Streaming Media

In prehistoric times if you wanted to watch a movie online or listen to a song, you had to wait for the file to download onto your computer before you could begin watching or listening.  These days you don’t have to.  Even if you’ve never heard of streaming you have more than likely encountered it.  Thanks to streaming you can now visit the BBC’s iplayer website and get access to video and radio programs without having to go and make yourself a coffee (or tea if that’s your preference) while you wait for the file to download.  Probably the most notorious of services indebted to streaming is youtube.  The site takes videos uploaded by users in a variety of different formats, converts them to Flash format using whats known as the Sorensen Spark H.263 Codec and streams the video to other users using a interface based upon Macromedia’s flash player.  The benefits of streaming are obvious and without it websites like youtube or iplayer would be stuck in the Dark Ages…

Lets take a look at how it works…

First of all you should know that streaming uses up bandwidth, this being the capacity you have to transfer data over a network ie the Internet.  This means that in order to playback media without slowing down your connection the files must first be compressed.

Streaming media storage size is calculated in the following way…

storage size (in megabytes) = length (in seconds) * bit rate (in kbit/s) / (8 * 1024) (since 1 megabyte = 8 * 1,024 kbits)

In reality this means…

One hour of video encoded at 300 kbit/s will be:

(3,600 s * 300 kbit/s) / (8*1024) gives around 130 MB of storage.

Once encoded this is what happens…

You the user, sends a request for a video, lets say Michael Jackson’s Smooth Criminal.  You do this by clicking on a HTML link.  A player is loaded and requests the data from a media server.  Data is transferred using one of many protocols depending on the particular site/service requirements.  This data is received and held in whats known as a buffer.  Once the buffer has enough of the data to allow you to start watching, it does.  As you watch, the rest of the data is transferred and the idea is that you’ll never know it wasn’t there to start with!

Live Streaming

Live streaming is where things get tricky.  To start with you’ll need to make sure that your web server is capable, not all servers can accomplish the task.  You’ll also need to install some broadcaster software like SAM Broadcaster Once you have configured the software you’ll need to encode the file by using the software to create an SDP file, this is uploaded to your web server.  Once uploaded, start the capture software within your broadcaster software to begin streaming.  Obviously you’ll need some basic knowledge of the web in order to configure your website to house the streamed content but that’s how it works in a nut shell…

Applications

As I’ve already discussed, online streaming has many applications and its visible all over the Internet.  Its an effective way to deliver content quickly.   However, live streaming is costly, it requires a higher degree of technical know how and if you are running a live stream to multiple users then you cant afford to make mistakes.  Youtube has talked about a live streaming service many times and co founder Steve Chen said earlier this year that 2008 would see its arrival, however as of today (23/10/08) it is yet to appear…

Useful Links

http://www.publicsource.apple.com/projects/streaming/StreamingServerHelp/pgs/ss04.html

http://www.techcrunch.com/2008/02/29/confirmed-live-video-on-youtube-this-year/

http://mashable.com/2008/07/15/video-streaming-tools/

http://www.aaronsw.com/2002/howto/stream

http://newteevee.com/2008/10/02/youtube-to-live-stream-live-event/