信息技术 - UPnP设备架构 - 第20-12部分:音频视频设备控制协议 - 第4级 - 内容目录服务

[中文适用范围]： 本文件规定了名为ContentDirectory的UPnP网络服务的特征，该版本的服务定义符合UPnP设备架构1.0[14]。家庭网络中的许多设备包含各种类型的内容，其他设备希望访问这些内容（例如音乐、视频、静态图像等）。以为例，媒体服务器设备可能包含大量房主的音频、视频和静态图像库。为了使房主能够享受这些内容，房主需要能够浏览存储在MediaServer上的对象，选择一个特定的对象，并使其在适当的呈现设备上播放（例如音乐对象使用音频播放器，视频内容使用电视，静态图像使用电子相框等）。为了最大方便，房主应能够从各种用户界面设备发起这些操作。通常情况下，这些UI设备要么是渲染设备内置的UI，要么是独立的UI设备，例如无线PDA或平板电脑。无论如何，房主不太可能直接与包含内容的设备互动（即：房主无需走到服务器设备前）。为了实现此功能，服务器设备需要提供一种统一机制，使UI设备能够浏览服务器上的内容并获取单个内容对象的详细信息。这就是ContentDirectory服务的目的。ContentDirectory服务还提供了一个查找/存储服务，使客户端（例如UI设备）能够定位（并可能存储）服务器设备能够提供的单个对象（例如歌曲、电影、图片等）。例如，此服务可以用于枚举MP3播放器上存储的歌曲列表、各种幻灯片展示中的静态图像列表、DVD机匣中存储的电影列表、当前正在广播的电视节目列表（即EPG）、CD机匣中存储的歌曲列表、个人视频记录设备（PVR）上存储的节目列表等。几乎所有类型的内容都可以通过此ContentDirectory服务进行枚举。对于包含多种内容类型的设备（例如MP3、MPEG2、JPEG等），可以使用单个ContentDirectory服务实例来枚举所有对象，无论其类型如何。 [外文原描述]： ISO/IEC 29341-20-12:2017 specifies the characteristics of the UPnP networked service named ContentDirectory, version 4. This service definition is compliant with UPnP Device Architecture 1.0 [14]. Many devices within the home network contain various types of content that other devices would like to access (for example, music, videos, still images, etc). As an example, a MediaServer device might contain a significant portion of the homeowner's audio, video, and still-image library. In order for the homeowner to enjoy this content, the homeowner needs to be able to browse the objects stored on the MediaServer, select a specific one, and cause it to be played on an appropriate rendering device (for example, an audio player for music objects, a TV for video content, an Electronic Picture Frame for still-images, etc). For maximum convenience, it is highly desirable to let the homeowner to initiate these operations from a variety of UI devices. In most cases, these UI devices will either be a UI built into the rendering device, or it will be a stand-alone UI device such as a wireless PDA or tablet. In any case, it is unlikely that the homeowner will interact directly with the device containing the content (that is: the homeowner won't have to walk over to the server device). In order to enable this capability, the server device needs to provide a uniform mechanism for UI devices to browse the content on the server and to obtain detailed information about individual content objects. This is the purpose of the ContentDirectory service. The ContentDirectory service additionally provides a lookup/storage service that enables clients (for example, UI devices) to locate (and possibly store) individual objects (for example, songs, movies, pictures, etc) that the (server) device is capable of providing. For example, this service can be used to enumerate a list of songs stored on an MP3 player, a list of still-images comprising various slide-shows, a list of movies stored in a DVD-Jukebox, a list of TV shows currently being broadcast (a.k.a an EPG), a list of songs stored in a CD-Jukebox, a list of programs stored on a PVR (Personal Video Recorder) device, etc. Nearly any type of content can be enumerated via this ContentDirectory service. For devices that contain multiple types of content (for example, MP3, MPEG2, JPEG, etc.), a single instance of the ContentDirectory service can be used to enumerate all objects, regardless of their type.