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Guide

H.265/HEVC Video Codec: Complete Guide to High Efficiency Video Coding

PC By Pablo Cirre •

What Is H.265/HEVC?

H.265, also known as HEVC (High Efficiency Video Coding) and MPEG-H Part 2, is the successor to H.264. Published jointly by the ITU-T and ISO/IEC in 2013, HEVC achieves approximately 50% better compression efficiency than H.264 — it can deliver the same video quality at half the bitrate, or significantly better quality at the same bitrate.

HEVC powers:

  • 4K Ultra HD Blu-ray discs (the only disc format capable of 4K at acceptable quality)
  • 4K and 8K streaming on Netflix, Amazon Prime, Disney+, Apple TV+
  • HEIC photos (Apple's iPhone photo format uses HEVC for image compression)
  • HDR video (HDR10, HDR10+, HLG — all use HEVC's Main 10 profile)
  • Broadcast (DVB-T2, ATSC 3.0 / NextGenTV, DAB+)

HEVC vs H.264: Key Technical Improvements

HEVC builds on H.264's foundation while introducing significantly more powerful tools:

Larger Block Structure: CTUs

H.264 uses fixed 16×16 macroblock units. HEVC replaces these with flexible Coding Tree Units (CTUs) of up to 64×64 pixels. CTUs are recursively split into smaller Coding Units (CUs) — 64×64, 32×32, 16×16, or 8×8 — using a quadtree structure based on image complexity.

This adaptive block size is transformative for high-resolution video: a 4K frame has large areas of uniform content (sky, walls) where a 64×64 block can be coded efficiently, and fine-detail areas where smaller blocks capture texture. H.264's fixed 16×16 macroblocks waste bits in smooth areas and lack precision in detail areas.

More Intra Prediction Modes

H.264 has 9 intra prediction modes for 4×4 luma blocks. HEVC has 35 intra prediction modes including 33 directional modes, a DC mode, and a planar mode. This finer-grained prediction drastically reduces residual energy for structured content like text, graphics, and detailed textures.

Improved Inter Prediction

  • Larger reference frame cache — more flexibility in temporal prediction
  • Advanced Motion Vector Prediction (AMVP) — more efficient motion vector coding
  • Merge mode — sharing motion vectors from neighboring blocks without signaling new vectors
  • Asymmetric Motion Partitioning (AMP) — non-square partition options for better object boundary prediction

Sample Adaptive Offset (SAO) Filter

HEVC adds SAO as a second in-loop filter (complementing the deblocking filter, which also improved from H.264). SAO reduces banding artifacts in smooth gradients and ringing near edges — common artifacts at lower bitrates.

Transform Options

  • 4×4, 8×8, 16×16, and 32×32 DCT transforms (H.264 maxes out at 8×8)
  • 4×4 DST (Discrete Sine Transform) for intra-coded residuals — more efficient than DCT for intra prediction residuals

CABAC Improvements

HEVC's CABAC entropy coder is more efficient than H.264's and redesigned for better parallelism, enabling multi-threaded encoding and decoding through:

  • Tiles — rectangular regions that can be decoded independently
  • Slices — independently decodable segments
  • Wavefront Parallel Processing (WPP) — pipeline-based parallelism

HEVC Profiles

Profile Bit depth Chroma HDR Typical use
Main 8-bit 4:2:0 No Standard HD/4K streaming
Main 10 8 or 10-bit 4:2:0 Yes (HDR10, HLG) 4K HDR, Blu-ray Ultra HD
Main Still Picture 8-bit 4:2:0 No HEIC photo format
Main 12 12-bit 4:2:0 Yes Professional production
Main 4:4:4 8-bit 4:4:4 No Chroma-sensitive production
Main 4:4:4 10 10-bit 4:4:4 Yes High-end production

Main 10 is the most important profile — it powers all 4K HDR consumer content (Netflix 4K HDR, Ultra HD Blu-ray, Apple TV 4K, YouTube HDR).

