SMPTE ST 337-2015 Format for Non-PCM Audio and Data in an AES3 Serial Digital Audio Interface.pdf

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1、 Approved March 27, 2015 Copyright 2015 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Table of Contents Page Foreword 2 Intellectual Property . 2 Introduction. 2 1 Scope 4 2 Conformance Notation 4 3 Normative References 4 4 Definitio

2、ns . 5 4.1 Frame Frequency 5 5 Overview . 5 6 Interface Format 6 6.1 Detailed Specifications 6 6.2 Channel Status Word 6 6.3 Sample Rate Synchronization . 8 7 Data Burst Format . 8 7.1 General 8 7.2 burst_preamble . 8 7.3 burst_payload 12 7.4 Burst Spacing 13 7.5 Data Type Dependent Fields 13 8 Cons

3、umer Format Compatibility (Informative) 14 8.1 General 14 8.2 Receiving Devices . 14 8.3 Source Devices . 14 8.4 Data Type Dependent Issues . 14 Annex A Auto-Detection of Audio / Data Mode (Informative) . 15 Annex B Equipment Compatibility Issues (Informative) 16 B.1 Data Mode 16 B.2 Channel Status

4、Usage . 16 B.3 Non-PCM Data Modification . 16 Annex C Bibliography (Informative) 17 SMPTE ST 337:2015 Revision of SMPTE 337-2008 SMPTE STANDARD Format for Non-PCM Audio and Data in an AES3 Serial Digital Audio Interface Page 1 of 17 pages SMPTE ST 337:2015 Page 2 of 17 pages Foreword SMPTE (the Soci

5、ety of Motion Picture and Television Engineers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Recommended

6、 Practices, and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and ITU. SMPTE Engineering Docume

7、nts are drafted in accordance with the rules given in its Standards Operations Manual. SMPTE ST 337 was prepared by Technology Committee 32NF. Intellectual Property At the time of publication no notice had been received by SMPTE claiming patent rights essential to the implementation of this Engineer

8、ing Document. However, attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. SMPTE shall not be held responsible for identifying any or all such patent rights. Introduction This section is entirely informative and does not form an integ

9、ral part of this Engineering Document. 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 channe

10、ls 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 pr

11、ograms, 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 ca

12、n 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 b

13、y 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

14、other information streams such as an associated video stream. Synchronization methods for specific non-PCM bitstreams are dependent on the data type carried within the bitstream and are beyond the scope of this standard. However, other standards and recommended practices may contain important and ne

15、cessary information regarding synchronization requirements for specific data types. In general, it is required to refer to such information in order to properly transmit and receive non-PCM streams using this standard. References to documents containing synchronization requirements for specific data

16、 types can be found in SMPTE ST 338. SMPTE ST 337:201 Page 3 of 17 pages Note: Because of the wide variety of data types that may potentially be conveyed according to this standard, no global synchronization requirements are specified in this standard. However, synchronization of non-PCM data conten

17、t, both in terms of the relationship of the coded audio sampling rate to the AES3 frame frequency (when conveying non-PCM audio) and in terms of time synchronization to other information streams, is very important to the proper use of this standard. Additionally, synchronization requirements for spe

18、cific data types may impose buffering requirements on devices that support these data types. Therefore, it is required that additional documents containing synchronization requirements for specific data types be referenced in order to maintain compatibility with these data types. A dedicated data ty

19、pe, the time stamp data type, is included to support synchronization methods. Many data types may make use of information contained in the time stamp data bursts, which can include SMPTE ST 12-1 time code information, to maintain time synchronization with other information streams. References for do

20、cuments describing the time stamp data type can be found in SMPTE ST 338. This standard is applicable to professional audio equipment only. Existing standards (IEC 61937 family) cover transport of non-PCM data in the consumer environment. Some interoperability between professional and consumer equip

21、ment is accommodated by this standard, and specific compatibility requirements are described. SMPTE ST 337:2015 Page 4 of 17 pages 1 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 interfac

22、e. 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

23、. 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. 2 Conformance Notation Normative text is text that describes elements of the design t

24、hat are indispensable or contains the conformance language keywords: “shall“, “should“, or “may“. Informative text is text that is potentially helpful to the user, but not indispensable, and can be removed, changed, or added editorially without affecting interoperability. Informative text does not c

25、ontain any conformance keywords. All text in this document is, by default, normative, except: the Introduction, any section explicitly labeled as “Informative“ or individual paragraphs that start with “Note:” The keywords “shall“ and “shall not“ indicate requirements strictly to be followed in order

26、 to conform to the document and from which no deviation is permitted. The keywords, “should“ and “should not“ indicate that, among several possibilities, one is recommended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but not neces

27、sarily required; or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited. The keywords “may“ and “need not“ indicate courses of action permissible within the limits of the document. The keyword “reserved” indicates a provision that is not defined at

28、this time, shall not be used, and may be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be defined in the future. Unless otherwise specified, the order of precedence of the types of normative information in this document sh

29、all be as follows: Normative prose shall be the authoritative definition; Tables shall be next; then formal languages; then figures; and then any other language forms. 3 Normative References The following standards contain provisions which, through reference in this text, constitute provisions of th

30、is 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 indicated below. Note: In some parts

31、of this standard, reference is made generically to “AES3”, rather than to a specific Part of the four-part AES Standard (AES3-1, AES3-2, AES3-3 and AES3-4). See the Normative References and Annex C Bibliography. AES3-1-2009, AES Standard for Digital Audio Digital Input-Output Interfacing Serial Tran

