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16 Chapter 1 Overview of QuickTime Streaming

Live Versus On-Demand Delivery

Real-time streaming media is delivered in two ways: live and on demand. QuickTime

Streaming Server delivers both.

Live events, such as concerts, speeches, and lectures, are commonly streamed over the

Internet as they happen, using broadcasting software such as QuickTime Broadcaster.

Broadcasting software encodes a live source, such as video from a camera, in real time

and delivers the resulting stream to the server. The server then serves, or “reflects,” the

live stream to clients. Regardless of when people connect to the stream, everyone sees

the same point in the stream at the same time. You can simulate a live experience with

recorded content by broadcasting from an archive source such as a tape deck or by

creating playlists of media on the server.

With on-demand delivery, such as a movie or an archived lecture, each customer

initiates the stream from the beginning, so no one comes in “late” to the stream. No

broadcasting software is required for on-demand delivery.

Progressive Download (HTTP) Delivery Versus Streaming (RTP/

RTSP) Delivery

Progressive download (sometimes called “Fast Start”) is a method of delivering a movie

over the Internet so that it can start playing before its file is fully downloaded. With

progressive download, a movie has all the data needed to start playing it at the

beginning of the file, so QuickTime can start to play the movie as soon as the first part

of the file is transferred. Unlike streaming, where you can watch movies without

downloading any files, Fast Start movies are actually downloaded to the viewer’s

computer.

A Fast Start movie can be self-contained, so that all the data is stored inside the movie

itself, or it can include pointers to data located on the Internet. You can watch

progressive download movies in a web browser using the QuickTime plug-in or using

QuickTime Player.

You can create progressive download movies for viewers with various connection

speeds (called “reference movies”) and a streaming movie for viewers with the fastest

connections.

Instant-On Streaming

Viewers watching a streaming video with QuickTime 6 and later will benefit from

Instant-On, an advance in Apple skip-protection technology that dramatically reduces

buffer, or wait, time for an instantaneous viewing experience. Viewers can click around

or scrub video as if it were on their hard disks.

Users must have a broadband connection to experience Instant-On streaming. The

responsiveness of Instant-On streaming is affected by available bandwidth and size, or

data rate, of the content. Responsiveness can also be affected by the codec used.

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