Format Identifier/Offset Pair
The second part of the property set stream contains one Format Identifier/Offset Pair. The FMTID is the name of the property set; it uniquely identifies how to interpret the contents of the following section. The Offset is the distance, in bytes, from the start of the whole stream to where the section begins.
The following structure is helpful in handling Format Identifier/Offset Pairs.
typedef struct tagFORMATIDOFFSET
{
FMTID fmtid ; // Name of the section.
DWORD dwOffset ; // Offset for the section.
} FORMATIDOFFSET;