Streaming Video - How it Works (and Why it Sometimes Doesn't)

Joe McCleskey
January 2002

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By now, you have at least heard of streaming video the exciting new technology that allows video producers to share their work inexpensively with a worldwide audience of Web surfers. Maybe you have viewed, or at least attempted to view, some streaming video yourself. And if you are among a select few, you have actually attempted the feat of creating your own streaming videos and placing them on your Web page Bravo! We salute your bravery.

Whatever your level of experience with streaming video, you should know (as a videographer and a reader of this magazine) that the technology that makes it happen, exciting though it is, does not always work the way it should. Streaming video has been touted as a means to give videographers everywhere their own television station and broadcasting license but if a television station operated as poorly as many streaming video sites do, it'd have very few viewers, due to the number of hiccups, false starts, glitches and system crashes they'd encounter while trying to watch their favorite programs.

In this article, we examine how streaming video technology works, in hopes of explaining why it sometimes doesn't. In the end, we hope to give you the means to avoid some of the common pitfalls that streaming video producers must face.

Before we attempt to launch into a discussion about streaming video, it may be helpful to cover just a couple of basics about how the Internet operates.

Basically, the Internet is a way to connect your computer to other computers around the world, in order to share information in the form of e-mail, Web pages, music, video, pictures, etc. The connection to other computers is not a direct connection, however; before your information can reach other people's machines, it must make a series of jumps from computer to computer as it traces a successful route. Packet servers, the big, powerful computers that form the backbone of the Internet, transmit information along in the form of distinct packets of data.

Furthermore, each packet you send over the Internet has the potential to take an entirely different route (i.e., jump through a different series of computers) than the packets that come before and after it . This is a built-in design feature of the Internet that allows information to flow around heavy traffic areas and broken-down links in the chain. It works very well when downloading Web pages, where it doesn't matter too much if the packets are mixed up, routed through a number of servers and arrive at different times. The various parts of a Web page do not need to arrive at your computer in any particular sequential or chronological order. Video is a different story however.

The preceding two concepts are crucial in understanding how streaming video works, as we'll see shortly. It's actually far more complex than that, but this simple view works for our purposes.

Another important piece of the Internet puzzle is the language that the computers hooked up to one another use to communicate. This machine language, or protocol, must be standardized and efficient to the task at hand.

The protocol that's ordinarily used to deliver Web content is the Hypertext Transfer Protocol (abbreviated HTTP). The Real Time Streaming Protocol (RTSP) specifically handles streaming video content. Both of these protocols can be used to deliver streaming video content; anyone who plans to develop streaming video content for the Web should understand the crucial differences between the two protocols, as this ultimately affects the way you encode your streaming videos.

As stated above, programmers designed the HTTP protocol to deliver Web pages, not to serve streaming video. Nonetheless, it is one of the most common ways to deliver streaming video. HTTP requires that a Web server deliver Web pages and media, but these servers are ubiquitous on every ISP that offers Web access. RTSP also requires a server, but this server is a specialized streaming video server, and these tend to be rather expensive and not as common as Web servers. When you deliver streaming video via the HTTP protocol using a Web server, here's what happens: you simply download the video the way you would a picture or any other file, but it plays on your computer as the download proceeds. They call this method progressive downloading or streaming. The main drawback to this kind of streaming is the simple fact that you must wait for the video to download completely before you can view the end of the movie. Unlike real-time streaming, you can't jump ahead to different portions of the video clip you're viewing; you have to wait for it to download first.

As progressive streaming is the least expensive approach, it's the method that's most often used by amateur videographers and allows video to be served directly from a Web site with no additional software. One example of progressive streaming is Apple's QuickTime, which kick-starts your browser and starts playing a progressive-streaming clip before it has completely downloaded. Although it was not designed with streaming in mind, even the venerable MPEG-1 format can be coaxed to progressively stream with many software players. In both situations, random access of the video is not possible and if you want to watch the last second of the video you will need to download the entire file.

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