HEVC or H.265

What is HEVC ?

-High Efficiency Video Coding or H.265 Media Encoding

High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, is a video compression standard, one of several potential successors to the widely used AVC (H.264 or MPEG-4 Part 10). In comparison to AVC, HEVC offers about double the data compression ratio at the same level of video quality, or substantially improved video quality at the same bit rate. It supports resolutions up to 8192×4320, including 8K UHD.

High Efficiency Video Coding (HEVC) is a new video compression standard, developed by the Joint Collaborative Team on Video Coding (JCT-VC).  The JCT-VC brings together image and video encoding experts from around the world, producing a single standard that is approved by two standards bodies;

• ITU-T Study Group 16 – Video Coding Experts Group (VCEG) – publishes the H.265 standard as ITU-T H.265, and
• ISO/IEC JTC 1/SC 29/WG 11 Motion Picture Experts Group (MPEG) – publishes the HEVC standard as ISO/IEC 23008-2.

The initial version of the H.265/HEVC standard was ratified in January, 2013.

HEVC was developed with the goal of providing twice the compression efficiency of the previous standard, H.264 / AVC.  Although compression efficiency results vary depending on the type of content and the encoder settings, at typical consumer video distribution bit rates HEVC is typically able to compress video twice as efficiently as AVC.  End-users can take advantage of improved compression efficiency in one of two ways (or some combination of both):

• At an identical level of visual quality, HEVC enables video to be compressed to a file that is about half the size (or half the bit rate) of AVC, or
• When compressed to the same file size or bit rate as AVC, HEVC delivers significantly better visual quality.

Block Diagram of HEVC(Source: WIKIPEDIA)

How can HEVC encode video files twice as efficiently as previous video coding standards?

• Most of the power of video compression standards comes from a technique known as motion compensated prediction.  Blocks of pixels are encoded by making reference to another area in the same frame (intra-prediction), or in another frame (inter-prediction).  Where H.264/AVC defines macroblocks up to 16×16 pixels, HEVC can describe a much larger range of block sizes, up to 64 x 64 pixels.

• HEVC allows predicted blocks to be coded in different block sizes than the residual error.  Each top level coding unit (or CTU) is first coded as a prediction quad-tree, where at each depth the encoder decides whether to encode with merge/skip, inter, or intra coding. The residual from those predictions is then coded with a second quad-tree which can optionally have greater depth than the prediction quad-tree.  For instance, this allows the residual error from a 32×32 inter coded coding unit (CU) to be represented by a mixture of 16×16, 8×8, and 4×4 transforms.

• HEVC can encode motion vectors with much greater precision, giving a better predicted block with less residual error.  There are 35 intra-picture directions, compared with only 9 for H.264/AVC.

• HEVC includes Adaptive Motion Vector Prediction, a new method to improve inter-prediction.

• An improved deblocking filter

• Sample Adaptive Offset – an additional filter that reduces artifacts at block edges

Two of the key features where HEVC was improved compared with H.264/MPEG-4 AVC was support for higher resolution video and improved parallel processing methods.

HEVC is targeted at next-generation HDTV displays and content capture systems which feature progressive scanned frame rates and display resolutions from QVGA (320x240) to 4320p (7680x4320), as well as improved picture quality in terms of noise level, color spaces, and dynamic range.


UHDTV – digital television formats with resolutions of 4K / 2160p (3840×2160) and 8K / 4320p (7680×4320)

• Rec. 2020 – ITU-R Recommendation for UHDTV with standard dynamic range
• Rec. 2100 – ITU-R Recommendation for HDTV and UHDTV with high dynamic range

Image file formats based on HEVC

• Better Portable Graphics – a file format for images based on HEVC
• High Efficiency Image File Format – a file format for images and image sequences based on HEVC

List of open-source codecs

• x265 – an open-source software implementation of HEVC

List of multimedia (audio/video) codecs

• H.264/MPEG-4 AVC – the video standard predecessor of HEVC
• VP9 – an open format developed by Google as a competitor to HEVC
• AV1 – an open format that is being developed by the Alliance for Open Media as a successor to VP9 and a competitor to HEVC
• Daala – an open format that is being developed by Mozilla Foundation and Xiph.Org Foundation as a competitor to HEVC
• Dirac (video compression format) – an open format that is being developed by the BBC Research & Development as a competitor to HEVC
• Thor (video codec) – an open format that is being developed by Cisco as a competitor to HEVC

Source:Wikipedia & x265.org