Progressive download – streaming?
Jul/090
Http streaming or as it is better known – progressive download, which has been developed as a marketing term by Macromedia as the “poor man’s streaming solution” for their Flash platform. Progressive download is available from Flash 7 onwards and in essence means a “play-as-you-download” method, that works with standard http web servers. The concept is not invented by Macromedia though, as it has existed for some time with the development of streamable file formats.
Progressive download streaming is achieved by downloading a file “progressively” i.e. from the start onwards up to the end and playing it. FlashVideo(FLV) is a streamable file format as the packets of video data are defined in a “row”(or queue) and can be interpreted one by one, without a need to read all the packets to the end first. As a result progressive streaming provides a similar experience to true media server streaming, but without the need of a media server.
Streaming Video
Jul/091
Streaming is the ability to use content without (down)loading it in whole first. This is very important for web video since a user would usually want to watch the video online instead of downloading it first. When it comes to web video on a technical level streaming is achieved in two main ways:
- Streaming network protocols – this is the low level concept it involves sending(or broadcasting) packets over an IP network. A media server is required for this process and a player compliant with that server’s protocol. This method is also referred as “true streaming” or “live streaming” when it is used with a real time feed. Examples of this concept are Macromedia(now under Adobe) Flash Media server and it’s RTMP protocol and Helix Server(Real Media) with the RTSP.
- File container formats – Some video container formats are designed to be like a stream of packets and can be used in a streaming context. This is also called “Progressive Download” a regular HTTP web server is used for the process. Examples of file formats used for streaming include: .flv(Flash Video), .wmv(Windows Media Video) and many others popular formats.
There is also a hack to progressive download called PHP Streaming. This hack concept solves(sort of) some of the limitations of progressive download namely: random access capability.