About Darwin streaming

    Streaming is a technology that lets you view multimedia as it arrives at your computer. With streaming, your users can tune in to broadcasts of live or prerecorded media, or they can view prerecorded media on demand. Users see streamed media as soon as it reaches the computer; they don't have to wait to download files.

    Media streams are sent from a server to a client computer in one of several ways: unicast, multicast, reflected unicast, or reflected multicast. Unicast is a one-to-one transmission. Each client computer that tunes in to a stream receives its own stream. A multicast stream is sent to a group address. This means several client computers can tune in to the same stream. With a reflected multicast, the server receives a multicast stream, then sends it to each client that tunes in to the stream.

    A QuickTime movie can be streamed only if it has been hinted. Hinting involves using software that analyzes the media data within a movie and creates hint tracks which tell the streaming server software how to package the data to send over the network. You can hint movies using the Pro version of QuickTime Player. When you hint a movie, QuickTime Player creates one hint track for each media track in the movie. The hint tracks are stored within the movie, and the movie becomes a hinted QuickTime movie.

    For more information about authoring media for QuickTime streaming, see the following Web site:
    QuickTime authoring Web site
    www.apple.com/quicktime/authoring/

Viewing streamed media: How it works

    A user can view streamed media by
    tuning in directly to a live or prerecorded broadcast using QuickTime Player
    using QuickTime Player to view multimedia on demand
    using a Web browser to point to a Web page that has streamed media embedded in the page

    When a user tunes in to a live broadcast, the QuickTime streaming client (for example, QuickTime Player) sends a request to the Darwin Streaming Server. The server looks for a Session Description Protocol (SDP) file, and if it's found, begins to send the media to the client computer. An SDP file contains information about the format, timing, and authorship of the live broadcast. SDP files are created by broadcast software on the computer that captures the live media, but the SDP file must be copied to the streaming server before the media can be broadcast.

    When a user tunes in to a prerecorded broadcast, a similar process happens: the server looks for an SDP file. In this case, an SDP file is created by PlaylistBroadcaster. If the SDP file isn't created on the streaming server, it must be copied to the streaming server before the prerecorded media can be broadcast.

    When a user uses QuickTime Player to view multimedia on demand, the client computer sends a request for the server to play the multimedia file. The server looks for the hinted movie file, and if it's found, sends the media to the client computer.

    When a user starts to play streamed media through a Web page, the QuickTime streaming plug-in sends a request to the server.

 


Table of contents