AudioHardwarePlugInInterface

Introduction

The CFPlugIn interface to a HAL plug-in.

Discussion

In CFPlugIn terms, AudioHardwarePlugInInterface is a subclass of IUnknown.

Functions

AddRef

The IUnknown method for retaining a reference to a CFPlugIn type.

DeviceAddIOProc

Registers the given AudioDeviceIOProc with the AudioDevice.

DeviceGetCurrentTime

Retrieves the current time from an AudioDevice. Note that the device has to be running.

DeviceGetNearestStartTime

Query an AudioDevice to get a time equal to or later than the given time that is the best time to start IO.

DeviceGetProperty

Queries an the AudioDevice object to get the data of the given property and places it in the provided buffer.

DeviceGetPropertyInfo

Retrieve information about the given property of an AudioDevice.

DeviceRead

Read some data from an AudioDevice starting at the given time.

DeviceRemoveIOProc

Unregisters the given AudioDeviceIOProc from the AudioDevice.

DeviceSetProperty

Tells the AudioDevice object to change the value of the given property using the provided data.

DeviceStart

Starts IO for the given AudioDeviceIOProc.

DeviceStartAtTime

Starts IO for the given AudioDeviceIOProc and aligns the IO cycle of the AudioDevice with the given time.

DeviceStop

Stops IO for the given AudioDeviceIOProc.

DeviceTranslateTime

Translates the time in the AudioDevice's time base from one representation to another. Note that the device has to be running

Initialize

This method is called to initialize the instance of the plug-in.

InitializeWithObjectID

This method is called to initialize the instance of the plug-in.

ObjectGetPropertyData

Queries an AudioObject to get the data of the given property and places it in the provided buffer.

ObjectGetPropertyDataSize

Queries an AudioObject to find the size of the data for the given property.

ObjectHasProperty

Queries an AudioObject about whether or not it has the given property.

ObjectIsPropertySettable

Queries an AudioObject about whether or not the given property can be set using AudioObjectSetPropertyData.

ObjectSetPropertyData

Tells an AudioObject to change the value of the given property using the provided data.

ObjectShow

Prints to standard out a textural description of the AudioObject.

QueryInterface

The IUnknown method for finding an interface on a CFPlugIn type.

Release

The IUnknown method for releasing a reference to a CFPlugIn type.

STDMETHODCALLTYPE *AddRef

The IUnknown method for retaining a reference to a CFPlugIn type.

STDMETHODCALLTYPE *QueryInterface

The IUnknown method for finding an interface on a CFPlugIn type.

STDMETHODCALLTYPE *Release

The IUnknown method for releasing a reference to a CFPlugIn type.

StreamGetProperty

Queries an the AudioStream object to get the data of the given property and places it in the provided buffer.

StreamGetPropertyInfo

Retrieve information about the given property of an AudioStream.

StreamSetProperty

Tells the AudioStream object to change the value of the given property using the provided data.

Teardown

This method is called to tear down the instance of the plug-in.

The IUnknown method for retaining a reference to a CFPlugIn type.

STDMETHODCALLTYPE *AddRef

ULONG (STDMETHODCALLTYPE *AddRef)(
    void*inSelf);  

Parameters

inSelf

The CFPlugIn type to retain.

Return Value

The resulting reference count after the new reference is added.

Registers the given AudioDeviceIOProc with the AudioDevice.

OSStatus (*DeviceAddIOProc)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioDeviceIOProc inProc, 
    void*inClientData);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to register the IOProc with.

inProc

The AudioDeviceIOProc to register.

inClientData

A pointer to client data that is passed back to the IOProc when it is called.

Return Value

An OSStatus indicating success or failure.

Discussion

A client may have multiple IOProcs for a given device, but the device is free to only accept as many as it can handle. Note that it is not recommended for clients to have more than a single IOProc registered at a time as this can be wasteful of system resources. Rather, it is recommended that the client do any necessary mixing itself so that only one IOProc is necessary.

Retrieves the current time from an AudioDevice. Note that the device has to be running.

OSStatus (*DeviceGetCurrentTime)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioTimeStamp*outTime);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to from which to get the time.

outTime

An AudioTimeStamp into which the current time is put.

