This has recently gotten attention when Apple adopted it as their internal format for iOS 11. Although they will export the images as JPEG they will use this format derived from HEVC video format internally and in the iCloud. The Apple implementation uses both Wide color and Deep Color HDR captured from its camera sensors using 10 bit per color. The format itself would support more than 10 bits with other implementations using 12 and even 16 bits. Transparency can also be supported. The downside of this format is that it is patent encumbered.
 Data features
HEIF files can store the following types of data: (copied from Wikipedia)
- 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 EXIF, XMP and similar metadata which accompany the images stored in the HEIF file.
There is a competitor called BPG available that is also based on HEVC. It has a lossless option as well.
HEVC (High Efficiency Video Coding) is officially using the H.265 codec and improves the compression by 2x for similar visual quality over H.264 and even more on JPG. It is the format used for UHD video on the newest Blu-Ray products.
 Dual Support
Since HEIF and HEVC are essentially the same, Apple can use this to feature the mixed video and still images in the Live format they use today.
Other uses for dual support are have multiple versions of the same image stored in the same file, edited versions such as cropped stored together. Multiple exposures could also be stored in the same file. Stills could be extracted directly from a Video.