In the first of a series of three media streaming articles, Naresh Sarwan describes how streamed media works and looks at two main methods: progressive download and true streaming. The other two articles in the series are Streaming Video Formats For Digital Asset Management and What Streaming Media Player Should Be Used With Digital Asset Management Systems?
What Is Streaming Video?
It is clear from discussing requirements with clients that there is widespread confusion about what streaming is, how it works and what the implications are. This is not entirely surprising, most of the available literature is highly technical and difficult to understand. In this article, I, attempt to present a simple overview of some of the basic concepts behind media streaming and why it is important.
Why Stream Media?
The main benefit of streaming is quite straightforward to understand. With streamed media, rather than needing to wait for an entire file to download, users can start viewing or listening to a clip as soon as enough data arrives for a player to begin displaying it. For live events, it is essential, there is no other feasible method of delivery. For archived media, the choice is less clear, but for the majority of Digital Asset Management scenarios, providing a streamed edition (at least for preview) is now simple to achieve using cheap widely available technology and a vendor (or development team) who has the necessary skills.
What Option Are Available For Streaming Digital Assets?
Once past the basic concepts of streaming, things get more complicated. There are essentially two further choices which begin to take the discussion into a more technical realm:
- The streaming method
- The streaming format
If chosen incorrectly, these can have some negative consequences in terms of performance and compatibility. Streaming itself divides into two broad techniques (there are others, but these are outside the scope of this article):
- Progressive Download
- True Streaming
Progressive Download or ‘Pseudo Streaming’ as it is sometimes called is probably the most popular type currently in use on most websites because it is very easy to implement. Although the user can begin playing back media as soon as it downloads, they cannot skip forward to a part of the media that has not downloaded yet. The advantage is that media can be delivered on the same web server as used to deliver a Digital Asset Management system (or website) and the streamed media merely needs to be placed with other files – like web pages, PDFs, images etc. The media player takes responsibility for managing the download and partially assumes the role that a true streaming server would have provided – this is what simplifies the process and makes it far cheaper than true streaming.
The disadvantage is that for longer footage like movies or TV programmes is that users cannot access any of the media that has not yet downloaded. If their connection is slow and the playback rate exceeds the amount downloaded, they must wait while the player buffers some more of the footage to allow playback to start again – this can happen repeatedly and interrupt the playback experience. If your Digital Asset Management system uses any kind of timeline metadata features (e.g. Edit Decision Lists, DVD style chapters, linking assets based on time codes etc.) then the Progressive Streaming approach might restrict the facilities you can reliably offer.
True Streaming uses a dedicated streaming server. This is not necessarily a hardware device, but special software that delivers the client player the section of the footage that the user is requesting – whether at the start, middle or end. Rather than needing to wait for the section of the media that the user wants to play, they can be given the exact entry point they require and the stream commences from there. True Streaming is the best approach for longer footage and is the method of choice for established broadcast media owners (the BBC iPlayer, is an example of true streaming). For advanced video operations involving manipulation of timeline metadata, like video editing applications, True Streaming is usually essential.
The main disadvantage of True Streaming is that it requires a special dedicated server and is therefore harder to setup and may involve some systems administration work to enable successful playback in more secure corporate IT environments where Digital Asset Management systems are likely to be used.
Despite these drawbacks, the process of setting up most modern streaming server is not especially complex for most systems administrator or engineers and the task is far simpler now than it was a few years ago. In addition, competitive vendors such as Wowza Media and and open source solutions like Red5 have reduced the entry costs considerably even when taking into account the set-up and configuration. For most Video Digital Asset Management or Media Asset Management systems for significant groups of users, I recommend clients use a streaming server implement all Video DAM systems to easily scale to accommodate one from the outset.
Read the follow up article: Streaming Video Formats For Digital Asset Management.