− Satoshi Hayama −
Video Streaming is a technology for distributing and watching digital video over the network. Rapid growth of the Internet enabled people to obtain a variety of information from office and home using WWW browser. People can access not only the text and still image data, but also video data, and can watch news and concerts from all over the world.
Conventionally, digital video can only be played after downloading the entire file to one's PC. Digital video data is massive compared to text and still image data and it takes long time to download. In order to solve this problem, a streaming technology has been developed that receives the data from a server and replays the video at the same time enabling the people to watch the video without waiting.
Video streaming technology is developed based on 2 key technologies, the video coding technology and scalable video distribution technology. It needs several 100 Mbit/s of the bandwidth if one simply tries to digitize the televised video. However, one can afford several 10 kbit/s to several 100 kbit of bandwidth on the Internet. The video coding technology can compress the data to 1/1000 - 1/10000.
The bandwidth between a video server and client machine changes from time to time since the Internet is the best effort network. The scalable video distributing technology flexibly overcomes the change in the bandwidth and distributes the video data without any deformation of the image. This technology can automatically adjust the amount of data according to the change in bandwidth.
Video streaming system consists of an encoder, distribution server and a client that receives the video data. The distribution server stores the encoded video data and begins to distribute it on the client's demand. People can watch the video whenever and wherever by accessing the server on the Internet. Encoding and distribution is carried out in real time in the case of live distribution. Load balance is considered by placing the relay server in the appropriate location on the network.
At the moment, the bandwidth used when accessing from the home is only several 10 kbit/s and the video quality is poor compared with the television. However, ADSL(Asymmetric Digital subscriber Line), other xDSL technologies and the use of CATV and satellites for Internet access are becoming popular, and high quality video data with several 100kbis/s - several Mbit/s will be distributed to the home over the network in the near future.
Video Streaming System
