Microsoft DirectX 8.1 (Visual Basic)

Retrieving Objects from an Audiopath

It is often necessary to retrieve a particular object within the audiopath. Common reasons to do so include the following:

To manipulate the 3-D properties of sounds by obtaining a DirectSound3DBuffer8 object.
To set global 3-D sound properties by obtaining an DirectSound3DListener8 object from the primary buffer.
To set effects on a secondary buffer by obtaining a DirectSoundSecondaryBuffer8 object.
To set effect parameters by obtaining a DMO such as DirectSoundFXI3DL2Reverb8.

Objects can be retrieved from an audiopath by calling DirectMusicAudioPath8.GetObjectInPath. The following table gives information about the parameters to this method.

*lStage*	*guidObject*	lPChannel used?	lIndex used?	iidInterface (typical)
DMUS_PATH_AUDIOPATH	Not supported in DirectX for Visual Basic. The application already has the DirectMusicAudioPath8 object from which GetObjectInPath was called.
DMUS_PATH_AUDIOPATH_GRAPH	Not supported in DirectX for Visual Basic.
DMUS_PATH_AUDIOPATH_TOOL	Not supported in DirectX for Visual Basic.
DMUS_PATH_BUFFER	GUID_ALL	Yes	No, identify by dwBuffer.	IID_DirectSoundSecondaryBuffer8
DMUS_PATH_BUFFER_DMO	DMO class ID, such as GUID_DSFX_STANDARD_GARGLE, or GUID_ALL to enumerate	Yes	No, identify by dwBuffer.	IID for standard DMO, such as IID_DirectSoundGargle
DMUS_PATH_MIXIN_BUFFER	GUID_ALL	No	Yes	IID_DirectSoundSecondaryBuffer8
DMUS_PATH_MIXIN_BUFFER_DMO	DMO class GUID, or GUID_ALL to enumerate	No	Yes	IID for standard DMO, such as IID_DirectSoundFXI3DL2Reverb
DMUS_PATH_PERFORMANCE	Not supported in DirectX for Visual Basic.
DMUS_PATH_PERFORMANCE_GRAPH	Not supported in DirectX for Visual Basic.
DMUS_PATH_PERFORMANCE_TOOL	Not supported in DirectX for Visual Basic.
DMUS_PATH_PORT	Not supported in DirectX for Visual Basic.
DMUS_PATH_PRIMARY_BUFFER	GUID_ALL	No	No	IID_DirectSound3DListener8
DMUS_PATH_SEGMENT (*)	GUID_ALL	No	No	IID_DirectMusicSegment8
DMUS_PATH_SEGMENT_GRAPH (*)	Not supported in DirectX for Visual Basic.
DMUS_PATH_SEGMENT_TOOL (*)	Not supported in DirectX for Visual Basic.
DMUS_PATH_SEGMENT_TRACK (*)	Not supported in DirectX for Visual Basic.

For more information on the values for lIndex when retrieving standard buffers, see Standard Audiopaths.

If you already have an object for an effects buffer, it is also possible to retrieve a DMO by using DirectSoundSecondaryBuffer8.GetObjectInPath.

You can retrieve a DirectSoundSecondaryBuffer8 object for any buffer in the audiopath, but some methods are not valid. For more information, see DirectSoundSecondaryBuffer8.

If you set a global variable to a buffer object obtained from the audiopath, be sure to set the variable to Nothing before calling DirectMusicPerformance8.CloseDown. If you fail to do so, CloseDown will destroy the buffer and then a memory access violation can occur when the variable goes out of scope as the program exits.