Video Streaming
Streaming video is content sent in compressed form over the Internet and displayed by the viewer in real time. With streaming video or streaming media, a web user does not have to wait to download a file to play it. Instead, the media is sent in a continuous stream of data and is played as it arrives. The user needs a player, which is a specific application that will uncompress and send video data to the display and audio data to speakers.
Streaming video is usually sent from pre-recorded video files, but can be distributed as part of a live broadcast 'feed'. In a live broadcast, the video signal is converted into a compressed digital signal and transmitted from a special Web server that is able to do multicast, sending the same file to multiple users at the same time.
Performance requirements
In order to enable video to be streamed in a clear viewable format there are some key considerations to systems specification.
- CPU power and bus bandwidth to support the required data rate.
- Operating system compatible with streaming applications
- Network or Broadband connection with enough bandwidth to stream data
- Sufficient local storage to save downloaded content
Advances in computer networking, powerful home computers and modern operating systems have made streaming media practical and affordable for ordinary consumers. In general, multimedia content has a large volume, so media storage and transmission costs are still significant; to offset this somewhat, media is generally compressed for both storage and streaming.
Increasing consumer demand for streaming of high definition (HD) content to different devices in the home has led the industry to develop a number of technologies, such as Wireless HD which is optimized for streaming HD content without forcing the user to install new networking cables.
A media stream can be on demand or live. Live streams are only available at one particular time, such as a video stream of a live sporting event. On demand streams however, are stored on a server for long periods of time and are available for transmission at a user's request. It is these streams that create increasing demand for storage devices.
Streaming bandwidth and storage
Streaming media storage size, in the common file system measurements megabytes, gigabytes and terabytes, is calculated from the streaming bandwidth and length of the media using the following formula (for a single user and file):
storage size (in MB’s) = length (in seconds) * bit rate (in bit/s) / (8 * 1024 * 1024) since 1 megabyte = 8 * 1024*1024 bits.
Real world example:
One hour of video encoded at 300 kbit/s will be:
(3,600 s * 300,000 bit/s) / (8*1024*1024) gives around 128 MB of storage.
If the file is stored on a server for on-demand streaming and this stream is viewed by 1,000 people at the same time the requirement is:
300 kbit/s * 1,000 = 300,000 kbit/s = 300 Mbit/s of bandwidth.
This is equivalent to around 135 GB per hour.
Summary
As we increase bandwidth and performance of the internet, along with the growth of social web sites or web 2.0 we will see more demand for online video. Additionally as new technologies such as IPTV & HD TV grow we will also be able to watch films on demand at the press of a button.
These applications require both fast streaming, to get data to the user quickly, and also high capacity storage systems to hold all available files. When you also think that people are uploading files daily to the web you can quickly see how storage demand is growing for companies hosting the video.
