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ILMADet

This is the interface for the LEAD Audio Detection Filter (2.0).

Data Types

AudDetStateConstants

Summary

List the possible values for the state of audio detection.

Syntax

typedef enum  
{ 
   AUDDET_STATE_STOPPED, 
   AUDDET_STATE_RUNNING, 
} AudDetStateConstants;

Members

AUDDET_STATE_STOPPED

The filter is not processing streaming data and the sound detection process is not running.

AUDDET_STATE_RUNNING

The filter is processing streaming data and the sound detection process has started.

Properties

Type	Name	Description
ILMADetUserCallback	CallbackObj	(write-only) Sets the callback object pointer. If not NULL, the CallbackProc method of this interface is called to report audio detection events.
		Set to NULL (or to "Nothing" in VB) in order to stop receiving notifications. (For example, before deleting the callback object interface).
VARIANT_BOOL	Enable	Enables or disables audio detection. Set to TRUE to enable audio detection and receive event notifications.
long	Threshold	The threshold (in dB) used to detect sound. The allowed range is 40 to 0.40 is equivalent to absolute silence and 0 is the loudest possible sound. All sounds below this threshold are considered silence. Set this depending on your microphone. Usually, a value between38 and 30 is used.
long	MinSilenceTime	The minimum length of silence periods (in milliseconds). Silences shorter than the MinSilenceTime are considered part of the sound. Set this value so short pauses do not trigger false silences. Most conversations contain short silences while the people talking draw their breath, or pause while they are thinking.
long	LeftLevel	(read-only) The intensity (power) of the signal in the left channel (in dB).
		Note: If the audio stream is mono, the values of LeftLevel and RightLevel are the same.
long	RightLevel	(read-only) The intensity (power) of the signal in the right channel (in dB).
		Note: If the audio stream is mono, the values of LeftLevel and RightLevel are the same.
long	Interval	The time intervals at which the filter will check the stream for audio data. This value is in milliseconds.
long	Delay	The amount of time the filter waits before it starts checking the stream for sound data (sound detection). This value is in milliseconds.
VARIANT_BOOL	AutoStart	Flag that indicates whether to start sound detection when streaming starts. Possible values are:
		• VARIANT_TRUE - Have the filter start sound detection when streaming starts.
		• VARIANT_FALSE - Starts sound detection manually.
		Note that if the Delay property has been set, sound detection does not begin, regardless of the value of AutoStart, until the delay period has elapsed.
AudDetStateConstants	State	(read only) Indicates the state of audio detection.
IUnknown	CallbackObj2	(write-only) Sets the callback object pointer.
		If not NULL, the CallbackProc method of this interface will be called to report audio detection events.
		Set to NULL (or to "Nothing" in VB in order to stop receiving notifications. (For example, before deleting the callback object interface).
		There are two types of callbacks that can be set:
		• ILMADetUserCallback uses variants.
		• ILMADetUserCallback2 uses a pointer to the data cast as LONGLONG (__int64).
		VB 6.0 or earlier users should use an ILMADetUserCallback interface, while C# and VB.NET users should use an ILMADetUserCallback2 interface.
		C/C++ users can use either interface.

Methods

HRESULT StartDetection();

Description

Starts sound detection manually. If the Delay property has been set, sound detection will not begin until the delay period has elapsed.

To have the filter automatically start sound detection when streaming starts, set the AutoStart property to VARIANT_TRUE and do not call this method. Again, even if AutoStart is set to VARIANT_TRUE, if the Delay property has been set, sound detection will not begin until the delay period has elapsed.

Returns

Return	Description
S_OK	The method succeeded.
VFW_E_NOT_CONNECTED	An error has occurred, either the input or output pin is not connected.
VFW_E_NOT_RUNNING	The filter in not in the running state.