Additional Entry-Point Functions for Audio Device Drivers

In addition to the installable-driver entry-point function, DriverProc, an audio device driver must have at least one of the following entry-point functions:

• The wodMessage function for waveform output drivers
• The widMessage function for waveform input drivers
• The modMessage function for MIDI output drivers and internal-synthesizer drivers
• The midMessage function for MIDI input drivers
• The auxMessage function for auxiliary audio drivers

Drivers that service more than one type of audio device must have one of these entry-point functions for each type of device serviced.

Note  ACM compression and decompression drivers use only the DriverProc entry point.

These functions process messages sent by MMSYSTEM to the driver as the result of an application call to a low-level audio function. For example, when an application opens a waveform output device with the waveOutOpen function, MMSYSTEM sends the specified waveform-output device driver a WODM_OPEN message. The driver's wodMessage function receives and processes this message. For the exact syntax of each of these entry-point functions, see the sections about writing drivers for specific types of audio devices, later in this main topic.