Nokia X10 Full Specification

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Aug 3, 2024, 11:10:56 AM8/3/24

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High Efficiency Image File Format (HEIF, ISO/IEC 23008-12) specifies the storage of individual images, image sequences and their metadata into a container file conforming to the ISO Base Media File Format (ISO/IEC 14496-12). HEIF includes the storage specification of HEVC intra images and HEVC image sequences in which inter prediction is applied in a constrained manner. Use cases supported by HEIF include:

Storage of still images as well as collection of images in a single container file,
Storage of burst photos,
Storage and efficient representation of video animations and cinemagraphs.
Support for simultaneous capture of video and still images, i.e. storing still images and timed image sequences into the same file.
Storage of images derived from other images of the file, either as derived images represented by non-destructive image editing operations or as pre-computed derived images.
Storage of focal and exposure stacks into the same container file.
Support for storing other media, such as audio and timed text, into the same container file with timed image sequences and synchronizing their playback.

As HEVC provides support for various chroma formats and sample fidelities up to lossless coding, the format can serve the whole spectrum of use cases from today's consumer devices storing images typically at 8 bits per sample to high-end professional devices with sample fidelity and dynamic range requirements going all the way up to 16 bits per sample.

Computational photography forms a new category of use cases that can benefit from the HEIF file format. Now a set of related images can be stored in a single file with associated metadata indicating relationships between different pictures.

HEIF specifies a structural format, from which codec-specific image formats can be derived. HEIF also includes the specification for encapsulating images and image sequences conforming to the High Efficiency Video Coding (HEVC, ISO/IEC 23008-2 ITU-T Rec. H.265).

In ISOBMFF, a continuous or timed media or metadata stream forms a track, whereas static media or metadata is stored as items. Consequently, HEIF has the following basic design:

1. Still images are stored as items. Typically image items are independently coded, and do not depend on any other item in their decoding. If predictively coded image items with coding dependencies are present, this is clearly signalled. Any number of image items can be included in the same file.
2. 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 of images. An image sequence track may be used instead of image items when there is coding dependency between images.

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

Files conforming to ISOBMFF consist of a sequence of data structures called boxes, each containing a four-character code (4CC) indicating the type of the box, the size of the box in terms of bytes, and the payload of the box. Boxes may be nested, i.e. a box may contain other boxes. ISOBMFF and HEIF specify constraints on the allowed box order and hierarchy.

Files conforming to HEIF start with a FileTypeBox as defined in the ISOBMFF standard, which contains a list of brands the file complies with. As the FileTypeBox is located at the start of the file, it provides easily accessible indications of the file contents to media players. Each brand is identified by its unique four-character code. The specification of a brand can include requirements and constraints for files of the brand and for file players supporting the brand. A brand included in the FileTypeBox permits a player that supports the requirements of the brand to play the file.

The brands specified in the HEIF standard are presented in Table I. The HEIF standard specifies the 'mif1' and 'msf1' structural brands. Additionally, HEVC-specific brands are specified as listed in Table I. The dedicated brand names, 'heic' and 'hevc' indicates that HEVC Main Profile is utilized.

Table I. Brands, MIME subtypes, and file extensions for HEIF. Brand Coding format Image or sequence? MIME Type MIME subtype File extension mif1 Any image image heif .heif msf1 Any sequence image heif-sequence .heif heic HEVC (Main or Main Still Picture profile) image image heic .heic heix HEVC (Main 10 or format range extensions profile) image image heic .heic hevc HEVC (Main or Main Still Picture profile) sequence image heic-sequence .heic hevx HEVC (Main 10 or format range extensions profile) sequence image heic-sequence .heic

Internet media types, also known as MIME (Multipurpose Internet Mail Extensions) types, are used by various applications to identify the type of a resource or a file. MIME types consist of a media type ('image' in the case of HEIF files), a subtype, and zero or more optional parameters. For multi-purpose files, the selection of the subtype can be made on the basis of the primary use of the file.

