Quicktime File Format (2012-08-14).pdf

Basic Data TypesGraphics ModesA transformation matrix defines how to map points from one coordinate space into another coordinate space.By modifying the contents of a transformation matrix, you can perform several standard graphics displayoperations, including translation, rotation, and scaling. The matrix used to accomplish two-dimensionaltransformations 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, whichcontains 32-bit fixed-point numbers divided as 2.30. Figure 5-1 (page 321) and Figure 5-2 (page 321) depict howQuickTime uses matrices to transform displayed objects.Figure 5-1 How display matrices are used in QuickTimea b ux y 1 x c d v = x' y' 1txtywFigure 5-2Applying the transformMovie atomAtom sizeType = 'moov'Movie header atomClipping atom'mvhd'‡'clip'One or more track atoms'trak'User data atomColor table atom'udta''ctab'‡ Required atomGraphics ModesQuickTime files use graphics modes to describe how one video or graphics layer should be combined with thelayers beneath it. Graphics modes are also known as transfer modes. Some graphics modes require a color tobe specified for certain operations, such as blending to determine the blend level. QuickTime uses the graphicsmodes defined by Apple’s QuickDraw.The most common graphics modes are and ditherCopy, which simply indicate that the image should notblend with the image behind it, but overwrite it. QuickTime also defines several additional graphics modes.Table 5-3 (page 322) lists the additional graphics modes supported by QuickTime.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.321