wiki：High Efficiency Image File Format

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High Efficiency Image File Format (HEIF)Filename extension.heif, .heicInternet media typeimage/heif, image/heic, image/heif-sequence, image/heic-sequenceUniform Type Identifier (UTI)public.heif, public.heicDeveloped byMoving Picture Experts Group (MPEG)Type of formatImage Container FormatStandardISO/IEC 23008-12Websitehttp://mpeg.chiariglione.org/standards/mpeg-h/image-file-format

High Efficiency Image File Format (HEIF, often pronouncedheef)^[1][2][3][4] is a file format for individual images and image sequences. It was developed by theMoving Picture Experts Group (MPEG) and is defined by MPEG-H Part 12 (ISO/IEC 23008-12).

The HEIF specification also defines the means of storing High Efficiency Video Codec (HEVC)-encoded intra images and HEVC-encoded image sequences in which inter prediction is applied in a constrained manner.

HEIF files are compatible with the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12) and can also include other media streams, such as timed text and audio.

Contents

• 1History
• 2Use cases
  • 2.1Digital cameras and smartphones
  • 2.2Web pages and Internet-connected image applications
  • 2.3Image editing
• 3Features
• 4HEVC Image File Format
  • 4.1Implementation
• 5Patent licensing
• 6Related standards
• 7See also
• 8References
• 9External links

History

The requirements and main use cases of HEIF were defined in 2013.^[5][6] The technical development of the specification took about 1.5 years and was finalized in summer 2015.^[7]

In June 2017, Apple announced support for HEIF in macOS High Sierra and iOS 11 which were released in September 2017.^[8][9][10]

Use cases

Some usage scenarios that are facilitated by HEIF are described below:

Digital cameras and smartphones

To save storage space, HEIF-encapsulated HEVC-coded images can be used for compressing the full-resolution images while keeping a lower-resolutionJPEG copy (e.g. at 4K resolution or below) for on-screen displaying purposes.

Digital cameras and smartphones can use HEIF to achieve single-file packaging of burst photos, focal stacks, and exposure stacks. Similarly, simultaneously captured video and still images can be stored in the same HEIF file. HEIF also enables storage of any image collections into a single file, which can be shared easily.

Web pages and Internet-connected image applications

The picture element of HTML5.2 provides the capability of indicating multiple alternatives for the same image, out of which the web browser can select the one that best suits its purpose. A motivation for web pages and connected applications to start using HEIF is to reduce the web page and image content download times.

Image editing

Changing of the orientation and cropping are basic features of HEIF and require no re-encoding of the images. Additionally, HEIF introduces a framework for non-destructive editing operations, which can be specified by external specifications. This feature can be used by image editing applications so that the editing instructions are kept in the same file as the original image.

Features

HEIF files can store the following types of data:^[11]

• 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 image data which complements another image item. An alpha plane or a depth map are examples for such images. 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.

HEVC Image File Format

• HEVC image players are required to support rectangular cropping and rotation by 90, 180, and 270 degrees. The primary use case for the mandatory support for rotation by 90 degrees is for the photo shooting situations in which the camera orientation is incorrectly detected or concluded. This requirement makes it possible to manually adjust the image or image sequence orientation afterwards without the need for re-encoding the image or image sequence. Similarly, cropping may be useful to enable post-shooting zoom without the need for re-encoding. As rotation by 90, 180, or 270 degrees as well as cropping are mandatory for all HEVC image file players, it is guaranteed that re-encoding is not required to carry out these operations.
• Samples in image sequence tracks must be either intra-coded images or inter-picture predicted images with reference to only intra-coded images. These constraints of inter-picture prediction reduce the decoding latency for accessing any particular image within an HEVC image sequence track.

Implementation

As HEIF is a container format, it can contain still images and image sequences that are coded in different formats, currently these include HEVC andH.264/MPEG-4 AVC (and JPEG for thumbnail/secondary images), though other coding formats may be added in the future. The two main filename extensions are.heif or .heic, along with a less common .avci that is typically used for H.264/AVC encoded files.

