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Movie formats

Most of our movie clips are provided in three different formats: MPEG, QuickTime and Animated GIF. Each has it's own advantages and disadvantages. You should select the format that is best suited to your computer configuration and (in case you accessing this remotely) network connection speed.

Animated GIFs

This is the simplest format, and most browsers will play these for you automatically, without the need for a plug-in or external application. You should just be able to click on the link and the movie will play. On the other hand, you can't control the speed of the playing, and can't start and stop the movie or step through it frame by frame. Finally, since this format is the largest, in general, so animated GIF movies will take the longest to download. To help decrease the size of the files, we have reduced the dimensions of the images in this format, so they will appear a bit smaller on screen.

MPEG format

MPEG movies provide for the best compression, so they are smaller files to download, in general; however, the quality is sometimes reduced by this, as well. You may find one of the other formats is clearer. You will also need a special plug-in to view these movies; Apple's QuickTime 4 (which is available for both Macintosh and Pentium-based (or compatible) MS-Windows platforms) should do the trick. Be sure you obtain the MPEG extension for QuickTime for this.

With this plug-in, you will be able to start and stop the movie, and step through it frame by frame. The MPEG format expects to have 30 frames per second, but this makes for some very large movie files. In order to reduce the file sizes, we used 7.5 frames per second, and had each frame repeated 4 times. This should play properly at 30 frames per second, while still making the files reasonably sized. If you step through the movie one frame at a time, however, you will need to step four frames before the image changes.

Under Linux and other variants of Unix, you can use mpeg_play, xanim and other more recent programs.

QuickTime format

This format provides for reasonable compression while still maintaining good quality images. The files are generally larger than the MPEG format, but still smaller than animated GIFs. You will need to use Apple's QuickTime plug-in (available for both Macintosh and Pentium-based (or compatible) MS-Windows platforms) in order to view these movies. With this, you will be able to start and stop the movie and step through it frame by frame. The compression method is the Sorenson video method, so you will need a version of QuickTime that support it. Versions 4 and above should do.

Under Linux and other variants of Unix, xanim can play several types of QuickTime movies, but the Sorenson video codec used for these movies is unfortunately not yet supported.