progressive download

progressive download

A method for streaming non-live video to the user for immediate playback. Supported in the user's media player, progressive downloads are like any other HTTP download from a Web site rather than streaming downloads from a streaming server. A huge number of Web sites favor this delivery method, including Google's YouTube. These sites use free, open source Web server software, rather than proprietary streaming servers, such as Windows Media Server and Flash Media Server, which are not free. See Apache.

Both Called "Streaming"
Although progressive downloading and streaming are both called "streaming," true streaming relies on the server side to detect the user's connection speed and select the file with the appropriate encoding rate for smooth, uninterrupted playback.

Problems and Solutions
Two earlier problems with progressive downloads were the inability to fast forward and the fact that the entire video file might be downloaded to a user with a high-speed connection even though the user might only view the beginning and stop. Enhancements to servers in content delivery networks (CDNs) have added fast forward and the capability of keeping download speed in sync with the encoding rate so as not to waste datacenter bandwidth. See CDN.

Progressive download may be set up to allow users a quality choice; for example, they could opt for higher quality on a slow dial-up connection. The video will halt at various stages waiting for more content, but the quality will be high when played. See streaming video.