What is HEVC?
HEVC stands for High Efficiency Video Coding. Also known as H.265, this new video codec will compress video files to half the size possible using the most-efficient current encoding format, MPEG-4, aka H.264 (used on Blu-ray discs and some satellite TV). That will be one-quarter the size of files compressed using the MPEG 2 codec that most cable-TV companies still employ. More importantly, HEVC will be used to compress video with 4K resolution and possibly eventually 8K resolution so it can be efficiently delivered.
What is a codec?
A codec (an abbreviation of the term "coder-decoder") is software that uses an algorithm to systematically compress raw video data into a compact form fit for broadcasting, transmitting over an Internet stream or storing on a Blu-ray disc, for example. At the receiving end, the same codec in your TV, computer or disc player uncompresses the data to display the video on your screen. Codecs also remove some detail from video to reduce its size, and a high level of compressions can drop too much data, resulting in choppy and blocky video. Most pay-TV services use aggressive compression to get all those channels into your cable or satellite receiver, which is one reason the video from your cable box does not look as good as that from a Blu-ray. A good codec will compress video down while causing few defects due to over-compression.
High-definition video can take a lot of data. A full-HD image has about two million pixels and up to several million colors per individual frame, with hundreds of thousands of frames making up a movie.
Why use HEVC for 4K video?
The current MPEG-4/H.264 codec makes it possible to compress the huge amount of information in a film down so that it can stream over Netflix, versus storing all of that data on a physical source like a Blu-ray. Those high-definition images from Netflix are in either 720p resolution (1280 x 720, or 0.92 million pixels) or 1080p resolution (1920 x 1080 resolution, 2 million pixels). The images from a 4K video to be displayed on a 4K television have 8 million pixels (3840 x 2160 resolution). Such a huge jump in detail requires a better way to compress the data in order to transmit or store it. HEVC is twice as efficient as MPEG-4/H.264, with only a minimal loss in quality. As a result, current content will need only half the data to stream over Netflix, and it will become viable to stream 4K content. (Netflix recommends a 15Mbps or better broadband connection for streaming 4K.)
What content will use HEVC?
Potentially everything. Individual services will each have to decide if they will send data using HEVC/H.265 instead of MPEG-4/H.264 or MPEG-2. Netflix has already announced that it will start using HEVC later this year, to stream 4K content. Amazon is shooting its original shows in 4K and will also likely stream that content in 4K using HEVC later this year. New televisions coming this year from LG, Samsung, Sony and Vizio will support HEVC and will be able to stream 4K video from Netflix. Individual cable companies will have to decide when to change both the data they are sending and the receiver to decode it to HEVC. But that likely won't happen for several years, when and if they broadcast in 4K.
It will also take new models before cellphones and tablets have hardware compatible with HEVC. Even then, some devices may not support HEVC: Google has announced its own 4K codec called VP9 that will be used with YouTube. Other companies may support that, or possibly support both 4K codecs.
Can I watch HEVC content now?
Not yet. Even when Netflix begins streaming in HEVC, you can only receive this content if you are watching on HEVC-compatible 4K televisions. Existing hardware — such as current game consoles, set-top boxes, mobile devices and computers — do not yet support HEVC.
How did HEVC come about?
Two tech-standards organizations, the International Telecommunication Union (ITU) and the Moving Pictures Expert Group (MPEG), developed HEVC. These same groups are also behind the MPEG-2 standard used in DVD, cable and other content formats for standard- and some high-definition video. ITU and MPEG also created the MPEG-4/H.264 standard used in Blu-ray, some cable satellite broadcasts and online for high-definition video.
What is HEVC? - High Efficiency Video Coding FAQ - Tom's Guide