Return Value

An OSStatus indicating success or failure. kAudioHardwareNotRunningError will be returned if the AudioDevice isn't running.

Query an AudioDevice to get a time equal to or later than the given time that is the best time to start IO.

OSStatus (*DeviceGetNearestStartTime)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioTimeStamp*ioRequestedStartTime, 
    UInt32 inFlags);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to query.

ioRequestedStartTime

A pointer to an AudioTimeStamp that, on entry, is the requested start time. On exit, it will have the a time equal to or later than the requested time, as dictated by the device's constraints.

inFlags

A UInt32 containing flags that modify how this function behaves.

Return Value

An OSStatus indicating success or failure. kAudioHardwareNotRunningError will be returned if the AudioDevice isn't running. kAudioHardwareUnsupportedOperationError will be returned if the AudioDevice does not support starting at a specific time.

Discussion

The time that is returned is dictated by the constraints of the device and the system. For instance, the driver of a device that provides both audio and video data may only allow start times that coincide with the edge of a video frame. Also, if the device already has one or more active IOProcs, the start time will be shifted to the beginning of the next IO cycle so as not to cause discontinuities in the existing IOProcs. Another reason the start time may shift is to allow for aligning the buffer accesses in an optimal fashion. Note that the device must be running to use this function.

Queries an the AudioDevice object to get the data of the given property and places it in the provided buffer.

OSStatus (*DeviceGetProperty)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    UInt32 inChannel, 
    Boolean isInput, 
    AudioDevicePropertyID inPropertyID, 
    UInt32*ioPropertyDataSize, 
    void*outPropertyData);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to query.

inChannel

The channel of the property to query where 0 is the master channel.

isInput

Which section of the AudioDevice to query.

inPropertyID

The AudioDevicePropertyID of the property to query.

ioPropertyDataSize

A UInt32 which on entry indicates the size of the buffer pointed to by outData and on exit indicates how much of the buffer was used.

outPropertyData

The buffer into which the object will put the data for the given property.

Return Value

An OSStatus indicating success or failure.

Retrieve information about the given property of an AudioDevice.

OSStatus (*DeviceGetPropertyInfo)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    UInt32 inChannel, 
    Boolean isInput, 
    AudioDevicePropertyID inPropertyID, 
    UInt32*outSize, 
    Boolean*outWritable);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to query.

inChannel

The channel of the property to query where 0 is the master channel.

isInput

Which section of the AudioDevice to query.

inPropertyID

The AudioDevicePropertyID of the property to query.

outSize

A pointer to a UInt32 that receives the size of the property data in bytes on exit. This can be NULL if the size information is not being requested.

outWritable

A pointer to a Boolean that receives indication of whether or not the given property can be set. This can be NULL if the writability is not being requested.

Return Value

An OSStatus indicating success or failure.

Read some data from an AudioDevice starting at the given time.

OSStatus (*DeviceRead)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    const AudioTimeStamp*inStartTime, 
    AudioBufferList*outData);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to read from.

inStartTime

An AudioTimeStamp indicating the time from which to read the data. In general, the valid range of time (in frames) is from the current time minus the maximum IO buffer size to the current time minus the safety offset.

outData

An AudioBufferList that must be the same size and shape as that returned by kAudioDevicePropertyStreamConfiguration. Further, the AudioBufferList must have been previously registered with the device via kAudioDevicePropertyRegisterBufferList. On exit, the mDataSize fields will be updated with the amount of data read.

Return Value

An OSStatus indicating success or failure. kAudioHardwareUnsupportedOperationError will be returned if the AudioDevice does not support direct reading.

Unregisters the given AudioDeviceIOProc from the AudioDevice.

OSStatus (*DeviceRemoveIOProc)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioDeviceIOProc inProc);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to unregister the IOProc from.

inProc

The AudioDeviceIOProc to unregister.

Return Value

An OSStatus indicating success or failure.

Tells the AudioDevice object to change the value of the given property using the provided data.

