This section shows you how to write a media control driver (MCD) by illustrating the programming interfaces used by streaming and nonstreaming MCDs. The following discussion focuses on the MCDs depicted in the Duet Player sample programs (see the OS/2 Multimedia Application Programming Guide for details.) The waveform audio MCD uses SPI data streaming services to handle the creation and management of source and target stream handlers. However, the CD audio MCD typically has no data flow associated with it as most CD audio devices process data internally (internal to the device without any help from the main CPU).

Source code is provided for the following media control driver samples located in the \TOOLKIT\SAMPLES\MM subdirectory:

Media Control Driver Template (MCDTEMP)

Provides a basic template to write an MCD. Refer to the ADMCT and CDMCIDRV subdirectories for specific streaming or MMIO samples.
Waveform Audio Media Control Driver (ADMCT)
Provides an example of how to control a streaming device. Streaming devices use the services of the Sync/Stream Manager (SSM) of OS/2 multimedia to control the data stream from a source location to a target location. For example, the audio adapter used in Duet Player I is a streaming device which plays back waveform audio files stored on the user's hard disk. The PM application sends a request to the Media Device Manager (MDM) to play the file. In turn, the MDM calls the waveform audio MCD, which uses stream handlers to buffer data from the waveform file on disk (source) to the audio adapter (target).
CD Media Control Driver (CDMCIDRV)
Provides an example of how to control a nonstreaming device. Nonstreaming devices stream data within the device. A device that streams data internally does not need to use buffered I/O because the source and destination of the data is within the device. Therefore, a nonstreaming device does not require the use of the SSM subsystem of OS/2 multimedia. For example, the CD-ROM device used in Duet Player II is a nonstreaming device. When the CD audio MCD receives a PLAY, PAUSE, or STOP command from the program, it issues the appropriate IOCtls to the CD-ROM device to perform the function. The hardware does all the work, relaying the digital information off the disc, translating it into an audio signal, and piping it to a port such as a headphone jack.

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