Video and audio tracks are the most common forms of QuickTime media tracks. A QuickTime video track can be created from digital video (DV), digitised analog video, a 2D or 3D animation program, or any other source capable of generating an image sequence in any of the file formats importable into QuickTime. Movies can have many video tracks, which can be edited, layered and have effects and transitions applied to them. One has complete control over such properties as frame size, frame rate (frames per second), data rate and video compression.

• Video compression: Video compression is necessary to make the movies play at full speed on most computers or to be small enough to view on the web. QuickTime supports a wide rage of codecs (compressors-decompressors), both lossless (high quality, large files) and lossy (lower quality, small files). To see the codec options, export the movie (using Export... in the File menu) as a QuickTime movie, choose Options... and then Video Setting ...The Apple Sorenson codec is recommended as a high-quality lossy codec for video and rendered animation.

• Audio compression: QuickTime offers a variety of sound and music compressors. QDesign’s music codec is recommended for its high quality and small-size files.

Streaming Using QuickTime

Streaming is the process of sending media over a network for viewing in real time. The data is simply being displayed as it arrives by the QuickTime plug-in and in QuickTime Player no copy remains on the viewer’s hard disk.

Viewing a Stream

One can view streamed media by:

• Tuning in directly to a live or pre-recorded 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

Fast Start Movies

With QuickTime, one can watch movies as they download using ordinary HTTP or FTP transfer protocols. This is not streaming but a unique feature of QuickTime called Fast Start or Progressive Download.

With Fast Start, the audience can download an entire QuickTime movie at the highest data rate that their connections can support. As soon as the initial part of the movie has been downloaded, QuickTime Plug-in begins to play it back in the browser while it continues to download the rest. The audience is left with a complete movie file that they can save and replay as often as they want. No special streaming software on the server is needed. All that one needs to create is a Fast Start movie (which you can do using QuickTime Player) and embed it in the web page.

A Fast Start movie can start playing long before the whole file has downloaded—typically within a few seconds of starting the file transfer. If the net connection is faster than the movie’s data rate, the movie plays smoothly as it arrives, with no waiting. It’s an optimal experience for the audience. A Fast Start movie can also include pointers to data located in other files on the web server, a local disk or CD, or any web URL.

Transport Protocols

QuickTime streams are sent using Real-Time Transport Protocol (RTP). RTP is similar to the more familiar HTTP and FTP file transfer protocols but it is tailored for the special needs of real-time streaming.

Unlike HTTP and FTP, RTP does not download an entire movie to the client computer. Instead, it siphons out a thin, one-way data stream at a constant data rate that plays the broadcast in real time. A streamed one-minute movie plays in exactly one minute. As long as the connection has enough bandwidth to handle the data stream, the movie will play. After the data is displayed, it is discarded. Viewers can see the broadcast again only by requesting it from the streaming server.