What Is High Efficiency Video Coding?

High Efficiency Video Coding (HEVC), also designated ITU-T H.265 and ISO/IEC 23008-2, is a video compression standard designed to reduce bitrate by approximately 50 percent compared to its predecessor H.264/AVC at equivalent perceptual quality. Standardized in January 2013 by the Joint Collaborative Team on Video Coding (JCT-VC), a partnership between ISO/IEC MPEG and ITU-T VCEG, HEVC addressed the growing demand for high-resolution and ultra-high-definition content delivery over bandwidth-constrained networks. The standard supports resolutions from 4K UHD (3840×2160) through 8K (8192×4320), bit depths up to 16 bits per sample, and chroma sampling formats including 4:2:0, 4:2:2, and 4:4:4.

HEVC builds directly on the architectural principles of H.264/AVC while expanding nearly every coding tool. The ISO/IEC 23008-2:2013 standard defines the normative specification for the codec, and subsequent amendments have added support for range extensions, scalable coding, multiview, and screen-content coding profiles.

Coding Architecture and Block Structure

The fundamental encoding unit in HEVC is the Coding Tree Unit (CTU), which replaces the fixed 16×16 macroblock of H.264 with a quad-tree structure supporting block sizes up to 64×64 pixels. Larger CTUs improve efficiency for high-resolution content by capturing spatial redundancies across broader image regions. Within each CTU, a recursive quad-tree partition divides into Coding Units (CUs), Prediction Units (PUs), and Transform Units (TUs), giving the encoder fine-grained control over the tradeoff between partition granularity and coding overhead. Intra-prediction in HEVC expands from four directional modes in H.264 to 35 modes, covering a full range of angular directions to exploit directional texture in natural images.

Motion Compensation and Entropy Coding

Inter-frame prediction in HEVC uses an Advanced Motion Vector Prediction (AMVP) scheme that draws from a candidate list of up to seven spatial and temporal motion vector predictors, compared to four in H.264. Fractional-pixel interpolation applies an 8-tap Luma filter and a 4-tap Chroma filter for sub-pixel accuracy. Entropy coding uses Context-Based Adaptive Binary Arithmetic Coding (CABAC) throughout, eliminating the Context Adaptive Variable Length Coding path that H.264 permitted. The Fraunhofer Heinrich Hertz Institute, which co-led development, reports that these combined improvements enable HEVC to encode a 1080p stream at roughly half the bitrate required by H.264 for the same quality.

Profiles, Tiers, and Deployment

HEVC defines profiles that restrict the feature set a decoder must support, with Main and Main 10 profiles covering 8-bit and 10-bit 4:2:0 content for consumer broadcast and streaming. High-tier bitrate limits accommodate cinema-grade and live-production workflows. The ATSC 3.0 standard, codified as ATSC A/341, adopted HEVC as the mandatory video codec for terrestrial broadcast in the United States, replacing the MPEG-2 baseline of ATSC 1.0. HEVC also underlies HDR workflows using the Hybrid Log-Gamma and PQ transfer functions defined in BT.2100, enabling high dynamic range delivery in both broadcast and streaming contexts. MPEG-4 AVC (H.264) remains dominant in legacy streaming infrastructure, but HEVC deployment expanded substantially with the rollout of 4K streaming platforms and satellite broadcasting.

Applications

High Efficiency Video Coding has applications in a wide range of fields, including:

• Ultra-high-definition streaming and over-the-top video delivery
• Terrestrial and satellite broadcast of 4K and HDR content
• Video surveillance and security systems using 4K sensors
• Videoconferencing systems requiring HD quality at constrained bandwidths
• Digital cinema and professional post-production workflows