信息技术.异构环境中的高效编码和媒体传送.第15部分:HDR/WCG视频的信号发送、向后兼容性和显示适配

[中文适用范围]： 本文件审查了 HDR/WCG 视频内容处理和编码的方法。本文件的目的是为 AVC 或 HEVC 视频编码系统提供一系列公开可引用的方法，以适应压缩 HDR/WCG 视频用于消费者分发应用的目的。本文件首先包括对适用于 HDR/WCG 视频的视频使用信息（VUI）指标和增强信息（SEI）消息的审查。它提供了从 4:4:4 RGB 线性光表示的视频信号转换为 ICTCP 颜色表示和感知量化器（PQ）传输函数，或具有 Y'CbCr 颜色表示和 HLG 传输函数的过程描述（ICTCP、PQ 和 HLG 在 Rec. ITU-R BT.2100-1 中定义）。一些压缩这些信号的高级方法使用了 Rec. ITU-T H.264 | ISO/IEC 14496-10 或 Rec. ITU-T H.265 | ISO/IEC 23008-2。还包括后解码处理步骤，用于将视频转换回线性光、4:4:4 RGB 表示。本文件还涉及标准动态范围（SDR）的向后兼容性，即与无法检测和正确显示 HDR/WCG 视频内容的传统解码系统兼容。它描述了使用三种不同解决方案实现此功能的例子：使用 HLG 作为向后兼容的传输函数、使用 CRI 和 TMI SEI 消息以及使用带有 HEVC 可扩展主 10 层和 SDR 兼容基层的双层方法。最后，本文件说明了如何使用 CRI SEI 消息将元数据传递给显示器，以使解码视频在显示端适应动态范围和颜色空间。 [外文原描述]： This document reviews approaches for processing and coding of HDR/WCG video content. The purpose of this document is to provide a set of publicly-referenceable methods for the operation of AVC or HEVC video coding systems adapted for compressing HDR/WCG video for consumer distribution applications. This document first includes a review of the video usability information (VUI) indicators and supplemental enhancement information (SEI) messages applicable for HDR/WCG video. It provides a description of processing steps for converting from 4:4:4 RGB linear light representation video signals into video signals with ICTCP colour representation and perceptual quantizer (PQ) transfer function, or with Y′CbCr colour representation and HLG transfer function (ICTCP, PQ and HLG are defined in Rec. ITU-R BT.2100-1). Some high-level approaches for compressing these signals using either Rec. ITU-T H.264 | ISO/IEC 14496-10 or Rec. ITU-T H.265 | ISO/IEC 23008-2 are provided. A description of post-decoding processing steps is also included for converting back to a linear light, 4:4:4 RGB representation. The document also addresses the standard dynamic range (SDR) backward compatibility, that is, the compatibility with legacy decoding systems that are not able to detect and properly display HDR/WCG video content. It describes example implementations of this feature using three different solutions: using HLG as a backward compatible transfer function, using CRI and TMI SEI messages, using dual-layer approach with the Scalable Main 10 profile of HEVC and an SDR compatible base layer. Finally, the document illustrates the usage of CRI SEI messages to convey metadata enabling the dynamic range and colour gamut adaptation at the display side of the decoded video to the display capabilities. NOTE The document complements the material provided in ITU-T H.Sup15 | ISO/IEC TR 23008-14, which is focused on conversion and coding practices for non-constant luminance (NCL) Y′CbCr video signals using the PQ transfer function.