32、smission Format for Two-Channel Linearly Represented Digital Audio Data Part 1: Audio Content AES3-2-2009, AES Standard for Digital Audio Digital Input-Output Interfacing Serial Transmission Format for Two-Channel Linearly Represented Digital Audio Data Part 2: Metadata and Subcode SMPTE ST 337:201

33、Page 5 of 17 pages AES3-3-2009, AES Standard for Digital Audio Digital Input-Output Interfacing Serial Transmission Format for Two-Channel Linearly Represented Digital Audio Data Part 3: Transport SMPTE ST 338:2015, Format for Non-PCM Audio and Data in AES3 Data Types 4 Definitions This document def

34、ines certain bit-field values. When they are expressed in binary representation they are enclosed in single quote marks (thus: ) and are stated with most-significant bit first (leftmost). e.g. 100 represents decimal 4. 4.1 Frame Frequency The frequency at which AES3 frames occur. When linear PCM aud

35、io is carried within the AES3 interface, the frame frequency is equivalent to the sampling rate of the linear PCM audio. 5 Overview SMPTE ST 337 defines a method for transporting non-PCM audio (such as compressed formats) using the AES3 interface standard. The logical format of the AES3 interface co

36、nsists of a sequence of subframes. Each subframe is intended to convey one linear PCM sample, and contains 32 time slots, each of which (excluding the four time slots used for synchronization purposes) can carry a single bit of information. A pair of subframes, each containing the PCM word of one au

37、dio channel, make up an AES3 frame containing two PCM words, one from channel 1 and one from channel 2. A sequence of 192 frames makes up a block. The 192 channel status bits for each channel during a block make up the 192-bit (24-byte) channel status word for that channel. SMPTE ST 337 adapts the s

38、tandard usage of the 32 AES3-3 subframe time slots when conveying non-PCM data. This usage shall be as shown in Table 1. Table 1 AES3-3 subframe bit field usage for non-PCM data Bit locations AES3-3 field designations Non-PCM data usage 0 3 AES Sync preamble As per AES3-3 4 7 Aux data field or 4 LSB

39、s of audio sample word Non-PCM data in 24-bit mode see Section 7.2 8 27 Audio sample word Non-PCM data 28 Validity (V) bit As per AES3-1 and AES3-3 29 User data (U) bit As per AES3-2 and AES3-3 30 Channel status (C) bit Bytes 0, 1, 2, 23 defined; other bytes undefined see Section 6.2 31 Parity (P) b

40、it As per AES3-3 SMPTE ST 337:2015 Page 6 of 17 pages The non-PCM data streams to be conveyed are formed into data bursts, each consisting of a preamble containing information about the burst followed by a data payload. The data bursts are placed in the audio sample word/aux data fields of AES3-3 su

41、bframes in one of two modes. In the frame mode, the data space from each subframe within an AES3-3 frame is combined to allow up to 48 bits of data to be placed in each frame. In the subframe mode, each channel is treated independently and data are not shared across subframes within a frame. In this

42、 mode, each subframe may contain either linear PCM audio or non-PCM data. This allows the AES3 interface to simultaneously convey two linear PCM channels, or one linear PCM channel and one set of non-PCM data bit streams, or two sets of non-PCM data bit streams. Data bursts are tagged with a number

43、indicating to which data stream they belong. Up to seven different non-PCM data streams, along with an additional stream type dedicated for time stamp data bursts, may be time multiplexed together to form a set of data bit streams. In the subframe mode, this allows up to 14 independent non-PCM data

44、streams to be multiplexed within a single AES3 interface. Data bursts are placed in the audio sample word/aux data fields of AES3-3 subframes using 16, 20, or 24 bits of the available space within each subframe. While the 24-bit mode allows more efficient use of the AES3 data capacity, the 16- and 2

45、0-bit modes might need to be used when interfacing with existing equipment that is limited to 16- or 20-bit operation. Annex B contains additional comments regarding the use of 20- and 24-bit data modes. 6 Interface Format 6.1 Detailed Specifications The logical interface format shall be as defined

46、in AES3-1, AES3-2, AES3-3 except as noted in this standard. When in the subframe mode and one channel is used to convey linear PCM, the channel conveying linear PCM shall be used in accordance with AES3. Non-PCM data shall be placed in the available AES3-3 data space in bursts as described in this s

47、tandard. The non-PCM data shall occupy some or all of bit locations 4-27 of the AES3-3 subframe. Unused bit locations within a sub-frame or in subframes between bursts shall be set to 0. 6.2 Channel Status Word The Channel Status Word structure shall be as defined in AES3-2. For AES3 channels that c

48、onvey non-PCM data, Channel Status byte 0, byte 1, byte 2, and byte 23 of the channel status word shall be used as described in this standard. The usage of the remaining bytes of the channel status word is undefined for channels that convey non-PCM data. It is recommended that each bit of the undefi

49、ned channel status bytes be set to 0. Byte 0 bit 0 of the channel status word shall be set to 1, indicating professional use of the channel status block. Consumer use of the AES3 bit stream is not considered in this standard. Byte 0 bit 1 shall be set to 1, indicating non-audio mode. Byte 0 bits 2-4 shall be set to 000. Byte 0 bit 5 shall be set according to AES3-2, but shall indicate the source frame frequency lock status. The source frame frequency shall be interpreted as the source rate from which the AES3 interface frame