This section gives the required and optional messages for waveform output device drivers. See “Audio Device Driver Reference,” later in this chapter, for detailed information on these messages.
The wodMessage entry-point function for waveform output drivers must support the following messages.
Breaks a playback loop.
Closes and deallocates a waveform output device.
Requests the capabilities of a waveform output device.
Requests the number of waveform output devices a driver supports.
Requests the current playback position for a waveform.
Opens and allocates a waveform output device.
Pauses waveform playback on a waveform output device.
Stops playback and returns all data blocks to the client application.
Continues playback after playback has been paused.
Sends a data block for playback.
The wodMessage entry-point function for waveform output drivers can optionally support the following messages, depending on the capabilities of the target hardware.
Requests the current pitch rate setting.
Requests the current playback rate setting.
Requests the current volume level setting.
Requests that the driver prepare a data block for playback.
Sets the pitch rate.
Sets the playback rate.
Sets the volume level.
Requests that a driver clean up the preparation previously done on a data block.
In addition to receiving messages, drivers must notify clients when certain events occur. Waveform output drivers notify clients by sending one of the following messages using the DriverCallback function.
Notifies a client application when a device is closed.
Notifies a client application when the driver is finished with a data block and is returning it to the client.
Notifies a client application when a device is opened.