OSStatus (*DeviceSetProperty)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    const AudioTimeStamp*inWhen, 
    UInt32 inChannel, 
    Boolean isInput, 
    AudioDevicePropertyID inPropertyID, 
    UInt32 inPropertyDataSize, 
    const void*inPropertyData);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to change.

inWhen

A pointer to an AudioTimeStamp that says when to change the property's value relative to the device's time base. NULL means execute the change immediately.

inChannel

The channel of the property to change where 0 is the master channel.

isInput

Which section of the AudioDevice to change.

inPropertyID

The AudioDevicePropertyID of the property to change.

inPropertyDataSize

A UInt32 indicating the size of the buffer pointed to by inData.

inPropertyData

The buffer containing the data to be used to change the property's value.

Return Value

An OSStatus indicating success or failure.

Starts IO for the given AudioDeviceIOProc.

OSStatus (*DeviceStart)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioDeviceIOProc inProc);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to start the IOProc on.

inProc

The AudioDeviceIOProc to start. Note that this can be NULL, which starts the hardware regardless of whether or not there are any IOProcs registered. This is necessary if any of the AudioDevice's timing services are to be used. A balancing call to AudioDeviceStop with a NULL IOProc is required to stop the hardware.

Return Value

An OSStatus indicating success or failure.

Starts IO for the given AudioDeviceIOProc and aligns the IO cycle of the AudioDevice with the given time.

OSStatus (*DeviceStartAtTime)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioDeviceIOProc inProc, 
    AudioTimeStamp*ioRequestedStartTime, 
    UInt32 inFlags);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to start the IOProc on.

inProc

The AudioDeviceIOProc to start. Note that this can be NULL, which starts the hardware regardless of whether or not there are any IOProcs registered.

ioRequestedStartTime

A pointer to an AudioTimeStamp that, on entry, is the requested time to start the IOProc. On exit, it will be the actual time the IOProc will start.

inFlags

A UInt32 containing flags that modify how this function behaves.

Return Value

An OSStatus indicating success or failure. kAudioHardwareUnsupportedOperationError will be returned if the AudioDevice does not support starting at a specific time and inProc and ioRequestedStartTime are not NULL.

Stops IO for the given AudioDeviceIOProc.

OSStatus (*DeviceStop)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    AudioDeviceIOProc inProc);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice to stop the IOProc on.

inProc

The AudioDeviceIOProc to stop.

Return Value

An OSStatus indicating success or failure.

Translates the time in the AudioDevice's time base from one representation to another. Note that the device has to be running

OSStatus (*DeviceTranslateTime)(
    AudioHardwarePlugInRef inSelf, 
    AudioDeviceID inDevice, 
    const AudioTimeStamp*inTime, 
    AudioTimeStamp*outTime);  

Parameters

inSelf

The plug-in instance that owns the AudioDevice.

inDevice

The AudioDevice whose time base governs the translation.

inTime

An AudioTimeStamp containing the time to be translated.

outTime

An AudioTimeStamp into which the translated time is put. On entry, the mFlags field specifies which representations to translate the input time into. Because not every device supports all time representations, on exit, the mFlags field will indicate which translations were actually done.

Return Value

An OSStatus indicating success or failure. kAudioHardwareNotRunningError will be returned if the AudioDevice isn't running.

This method is called to initialize the instance of the plug-in.

OSStatus (*Initialize)(
    AudioHardwarePlugInRef inSelf);  

Parameters

inSelf

The instance to initialize.

Return Value

An OSStatus indicating success or failure.

Discussion

As part of initialization, the plug-in should publish all the AudioObjects it knows about at the time.

This method is called to initialize the instance of the plug-in.

OSStatus (*InitializeWithObjectID)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID);  

Parameters

inSelf

The instance to initialize.

inObjectID

The AudioObjectID the plug-in is to use to identify itself.

Return Value

An OSStatus indicating success or failure.

Discussion

As part of initialization, the plug-in should publish all the AudioObjects it knows about at the time. This method supersedes the Initialize method for version 3 plug-ins so that an AudioObjectID can be associated with the plug-in right from the start.

Queries an AudioObject to get the data of the given property and places it in the provided buffer.

