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# 3.3.4 Library Interface

This section describes the Application Programming Interface (API) functions of the USB Audio v1.0 Host Client Driver Library.

Refer to each section for a detailed description.

## Audio Device Access Functions

Name | Description
USB_HOST_AUDIO_V1_AttachEventHandlerSet | Sets an attach/detach event handler.
USB_HOST_AUDIO_V1_ControlEntityGetFirst | Retrieves the handle to the first audio control entity.
USB_HOST_AUDIO_V1_ControlEntityGetNext | Retrieves the handle to the next audio control entity.
USB_HOST_AUDIO_V1_DeviceObjHandleGet | Returns the device object handle for this Audio v1.0 Device.
USB_HOST_AUDIO_V1_EntityObjectGet | Retrieves the entity object for the entity ID.
USB_HOST_AUDIO_V1_EntityRequestCallbackSet | Registers an audio entity request callback function with the Audio v1.0 Client Driver.
USB_HOST_AUDIO_V1_EntityTypeGet | Returns the entity type of the audio control entity.
USB_HOST_AUDIO_V1_FeatureUnitChannelMuteExists | Returns "true" if mute control exists for the specified channel of the feature unit.
USB_HOST_AUDIO_V1_FeatureUnitChannelMuteGet | Schedules a get mute control request to the specified channel.
USB_HOST_AUDIO_V1_FeatureUnitChannelMuteSet | Schedules a set mute control request to the specified channel.
USB_HOST_AUDIO_V1_FeatureUnitChannelNumbersGet | Returns the number of channels.
USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeExists | Returns "true" if volume control exists for the specified channel of the feature unit.
USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeGet | Schedules a get current volume control request to the specified channel.
USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeRangeGet | Schedules a control request to the Audio Device feature unit to get the range supported by the volume control on the specified channel.
USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeSet | Schedules a set current volume control request to the specified channel.
USB_HOST_AUDIO_V1_FeatureUnitIDGet | Returns ID of the Feature Unit.
USB_HOST_AUDIO_V1_FeatureUnitSourceIDGet | Returns the ID of the unit or terminal to which this feature unit is connected.
USB_HOST_AUDIO_V1_TerminalAssociationGet | Returns the associated terminal ID of the audio control terminal.
USB_HOST_AUDIO_V1_TerminalIDGet | Returns the terminal ID of the audio control entity.
USB_HOST_AUDIO_V1_TerminalInputChannelNumbersGet | Returns the number of logical output channels in the terminal's output audio channel cluster.
USB_HOST_AUDIO_V1_TerminalSourceIDGet | Returns the ID of the unit or terminal to which this terminal is connected.
USB_HOST_AUDIO_V1_TerminalTypeGet | Returns the terminal type of the audio control entity.

## Audio Stream Access Functions

Name | Description
USB_HOST_AUDIO_V1_StreamClose | Closes the audio stream.
USB_HOST_AUDIO_V1_StreamEventHandlerSet | Registers an event handler with the Audio v1.0 Client Driver stream.
USB_HOST_AUDIO_V1_StreamingInterfaceBitResolutionGet | Returns the bit resolution of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceChannelNumbersGet | Returns the number of channels of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceDirectionGet | Returns the direction of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceFormatTagGet | Returns the format tag of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceGetFirst | Gets the first streaming interface object from the attached Audio Device.
USB_HOST_AUDIO_V1_StreamingInterfaceGetNext | Gets the next streaming interface object from the attached Audio Device.
USB_HOST_AUDIO_V1_StreamingInterfaceSamplingFrequenciesGet | Returns the sampling frequencies supported by the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceSamplingFrequencyTypeGet | Returns the sampling frequency type of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceSet | Schedules a SET_INTERFACE request to the specified audio stream.
USB_HOST_AUDIO_V1_StreamingInterfaceSettingGetFirst | Gets the first streaming interface setting object within an audio streaming interface.
USB_HOST_AUDIO_V1_StreamingInterfaceSettingGetNext | Gets the next streaming interface setting object within an audio streaming interface.
USB_HOST_AUDIO_V1_StreamingInterfaceSubFrameSizeGet | Returns the sub-frame size of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamingInterfaceTerminalLinkGet | Returns the terminal link of the specified streaming interface setting.
USB_HOST_AUDIO_V1_StreamOpen | Opens the specified audio stream.
USB_HOST_AUDIO_V1_StreamRead | Schedules an audio stream read request for the specified audio stream.
USB_HOST_AUDIO_V1_StreamSamplingFrequencyGet | Schedules an audio stream get sampling rate request for the specified audio stream.
USB_HOST_AUDIO_V1_StreamSamplingFrequencySet | Schedules an audio stream set sampling rate request for the specified audio stream.
USB_HOST_AUDIO_V1_StreamWrite | Schedules an audio stream write request for the specified audio stream.

