QuickTime 4 Reference

Specifying a Part of a File to Import

When using certain movie import components, applications can import data from a part of a file rather than the entire file by calling MovieImportSetOffsetAndLimit or MovieImportSetOffsetAndLimit64 . The latter function accomodates 64-bit offsets instead of just 32-bit offsets. These functions let an application specify a byte offset into the file at which the import operation begins and another offset, known as the limit, that indicates the last data in the file that can be imported. This function is especially useful when one file format is embedded in another; it allows an application to skip header data for the enclosing file and begin importing data at the start of the desired format.

Not all movie import components support the MovieImportSetOffsetAndLimit or MovieImportSetOffsetAndLimit64 function. Those that do include the movie import components provided with QuickTime for the kQTFileTypeAIFF , kQTFileTypeWave , and kQTFileTypeMuLaw file types. Those that do not return the result code badComponentSelector in response to a MovieImportSetOffsetAndLimit or MovieImportSetOffsetAndLimit64 call. If your export component implements MovieImportSetOffsetAndLimit64 , it should implement MovieImportSetOffsetAndLimit too, since older clients may not use the new 64-bit offset version of the call.