QuickTime 4 Reference

How the Base Exporter Chooses a Mode

When an application calls GraphicsExportDoExport , the base exporter asks the following questions:

Can QuickTime transcode?

It calls the format-specific exporter's GraphicsExportCanTranscode function. If the answer is yes, it calls the exporter's GraphicsExportDoTranscode function.

Otherwise,

Can QuickTime use a compressor?

It calls the format-specific exporter's GraphicsExportCanUseCompressor function.

If the answer is yes, it calls the Image Compression Manager to compress using the compressor and parameters specified in the atom container. This is done in the base exporter's GraphicsExportDoUseCompressor function. (Usually the format-specific exporter does not need to override this function and should simply delegate it. If the format-specific exporter's format is a container format [such as a PICT or QuickTime Image], it can override and delegate this in order to encapsulate the compressed data in the container format.)

Otherwise,

QuickTime must perform a standalone export.

If neither transcoding nor compressing is appropriate, it calls the format-specific exporter's GraphicsExportDoStandaloneExport function.

For more information on the implementation of these functions, see their entries in "Graphics Exporter Components Reference" .