High Efficiency Image File Format Explained

High Efficiency Image File Format (HEIF)
Extension:.heif, .heifs; .heic, .heics; .avci, .avcs; .HIF
Nomimecode:1
Mime:image/heif, image/heif-sequence; image/heic, image/heic-sequence; image/avif
Uniform Type:public.heif, public.heic
Developer:Moving Picture Experts Group (MPEG)
Type:Image container
Open:Depends on contained format (e.g. HEIC vs. free AV1 Image File Format)
Extended From:ISOBMFF
Standard:ISO/IEC 23008-12 (MPEG-H Part 12)

High Efficiency Image File Format (HEIF) is an international standard defined by MPEG-H Part 12 (ISO/IEC 3008-12), first published by ISO in 2017. It is designed as a container for photographic images in any image encoding. HEIF is a special case of the general ISO BMFF format, in which all data is encapsulated in typed boxes, with a mandatory ftyp box that is used to indicate particular file types. The initial specification for HEIF provided usage details for three compression schemes, the widely supported JPEG encoding for still raster images and two video encodings that are also applicable to still image items, namely Advanced Video Coding (AVC, aka MPEG-4, Part 10 and H.264) and High Efficiency Video Coding (HEVC aka PEG-H Part 2 and H.265).

ISO Base Media File Format official specification (of which HEIF is a special case) defines multiple subtypes in relations to possible encodings:

BMFF HEIC/HEIX Registered Brands

Specific implementations of HEIF encoding are registered by MP4RA and are officially called "brands".

According to official specifications Apple HEIC registered brand is using Main or Main Still Picture profile of HEVC with an 8-bit per channel color depth and chroma subsampling of 4:2:0, while Sony and Canon HIEX registered brand may additionally increase the bit-depth to 10 bits per channel and chroma subsampling to 4:2:2 or 4:4:4.

Licensing and Patents

If BMFF HEIF is used with HEVC encoding it is worth noting that HEV is heavily encumbered with patents and Library of Congress does not recommend of using such heavily patent troublesome formats. The parties holding patents on HEVC include but are not limited to:

The uncertainty of patent encumbering is farther strengthened by unclear patents holders wordings. Holders of relevant patents, stated to the ISO that "the holders of these patent rights have assured the ISO and IEC that they are willing to negotiate licenses under reasonable and non-discriminatory terms." The specification also cautions that "some of the elements . . . may be the subject of patent rights other than those identified."

History

The requirements and main use cases of HEIF were defined in 2013.[1] [2] The technical development of the specification took about one and a half years and was finalized in the middle of 2015.[3]

Apple was the first major adopter of the format in 2017 with the introduction of iOS 11 using HEIC variant. While HEIC became the default for iPhones, it remains possible to revert the settings to allow photos to be recorded in the more recognizable JPEG format.[4]

Android devices containing the appropriate hardware encoders received support for HEIC files with the release of Android 10 (2019).[5]

On some systems, pictures stored in the HEIC format are converted automatically to the older JPEG format when they are sent outside of the system, although incompatibility has led to problems such as US Advanced Placement test takers failing due to their phones uploading unsupported HEIC images by default,[6] leading the College Board to request students change the settings to send only JPEG files.[7]

Although HEIC is gaining in popularity there are issues with compatibility, Adobe Photoshop is an example of a popular image editing software that only supports 8-bit HEIC and not 10-bit or 12-bit HEIC yet.[8]

Camera hardware (including mobile devices) are increasingly supporting outputting HEIC files and with color depth often higher than 8-bit color.[9]

Specifications

HEIF files can store the following types of data:[10]

Image items: Storage of individual images, image properties and thumbnails.
  • Image derivations: Derived images enable non-destructive image editing, and are created on the fly by the rendering software using editing instructions stored separately in the HEIF file. These instructions (rectangular cropping, rotation by one, two or three quarter-turns, timed graphic overlays, etc.) and images are stored separately in the HEIF file, and describe specific transformations to be applied to the input images. 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 when many images are stored in the same HEIF file.
  • Auxiliary image items: Storage of image data, such as an alpha plane or a depth map, which complements another image item. These data are not displayed as such, but used in various forms to complement another image item.
  • Image metadata: Storage of EXIF, XMP and similar metadata which accompany the images stored in the HEIF file.
  • Encodings inside the container

    HEIF container specification describes various encodings that can be stored inside:

    These may lead to confusion, as users cannot easily tell what kind of encoding has been used. In particular, if a user creates or receives a .heif image, they cannot immediately determine which image encoding was used. Further, presenting HEIF as better than JPEG may be misleading since truth of that statement depends on chosen encoding.

    MIAF

    The Multi-Image Application Format (MIAF) is a restricted subset of HEIF specified as part of MPEG-A.It defines a set of additional constraints to simplify format options, specific alpha plane formats, profiles and levels as well as metadata formats and brands, and rules for how to extend the format.

