Quicktime File Format (2012-08-14).pdf

MetadataMetadata Item Keys AtomThis atom has the following structure:SizeA 32-bit unsigned integer that indicates the size in bytes of the atom structureTypeA 32-bit unsigned integer value set to 'keys'VersionOne byte that is set to 0FlagsThree bytes that are set to 0Entry_countA 32-bit integer indicating the number of key arrays to follow in this atomKey_sizeA 32-bit integer indicating the size of the entire structure containing a key definition. Therefore thekey_size = sizeof(key_size) + sizeof(key_namespace) + sizeof(key_value). Since key_size and key_namespaceare both 32 bit integers, together they have a size of 8 bytes. Hence, the key_value structure will be equalto key_size - 8.Key_namespaceA 32-bit integer defining a naming scheme used for metadata keys. Location metadata keys, for example,use the ‘mdta’ key namespace.Key_value[Key_size-8]An array of 8-bit integers, each containing the actual name of the metadata key. Keys with the ‘mdta’namespace use a reverse DNS naming convention. For example, the location metadata coordinates usea metadata key_value of ‘com.apple.quicktime.location.ISO6709’.Note that:●●●Indexes into the metadata item keys atom are 1-based (1…entry_count).Zero (0) is reserved and never used as an index.The structure of key_value depends upon the key namespace.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.136