USB Device Class Definition for Audio Devices
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Table A-16: Decoder Type Codes.......................................................................................135
Table A-17: Clock Source Control Selectors....................................................................135
Table A-18: Clock Selector Control Selectors..................................................................136
Table A-19: Clock Multiplier Control Selectors.................................................................136
Table A-20: Terminal Control Selectors............................................................................136
Table A-21: Mixer Control Selectors..................................................................................136
Table A-22: Selector Control Selectors.............................................................................137
Table A-23: Feature Unit Control Selectors......................................................................137
Table A-24: Reverberation Effect Unit Control Selectors................................................138
Table A-25: Reverberation Effect Unit Control Selectors................................................138
Table A-26: Modulation Delay Effect Unit Control Selectors..........................................139
Table A-27: Dynamic Range Compressor Effect Unit Control Selectors.......................139
Table A-28: Up/Down-mix Processing Unit Control Selectors........................................140
Table A-29: Dolby Prologic Processing Unit Control Selectors.....................................140
Table A-30: Stereo Extender Processing Unit Control Selectors...................................141
Table A-31: Extension Unit Control Selectors..................................................................141
Table A-32: AudioStreaming Interface Control Selectors...............................................141
Table A-33: Encoder Control Selectors.............................................................................142
Table A-34: MPEG Decoder Control Selectors.................................................................142
Table A-35: AC-3 Decoder Control Selectors....................................................................143
Table A-36: WMA Decoder Control Selectors...................................................................143
Table A-37: DTS Decoder Control Selectors.....................................................................143
Table A-38: Endpoint Control Selectors............................................................................144
USB Device Class Definition for Audio Devices
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List of Figures
Figure 3-1: Audio Function Global View..............................................................................18
Figure 3-2: Inside the Audio Function.................................................................................25
Figure 3-3: Input Terminal Icon............................................................................................28
Figure 3-4: Output Terminal Icon.........................................................................................29
Figure 3-5: Mixer Unit Icon....................................................................................................29
Figure 3-6: Selector Unit Icon...............................................................................................30
Figure 3-7: Feature Unit Icon................................................................................................30
Figure 3-8: Sampling Rate Converter Unit Icon..................................................................31
Figure 3-9: PEQS Effect Unit Icon........................................................................................32
Figure 3-10: Reverberation Effect Unit Icon........................................................................32
Figure 3-11: Modulation Delay Effect Unit Icon..................................................................33
Figure 3-12: Dynamic Range Compressor Transfer Characteristic.................................33
Figure 3-13: Dynamic Range Compressor Effect Unit Icon...............................................33
Figure 3-14: Up/Down-mix Processing Unit Icon...............................................................34
Figure 3-15: Dolby Prologic Processing Unit Icon.............................................................35
Figure 3-16: Stereo Extender Processing Unit Icon...........................................................35
Figure 3-17: Extension Unit Icon..........................................................................................36
Figure 3-18: Clock Source Icon............................................................................................37
Figure 3-19: Clock Selector Icon..........................................................................................37
Figure 3-20: Clock Multiplier Icon........................................................................................37
Figure 4-1: Mixer internals....................................................................................................56
USB Device Class Definition for Audio Devices
Release 2.0
May 31, 2006 13
1 Introduction
1.1 Scope
The Audio Device Class Definition applies to all devices or functions embedded in composite devices that are used to manipulate audio, voice, and sound-related functionality. This includes both audio data (analog and digital) and the functionality that is used to directly control the audio environment, such as Volume and Tone Control. The Audio Device Class does not include functionality to operate transport mechanisms that are related to the reproduction of audio data, such as tape transport mechanisms or CD-ROM drive control. Handling of MIDI data streams over the USB is directly related to audio and thus covered in this document.
1.2 Purpose
The purpose of this document is to describe the minimum capabilities and characteristics an audio device must support to comply with the USB. This document also provides recommendations for optional features.
1.3 Related Documents
• Universal Serial Bus Specification, Revision 2.0 (referred to in this document as the USB Specification). In particular, see Chapter 5, “USB Data Flow Model” and Chapter 9, “USB Device Framework.”
• Universal Serial Bus Device Class Definition for Audio Data Formats (referred to in this document as USB Audio Data Formats).
• Universal Serial Bus Device Class Definition for Terminal Types (referred to in this document as USB Audio Terminal Types).
• ANSI S1.11-1986 standard.
• MPEG-1 standard ISO/IEC 111172-3 1993.
• MPEG-2 standard ISO/IEC 13818-3 Feb. 20, 1997.
• Digital Audio Compression Standard (AC-3), ATSC A/52A Aug. 20, 2001. (available from Error! Hyperlink reference not valid.)
• ANSI/IEEE-754 floating-point standard.
• ISO/IEC 60958 International Standard: Digital Audio Interface and Annexes.
• ISO/IEC 61937 standard.
1.4 Terms and Abbreviations
This section defines terms used throughout this document. For additional terms that pertain to the Universal Serial Bus, see Chapter 2, “Terms and Abbreviations,” in the USB Specification.
Audio Channel Cluster Group of logical audio channels that carry tightly related synchronous audio information. A stereo audio stream is a typical example of a two-channel audio channel cluster.
Audio Control Attribute Parameter of an Audio Control. Examples are Current, Minimum, Maximum and Resolution attributes of a Volume Control.
Audio Control Logical object that is used to manipulate a specific audio property. Examples are Volume Control, Mute Control, etc.
Audio data stream Transport medium that can carry audio information.
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Audio Function Independent part of a USB device that deals with audio-related functionality.
Audio Interface Collection (AIC) Grouping of a single AudioControl interface, zero or more AudioStreaming interfaces and zero or more MIDIStreaming interfaces that together constitute a complete interface to an audio function.
AudioControl interface (ACI) USB interface used to access the Audio Controls inside an audio function.
AudioStreaming interface (ASI) USB interface used to transport audio streams into or out of the audio function.
Effect Unit (EU) Provides advanced audio manipulation on the incoming logical audio channels.
Entity Addressable logical object inside an audio function.
Extension Unit (XU) Applies an undefined process to a number of logical input channels.
Feature Unit (FU) Provides basic audio manipulation on the incoming logical audio channels.
FUD Acronym for Feature Unit Descriptor.
Input Pin Logical input connection to an Entity. Carries a single audio channel cluster.
Input Terminal (IT) Receptacle for audio information flowing into the audio function.
ITD Acronym for Input Terminal Descriptor.
Logical Audio Channel Logical transport medium for a single audio channel. Makes abstraction of the physical properties and formats of the connection. Is usually identified by spatial location. Examples are Left channel, Right Surround channel, etc.
MIDIStreaming interface (MSI) USB interface that may be used to transport MIDI data streams into or out of the audio function.
Mixer Unit (MU) Mixes a number of logical input channels into a number of logical output channels.
MUD Acronym for Mixer Unit Descriptor.
OTD Acronym for Output Terminal Descriptor.
Output Pin Logical output connection to an Entity. Carries a single audio channel cluster.
Output Terminal (OT) An outlet for audio information flowing out of the audio function.
Processing Unit (PU) Applies a predefined process to a number of logical input channels.
PUD Acronym for Processing Unit Descriptor.
Selector Unit (SU) Selects from a number of input audio channel clusters.
SUD Acronym for Selector Unit Descriptor.
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Terminal Addressable logical object inside an audio function that represents a connection to the audio function’s outside world.
Unit Addressable logical object inside an audio function that represents a certain audio subfunctionality.
XUD Acronym for Extension Unit Descriptor.
最終更新：2011年05月08日 13:35