## Other Functions

Name | Description
USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeSubRangeNumbersGet | Schedules a control request to an Audio Device feature unit to get the number of sub-ranges supported by the volume control on the specified channel.
USB_HOST_AUDIO_V1_TerminalInputChannelConfigGet | Returns a structure that describes the spatial location of the logical channels of in the terminal's output audio channel cluster.

## Data Types and Constants

Name | Description
USB_HOST_AUDIO_V1_ATTACH_EVENT_HANDLER | USB Host Audio v1.0 Client Driver attach event handler function pointer type.
USB_HOST_AUDIO_V1_CONTROL_ENTITY_OBJ | Defines the type of the Audio v1.0 Host control entity object.
USB_HOST_AUDIO_V1_ENTITY_REQUEST_CALLBACK | USB Host Audio v1.0 class driver control transfer complete callback function pointer type.
USB_HOST_AUDIO_V1_EVENT | Identifies the possible events that the Audio v1.0 Class Driver attach event handler can generate.
USB_HOST_AUDIO_V1_OBJ | Defines the type of the Audio v1.0 Host client object.
USB_HOST_AUDIO_V1_REQUEST_HANDLE | USB Host Audio v1.0 Client Driver request handle.
USB_HOST_AUDIO_V1_RESULT | USB Host Audio v1.0 Class Driver result enumeration.
USB_HOST_AUDIO_V1_STREAM_DIRECTION | USB Host Audio v1.0 Class Driver stream direction.
USB_HOST_AUDIO_V1_STREAM_EVENT | Identifies the possible events that the Audio v1.0 Stream can generate.
USB_HOST_AUDIO_V1_STREAM_EVENT_HANDLER | USB Host Audio v1.0 Class Driver stream event handler function pointer type.
USB_HOST_AUDIO_V1_STREAM_EVENT_INTERFACE_SET_COMPLETE_DATA | USB Host Audio v1.0 class stream control event data.
USB_HOST_AUDIO_V1_STREAM_EVENT_READ_COMPLETE_DATA | USB Host Audio v1.0 class stream data transfer event data.
USB_HOST_AUDIO_V1_STREAM_EVENT_RESPONSE | Returns the type of the USB Host Audio v1.0 stream event handler.
USB_HOST_AUDIO_V1_STREAM_EVENT_SAMPLING_RATE_SET_COMPLETE_DATA | USB Host Audio v1.0 class stream control event data.
USB_HOST_AUDIO_V1_STREAM_EVENT_WRITE_COMPLETE_DATA | USB Host Audio v1.0 class stream data transfer event data.
USB_HOST_AUDIO_V1_STREAM_HANDLE | Defines the type of the Audio v1.0 Host stream handle.
USB_HOST_AUDIO_V1_STREAM_TRANSFER_HANDLE | USB Host Audio v1.0 Class Driver stream data transfer handle.
USB_HOST_AUDIO_V1_STREAMING_INTERFACE_OBJ | Defines the type of the Audio v1.0 Host streaming interface object.
USB_HOST_AUDIO_V1_STREAMING_INTERFACE_SETTING_OBJ | Defines the type of the Audio v1.0 Host streaming interface setting object.
USB_HOST_AUDIO_V1_INTERFACE | USB HOST Audio v1.0 Client Driver interface.
USB_HOST_AUDIO_V1_REQUEST_HANDLE_INVALID | USB Host Audio v1.0 Client Driver invalid request handle.
USB_HOST_AUDIO_V1_SAMPLING_FREQUENCIES_NUMBER | This structure defines USB Host audio stream information structure.
USB_HOST_AUDIO_V1_STREAM_HANDLE_INVALID | Defines Audio v1.0 Host stream invalid handle.
USB_HOST_AUDIO_V1_STREAM_TRANSFER_HANDLE_INVALID | USB Host Audio v1.0 Class Driver invalid stream data transfer handle.
USB_HOST_AUDIO_V1_STREAM_EVENT_SAMPLING_RATE_GET_COMPLETE_DATA | USB Host Audio v1.0 class stream control event data.