of digital data, streaming protocols
prioritize data packets so that they arrive (mostly) in the order they are
sent. Streaming protocols can also allow for lost data packets so that the
streaming video continues to play even if a few packets are lost.
One of these streaming protocols is known as Real-Time Streaming Protocol
(RTSP) which allows the viewer to remotely control the data stream so that the
streaming video can be paused, rewound or fast-forwarded. Actual delivery of
the video stream is handled by the Real-Time Transport Protocol (RTTP) and the
Real-Time Control Protocol (RTCP).
Video Broadcasts
Video broadcasts on the Internet are sometimes called webcasts, and use the
same basic principles of video streaming. Unlike most video streams, however,
webcasts are 'live' and can only be viewed at one particular time, just like a
TV broadcast.
Webcasts usually require more resources than simple video streaming because of
the (potentially) large number of viewers that can be watching at the same
time. Each viewer requires a certain bandwidth (the rate of data transmission),
so once the amount of bandwidth reaches the maximum capacity of the server, no
more viewers can watch the webcast.
One way around this is to use a protocol called 'multicast' in which one data
stream can be viewed simultaneously by many people. Multicasts are often
blocked by firewalls, however, limiting their usefulness to private networks.
Video Conferencing
Internet video conferencing is sometimes called web conferencing. This involves
setting up a two-way (or multi-way) communication channel so that each
participant can see and talk to the other participants.
Web conferencing is based on the same technology as webcasts, since by their
nature they must be 'live' but because each party needs to interact with the
others it can be even more technologically demanding than webcasting.