An optional codecs MIME parameter can be present to indicate the used coding formats of the tracks and items present in the file. The codecs MIME parameter also includes the profile-tier-level value to which an HEVC-coded image item or an image sequence track conforms. More information about the MIME type registration and optional parameter can be found in Annex D and Annex E of the HEIF standard.

Table IX provides a comparison of the features of HEIF to other selected image formats. It can be observed that HEIF is more extensible and comprehensive than the other compared file formats. Particularly the possibility to include other media types, the advanced multi-picture features, and the support for non-destructive editing make HEIF more advanced than the other formats. The rich set of features make HEIF suitable for a broad range of devices and applications, including for example burst photography.

1 In GIF and indexed color PNG encoding, lossy color quantization is applied while the color-quantized image is losslessly compressed.
2 PCM, -Law PCM and ADPCM encapsulated in RIFF WAV
3 Only for animations and tiling/overlaying
4 JPX is a box-structured format compatible with ISOBMFF. However, only the File Type box is common in JPX and ISOBMFF.
5 Encapsulation of JPEG-2000 and JPEG-XR have been specified for JPX container. Mappings for other codecs could be similarly specified.
6 JPX (ITU-T T.800 and T.801) specifies an own metadata schema, but is capable of carrying an XML formatted metadata, such as XMP.
7 JPX can contain media complying with ISOBMFF (or derivatives thereof). No accurate synchronization between JPX animations and other media.
8 TIFF as a container format facilitates extensions to other coding formats.
9 Only for animations, thumbnails, and alpha planes. Non-timed image collections not supported.
10 HEVC Main 4:4:4 16 Still Picture profile, Level 8.5, with additional constraints
11 Can be enabled through the MP extension
12 A palette index for fully transparency can be specified

It is acknowledged that a summary such as that in Table II might be somewhat incomplete when it comes to features of different formats. For example, the table does not cover some of the extensions of JPEG. We welcome feedback and corrections to the table.

Table IV illustrates coding efficiency of HEVC intra coding with respect to well-known still picture codecs. The results indicate that JPEG would require on average 139 % higher bitrate than HEVC (i.e. 2.39 times the file size) in order to achieve the same objective picture quality. For JPEG-XR and JPEG-2000 the average increase in bitrates are 66 % and 44 %, respectively.

Table V indicate that one can expect that for natural content the restricted inter coding can typically provide two to three times better compression than intra picture coding. In special cases like animations where majority of the scene is static the compression efficiency can significantly exceed those levels and be tens of times more efficient than intra coding.

Multiple images can be stored in a HEIF file. It can be useful to differentiate between them by assigning them certain roles. The roles specified in HEIF are listed and described in Table VI. Note that a single image can be associated with more than one role.

Table VI. Roles of images. Role Description cover image A representative image of the image items and image sequence tracks of the file.
The cover image should be displayed when no other information is available on the preference to display the image items of the file. The file can have only one cover image. thumbnail image A smaller-resolution representation of a master image. auxiliary image An image that complements a master image. For example, an alpha plane or a depth map.
Can assist in displaying the master image but is not typically displayed as such. master image An image that is not a thumbnail image or an auxiliary image. Typically represents a full-resolution displayable image. hidden image An image that should never be displayed. Can be present in the file for example as an input image for a derived image. pre-derived coded image A coded image that has been derived from other images.
For example, a high dynamic range image derived from an exposure-bracketed set of images. coded image A coded representation of an image. derived image An image that is represented in a file by an indicated operation to indicated input images and can be obtained by performing the indicated operation to the indicated input images.

HEIF allows the storage of image properties which are shared among different image items in a compact way. These properties are stored in ItemPropertyContainerBox. There are mainly two types of properties: descriptive and transformative. Descriptive properties provide information about the image item without applying modifications on the image itself. Transformative properties provide information about the transformative modification that needs to be done on the image item. The order of application of these properties to the image items are defined in the standard. Table VII lists currently defined properties. In addition to descriptive image properties, image items can optionally be characterized with metadata items, the format of which follows Exif, XMP, or MPEG-7 metadata.