信息技术 多媒体应用格式（MPEG-A） 第19部分：分段媒体的通用媒体应用格式（CMAF）

[中文适用范围]： 本文档规定了 CMAF 多媒体格式，其中包含针对自适应多媒体演示中最终用户设备上的流式传输和解码而优化的分段媒体对象。CMAF 指定从 ISO 基础媒体文件格式派生的轨道格式，然后从可用于存储和交付的 CMAF 轨道派生可寻址媒体对象。CMAF 指定共享编码和封装约束的轨道集，这些轨道集允许选择多个轨道以形成多媒体演示，并允许以不同的比特率、帧速率、分辨率等无缝切换相同内容的替代编码。CMAF 指定了一个假设的应用程序模型，该模型确定如何组合和同步 CMAF 演示中的轨道以形成多媒体演示。该模型抽象了交付以允许任何交付方法。假设的应用程序模型假设清单和播放器，但 CMAF 未指定清单、播放器或交付协议，目的是可以使用任何支持假设的应用程序模型的协议。 CMAF 指定媒体配置文件和品牌，以限制 CMAF 轨道的媒体编码和封装，从而实现轨道的无缝自适应切换，并允许设备通过其品牌识别兼容内容。CMAF 指定演示配置文件，有条件地要求符合指定媒体配置文件的 CMAF 轨道集，并允许内容创建者和设备识别兼容的多媒体演示。CMAF 通过指定如何指定和识别新的媒体配置文件和演示配置文件来实现可扩展性，并包含这些规范的指南。 [外文原描述]： This document specifies the CMAF multimedia format, which contains segmented media objects optimized for streaming delivery and decoding on end user devices in adaptive multimedia presentations. CMAF specifies a track format derived from the ISO base media file format, then derives addressable media objects from CMAF tracks that can be used for storage and delivery. CMAF specifies sets of tracks that share encoding and packaging constraints that enable the selection of multiple tracks to form a multimedia presentation and allow seamless switching of alternative encodings of the same content at different bit rates, frame rates, resolution, etc. CMAF specifies a hypothetical application model that determines how tracks in a CMAF presentation are intended to be combined and synchronized to form a multimedia presentation. The model abstracts delivery to allow any delivery method. The hypothetical application model assumes a manifest and player, but CMAF does not specify a manifest, player, or delivery protocol, with the intent that any that support the hypothetical application model can be used. CMAF specifies media profiles and brands that constrain media encoding and packaging of CMAF tracks to enable seamless adaptive switching of tracks and allow devices to identify compatible content by its brand. CMAF specifies presentation profiles that conditionally require sets of CMAF tracks conforming to specified media profiles and allow content creators and devices to identify compatible multimedia presentations. CMAF enables extensibility by specifying how new media profiles and presentation profiles can be specified and identified and includes guidelines for those specifications.