In Apple's implementation, for single images they have chosen the latter .heic filename extension as the only one they will produce for photos, which indicates clearly that it went through HEVC encoding.^[12] However, they will support playback of both H.264/AVC encoded .avci files, and also.heif files created on other devices that are encoded using any codec, provided that codec is supported by them.^[13]

The same guidelines apply for image sequences, where a file may contain more than one single image. The only difference being the filename extensions change slightly, with Apple using the.heics extension for sequences produced by Apple devices (again, thus using HEVC encoding), along with playback support for H.264/AVC encoded.avcs image sequence files, and .heifs for image sequence files created using any other codecs they support.^[14]

Patent licensing

HEIF itself is a container, and when containing images and image sequences encoded in a particular format (e.g., HEVC or H.264/AVC), its use becomes subject to the licensing of patents on the coding format.^[15][16][17] Generally, lawful use of a patented invention requires the patent holder's permission in countries where the patent is in force (seepatent infringement).

Related standards

• ISO Base Media File Format – a file format standard that covers HEIF and other similarly formatted multimedia files, first standardized in 2001
• MPEG-H – a suite of standards that includes HEIF and HEVC
• High Efficiency Video Coding (H.265) – an encoding format for video and images, first standardized in 2013
• Advanced Video Coding (H.264) – an older encoding format for video and images, first standardized in 2003

See also

• Better Portable Graphics – another image file format using HEVC encoding, published by an individual author in 2014

References

1. 
   

Ward, Mikey (September 21, 2017)."Your photos just had a massive change with iOS 11. Here's what happened". Popular Science. RetrievedNovember 22, 2017.

Ward, Mikey (June 8, 2017)."New HEVC & HEIF Media Formats: What You Need to Know". Big Nerd Ranch. RetrievedNovember 22, 2017.

Turnquist, Erik (June 9, 2017)."Working with HEIF and HEVC". Apple. Event occurs at 0:00:01. Retrieved November 20, 2017. My name is Erik Turnquist and today Brad and I are going to talk about working with HEIF (heef) and HEVC...

Richie, Rene (November 14, 2017)."MacBreak Weekly 584 - A Free Pass From Darwin". MacBreak Weekly. Event occurs at 1:54:20. RetrievedNovember 20, 2017. ...you can tap between JPEG and now HEIF (heef) and RAW...

"Requirements for still image coding using HEVC | MPEG". mpeg.chiariglione.org. Retrieved2015-11-25.

"Requirements for HEVC image sequences | MPEG". mpeg.chiariglione.org. Retrieved2015-11-25.

"Evidence motivates MPEG to launch new standardization effort for HDR".

Hollister, Sean (June 5, 2017)."Apple answers iPhone storage woes with smaller photos, videos". CNET.CBS Interactive. Retrieved September 30, 2017.

Snell, Jason (September 20, 2017)."iOS 11: HEVC, HEIF, and what you need to know about these new video and photo formats".Macworld. RetrievedSeptember 30, 2017.

Shu, Lee (September 19, 2017)."Here's what HEIF and HEVC are, and why they'll improve your iPhone with iOS 11".Digital Trends. RetrievedSeptember 30, 2017.

M. M. Hannuksela; E. B. Aksu; V. K. Malamal Vadakital; J. Lainema."Overview of the High Efficiency Image File Format". JCT-VC document JCTVC-V0072, Oct. 2015.

Shankland, Stephen (June 16, 2017)."How Apple is squeezing more photos into your iPhone – FAQ: Apple's newest iPhone software attempts to move the world out of the JPEG era".CNET. RetrievedNovember 21, 2017.

"Introducing HEIF and HEVC".Apple. June 6, 2017. Event occurs at 0:13:47. RetrievedNovember 22, 2017.

"High Efficiency Image File Format".Apple. June 2017. Event occurs at 0:09:26. RetrievedNovember 22, 2017.

"macOS High Sierra tech preview: A quick look at the stuff you can't see". 2017-06-19. Retrieved4 July 2017. 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.

"Converting a JPEG to the new HEIF format". Retrieved4 July 2017. HEIF and HEVC are extensively covered by patents, which means there could be legal implications to implementing HEIF support, particularly in paid software or a hardware product.

17. Jan Ozer; Dror Gill (12 June 2017)."Apple Endorses New Image Format, HEIF". Retrieved31 October 2017.

External links

• HEIF – MPEG Image File Format standard site
• HEIF – format site atNokia
• HEIF – source code atGitHub