Asynchronous ACM drivers are responsible for notifying clients upon the completion of certain driver events. When a client sends an ACMDM_STREAM_OPEN message, it indicates the type of notification, if any, it expects to receive. A client can specify any of the following notification targets:
ACM drivers notify clients by calling the DriverCallback function in winmm.dll. This function delivers a message to the client’s notification target. The DriverCallback function also delivers message parameters, if the target type accepts parameters.
Asynchronous ACM drivers must send MM_ACM_OPEN, MM_ACM_CLOSE, and MM_ACM_DONE messages to clients.
Because the sample ACM drivers provided with this DDK operate synchronously, they do not send notification messages.