HEVC and HEIF: new video and still image formats

Whether or not High Sierra can make Apple’s new file system your default, the upgrade’s other significant new feature is support for HEVC (High Efficiency Video Coding, also known as H.265) video, and HEIF still image encoding and decoding. This article looks briefly at what those have to offer you.

HEIF is a very new still image format intended to replace the likes of JPEG, for compressing still images, and is based on HEVC. The latter is also relatively recent, and intended to replace H.264, or MPEG-4 AVC to give it its fuller name.

There’s nothing intrinsically wrong with the older standard, which is now very widely used for encoding a wide range of types of video. HEVC is intended for the next generation of video, supporting resolutions up to 8192 x 3220, which includes 8K Ultra-High Definition (UHD) and 10-bit deep colour, and should produce files which are roughly half the size of H.264 for similar quality (or the same size at much improved quality).

There are a couple of snags with HEVC and HEIF, though. First is the fact that both are covered by patents, and royalties are payable on some encoded content. There are several projects to produce open source implementations, but for the moment you’re unlikely to come across much non-commercial software which works with these standards, and distributing commercial content encoded in HEVC may require payment of royalties.

The other snag is that encoding and, to a lesser extent decoding, is slow unless performed using graphics chip support. You wouldn’t want to have to encode UHD video on an older Mac using software alone, and even replaying it may well prove disappointing. If you’re going to record your own HEVC clips, and create compressed still images, your computer will really need a recent chipset which is designed to accelerate the process using its hardware.

So what use will HEVC and HEIF support be?

Because of their licensing requirements, they are very little used for online media, although there’s always the possibility that the iTunes Store will offer movies in HEVC format in the future. Because relatively few other systems yet have bundled support for them, you’re probably not going to want to send your next family movie in HEVC, or embed HEIF images in PDFs.

Where these new more efficient formats win is in storing movies and still images created on your iPhone and iPad. At around half the size for equivalent quality, you will be able to keep more of your content on your iOS devices, and more in iCloud.

This is fine if you upgrade all your iOS devices to iOS 11, and your Macs to High Sierra, and never share video or images with anyone who also hasn’t done so. Apple does cater for other systems, though, through on-the-fly conversion of iCloud content. The concept is elegant and effective: if you try to access, say, an HEVC-encoded movie which is to be delivered by iCloud, then iCloud checks whether your device can decode it. If it can’t, it delivers the movie transcoded to a form which your device can access.

This has been tested during the beta process this summer, and although at that stage it doesn’t always seem to have worked perfectly, beta-testers have been able to access HEVC and HEIF content in compatible formats. Whether this will work seamlessly when there are tens of millions of iPhones and iPads using iCloud in this way, we will only know once iOS 11 and High Sierra have been released.

There are also some important cases which will need special consideration: emailing a bunch of HEIFs to people who can’t read them, or uploading an HEVC movie to your website, will clearly cause problems, so we will all have to be more careful what we do with content which is likely to have been so encoded. Microsoft has already released an HEVC app extension for Windows 10, but only certain PC hardware can now play back HEVC video within an app.

None of this is made any simpler by the hardware requirements for HEVC and HEIF. According to Apple’s initial information, the following devices will be able to create and encode HEVC and HEIF:

  • iOS devices with an A10 Fusion chip or better, i.e. iPhone 7, 7 Plus, or iPad Pro (except 2015 12.5 inch iPad Pros), running iOS 11,
  • all Macs running High Sierra, but only those with Skylake or Kaby Lake chipsets will have hardware acceleration.

All iOS devices and Macs running iOS 11 or High Sierra, respectively, will be able to decode and display HEVC and HEIF. However, this will only benefit from hardware acceleration on the following:

  • iPhone 6 Plus, 6S, SE, and later, and iPad Pro (all versions) and iPad (5th gen) and later,
  • Macs with Skylake or Kaby Lake chipsets.

How usable HEVC will prove on systems which cannot use hardware acceleration is an issue which we will only discover when iOS 11 and High Sierra are released.

The benefits of HEVC and HEIF support in iOS 11 and High Sierra will therefore vary widely according to the hardware you have, which of your systems to upgrade, and what you do with your content. For many users they may prove a big step forward; for others, they may – for the moment – be of little consequence.

It is also worth bearing in mind that HEVC and HEIF are not the only new and highly efficient formats poised to come to our systems, and may not prove to be the winners, however much Apple supports them. Many of the big players, including Amazon, Google, Microsoft, and Netflix, are backing a new AV1 coding format, which will be royalty-free. For still images, there is also BPG (based on HEVC), FLIF, WebP, and others.


Wikipedia on HEVC – a detailed account.
Wikipedia on HEIF.
BPG image comparisons.