Audio Device Instances (Windows Embedded CE 6.0)
1/6/2010
Audio drivers respond to the WODM_OPEN message by creating a device instance, or stream, handle and passing it back through the dwUser member of the MMDRV_MESSAGE_PARAMS structure.
The other waveform output messages, such as WODM_WRITE can then use the dwUser field of the message to distinguish one audio stream from another.
Audio drivers that support hardware mixing can allow multiple device instances to be created and played at the same time. The device instance is passed in the dwUser MMDRV_MESSAGE_PARAMS structure. Audio drivers that only support a single audio source can ignore the device instance parameter.
The waveform API manager provides a software mixer that allows multiple application-level audio streams to be played simultaneously.