The The Item Location Box provides a directory of resources in this or

other files, by locating their containing file, their offset within that file, and their length. Placing this in binary format enables common handling of this data, even by systems which do not understand the particular metadata system (handler) used. For example, a system might integrate all the externally referenced metadata resources into one file, re-adjusting file offsets and file references accordingly.

Items may be stored fragmented into extents, e.g. to enable interleaving. An extent is a contiguous subset of the bytes of the resource; the resource is formed by concatenating the extents. If only one extent is used then either or both of the offset and length may be implied:

• If the offset is not identified (the field has a length of zero), then the beginning of the file (offset 0) is implied.

or items divided into more than one extent, should have an explicit offset and length, or use a MIME type requiring a different interpretation of the file, to avoid infinite recursion.

The size of the item is the sum of the extentLengths. Note: extents may be interleaved with the chunks defined by the sample tables of tracks.

The dataReferenceIndex may take the value 0, indicating a reference into the same file as this metadata, or an index into the dataReference table.

Some referenced data may itself use offset/length techniques to address resources within it (e.g. an MP4 file might be included in this way). Normally such offsets are relative to the beginning of the containing file. The field base offset provides an additional offset for offset calculations within that contained data. For example, if an MP4 file is included within a file formatted to this specification, then normally data-offsets within that MP4 section are relative to the beginning of file; baseOffset adds to those offsets.

• author: Sven Vollbehr <svollbehr@gmail.com>
• version: $Rev: 92 $
• copyright: Copyright (c) 2008 The PHP Reader Project Workgroup
• license: New BSD License

Located in /ISO14496/Box/ILOC.php (line 86)

ISO14496_Box
   |
   --ISO14496_Box_ILOC

Inherited Variables

Inherited from ISO14496_Box

ISO14496_Box::$_reader

Inherited Methods

Inherited From ISO14496_Box

ISO14496_Box::__construct()
ISO14496_Box::addBox()
ISO14496_Box::constructBoxes()
ISO14496_Box::getBoxes()
ISO14496_Box::getBoxesByIdentifier()
ISO14496_Box::getContainer()
ISO14496_Box::getOffset()
ISO14496_Box::getOption()
ISO14496_Box::getOptions()
ISO14496_Box::getParent()
ISO14496_Box::getSize()
ISO14496_Box::getType()
ISO14496_Box::hasBox()
ISO14496_Box::isContainer()
ISO14496_Box::setContainer()
ISO14496_Box::setOffset()
ISO14496_Box::setOption()
ISO14496_Box::setOptions()
ISO14496_Box::setParent()
ISO14496_Box::setSize()
ISO14496_Box::setType()
ISO14496_Box::__get()
ISO14496_Box::__isset()
ISO14496_Box::__set()
ISO14496_Box::__toString()
ISO14496_Box::__unset()