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Matrices

QuickTime files use matrices to describe spatial information about many objects, such as tracks within a movie.

A transformation matrix defines how to map points from one coordinate space into another coordinate space. By modifiying the contents of a transformation matrix, you can perform several standard graphics display operations, including translation, rotation, and scaling. The matrix used to accomplish two-dimensional transformations is described mathematically by a 3-by-3 matrix.

All values in the matrix are 32-bit fixed-point numbers divided as 16.16, except for the {u, v, w} column, which contains 32-bit fixed-point numbers divided as 2.30. Figure 4-1 depicts how QuickTime uses matrices to transform displayed objects.


Figure 4-1 How display matrices are used in QuickTime

Figure 4-1 How display matrices are used in QuickTime

Figure 4-2 Applying the transform

Figure 4-2 Applying the transform


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Last updated: 2001-03-01

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