Using QTSetAtomData

Q:  I'm using QTSetAtomData to modify some atom data, but I'd like to know what this call does with the atomData pointer being passed to it.

A: QTSetAtomData is used to change the data of a leaf atom. It copies the number of bytes passed in as dataSize from the address atomData to the contents of atom. It will resize the atom if necessary.

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OSErr QTSetAtomData(QTAtomContainer container, QTAtom  atom, long dataSize, void *atomData)

When using this function be aware that the position (offset) of any atoms within the QTAtomContainer greater than the passed in QTAtom will need to be re-found using QTFindChildByID or QTFindChildByIndex. Also, the passed in QTAtomContainer must be unlocked; this call will fail if you've locked the atom container by calling QTLockAtomContainer.

Understanding QuickTime Atoms

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