.HEVC

Introduction

A .hevc, .h265 or .265 file holds H.265 video exactly as an encoder produced it, with no container. H.265, also called HEVC (High Efficiency Video Coding) or MPEG-H Part 2, is defined by ITU-T H.265 and ISO/IEC 23008-2. It is the successor to H.264 and needs about half the bit rate for the same quality, which made it the usual codec for 4K and HDR video.

Like a raw H.264 stream, the file has no audio, no index and usually no timestamps. It is used for testing and as a step before the video is put into an MP4, MOV or MKV file.

Structure

The stream uses the Annex B byte stream format: NAL units, each preceded by the start code 00 00 01 or 00 00 00 01, with emulation prevention bytes inserted as in H.264. Unlike H.264, each NAL unit has a 2-byte header: a forbidden bit, a 6-bit nal_unit_type, a 6-bit layer ID and a 3-bit temporal ID plus one.

Common NAL unit types are 32, the video parameter set; 33, the sequence parameter set; 34, the picture parameter set; 19 and 20, IDR slices where decoding can start; 21, a clean random access slice; 35, an access unit delimiter; and 39 and 40, supplemental enhancement information. A stream normally starts with the VPS, SPS and PPS.

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