本标准定义了4字节有效载荷标识符的规范，该标识符描述了SMPTE串行数字接口（SDI）上承载的有效载荷的各个方面，例如:数字接口标准；图像速率；抽样结构；纵横比；比色法；位深度和通道或链路分配。有效载荷的其他特定于应用的方面，例如音频信道的使用，可以可选地在参考SMPTE ST 352的特定于应用的文档中描述。有效载荷标识符适用于所有串行数字接口和在显示设备上产生直接可视图像的所有有效载荷。此外，可视图像必须是源图像内容的可识别表示。有效载荷标识符对于某些参考标准是强制性的，而对于其他参考标准是可选的。 有关SMPTE ST 352有效负载标识符的强制或可选使用的更多信息，请参阅适用参考标准。根据SMPTE ST 291-1，该标准定义了有效载荷标识符如何放入10位辅助数据包中。它还规定了辅助数据包的重复率，并为在不同的数字接口中放置数据包提供了首选的水平和垂直位置。该标准定义了4字节有效负载标识符每个字节的一些位字段的值，尽管其他位字段的值可以有自定义定义。该标准还定义了有效载荷识别码分配过程和字节1值的相关在线寄存器。 有关如何注册新值的详细信息，请参见附录A。附录B和附录C定义了遗留系统分配的有效载荷识别码和字节2、3和4值。附录D显示了有效载荷标识符从SMPTE ST 291-1的辅助数据包结构到SMPTE ST 336的K-L-V数据结构作为固定长度数据包的映射。

This standard defines the specification of a 4-byte payload identifier that describes aspects of the payload carried on the SMPTE Serial Digital Interface (SDI) such as: the digital interface standard; picture rate; sampling structure; aspect ratio; colorimetry; bit depth and channel or link assignment. Other application specific aspects of the payload such as audio channel usage, may optionally be described in application specific documents that reference SMPTE ST 352.The payload identifier is applicable to all serial digital interfaces and all payloads that produce a directly viewable image on a display device. Furthermore, the viewable image must be a recognizable representation of the source image content.The payload identifier is mandatory for some reference standards and optional in other reference standards. Refer to the applicable reference standards for further information on mandatory or optional usage of the SMPTE ST 352 payload identifier.The standard defines how the payload identifier is placed into a 10-bit ancillary data packet according to SMPTE ST 291-1.It also specifies the repetition rate of the ancillary data packet, and provides the preferred horizontal and vertical location for the placement of the packet in different digital interfaces.The standard defines values for some of the bit fields of each byte of the 4-byte payload identifier, although the values for other bit fields can have custom definitions.The standard also defines the Payload Identification Code assignment process and associated on-line register for Byte 1 Values. See Annex A for details on how to register new values.Annex B and Annex C define the assigned Payload Identification codes and byte 2, 3 and 4 values for legacy systems.Annex D shows the mapping of the payload identifier from the ancillary data packet structure of SMPTE ST 291-1 to the K-L-V data structure of SMPTE ST 336 as a fixed-length data pack.