HEVC and HDR

HEVC Main 10 profile (10-bit color depth) is the technical foundation for HDR video:

HDR10

  • Static HDR metadata (MaxCLL, MaxFALL) — same metadata for entire film
  • SMPTE ST 2084 (PQ — Perceptual Quantizer) transfer function
  • BT.2020 color space (wide color gamut)
  • Open standard, royalty-free
  • Supported by: all 4K HDR displays, Ultra HD Blu-ray, most streaming services

HDR10+

  • Dynamic HDR metadata — scene-by-scene or frame-by-frame tone mapping
  • Same PQ + BT.2020 as HDR10 but adds Samsung SMPTE ST 2094-40 dynamic metadata
  • Supported by Samsung TVs, Amazon Prime Video

HLG (Hybrid Log-Gamma)

  • Designed for broadcast TV (NHK, BBC developed jointly)
  • Backward compatible with SDR displays (non-HDR TVs show correct SDR image from HLG signal)
  • Used in terrestrial HDR broadcasts, some streaming

HEVC Encoding with x265

x265 is the primary open-source HEVC encoder.

# CRF 28 (roughly equivalent to x264 CRF 23)
ffmpeg -i input.mp4 -c:v libx265 -crf 28 -preset medium output.mp4

# High quality master (CRF 18)
ffmpeg -i input.mp4 -c:v libx265 -crf 18 -preset slow output.mp4

# 4K HDR10 encoding
ffmpeg -i input.mp4 -c:v libx265 -crf 20 -preset slow \
  -x265-params "colorprim=bt2020:transfer=smpte2084:colormatrix=bt2020nc:hdr10=1:max-cll=1000,400:master-display=G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(10000000,50)" \
  -pix_fmt yuv420p10le -c:a copy output.mp4

# HEVC with Main 10 profile (10-bit, for wide color)
ffmpeg -i input.mp4 -c:v libx265 -crf 20 -pix_fmt yuv420p10le \
  -x265-params "profile=main10" output.mp4

x265 CRF Calibration

x265 CRF values are not directly comparable to x264 CRF values. A rule of thumb:

  • x265 CRF 28 ≈ x264 CRF 23 (similar visual quality, smaller file)
  • x265 CRF 24 ≈ x264 CRF 19
  • x265 CRF 20 = very high quality for HEVC

For a given quality level, x265 produces files approximately 50% smaller than x264.

HEVC Patent Licensing

HEVC has a complex and fragmented patent licensing landscape involving multiple patent pools:

  • HEVC Advance — covers ~4,000 patents from 40+ companies
  • Via LA HEVC — covers patents from Dolby, GE, Philips, etc.
  • Velos Media — covers additional patents

Royalties apply to encoders, decoders, and content distribution in some interpretations. This patent complexity partly drove the development of AV1 as a royalty-free alternative. However, hardware support for HEVC is nearly universal in modern devices, and the practical impact of patent fees on end users and open-source software has been limited.

HEVC Hardware Support

Nearly all devices manufactured after 2015 have dedicated HEVC hardware decode support:

Device HEVC decode HEVC encode
iPhone (A9+) ✅ ✅ (A10+)
Android (2016+) ✅ Most Varies
Apple Silicon Mac ✅ ✅
Intel (6th gen+) ✅ ✅ (7th gen+)
AMD (RX 400+) ✅ ✅
NVIDIA (GTX 950+) ✅ ✅
Smart TVs (2014+) ✅ Most —

Hardware encoding is much faster than software (x265) but generally lower quality at the same bitrate.

H.264 vs. H.265 vs. AV1 Comparison

Feature H.264 H.265/HEVC AV1
Year 2003 2013 2018
Compression vs H.264 Baseline ~50% better ~30% better than HEVC
Patent status Licensed Complex Royalty-free
Browser support Universal Partial (Safari) Chrome, Firefox, Edge
Hardware decode Universal Nearly universal Growing (2021+)
Encoding speed Fast Medium (x265) Slow (libaom) / fast (SVT-AV1)
HDR support Limited ✅ (Main 10) ✅
8K support Limited ✅ ✅

Practical recommendation:

  • Archive storage: HEVC (50% smaller than H.264 at same quality)
  • Web streaming: H.264 for maximum compatibility; AV1 for bandwidth savings on modern browsers
  • 4K HDR content: HEVC (hardware support is universal)
  • Professional production: Apple ProRes or HEVC Main 10

Related conversions

Common video conversions that pair well with this guide:

Frequently Asked Questions

At the same visual quality, H.265 (HEVC) files are approximately 40-50% smaller than H.264 files. This means a 1080p movie that takes 4 GB as H.264 would take about 2 GB as H.265 at the same quality. For 4K content the savings are even more pronounced. In terms of bitrate: a 1080p stream that requires 8 Mbps in H.264 needs only about 4-5 Mbps in H.265 for the same quality. This is why streaming services use HEVC for 4K HDR — delivering 4K over typical home broadband connections would not be practical with H.264.

At the same visual quality, H.265 (HEVC) arquivos são approximately 40-50% menor que H.264 files. This means a 1080p movie that takes 4 GB as H.264 would take about 2 GB as H.265 at the same quality. para 4K content the savings are even more pronounced. In terms of bitrate: a 1080p stream that requires 8 Mbps in H.264 needs only about 4-5 Mbps in H.265 para the same quality. This is why streaming services usar HEVC para 4K HDR — delivering 4K over typical home broadband connections would not be practical com H.264.

At the same visual quality, H.265 (HEVC) Dateien are approximately 40-50% kleiner als H.264 files. This means a 1080p movie that takes 4 GB as H.264 would take about 2 GB as H.265 at the same quality. für 4K content the savings are even more pronounced. In terms von Bitrate: a 1080p stream that requires 8 Mbps in H.264 needs only about 4-5 Mbps in H.265 für the same quality. This is why streaming services verwenden HEVC für 4K HDR — delivering 4K over typical home broadband connections would not be practical mit H.264.

At the same visual quality, H.265 (HEVC) archivos are approximately 40-50% más pequeño que H.264 files. This means a 1080p movie that takes 4 GB as H.264 would take about 2 GB as H.265 at the same quality. para 4K content the savings are even more pronounced. In terms de bitrate: a 1080p stream that requires 8 Mbps in H.264 needs only about 4-5 Mbps in H.265 para the same quality. This is why streaming services usar HEVC para 4K HDR — delivering 4K over typical home broadband connections would not be practical con H.264.

AV1 is the most efficient (royalty-free, ~30% smaller than H.265) but encoding is slow. H.265 (HEVC) saves ~30–50% over H.264 and is supported by every modern phone and desktop. H.264 remains the safest baseline for legacy compatibility. Rule of thumb: archives → AV1, daily use → H.265, broadest reach → H.264.

HEVC encoding is computationally expensive because of its more complex tools: CTU quadtree analysis (evaluating many possible block splits), 35 intra prediction modes instead of 9, larger transform sizes, and more sophisticated motion estimation. The x265 software encoder is typically 5-10 times slower than x264 at equivalent quality settings. For faster encoding, use hardware encoders (NVENC on NVIDIA GPUs, VideoToolbox on Apple Silicon, Intel QuickSync) — they encode in real-time or faster, though with somewhat lower quality efficiency than software x265. The slow preset provides excellent compression but very slow encoding; use medium or fast presets when speed matters.

CRF (Constant Rate Factor) is the best default for offline files: ffmpeg picks the bitrate frame-by-frame to maintain perceived quality. Two-pass is only better when you must hit an exact final size (DVD targets). Constant bitrate is for streaming with a fixed channel. For "smallest at quality X" always use CRF.

The Main profile uses 8-bit color depth (256 levels per channel), the same as standard JPEG and H.264. Main 10 uses 10-bit depth (1024 levels per channel). The additional 2 bits provide: (1) Finer gradient rendering — banding artifacts in smooth gradients (sunsets, skies) are eliminated. (2) HDR support — HDR10 and HLG HDR formats require 10-bit to represent the expanded brightness range without clipping. (3) Better editing latitude — 10-bit video survives color grading with fewer artifacts. All 4K HDR content (Netflix, Ultra HD Blu-ray, Apple TV) uses Main 10. For SDR 8-bit content, Main profile is sufficient and slightly more compatible with older devices.

