Release 3.0 September 22, 2016 1
UNIVERSAL SERIAL BUS
DEVICE CLASS DEFINITION
FOR
AUDIO DEVICES
Release 3.0
September 22, 2016
Release 3.0 September 22, 2016 2
SCOPE OF THIS RELEASE
This document is the Release 3.0 of this Device Class Definition.
CONTRIBUTORS
Joe Scanlon Advanced Micro Devices
Rhoads Hollowell Apple Inc.
Girault Jones Apple Inc.
Matthew X. Mora Apple Inc.
Tzung-Dar Tsai C-Media Electronics, Inc.
Brad Lambert Cirrus Logic, Inc.
Dan Bogard Conexant Systems, Inc.
Pete Burgers DisplayLink (UK), Ltd.
David Roh Dolby Laboratories, Inc.
Leng Ooi Google, Inc.
Pierre-Louis Bossart Intel Corporation
David Hines Intel Corporation
Abdul Rahman Ismail (Co-Chair) Intel Corporation
Devon Worrell Intel Corporation
Chandrashekhar Rao Logitech, Inc.
Terry Moore MCCI Corporation
Alex Lin MediaTek, Inc.
Bala Sivakumar Microsoft Corporation
Geert Knapen (Co-Chair & Editor) NXP Semiconductors
PL Mobile Audio
411 E. Plumeria drive
San Jose, CA 95134, USA
E-mail: geert.knapen@nxp.com
James Goel Qualcomm, Inc.
Andre Schevciw Qualcomm, Inc.
Jin-Sheng Wang Qualcomm, Inc.
Morten Christiansen Synopsys
REVISION HISTORY
Revision
Date
Filename
Description
1.0
Mar. 18, 98
Audio10.pdf
Release 1.0
2.0
May. 31, 06
Audio20 final.pdf
Release 2.0
3.0
Sep. 22, 16
Audio30.pdf
Release 3.0
Release 3.0 September 22, 2016 3
Copyright © 1997-2016 USB Implementers Forum, Inc.
All rights reserved.
INTELLECTUAL PROPERTY DISCLAIMER
A LICENSE IS HEREBY GRANTED TO REPRODUCE THIS SPECIFICATION FOR INTERNAL USE ONLY. NO OTHER LICENSE,
EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED OR INTENDED HEREBY.
USB-IF AND THE AUTHORS OF THIS SPECIFICATION EXPRESSLY DISCLAIM ALL LIABILITY FOR INFRINGEMENT OF
INTELLECTUAL PROPERTY RIGHTS RELATING TO IMPLEMENTATION OF INFORMATION IN THIS SPECIFICATION. USB-
IF AND THE AUTHORS OF THIS SPECIFICATION ALSO DO NOT WARRANT OR REPRESENT THAT SUCH
IMPLEMENTATION(S) WILL NOT INFRINGE THE INTELLECTUAL PROPERTY RIGHTS OF OTHERS.
THIS SPECIFICATION IS PROVIDED “AS IS” AND WITH NO WARRANTIES, EXPRESS OR IMPLIED, STATUTORY OR
OTHERWISE. ALL WARRANTIES ARE EXPRESSLY DISCLAIMED. USB-IF, ITS MEMBERS AND THE AUTHORS OF THIS
SPECIFICATION PROVIDE NO WARRANTY OF MERCHANTABILITY, NO WARRANTY OF NON-INFRINGEMENT, NO
WARRANTY OF FITNESS FOR ANY PARTICULAR PURPOSE, AND NO WARRANTY ARISING OUT OF ANY PROPOSAL,
SPECIFICATION, OR SAMPLE.
IN NO EVENT WILL USB-IF, MEMBERS OR THE AUTHORS BE LIABLE TO ANOTHER FOR THE COST OF PROCURING
SUBSTITUTE GOODS OR SERVICES, LOST PROFITS, LOSS OF USE, LOSS OF DATA OR ANY INCIDENTAL,
CONSEQUENTIAL, INDIRECT, OR SPECIAL DAMAGES, WHETHER UNDER CONTRACT, TORT, WARRANTY, OR
OTHERWISE, ARISING IN ANY WAY OUT OF THE USE OF THIS SPECIFICATION, WHETHER OR NOT SUCH PARTY HAD
ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
NOTE: VARIOUS USB-IF MEMBERS PARTICIPATED IN THE DRAFTING OF THIS SPECIFICATION. CERTAIN OF THESE
MEMBERS MAY HAVE DECLINED TO ENTER INTO A SPECIFIC AGREEMENT LICENSING INTELLECTUAL PROPERTY
RIGHTS THAT MAY BE INFRINGED IN THE IMPLEMENTATION OF THIS SPECIFICATION. PERSONS IMPLEMENT THIS
SPECIFICATION AT THEIR OWN RISK.
Dolby™, AC-3™, Pro Logic™ and Dolby Surround™ are trademarks of Dolby Laboratories, Inc.
All other product names are trademarks, registered trademarks, or service marks of their respective owners.
