When you record a video on your phone or stream a movie from the web, you’re almost certainly dealing with a video compressed using the H.264 codec. The same group that brought you H.264, the MPEG (Motion Picture Experts Group) standards body, has created the successor to H.264, a codec called HEVC.
HEVC (High Efficiency Video Coding) is the common name for H.265. Like H.264 and H.263 before it, HEVC was designed as a best in class codec, offering high visual quality at low data rates in exchange for high computational costs. HEVC was originally standardized in 2013, but it’s starting to reach prominence with the addition of hardware support in modern CPUs, GPUs and smartphones. Using more computationally intensive techniques, HEVC is able to squeeze out as much as an additional 50% data savings at the same quality. As 4k video becomes increasingly common, data rates in H.264 are simply too high for many applications, requiring the move to a new, more efficient codec. In addition, hard limits in the codec restrict H.264 to 4K frame sizes, and HEVC lifts that restriction, allowing for videos up to 8K.
Compression
HEVC gets its data savings through the combination of two techniques: segmenting the image into a series of smaller regions (macroblocks) and reducing their complexity (Intraframe compression) and reusing redundant regions between frames (Interframe compression). Most of it increased efficiency over H.264 is by allowing larger search windows for motion and larger macroblocks used in the actual compression of frames. The tradeoff is that HEVC is a much more difficult codec to encode and playback. This is why widespread adoption has hasn’t occurred until now, when the hardware allows for a smooth user experience.
Hardware Support
Computer and phone vendors are building hardware acceleration into their products to lessen the CPU and power drain. This includes recent iPhones and current gen Macs.
| 8 bit decode | 10 bit decode | 8 bit encode | 10 bit encode | |
|---|---|---|---|---|
| iOS devices A9 chip |
(software only) | |||
| iOS devices A10 Fusion chip |
||||
| macOS devices 6th Generation Intel Core |
(software only) | |||
| macOS devices 7th Generation Intel Core |
(software only) |
On macOS, this hardware acceleration is only enabled on systems running macOS 10.13 High Sierra. On iOS, HEVC encoding and decoding is enabled by iOS11 (on supported devices). Software only playback is possible in earlier versions in some third party applications.
7th Generation Intel Core processors do support 10bit HEVC encode, but at this has not be implemented by Apple in the initial release of macOS 10.13 High Sierra.