The Main profile uses 8-bit color depth (256 levels per channel), o mesmo que padrão JPEG e H.264. Main 10 uses 10-bit depth (1024 levels per channel). The additional 2 bits provide: (1) Finer gradient rendering — banding artifacts in smooth gradients (sunsets, skies) are eliminated. (2) HDR support — HDR10 e HLG HDR formatoos require 10-bit to represent the expanded brightness range sem clipping. (3) Better editando latitude — 10-bit video survives color grading com fewer artifacts. All 4K HDR content (Netflix, Ultra HD Blu-ray, Apple TV) uses Main 10. para SDR 8-bit content, Main profile is sufficient e slightly more compatível com older devices.

The Main profile uses 8-bit color depth (256 levels per channel), gleich wie Standard JPEG und H.264. Main 10 uses 10-bit depth (1024 levels per channel). The additional 2 bits provide: (1) Finer gradient rendering — banding artifacts in smooth gradients (sunsets, skies) are eliminated. (2) HDR support — HDR10 und HLG HDR Formate require 10-bit to represent the expanded brightness range ohne clipping. (3) Better editing latitude — 10-bit video survives color grading mit fewer artifacts. All 4K HDR content (Netflix, Ultra HD Blu-ray, Apple TV) uses Main 10. für SDR 8-bit content, Main profile is sufficient und slightly more kompatibel mit older devices.

The Main profile uses 8-bit color depth (256 levels per channel), igual que estándar JPEG y H.264. Main 10 uses 10-bit depth (1024 levels per channel). The additional 2 bits provide: (1) Finer gradient rendering — banding artifacts in smooth gradients (sunsets, skies) are eliminated. (2) HDR support — HDR10 y HLG HDR formatoos require 10-bit to represent the expanded brightness range sin clipping. (3) Better editing latitude — 10-bit video survives color grading con fewer artifacts. All 4K HDR content (Netflix, Ultra HD Blu-ray, Apple TV) uses Main 10. para SDR 8-bit content, Main profile is sufficient y slightly more compatible con older devices.

Common causes: (1) variable framerate source rendered as constant (use <code>-vsync vfr</code> to preserve VFR); (2) different audio sample rates not resampled (add <code>-ar 48000</code>); (3) container limitations (MP4 with variable framerate misbehaves — prefer MKV during editing, encode to MP4 only at the end). Always run <code>ffprobe</code> on both source and output to compare timing.

No — this is HEVC's main limitation on the web. Safari (macOS and iOS) supports HEVC natively. Chrome and Edge support HEVC on Windows 11 and macOS machines with hardware HEVC decode support, but this support is not guaranteed on all systems. Firefox does not support HEVC. For reliable web video delivery, H.264 is still the safest choice. For web delivery with better compression, AV1 (supported by Chrome, Firefox, Edge) is often preferred over HEVC because of its royalty-free status and better browser support. Use HEVC primarily for downloaded content, local playback, and streaming services that control the full playback environment (native app, smart TV, etc.).

No — this is HEVC's main limitation no web. Safari (macOS e iOS) suporta HEVC natively. Chrome e Edge support HEVC no Windows 11 e macOS machines com hardware HEVC decode support, mas this support is not guaranteed on all systems. Firefox does not support HEVC. para reliable web video delivery, H.264 is still the safest choice. para web delivery com better compressão, AV1 (supported by Chrome, Firefox, Edge) is often preferred over HEVC because of its royalty-free status e better browser support. usar HEVC primarily para baixado content, local playback, e streaming services that control the full playback environment (native app, smart TV, etc.).

Yes if you only change the container: <code>ffmpeg -i in.mkv -c copy out.mp4</code>. This remuxes the stream without re-encoding, takes seconds even for hours of footage. Limitations: codec must be supported by the target container (e.g. you cannot put H.264 in WebM, only VP8/VP9/AV1). To shrink size you must re-encode.