QuickTime 4 Reference

QuickTime Vector Data Streams

In QuickTime, paths and their characteristics are represented by a series of atoms in a QT atom container. This ordered series of atoms is called a vector data stream. For more information about QT atom containers, see "QuickTime Atoms" (page 47) .

A vector data stream contains atoms for paths, atoms that specify attributes of paths, and a final atom that marks the end of the data stream. To draw paths, QuickTime traverses the atoms in a vector data stream in order. When it finds an atom for a path, it draws the path using the current attribute values. When it finds an atom for an attribute, the new attribute value replaces the previous value of the attribute. If QuickTime has not found an atom for a particular attribute before drawing a path, it uses the default value for the attribute.

Within a vector data stream, all values must be aligned on long-word boundaries and stored in big-endian format. Values that you add using vector component functions automatically have the proper alignment and format. For descriptions of these functions, see "Vector Codec Component Functions" .

Contents of a Vector Data Stream