TV and digital movies by interet
/cdn.vox-cdn.com/uploads/chorus_image/image/57130835/DSCF2345.0.jpg)
By digitizing a real analog video signal (for example, a film or television broadcast) in high or even medium quality, you get a huge amount of data. Such an amount of digital information is impossible not only to transmit over the Internet, but even to record on the media available now. Therefore, special data compression, or compression, methods have been developed for storing and transferring video files.
There is currently no single generally accepted compression standard. Among the most used are MPEG, AVI, RealVideo and QuickTime. These algorithms are characterized by different compression rates and, consequently, different quality of the resulting “image”. (Compression implies the loss of certain information). If you only need to save your video material to CD-ROM or DVD-ROM, you can use algorithms that provide higher image quality. But if you want to stream video over internet channels with limited bandwidth, then the compression ratio should be significantly higher.
To transmit video information over the Web, in addition to its compression, special “transport” programs are required, each of which includes a transmitting part located on the server and a receiving part (video player) on the server. user’s computer. The most popular programs today are Microsoft’s Windows Media Service and Real Networks’ RealVideo, which uses the compression format of the same name.
The task of the broadcast transport program is to deliver the video signal in real time immediately after the user presses the corresponding button. In this case, the video transmission can be carried out according to various schemes. For example, Unicast technology is suitable for viewing video files, when the server sends multiple copies of the same data, one copy for each user. However, with a large number of identical requests, the load on the line increases dramatically. Therefore, for the transmission of terrestrial television programs to a wide audience, the technology of “group transmission” (Multicast) is used. In this case, the video server sends only one copy of the data, “spread” by the routers on the network. At the same time, the network is not overloaded, because no more than one copy of data passes along each line, regardless of the number of connected users.
