Technical Q&A's

QTPC 06 - Creating Sample Descriptor Atoms for a Non-Mac Device (1-Aug-95)

Q We have a non-Mac device that creates and reads QuickTime movies, and we need to pass additional information about the images between the non-Mac device and our QuickTime codec. It seems that the logical place to put this information is in an ImageDescription extension (within the 'stsd' atom), since this is about all that's accessible to a codec. Is the format of this extension documented anywhere? We've managed to look at the extension created by SetImageDescriptionExtension, and the format seems simple, but it'd be nice to know what the "official" format for this is.

A Appendix A of Inside Macintosh: QuickTime has a listing of the atoms and their formats on page 4-35. Note that each media format has its own sample-description tables. In some cases, these are not directly accessible (Music architecture) unless you dump the information yourself.

The official guideline is to use, if possible, the provided APIs for creating sample descriptor atoms. If you are working on a platform for which we don't have these toolbox APIs, you have to either reverse-engineer it, or ask for a source-code license agreement to get real source code showing how the atoms are constructed.
For details regarding licensing part or all of the QuickTime source code, Contact Apple Software Licensing (AppleLink SW.LICENSE).

Technical Support
Technical Q&As
Previous Question | Contents | Next Question