QuickTime Overview

Overview

QuickTime is a cross platform system-level software package for Macintosh, Windows and Java which adds the capability to play movies, synthesize music, display animations, view virtual reality worlds and add multimedia capability to the computer desktop.

QuickTime is implemented as a set of extensions on the Macintosh platform and a dynamic-link library (DLL) on Windows. It can process video data, still images, animated images (also known as sprites), vector graphics, multiple sound channels, MIDI music, 3D objects, virtual reality objects, panoramas and text. The number of data formats QuickTime recognizes is impressive. Currently, more than 70 different formats can be imported or exported and as formats are added, applications created today will work with them automatically.

QuickTime is readily extensible. It is built in a modular fashion made up of many software components installed and accessed through the Component Manager. These built-in components handle the most common multimedia tasks. Developers can expand on these capabilities by writing custom components to augment or completely replace QuickTime's capabilities if desired.

An important concept to remember is the idea of "time-based media" and how it can be manipulated. QuickTime is a generalized way to define time lines and organize information along these time lines.

The QuickTime API is large to say the least, and attempting to understand it all is a daunting task. However, QuickTime's modularity allows you to do many things easily and quickly with as little has a half dozen calls! For example, you can selectively work with the Movie Toolbox alone or Graphics Importers without needing to visualize all of the underlying components or API calls. You don't need to understand it all to start working with it.

Architecture

QuickTime comprises two main managers - the Movie Toolbox and the Image Compression Manager - plus a set of built-in components.

The diagram shows the relationships between these managers and components for an application playing a movie.

Movie Toolbox

Applications gain access to the capabilities of QuickTime by calling functions in the Movie Toolbox. The Movie Toolbox lets an application store, retrieve, and manipulate time-based data and provides functions for editing movies.

Image Compression Manager

Single image data may require a large amount of storage space. A sequence of images, like those contained in a QuickTime movie can demand many times as much space. The Image Compression Manager provides a device-independent and driver-independent means of compressing and decompressing images and sequences of images, thereby minimizing the storage requirements for any application that works with images.

In most cases applications use the Image Compression Manager indirectly by calling Movie Toolbox functions or by displaying a compressed picture. However, if an application compresses images or makes movies with compressed images, it may call some Image Compression Manager functions directly.

Components

Apple ships a number of built-in components with QuickTime. These built-in components provide essential services to applications and to the managers that make up the QuickTime architecture. The Apple-defined component types include image processors, media handlers, and miscellaneous utilities.

QuickTime's built-in data processing components perform these tasks:

• Movie controller components let applications play movies through a standard user interface.
• Image compressor components compress and decompress image data.
• Image compression dialog components let the user specify the parameters for compression operations.
• Image transcoder components convert compressed files from one format to another.
• Video digitizer components let applications control video digitization by external devices.
• Movie data-exchange components (also known as Movie Import and Movie Export components) let applications move various types of data into and out of QuickTime movies.
• Video output components convert QuickTime movies into video streams.
• Graphics import components let applications work with still image files by providing a simple API that works with a wide variety of image file formats.
• Graphics export components let applications export still image files using a standard easy to use API.
• Music components process and synthesize music tracks in QuickTime movies.
• Effects and transitions components implement video synthesis, video filters and video transitions, including the 133 standard SMPTE transitions. These components are implemented as a subcategory of image decompressor components.
• Preview components are used by the Movie Toolbox's standard file preview functions to display and create visual previews of file contents.

QuickTime built-in media handling components:

Media handler components implement the behavior of different track types. They deal with the specifics of how a particular track's media data should be presented to the viewer.

• Video media handler Component implements video tracks by calling the Image Compression Manager to display video samples.
• Sound media handler Component implements sound tracks by calling the Sound Manager to play sound samples.

QuickTime built-in utilities perform these tasks:

• Clock components provide timing services for applications that use QuickTime.
• Standard Sound component lets an application present the user with a dialog for configuring sound settings.
• Sequence grabber components let applications preview and record video and sound data as QuickTime movies.
• Sequence grabber channel components handle the acquisition of individual data streams for sequence grabber components. For example, the video sequence grabber channel component acquires video.
• Text channel components are sequence grabber channel components for text.
• Sequence grabber panel components let sequence grabber components obtain configuration information from the user for a particular sequence grabber channel component.

References

Technical Publications - Introduction to QuickTime

Movie Toolbox

Component Manager

Image Compression Manager

Media Handlers