OSStatus (*ObjectGetPropertyData)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID, 
    const AudioObjectPropertyAddress*inAddress, 
    UInt32 inQualifierDataSize, 
    const void*inQualifierData, 
    UInt32*ioDataSize, 
    void*outData);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to query.

inAddress

An AudioObjectPropertyAddress indicating which property is being queried.

inQualifierDataSize

A UInt32 indicating the size of the buffer pointed to by inQualifierData. Note that not all properties require qualification, in which case this value will be 0.

inQualifierData,

A buffer of data to be used in determining the data of the property being queried. Note that not all properties require qualification, in which case this value will be NULL.

ioDataSize

A UInt32 which on entry indicates the size of the buffer pointed to by outData and on exit indicates how much of the buffer was used.

outData

The buffer into which the AudioObject will put the data for the given property.

Return Value

An OSStatus indicating success or failure.

Queries an AudioObject to find the size of the data for the given property.

OSStatus (*ObjectGetPropertyDataSize)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID, 
    const AudioObjectPropertyAddress*inAddress, 
    UInt32 inQualifierDataSize, 
    const void*inQualifierData, 
    UInt32*outDataSize);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to query.

inAddress

An AudioObjectPropertyAddress indicating which property is being queried.

inQualifierDataSize

A UInt32 indicating the size of the buffer pointed to by inQualifierData. Note that not all properties require qualification, in which case this value will be 0.

inQualifierData,

A buffer of data to be used in determining the data of the property being queried. Note that not all properties require qualification, in which case this value will be NULL.

outDataSize

A UInt32 indicating how many bytes the data for the given property occupies.

Return Value

An OSStatus indicating success or failure.

Queries an AudioObject about whether or not it has the given property.

Boolean (*ObjectHasProperty)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID, 
    const AudioObjectPropertyAddress*inAddress);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to query.

inAddress

An AudioObjectPropertyAddress indicating which property is being queried.

Return Value

A Boolean indicating whether or not the AudioObject has the given property.

Queries an AudioObject about whether or not the given property can be set using AudioObjectSetPropertyData.

OSStatus (*ObjectIsPropertySettable)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID, 
    const AudioObjectPropertyAddress*inAddress, 
    Boolean*outIsSettable);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to query.

inAddress

An AudioObjectPropertyAddress indicating which property is being queried.

outIsSettable

A Boolean indicating whether or not the property can be set.

Return Value

An OSStatus indicating success or failure.

Tells an AudioObject to change the value of the given property using the provided data.

OSStatus (*ObjectSetPropertyData)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID, 
    const AudioObjectPropertyAddress*inAddress, 
    UInt32 inQualifierDataSize, 
    const void*inQualifierData, 
    UInt32 inDataSize, 
    const void*inData);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to change.

inAddress

An AudioObjectPropertyAddress indicating which property is being changed.

inQualifierDataSize

A UInt32 indicating the size of the buffer pointed to by inQualifierData. Note that not all properties require qualification, in which case this value will be 0.

inQualifierData

A buffer of data to be used in determining the data of the property being queried. Note that not all properties require qualification, in which case this value will be NULL.

inDataSize

A UInt32 indicating the size of the buffer pointed to by inData.

inData

The buffer containing the data to be used to change the property's value.

Return Value

An OSStatus indicating success or failure.

Prints to standard out a textural description of the AudioObject.

void (*ObjectShow)(
    AudioHardwarePlugInRef inSelf, 
    AudioObjectID inObjectID);  

Parameters

inSelf

The plug-in instance that owns the AudioObject.

inObjectID

The AudioObject to show.

The IUnknown method for finding an interface on a CFPlugIn type.

STDMETHODCALLTYPE *QueryInterface

HRESULT (STDMETHODCALLTYPE *QueryInterface)(
    void*inSelf, 
    REFIID inUUID, 
    LPVOID*outInterface);  

Parameters

inSelf

The CFPlugIn type to query.

inUUID

The UUID of the interface to find.

outInterface

The returned interface or NULL if none was found.

Return Value

An error code indicating success of failure.

The IUnknown method for releasing a reference to a CFPlugIn type.

