---

QuickTime in Perspective

The QuickTime API is dedicated to extending the reach of application developers by letting them invoke the full range of multimedia’s capabilities. It supports a wide range of standards-based formats, in addition to proprietary formats from Apple and others. The QuickTime API is not static, however, and has evolved over the course of the last decade to adopt new idioms, new data structures, and new ways of doing things.

The C/C++ portion of the QuickTime API comprises more than 2500 functions that provide services to applications. These services include audio and video capture and playback; movie editing, composition, and streaming; still image import, export, and display; audio-visual interactivity, and more.

A new Cocoa (Objective-C) API for QuickTime, available in Mac OS X v10.4 and v10.3, provides a much less complex programmer interface, and represents a distillation and abstraction of the most essential QuickTime functions as a small set of classes and methods. A great deal of functionality has been packed into a relatively small objective API.

In this section:

New Features of QuickTime 7
New Directions in QuickTime 7
In Summary QuickTime 6 through QuickTime 7

New Features of QuickTime 7

This release of QuickTime includes a number of major new features for users, developers, and content creators, including improvements in the QuickTime architecture, file format, user interface, and API. There are significant improvements in the audio, video, and metadata capabilities, as well as a new Cocoa API, and numerous other enhancements.

• “Changes to QuickTime Player and QuickTime Pro” describes the new user interface for QuickTime Player and QuickTime Pro and some of the changes from previous versions of the player.

• “New QuickTime Kit Framework” describes a new Cocoa (Objective-C) framework for developing QuickTime applications. This new API opens the world of QuickTime programming to a new group of developers without requiring them to learn the large, complex C/C++ QuickTime API. The new framework encapsulates a tremendous amount of QuickTime functionality in a small, easily-mastered API with a handful of new objects, classes, and methods.

• “Audio Enhancements” describes the many new audio features of QuickTime 7, including support for multichannel sound, playback, capture, compression, and export of high-resolution audio, a new sound description, and new functions for movie audio control, audio conversion configuration, audio extraction, movie export, and level and frequency metering.

• “Video Enhancements” describes QuickTime’s new support for frame reordering video compression and the H.264 codec. Frame reordering support is a major advance that involves new sample tables for video, allowing video frames to have independent decode and display times. This allows improved display, editing, and compression of H.264 and other advanced video codecs. A new set of functions and structures are introduced to allow developers to work with samples that have independent decode and display times.

• “New Abstractions Layers For OpenGL Rendering” describes the new Visual Context, an abstraction layer that eliminates dependence on graphics worlds (GWorlds) and supports rendering directly to engines such as OpenGL.

• “Replacing NewMovieFrom... Functions” describes the NewMovieFromProperties function, which allows you to set up properties before creating a movie. This function also allows you to create movies that are not necessarily associated with a graphics world, movies that can render their output to a visual context, such as an OpenGL texture buffer, and movies that play to a particular audio device.

• “QuickTime Metadata Enhancements and API” describes the new QuickTime extensible metadata format, allowing developers to efficiently reference text, audio, video, or other material that describes a movie, a track, or a media. Support is also added for including metadata from other file types in native format; the QuickTime 7 release includes native support for iTunes metadata.

• “QuickTime Sample Table API” describes the new API for working with QT Sample Tables, a logical replacement for arrays of media sample references. The new API greatly extends the functionality of media sample references, and the new API supports frame reordering compressed media.

• “JavaScript Support and Accessibility in Safari” describes the JavaScript support for the Safari browser. This means you can now use JavaScript to control QuickTime when web pages are viewed using Safari.

• “Other Changes and Enhancements” discusses QuickTime 7’s new persistent cache option, which is important for web authors and content developers to understand because it may impact the way that QuickTime content is downloaded and saved from their websites. New updates and fixes to QuickTime for Java are also discussed in this section.

New Directions in QuickTime 7

Key areas of change evident in QuickTime 7 are:

• A shift of emphasis toward a Core Audio approach to sound, and away from the Sound Manager approach, throughout QuickTime.

• A shift of emphasis toward configuring components using component properties and an abstraction layer, or context, and away from the exclusive use of standard dialogs supplemented by direct access to low-level components.

• A shift of emphasis toward a more object-oriented organization, with more high-level functionality in QuickTime itself supporting lighter-weight applications.

What Developers Need To Do

If you work with audio at a relatively low level, you should become familiar with the Mac OS X Core Audio framework and learn how it differs from the older Sound Manager. The use of Core Audio concepts and data structures is becoming ubiquitous in QuickTime for both Mac OS X and Windows. For details, see Apple’s Core Audio documentation.

If you work directly with components, you should become familiar with the API for discovering, getting, and setting component properties. While standard dialogs for configuration are still common, there are often times when either no dialog or an application-specific dialog is preferable, as well as cases where low-level control or device-specific configuration is needed that a standard dialog cannot supply.

For example, the component property API allows configuration at any level of detail without requiring a user interface dialog or direct communication with low-level components. In many cases, an abstraction layer, or context––either visual or audio––can be created, allowing transparent connection to different kinds of low-level components, devices, or rendering engines.

The new extensible QuickTime metadata format, discussed in the section “QuickTime Metadata Enhancements and API,” uses a similar method of configuration through an abstract set of properties, as a means of “future-proofing” the architecture. The same is true of the new API for working with QuickTime sample tables, described in the section “QuickTime Sample Table API.”

Object Model Evolution

A substantial reorganization of the QuickTime engine has been taking place “under the hood” in this software release. This reorganization is intended to allow increased access to QuickTime functionality from object-oriented frameworks such as Cocoa (Objective-C).

As the QuickTime document object model continues to evolve, the goal is to provide developers with easier access to the more powerful parts of the QuickTime engine using relatively lightweight object-oriented applications or even scripts––without having to delve into the large and sometimes complex procedural C/C++ QuickTime API. If you haven’t experimented with Cocoa and the Xcode tools yet, this is a good time to get started.

In Summary QuickTime 6 through QuickTime 7

The following table summarizes the point releases of QuickTime 6 and the features of QuickTime 7.

---