    AVCI: AVC in HEIF

    Advanced Video Coding (AVC, ITU-T H.264) is an older encoding format for video and images, first standardized in 2003.It is also specified as a codec to be supported in HEIF in normative Annex 5 to ISO/IEC 23008-12.The registered MIME types are image/avci for still images and image/avcs for sequences. The format is simply known as AVCI.

    Apple products support playback of AVC-encoded .avci still image files and .avcs image sequence files[11] but will only generate .heic files.

    AVIF: AV1 in HEIF

    See main article: AVIF. AV1 is a video encoding format that is intended to be royalty-free, developed by the Alliance for Open Media (AOMedia). AV1 Image File Format (AVIF) is an image format based on this codec.[12]

    The registered MIME type is image/avif for both still images and image sequences, and .avif is the file name extension.[13]

    JPEG compression formats in HEIF files

    The original JPEG standard is the most commonly used and widely supported lossy image coding format. It was first released in 1992 by ITU-T and ISO/IEC. Although Annex H to ISO/IEC 23008-12 specifies JPEG (and indirectly Motion JPEG) as a possible format for HEIF coded image data, it is used in HEIF only for thumbnails and other secondary images. Therefore, neither a dedicated MIME subtype nor a special file extension is available for storage of JPEG files in HEIF container files.

    Several other compression formats defined by the JPEG group can be stored in HEIF files:

    In 2017, Apple announced that it would adopt HEIC as the default image format in its new operating systems, gradually replacing JPEG.[21]

    WXAM, SharpP

    The proprietary image format WXAM (or wxHEPC) developed by Tencent (used within, e.g., WeChat) is apparently based upon HEVC,[22] as is SharpP, which was developed by their SNG (Social Network Group) division.[23] [24] However, their container format may not be HEIF-compatible. In March 2017, SharpP switched to AVS2[25] and was renamed TPG (Tiny Portable Graphics).[24] [26]

    Support

    Operating systems

    Web browsers

    , only Safari supports HEIC format natively.[46]

    For AVIF, Chrome, Firefox and Opera for desktop and Android support it. Safari on iOS 16 and iPadOS 16 supports AVIF format.[47]

    Image editing software

    Hardware

    Websites

    Patent licensing

    HEIF itself is a container that may not be subject to additional royalty fees for commercial ISOBMFF licensees. Note however that Nokia also grants its patents on a royalty-free basis for non-commercial purposes.[77] When containing images and image sequences encoded in a particular format (e.g. HEVC or AVC) its use becomes subject to the licensing of patents on the coding format.[78] [79] [80]

    See also

    External links

    Notes and References

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    2. Web site: Requirements for HEVC image sequences . mpeg.chiariglione.org . 2018-08-24 . 2013-07-29 . 2021-05-17 . https://web.archive.org/web/20210517080156/https://mpeg.chiariglione.org/standards/mpeg-h/high-efficiency-video-coding/requirements-hevc-image-sequences . live .
    3. Web site: Evidence motivates MPEG to launch new standardization effort for HDR . chiariglione.org . 2015-06-26 . 2018-08-24 . 2021-04-15 . https://web.archive.org/web/20210415074444/https://mpeg.chiariglione.org/sites/default/files/files/meetings/docs/w15328.docx . live .
    4. Web site: How to Stop iPhone from Taking Photos in HEIC-HEIF . Heic.Info . 15 April 2024.
    5. Web site: HEIF Imaging . 2023-11-11 . Android Open Source Project . en.
    6. Web site: Students are failing AP tests because the College Board can't handle iPhone photos . 2020-05-02 . 2022-08-25 . . Monica Chin.
    7. CollegeBoard . 1260208235132436480 . If you want to submit a photo of a handwritten AP Exam answer from an iPhone or iPad, make sure to change your camera settings so your photos are saved as JPEGs, not HEICs..
    8. Web site: File formats in Adobe Photoshop .
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    10. Web site: Overview of the High Efficiency Image File Format . JCT-VC . document JCTVC-V0072 . October 2015 . M. M. Hannuksela . E. B. Aksu . V. K. Malamal Vadakital . J. Lainema . 2015-11-25 . 2021-11-24 . https://web.archive.org/web/20211124172021/http://phenix.int-evry.fr/jct/doc_end_user/current_document.php?id=10265 . live .
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    78. Web site: macOS High Sierra tech preview: A quick look at the stuff you can't see . 2017-07-04 . 2017-06-19 . If there's one major downside to both HEVC and HEIF, it's that they're covered by patents that may need to be licensed for use in various apps and services. . 2017-06-20 . https://web.archive.org/web/20170620001037/https://arstechnica.com/apple/2017/06/macos-high-sierra-tech-preview-a-quick-look-at-the-stuff-you-cant-see/ . live .
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