Introduction to Streaming Media
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Streaming Media may be defined as listening or viewing media in real time as it comes across the World Wide Web. With streaming technology, users can watch and listen to media while it is being sent to their browser, instead of waiting for it to completely download and then playing it. Before streaming technology was available, a user might wait an hour (or more!) to completely download a short media file.

In general, media files are huge. For example, five minutes of uncompressed video would require almost one gigabyte of space! So, when the audio and video is prepared for streaming, the media file is compressed to make the file size smaller. When a user requests the file, the compressed file is sent from the video server in a steady stream and is decompressed by a steaming media player on the user's computer to play automatically in real time. A user can jump to any location in the video or audio presentation. Streaming media generally tries keep pace with the user's connection speed in order to reduce interruptions and stalling. Though general network congestion is unavoidable, the streaming server attempts to compensate by maintaining a constant connection.

Streaming Media Player Required

Streaming technology allows users to receive live or pre-recorded audio and video, as well as "illustrated audio" (sound synchronized to still pictures). To access streaming media, the user must have a player capable of displaying the presentation. The College of DuPage uses Windows Media software to encode streaming media. To access and view streaming media files, users must have the free Windows Media Player.

Once the Windows Media Player is installed, a user may simply click a link to a Windows Media file. This prompts the player to launch automatically and begin playing the requested file within seconds. Windows Media files can be linked like any other file type; however, the most common way is to embed the file in a Web page.

Terms and Concepts to Know

Bandwidth: A measurement of the amount of data that can be transmitted or received in a specified amount of time. When discussing streaming media, bandwidth is usually expressed in terms of bits per second (bps) or kilobits per second (kbps). (Modems are rated in terms of kbps and usually abbreviated as k. A 56.k modem has twice the bandwidth of a 28.8 k modem.)

Bandwidth is an important consideration when dealing with streaming media. Simply put, more bandwidth is required for more complex data. Therefore, it requires more bandwidth per second to display a photograph that it takes to display text. When delivering streaming media (large audio and video files), a great deal of bandwidth is required to achieve an acceptable level of performance.

Server vs. Server-less Delivery: Streaming media files is most efficiently delivered using a dedicated streaming server. However, content may be uploaded and delivered from servers other than a dedicated streaming server. Here is an example of the same content delivered from a web server and the streaming video server:
Link 1 (web server)
Link 2 (video server)
Depending upon the current activity of the web server, you may not have noticed much of a difference between the two files. But, if there was some network congestion on the web server, you probably noticed a great deal of stalling. In contrast, there was probably little or no stalling on the video server.

Another reason to use the dedicated video server is space. The typical web server is configured up to hold a great many HTML and graphic files, which are generally small. The typical video server is configured with very large storage capacities, as audio and video files may be huge. File size management is critical since any server has a finite storage capacity.

Streaming: Delivery of audio and video over the World Wide Web in real time. With streaming technology, the browser can start displaying the data before the entire file has been sent.

Unicasting: Networking in which computers establish two-way, point-to-point connections. This means when a user requests a file, and the server sends the file to that user only. Unicasting allows a user to pause, or skip around in a streaming media presentation. Because this method requires sending multiple copies of the data to multiple users, bandwidth requirements are high.

Broadcasting: To simultaneously send the same message to all users on the network. Broadcasting sends a message to the whole network, whether or not the data is wanted.

Multicasting: In contrast to broadcasting, where data is sent to the entire network, multicasting sends a single copy of the data only to those users who request it. Multiple copies are not sent across the network, nor is data sent to clients who do not want it. This reduces bandwidth requirements, but as a trade-off, users are unable to control the streaming media and thus cannot pause or skip forward or backward in the presentation.

Webcasting: Using the Internet to broadcast live or pre-recorded audio or video.

Embed: To place the source within a document. The source cannot be edited.

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