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| These components and the interfaces they support are discussed in Inside Macintosh: QuickTime Components. | | These components and the interfaces they support are discussed in Inside Macintosh: QuickTime Components. |
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| + | =Movie Toolbox= |
| + | QuickTime allows you to manipulate time-based data such as video sequences, audio sequences, financial results from an ongoing business operation, laboratory data recorded over time, and so on. QuickTime uses the metaphor of a movie to describe time-based data. Therefore, QuickTime stores time-based data in objects called movies. |
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| + | Just as a cinematic movie can contain several tracks (for example, a video track and a sound track), a single QuickTime movie can contain more than one stream of data. Following the movie metaphor, each of these data streams is called a track. Tracks in QuickTime movies do not actually contain the movie's data. Rather, each track refers to a single media that, in turn, contains references to the actual media data. The media data may be stored on disks, CD-ROM volumes, videotape, or other appropriate storage devices. |
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| + | At the most basic level, the Movie Toolbox allows you to process time-based data. As such, the Movie Toolbox must provide a description of the time basis of that data as well as a definition of the context for evaluating that time basis. In QuickTime, a movie's time basis is referred to as its time base. Geometrically, you can think of the time base as a vector that defines the direction and velocity of time for a movie. The context for a time base is called its time coordinate system. Essentially, the time coordinate system defines the axis on which the time base vector is plotted. The smallest single unit of time marked on that axis is defined by the time scale as the units per absolute second. |
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| + | ===Tracks=== |
| + | A movie can contain one or more tracks. Each track refers to media data that can be interpreted within the movie's time coordinate system. Each track begins at the beginning of the movie. However, a track can end at any time. In addition, the actual data in the track may be offset from the beginning of the movie. Tracks with data that does not commence at the beginning of a movie contain empty space that precedes the track data. |
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| + | All of the tracks in a movie use the movie's time coordinate system. That is, the movie's time scale defines the basic time unit for each of the movie's tracks. Each track begins at the beginning of the movie, but the track's data might not begin until some time value other than 0. This intervening time is represented by blank space--in an audio track the blank space translates to silence; in a video track the blank space generates no visual image. Each track has its own duration. This duration need not correspond to the duration of the movie. Movie duration always equals the maximum duration of all the tracks. |
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| + | A track is always associated with one media. The media contains control information that refers to the data that constitutes the track. The track contains a list of references that identify portions of the media that are used in the track. In essence, these references are an edit list of the media. Consequently, a track can play the data in its media in any order and any number of times. |
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| =Notes= | | =Notes= |