High Efficiency Video Coding (HEVC / H.265 / MPEG-H Part 2)

HEVC (High Efficiency Video Coding), also known as H.265 or MPEG-H Part 2, is a video compression standard designed to improve upon H.264/AVC. It delivers approximately twice the data compression ratio at the same video quality, or significantly improved video quality at the same bit rate.

Key features of H.265/HEVC include:

  • Superior Compression - Achieves up to 50% better compression than H.264/AVC at the same quality level

  • Support for Higher Resolutions - Designed for 4K, 8K, and even 16K video content

  • Flexible Block Structure - Uses Coding Tree Units (CTUs) up to 64x64 pixels, compared to H.264’s 16x16 maximum

  • Improved Predictive Coding - More efficient intra and inter prediction modes with 35 directional modes vs H.264’s 9

  • Hardware Acceleration - Supported by modern GPUs including NVIDIA NVENC/NVDEC and Apple Video Toolbox

HEVC is used in 4K UHD broadcasting, streaming services (Apple TV+, Amazon Prime Video), video conferencing, and next-generation video storage.

HEVC Stream Formats

HEVC video can be stored in different formats, with the two most common being:

Annex B Format

  • Start code format - NAL units are separated by start codes (0x000001 or 0x00000001)

  • Used in streams - Elementary streams, MPEG-TS, broadcasting, and real-time transmission

  • Self-contained - VPS/SPS/PPS are embedded in the stream itself

  • Stream-friendly - Can be decoded directly without additional metadata

HEVC1 (HEVCC Format)

  • Length-prefixed format - Each NAL unit is prefixed with its length (typically 4 bytes)

  • Used in containers - MP4, MOV, MKV, and other container formats

  • Requires extradata - VPS/SPS/PPS (Video/Sequence/Picture Parameter Sets) are stored separately in the container header

  • Not self-contained - Cannot be decoded without the extradata from the container

The choice between formats depends on the application: HEVC1 for file storage and containers, Annex B for streaming and broadcasting.

HEVC Encoding

HEVC Decoding