Progressive downloads, streaming and bandwidth
Introduction
A lot of people watch videos on computers these days and use the Internet to access the video. You can pay to download movies or TV episodes, for example, or you might watch free videos on sites like Vimeo, YouTube and many others. It is also very easy nowadays to add video straight from your camera or phone to a website such as Facebook. It is therefore important to understand how the technology behind video works.
Progressive download and streaming
A video can be watched in one of two ways. You can either download and watch the video using the http protocol from a normal web server (one that stores web sites, pictures, files and so on) by clicking on the video link on a web page to start it downloading to your hard drive, or you can click on it and start watching it straightaway.
Progressive download
A 'progressive download' is the fancy name for the first method. You click on a link for a video and it starts to download to your computer. You will have a copy of the entire video when it has been downloaded. You can start watching the video before the whole file has been downloaded, however, (just like streaming) as long as a certain amount of key information (called metadata) has been downloaded from the video file header and stored in a buffer on your computer. It is played back from your computer, unlike streaming. Once the video file has been fully downloaded, however, you have a copy of the video that should play without any problems and you won't need an Internet connection to watch it again.
Streaming
The second method, streaming, is when you click on a link to a video. The video is sent to you from a specially set up 'streaming server' as opposed to a web server, and it sends you a part of the video at a time. That part then plays and while you are watching it, the second part is sent, and then played when the first part has finished. Part three is sent while you are watching part two, and so on. This continues until all the parts have been sent and played. As long as your Internet connection can download data fast enough (in other words, you have a high enough 'bandwidth'), you should be able to watch the video without it stopping or stop-starting all the time. If your Internet connection is slow, you may experience problems. When you have finished watching the video, you won't have a copy on your hard drive, unlike with a progressive download. If you want to watch it again, you have to click on the link and stream it again.
Bandwidth
Bandwidth is the term used to describe the volume of data that can be sent or received. It isn't the speed of data, but the amount of data, the volume of data. If you think of a water pipe for a moment. A small diameter pipe will allow only so much water to flow through it. If you have a bigger diameter pipe, more water can pass through it. In both cases, the speed that the water travels is the same, it's just the volume of water that passes a particular point differs. The same idea can be applied to bandwidth. The better your Internet connection, the higher your bandwidth, and the more data you can send and receive. You always need a good Internet connection if you are downloading video, and certainly, you need a high bandwidth connection if you want to stream video. Broadband is excellent for this but a dial-up modem wouldn't be. If you are in a school with a lot of people streaming video or downloading music, then you need a very high bandwidth connection to the Internet.
Why use progressive downloads compared to streaming?
Video delivered via the progressive download and streaming methods appear similar; you click on a video file and it starts playing straight away. The important thing about progressive downloads, however, is that the video file can be at a higher 'encoding' (better quality) than streaming. This is because even if your bandwidth isn't very good and you have problems watching it when you click on it, eventually, you will have downloaded the entire video file to your computer. You can then watch it without a problem because the video file will be playing from the file on the hard drive. Video producers like streaming, however, because copies aren't stored locally on their viewers' computers so they can't easily be copied and shared - they are more secure. Progressive downloads can easily be shared and distributed.