STDMETHODCALLTYPE *Release

ULONG (STDMETHODCALLTYPE *Release)(
    void*inSelf);  

Parameters

inSelf

The CFPlugIn type to release.

Return Value

The resulting reference count after the reference has been removed.

The IUnknown method for retaining a reference to a CFPlugIn type.

AddRef

ULONG (STDMETHODCALLTYPE *AddRef)(
    void*inSelf);  

Parameters

inSelf

The CFPlugIn type to retain.

The IUnknown method for finding an interface on a CFPlugIn type.

QueryInterface

HRESULT (STDMETHODCALLTYPE *QueryInterface)(
    void*inSelf, 
    REFIID inUUID, 
    LPVOID*outInterface);  

Parameters

inSelf

The CFPlugIn type to query.

inUUID

The UUID of the interface to find.

outInterface

The returned interface or NULL if none was found.

The IUnknown method for releasing a reference to a CFPlugIn type.

Release

ULONG (STDMETHODCALLTYPE *Release)(
    void*inSelf);  

Parameters

inSelf

The CFPlugIn type to release.

Queries an the AudioStream object to get the data of the given property and places it in the provided buffer.

OSStatus (*StreamGetProperty)(
    AudioHardwarePlugInRef inSelf, 
    AudioStreamID inStream, 
    UInt32 inChannel, 
    AudioDevicePropertyID inPropertyID, 
    UInt32*ioPropertyDataSize, 
    void*outPropertyData);  

Parameters

inSelf

The plug-in instance that owns the AudioStream.

inStream

The AudioStream to query.

inChannel

The channel of the property to query where 0 is the master channel.

inPropertyID

The AudioDevicePropertyID of the property to query.

ioPropertyDataSize

A UInt32 which on entry indicates the size of the buffer pointed to by outData and on exit indicates how much of the buffer was used.

outPropertyData

The buffer into which the object will put the data for the given property.

Return Value

An OSStatus indicating success or failure.

Retrieve information about the given property of an AudioStream.

OSStatus (*StreamGetPropertyInfo)(
    AudioHardwarePlugInRef inSelf, 
    AudioStreamID inStream, 
    UInt32 inChannel, 
    AudioDevicePropertyID inPropertyID, 
    UInt32*outSize, 
    Boolean*outWritable);  

Parameters

inSelf

The plug-in instance that owns the AudioStream.

inStream

The AudioStream to query.

inChannel

The channel of the property to query where 0 is the master channel.

inPropertyID

The AudioDevicePropertyID of the property to query.

outSize

A pointer to a UInt32 that receives the size of the property data in bytes on exit. This can be NULL if the size information is not being requested.

outWritable

A pointer to a Boolean that receives indication of whether or not the given property can be set. This can be NULL if the writability is not being requested.

Return Value

An OSStatus indicating success or failure.

Tells the AudioStream object to change the value of the given property using the provided data.

OSStatus (*StreamSetProperty)(
    AudioHardwarePlugInRef inSelf, 
    AudioStreamID inStream, 
    const AudioTimeStamp*inWhen, 
    UInt32 inChannel, 
    AudioDevicePropertyID inPropertyID, 
    UInt32 inPropertyDataSize, 
    const void*inPropertyData);  

Parameters

inSelf

The plug-in instance that owns the AudioStream.

inStream

The AudioStream to change.

inWhen

A pointer to an AudioTimeStamp that says when to change the property's value relative to the device's time base. NULL means execute the change immediately.

inChannel

The channel of the property to change where 0 is the master channel.

inPropertyID

The AudioDevicePropertyID of the property to change.

inPropertyDataSize

A UInt32 indicating the size of the buffer pointed to by inData.

inPropertyData

The buffer containing the data to be used to change the property's value.

Return Value

An OSStatus indicating success or failure.

This method is called to tear down the instance of the plug-in.

OSStatus (*Teardown)(
    AudioHardwarePlugInRef inSelf);  

Parameters

inSelf

The instance to tear down.

Return Value

An OSStatus indicating success or failure.

Globals

A standard part of the IUnknown interface.

void* _reserved;  

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Last Updated: 2006-10-25