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IBasicAudiois an interface that supports the filter graph's audio component. It allows access to volume and balance functionality.
The Volumeproperty is a value between –10,000 and 0 representing a set of logarithmic steps. This follows the DirectSound model. Not all devices support 10,000 distinguishable steps.
The Balanceproperty is a value between –10,000 and 10,000. A value of –10,000 indicates that the right speaker has been disabled and only the left speaker is receiving an audio signal. A value of 0 indicates that both speakers are receiving equivalent audio signals. A value of 10,000 indicates that the left speaker has been disabled and only the right speaker is receiving an audio signal.
When to Implement
The audio renderer filter supplied with Microsoft DirectShow implements this interface. It is also implemented by the filter graph manager (by means of a plug-in distributor) to pass method calls from the application to the audio renderer filter's implementation of the interface.
Implement this interface if you are writing a replacement audio renderer filter or a replacement DirectShow plug-in distributor. You can use the CBasicAudioclass, which handles the IDispatchimplementation for Automation, to help implement this interface.
When to Use
When the filter graph manager exposes this interface, it is used by applications that need to control the properties of the audio renderer filter. Applications should not use the interface exposed by the audio renderer directly. When the audio renderer filter exposes this interface, it is used by plug-in distributors, such as the DirectShow plug-in distributor, which pass calls from the application.
Methods in Vtable Order
| IUnknown methods | Description |
|---|---|
| QueryInterface | Returns pointers to supported interfaces. |
| AddRef | Increments the reference count. |
| Release | Decrements the reference count. |
| IDispatch methods | Description |
| GetTypeInfoCount | Determines whether there is type information available for this dispinterface. |
| GetTypeInfo | Retrieves the type information for this dispinterface if GetTypeInfoCountreturned successfully. |
| GetIDsOfNames | Converts text names of properties and methods (including arguments) to their corresponding DISPIDs. |
| Invoke | Calls a method or accesses a property in this dispinterface if given a DISPID and any other necessary parameters. |
| IBasicAudio methods | Description |
| put_Volume | Sets the volume (amplitude) of the audio signal. |
| get_Volume | Retrieves the volume (amplitude) of the audio signal. |
| put_Balance | Sets the balance for the audio signal. |
| get_Balance | Retrieves the balance for the audio signal. |