AES3接口中的非PCM音频传输标准——SMPTE 337解析
AES3接口中的非PCM音频传输标准——SMPTE 337解析
SMPTE 337文档是关于非PCM音频在AES3串行数字音频接口中传输标准的详细规范，涵盖了通道状态数据和预加重数据格式的定义。SMPTE（Society of Motion Picture and Television Engineers）337标准主要关注的是在专业应用中，如何使用AES3（AES-3id）接口来传输非脉冲编码调制（PCM）音频和数据。AES3接口是一种广泛用于专业音频领域的数字音频传输标准，它能够提供高质量、低噪声的音频信号传输。
范围
SMPTE 337标准定义了一个接口格式，允许在不同的设备之间交换非PCM音频和数据。这个标准不仅包含了物理层面的规定，如信号电平、时钟同步等，还涉及到逻辑层面的协议，如数据包的结构和编码方式。标准支持多种非PCM音频和数据格式，并能在单一接口中传输多个数据流。此外，它还提供了时间码或时间对齐信息的携带方式，确保通过该接口传递的信息可以与通过其他接口传递的内容同步。
引用标准
SMPTE 337依赖于其他标准，如AES3-1992（数字音频工程—串行数字音频接口）。这些引用的标准提供了接口设计的基础，包括信号格式、错误检测和校正等方面。在使用SMPTE 337时，应该注意检查引用标准的最新版本，以获取最新的技术要求。
数据传输
非PCM音频，如杜比AC-3或DTS等环绕声格式，可以通过AES3接口按照SMPTE 337定义的方式进行传输。这些非PCM音频通常包含多声道信息，需要特定的编码和打包方法以适应AES3的帧结构。数据状态通道（channel status data）则包含了音频流的元信息，如声道配置、采样率和位深度等。
时间码和同步
为了实现不同系统间的精确同步，SMPTE 337标准提供了时间码的携带机制，如SMPTE时间码（STC）或飞利浦UTC码。这些时间码可以是嵌入在音频数据流中，或者通过单独的通道进行传输，确保音频和视频或者其他数据流的时间一致性。
兼容性和互操作性
SMPTE 337标准的设计目的是提高不同设备之间的兼容性和互操作性。通过定义统一的接口标准，制造商可以在其产品中实现与其它遵循该标准的设备无缝对接，简化系统集成，降低用户在多设备环境下遇到的兼容问题。
总结来说，SMPTE 337是音频工程领域的一个关键标准，它规定了非PCM音频和数据在AES3接口中的传输规范，确保了多设备环境下的高效、同步和兼容的数据交换。了解并遵循这一标准对于开发和维护专业音频系统至关重要。
Scope
This standard specifies an interface format for the transport of non-PCM audio and data in professional applications using the AES3 serial digital audio interface. This standard includes both physical and logical specifications, based on the existing AES3 format, to allow exchange of non-PCM data between different devices. The standard accommodates multiple non-PCM audio and data formats and allows carriage of multiple data streams within a single interface. This standard provides means for carrying time code or time alignment information so that the information conveyed over this interface may be synchronized with information content delivered over other interfaces.
Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards
AES3-1992, Digital Audio Engineering— Serial Transmission Format for Two-Channel Linearly Represented Digital Audio Data
SMPTE 338M-2000, Television — Format for Non-PCM Audio and Data in AES3 — Data Types
Definition
3.1 frame frequency: The frequency at which AES3 frames occur. When linear PCM audio is carried within the AES3 interface, the frame frequency is equivalent to the sampling rate of the linear PCM audio.
Introduction
The AES3 standard is widely used in industry to convey linear PCM audio between digital audio devices. However the AES3 standard is limited to two channels of audio. Significant issues arise when multiple AES3 channels are used to convey greater than two channels of associated audio. This standard defines a method in which the existing AES3 format is modified to convey non-PCM data, including non-PCM audio bit streams which are typically, but not necessarily, bit-rate reduced. This allows a single audio program of more than 2 channels or multiple audio programs, each potentially consisting of more than 2 channels, to be carried over a single AES3 interface.
This standard specifies a modification to the logical portion of the AES3 standard and is compatible with the existing AES3 standard for transport of linear PCM audio. Therefore, this standard can facilitate the interconnection of equipment which may be capable of working with either linear PCM or non-PCM audio and data. This method may allow some existing equipment which is capable of recording linear PCM to also record non-PCM data. Independent use of the AES3 channels is also supported by this standard to allow both one channel of linear PCM audio and non-PCM data to be carried within a single AES3 signal.
This standard accommodates methods of synchronization both for reconstruction of the original source audio signals coded within non-PCM audio streams and for time alignment with other information streams
Approved April 6, 2000
Copyright © 2000 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS
595 W. Hartsdale Ave., White Plains, NY 10607
(914) 761-1100
for Television — Format for Non-PCM Audio
and Data in an AES3 Serial Digital Audio Interface
SMPTE 337M-2000
SMPTE STANDARD