Please send comments via electronic mail to audio-chair@usb.org
Release 3.0 September 22, 2016 4
TABLE OF CONTENTS
Scope of This Release ................................................................................................................................................ 2
Contributors............................................................................................................................................................... 2
Revision History ......................................................................................................................................................... 2
Table of Contents ...................................................................................................................................................... 4
List of Tables .............................................................................................................................................................. 8
List of Figures ........................................................................................................................................................... 12
1 Introduction ..................................................................................................................................................... 13
1.1 Scope ....................................................................................................................................................... 13
1.2 Purpose .................................................................................................................................................... 13
1.3 Related Documents ................................................................................................................................. 13
1.4 Terms and Abbreviations ......................................................................................................................... 13
2 Management Overview ................................................................................................................................... 16
2.1 Overview of Key Differences between ADC v2.0 and v3.0 ...................................................................... 16
3 Functional Characteristics ............................................................................................................................... 18
3.1 Introduction ............................................................................................................................................. 18
3.2 Basic Audio Device Definition .................................................................................................................. 20
3.3 Backwards Compatibility ......................................................................................................................... 20
3.4 Audio Interface Association (AIA) and Interface Association Descriptor ................................................. 21
3.4.1 Audio Function Class ........................................................................................................................ 21
3.4.2 Audio Function Subclass .................................................................................................................. 21
3.4.3 Audio Function Protocol .................................................................................................................. 21
3.5 Audio Interface Class ............................................................................................................................... 21
3.6 Audio Interface Subclass .......................................................................................................................... 22
3.7 Audio Interface Protocol .......................................................................................................................... 22
3.8 Audio Function Category ......................................................................................................................... 22
3.9 Clock Domains ......................................................................................................................................... 23
3.10 Power Domains ........................................................................................................................................ 23
3.11 Audio Synchronization Types ................................................................................................................... 23
3.11.1 Asynchronous .................................................................................................................................. 23
3.11.2 Synchronous .................................................................................................................................... 24
3.11.3 Adaptive ........................................................................................................................................... 24
3.11.4 Implications of the Different Synchronization Types ....................................................................... 24
3.12 Inter Channel Synchronization................................................................................................................. 26
3.13 Audio Function Topology ......................................................................................................................... 26
3.13.1 Cluster .............................................................................................................................................. 30
3.13.2 Input Terminal ................................................................................................................................. 30
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3.13.3 Output Terminal .............................................................................................................................. 31
3.13.4 Mixer Unit ........................................................................................................................................ 32
3.13.5 Selector Unit .................................................................................................................................... 33
3.13.6 Feature Unit ..................................................................................................................................... 33
3.13.7 Sampling Rate Converter Unit ......................................................................................................... 34
3.13.8 Effect Unit ........................................................................................................................................ 35
3.13.9 Processing Unit ................................................................................................................................ 38
3.13.10 Extension Unit .................................................................................................................................. 41
3.13.11 Clock Entities .................................................................................................................................... 41
3.14 Operational Model................................................................................................................................... 43
3.14.1 AudioControl Interface .................................................................................................................... 44
3.14.2 AudioStreaming Interface ................................................................................................................ 44
3.14.3 Clock Model ..................................................................................................................................... 46
3.14.4 Power Domains Model .................................................................................................................... 46
3.14.5 Additional Power Considerations and Requirements ...................................................................... 47
3.14.6 Binding between Physical Buttons and Audio Controls ................................................................... 48
4 Descriptors ....................................................................................................................................................... 49
4.1 Standard Descriptors ............................................................................................................................... 49
4.2 Class-Specific Descriptors ........................................................................................................................ 49
4.2.1 Traditional Class-Specific Descriptors .............................................................................................. 50
4.2.2 High Capability Class-Specific Descriptors ....................................................................................... 50
4.3 Cluster Descriptor .................................................................................................................................... 51
4.3.1 Cluster Descriptor Header ............................................................................................................... 52
4.3.2 Cluster Descriptor Block................................................................................................................... 53
4.3.3 Example Cluster descriptor .............................................................................................................. 60
4.3.4 CEA-861.2 Channel Mapping ........................................................................................................... 62
4.4 Physical versus Logical Cluster ................................................................................................................. 62
4.4.1 Mapping between Physical and Logical Clusters ............................................................................. 62
4.5 AudioControl Interface Descriptors ......................................................................................................... 64
4.5.1 Standard AC Interface Descriptor .................................................................................................... 65
4.5.2 Class-Specific AC Interface Descriptor ............................................................................................. 65
4.6 AudioControl Endpoint Descriptors ......................................................................................................... 95
4.6.1 AC Control Endpoint Descriptors ..................................................................................................... 95
4.6.2 AC Interrupt Endpoint Descriptors .................................................................................................. 95
4.7 AudioStreaming Interface Descriptors .................................................................................................... 96
4.7.1 Standard AS Interface Descriptor .................................................................................................... 96
4.7.2 Class-Specific AS Interface Descriptor ............................................................................................. 97
4.7.3 Class-Specific AS Valid Frequency Range Descriptor ....................................................................... 98
