High Efficiency Image File Format: Difference between revisions

Revision as of 14:36, 25 November 2015

Revision as of 15:00, 25 November 2015

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== Features ==

In [[ISO base media file format|ISOBMFF]], a continuous or timed media/metadata stream forms a ''track'', whereas static media or metadata are stored as ''items''. Consequently, HEIF has the following basic design:

* Still images are stored as items. All image items are ''independently'' encoded and do not depend on any other item in their decoding. Any number of image items can be included in the same file.

* Image sequences are stored as ''tracks''. An image sequence track can be indicated to be displayed either as a timed sequence or in a non-timed manner, such as a gallery or album of images. When there is coding dependency between images, an image sequence track is used instead of image items.

* A file may contain both image items and image sequence tracks along with other media. For example, it is possible to create a HEIF file, which includes image items or image sequence tracks conforming to HEIF, and audio and/or timed text tracks conforming to any derivative format of the ISOBMFF

Keeping the above-mentioned design principles in mind, HEIF files can store the following types of data<ref>{{Cite web|url = http://phenix.int-evry.fr/jct/doc_end_user/current_document.php?id=10265|title = Overview of the High Efficiency Image File Format|date = |accessdate = |website = |publisher = JCT-VC document JCTVC-V0072, Oct. 2015|last = M. M. Hannuksela, E. B. Aksu, V. K. Malamal Vadakital, J. Lainema|first = }}</ref>:

* '''Image Items:''' storage of individual images, image properties and thumbnail(s).

* '''Image Derivations:''' derived images are generated during run-time based on descriptions such as rotation, grid and overlay. These images depend on other images stored in the HEIF file. The storage overhead of derived images is small.

* '''Image Sequences''': storage of multiple time-related and/or temporally predicted images (like a burst-photo shot or cinemagraph animation), their properties and thumbnails. Different prediction options can be used in order to exploit the temporal and spatial similarities between the images. Hence, ''file sizes can be drastically reduced'' even when tens of images are stored in the same HEIF file.

* '''Auxiliary Image Items:''' storage of an image data which complements another image item. An alpha plane or a depth map are examples for such images. This data is not displayed as such, but used in various forms to complement another image item.

* '''Image Metadata:''' storage of [[Exchangeable image file format|EXIF]], [[Extensible Metadata Platform|XMP]] and similar metadata which accompany the images stored in the HEIF file.

Examples of above-mentioned entities can be found [http://nokiatech.github.io/heif/examples.html here].

== References ==