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Introduction to Darwin Streaming Server
Streaming media is an increasingly popular way to distribute information on the Internet. News releases, special company events, even your private home movie library just about everyone has content that can be streamed, but very few want to make the perceived investment necessary to support streaming services. With Apple's Darwin Streaming Server (abbreviated here as DSS, it's the open source version of the official QuickTime Streaming Server [QTSS] available on Tiger Server), this investment is reduced to any modern operating system (the server runs on Windows, Linux, or Mac OS X), a Macintosh for broadcasting live events, and a means of getting video into your computer. If the explosion of iMovie HD and other video editing tools is any indication, many modern households already have the necessary infrastructure!
So, what exactly is streaming? In short, streamed video or audio does not require a user to download an entire file to view or listen to the content. Playback begins virtually instantly and the user has the ability to fast forward or rewind the content (unless it is a live stream!) just as he would a local file.
Using Darwin Streaming Server, you can stream prerecorded content, live events, and multiple media files arranged in a playlist just like iTunes. Streams created using the MPEG-4 standard or based on audio MP3s can be viewed and listened to on a variety of platforms not just QuickTime.
There are a number of different ways in which DSS can be set up and used. Large-scale installations would likely take advantage of the MBone (Multicast Backbone) or a multicast-enabled network. Multicasting takes advantage of a properly configured network's capability to broadcast a single transmission of packets to multiple machines. Multicasting reduces the total bandwidth needed for a large audience and greatly increases the number of clients that can be handled by a single server. Unfortunately, multicasting requires network setup that is beyond simply tweaking Tiger. For our purposes, we will look at a unicast configuration similar to that of Figure 25.1.
Figure 25.1. Our QTSS setup will use a single streaming server and QuickTime Broadcaster.
Unicasting, unlike multicasting, doesn't require any special network considerations. Instead of transmitting one stream to multiple clients, a unicast sends an individual stream to each viewing user. Although it consumes more bandwidth and limits the total number of simultaneous viewers, this approach is usually sufficient for modest deployments in which thousands of connections aren't likely. Unicasting is also much easier to configure, diagnose, and maintain.
Two protocols are used for delivering QuickTime streams: RTP and RTSP.
The remainder of this chapter will first focus on getting Darwin Streaming Server up and running on your Tiger computer, followed by creating live streams using the Apple QuickTime Broadcaster tool. In short, everything you need to claim your place in the online world of media broadcasting!
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