SAMPLE: LLStream.exe Plays Streaming Audio Files

MORE INFORMATION

The following files are available for download from the Microsoft Download Center:
The sample uses several low-level functions in the Windows API to work around the Multimedia Control Interface. You must be familiar with using Visual Basic to call the Windows API functions to understand how this sample works.

When you run the self-extracting executable file, the following files are expanded into the Low-Level Streaming Audio Sample Project directory:

• Form1.frm (3Kb) - the main form
• Module1.bas (12Kb) - the module containing the function declarations
• Project1.vbp (1Kb) - the main project file
• Project1.vbw (1Kb) - the project workspace
• Readme.txt - overview of the sample and download information

The Multimedia Control Interface (MCI) is the one way to add multimedia capabilities to your program in Visual Basic. However, when you use the MCI to play audio files continuously, you can slow down or lock the operating system.

This sample shows how to call the appropriate functions directly to work around the limitations of the MCI. Because the sample hooks into a Windows process, you should compile this sample and run the executable file rather than running the sample from the Visual Basic design environment.

The sample uses the following functions in the Windows API:

   GlobalAlloc
   GlobalFree
   GlobalLock
   mmioAscend
   mmioClose
   mmioDescend
   mmioDescendParent
   mmioOpen
   mmioRead
   mmioReadString
   mmioSeek
   mmioStringToFOURCC
   PostWavMessage
   RtlMoveMemory
   waveOutClose
   waveOutGetDevCaps
   waveOutGetErrorText
   waveOutGetNumDevs
   waveOutGetPosition
   waveOutOpen
   waveOutPrepareHeader
   waveOutReset
   waveOutUnprepareHeader
   waveOutWrite