SAMPLE: How to Use Multimedia Timer Services on Windows 95

ID: Q153400

The information in this article applies to:

SUMMARY

MTHUNK32 contains a sample application that demonstrates the implementation of thunking code necessary for 32-bit applications running on Windows 95 to obtain reliable performance when using high-resolution multimedia timer services.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library: 

 ~ MTHUNK32.EXE (size: 100713 bytes)
For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base: 

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from
               Online Services
32-bit multimedia timer callbacks on Windows 95 are subject to noticeable performance problems due to the demands of preemptive multitasking and limitations in the Windows 95 system architecture. Running a 32-bit application at high priority does not solve this problem, but thunking to a 16-bit DLL does the job. MTHUNK32 demonstrates how a 32-bit application running on Windows 95 can utilize flat thunks via a 32-bit thunking DLL to call a 16-bit DLL that invokes a multimedia timer and services the timer callbacks.

MTHUNK32 also implements a shared memory technique using the 16-bit and 32-bit DLLs, and a user interface for manipulating parameters in shared memory. This design allows the user to interact through the 32-bit application's GUI to modify data while it is being played back with the 16-bit multimedia services. This sort of design is needed by MIDI sequencer applications which allow a user to modify MIDI data for entire tracks or channels during playback by manipulating graphical controls or manually entering new parameters. To implement this technique on Windows 95, the 32-bit application and 16-bit DLL must share one or more blocks of fixed memory that are allocated by the 16-bit DLL. The DLL passes a pointer to the memory block through the thunking layer back to the application which then can reference the memory.

Additional query words: timeSetEvent TimerProc kbfile MTHUNK32.EXE 

Keywords          : kbmm kbSDKWin32 kbWinOS95 MMTimer 
Version           : 4.00
Platform          : WINDOWS

Last Reviewed: December 9, 1998