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Other Changes and Enhancements

This section discusses the following changes and enhancements that are available in QuickTime 7.

In this section:

New Persistent Cache Option
Updates to QuickTime for Java
Support for Quartz Composer

New Persistent Cache Option

QuickTime 7 introduces a new persistent cache option, which is enabled in the System Preferences > QuickTime > Browser panel, as shown in Figure 2-38. Users, web authors, and web content developers should understand the consequences of this new option because it may impact the way that QuickTime content is downloaded and saved from their websites. The reason is that QuickTime’s caching behavior has changed in this release.

Changes to File Caching

By default, the user preference is set to “Save movies in disk cache.” This means that files downloaded by QuickTime and written to the cache will now stay in the cache when the last connection to the file is closed. By contrast, in pre-QuickTime 7 versions, downloaded files would be written to disk and but only remain there as long as the user kept open a connection to the file. After the movie was closed, the local file would be deleted. If you wanted to look at the movie again, you would have to download the file in its entirety another time.

If the user unchecks the preference, QuickTime’s old behavior prevails—that is, movies downloaded to disk will only be saved as long as they remain open. There may be situations, for example, when unchecking the box is warranted: users don’t want any QuickTime content to be cached perhaps for privacy reasons, or if they don’t have enough disk space on their computers.

When the preference is checked, movies downloaded by QuickTime will be saved in the cache. The slider allows the user to set the maximum size of the cache (the minimum is 100 MB). Note that QuickTime’s cache is per user, not computer wide. This means that if you have more than one account on the computer, each user’s setting and cached movies are for themselves only.

When the cache is on, files may not remain in the persistent cache because of settings on the server. If you have administrator (admin) access to a server, you can tell the server to include information in the file header that specifies how long it is allowed to stay on the user’s computer. The header can say, “Don’t cache this at all.” Or, “Only keep it for a week.” QuickTime pays close attention to the information that is stored in the headers.

In particular, when the cache is enabled QuickTime honors the “expiration date,” often supplied by web servers to inform clients of how long a file remains valid after it has been downloaded. Until the expiration date supplied by the server is reached, QuickTime will respond to additional requests for the file by supplying the file from the cache instead of by fetching it again from the server. This remains true even if the file is changed on the server before the expiration date is reached. Previous versions of QuickTime as described above always downloaded a file afresh, if a previous version of it was no longer still open and in use, and therefore changes to files made before the expiration date would often be accessible immediately.

How To Control File Caching

There are several ways to control QuickTime’s file caching behavior. Each step, listed below, may be appropriate for a different situation:

• HTTP headers. Useful only if you have admin access to the server on which the files are posted. Consult your web server documentation for specifics (for example, look for “Cache-Control: no-cache” and “Expires:”).

• “cache” EMBED/OBJECT attribute. Useful if your movies are embedded in HTML pages, but you don’t have adminaccess to the server. This is a very common situation.

  In previous versions of QuickTime, this tag told the plug-in to ask the browser not to keep an embedded movie in its cache. This is still true, but now it also tells the plug-in to not keep the movie in the QuickTime persistent cache either.

• XML movies. The “cache” attribute has been added to QuickTime Media Link importer. Adding ‘cache=”false”’ to a media link movie will keep it from being saved in QuickTime’s persistent cache. See the documentation QuickTime Media Links XML Importer for more information about this movie importer.

When a movie is tagged as “not cacheable” with any of these methods, QuickTime will not keep the movie or any media loaded by it in the persistent cache (for example, sprite images loaded by URL).

Updates to QuickTime for Java

QuickTime for Java (QTJ) is now fully supported in QuickTime 7. QTJ is now installed by default in QuickTime 7.

This release includes a number of important bug fixes requested by QuickTime for Java developers. These are as follows:

• Major fixes for issues related to drawing and correct QTComponent rendering

• Compatibility with headless applications

• Fixes for issues related to movie progress procedures and movie exporting

• Fixes for Applet issues, including support for MPEG video playback in an applet

• Support for 2-byte character file names

• Security fixes

Support for Quartz Composer

QuickTime can read Quartz Composers. Also, Quartz Composer compositions can be exported as QuickTime movies.

You can accomplish this either by using the Export menu command in the Quartz Composer Editor, or by opening the composition in QuickTime Player and saving it as a movie.

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