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== HEVC Image File Format ==
The HEIF standard includes the specification of encapsulating [[High Efficiency Video Coding|HEVC]]-coded images and image sequences into HEIF-compliant files. The specification includes the following aspects:
* The sample entry format and the sample format of HEVC image sequence tracks are identical to those of the HEVC video tracks specified in [[ISO/IEC 14496-15]]. For compatibility with HEVC-capable video players, it is therefore advisable to create both an HEVC image sequence track and an HEVC video track that refer to the same coded images.
* The format of the decoder configuration information in the image entry item is identical to that in the sample entry format. Likewise, the item format is identical to the sample format of HEVC video and image sequence tracks. This enables having the same intra-coded image as an image item and as a sample in an HEVC image sequence or video track.
* The configuration information of alpha planes and depth maps follows the respective supplemental enhancement information of HEVC.
* 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.
== Brands and MIME Types ==
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 the table below. 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.
{| class="MsoNormalTable"
! colspan="6" |'''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
|}
== References ==
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