Mmmctrl.exe Demonstrates Using Multiple Sound Cards

ID: Q182799

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

Mmmctrl.exe is a self-extracting compressed file that contains a Visual Basic project demonstrating how to detect and use multiple MCI devices in a system. The techniques shown and the Windows API functions used in this sample project allow your program to have multiple sound card support so you can enable one sound card for recording sounds and another sound card for playing sounds.

MORE INFORMATION

The following files are available for download from the Microsoft Download Center. Click the file names below to download the files:

Mmmctrl.exe

For more information about how to download files from the Microsoft Download Center, please visit the Download Center at the following Web address

http://www.microsoft.com/downloads/search.asp

and then click How to use the Microsoft Download Center. When you run the self-extracting executable file, the following files are expanded to the Multiple Multimedia Control Sample project directory:

Form1.frm(11K)-the main form of the project

Module1.bas(18K)-the Basic module with the function declarations

Project1.vbp(1K)-the project file

Project1.vbw(1K)-the project workspace file

Readme.txt-you are currently reading this file.

The next section shows how to start and use the sample project.

How to Use the Sample Project

When you run the project from the Visual Basic IDE, the Multiple Multimedia Control Sample form displays. The form is divided into a Play section and a Record section.

The Play section has a Wave Output Devices list box that shows all the wave output devices available for playing wave files. Select one of the output devices in the list box. Open File shows a dialog box so you can select a wave file to play. The file name and path are displayed in the text box. When you select a wave file, the appropriate multimedia control buttons are enabled.

If you select a file without selecting a wave device, the following error message displays:

The specified parameter is out of range for the specified command.

To prevent displaying this error message, select a wave device before opening a file.

The Record section also has a listbox that displays all wave input devices. Select one of the input devices in the list box. Open enables the selected wave input device for recording and enables the appropriate multimedia control buttons.

If you check the Use Control Panel Recording Format check box, the wave input device will record in the format, sample rate, and number of channels set in the Multimedia Properties dialog box of Control Panel. If the Use Control Panel Recording Format check box is cleared, then the wave input device will record at the default MCI setting of 8-bit mono using a 11kHz sampling rate.

Save opens a dialog box so that you can save the wave file you just recorded.

How the Sample Works

In the Form Load event, the number wave input and output devices are retrieved using the waveOutGetNumDevsA function for output devices and waveInGetNumDevCapsA function for input devices. The type and capabilities of each device are retrieved using the waveOutGetDevCaps for output devices and waveInGetDevCaps for input devices. The capabilities are stored in a user-defined variable. The name of each device is added to the appropriate list box.

When you open a file to record or for playback, you also enable the appropriate multimedia control for this task. Depending on the multimedia control command you select, the event executes the appropriate mciSendCommandA function.

If the Use Control Panel Recording Format check box is checked, the a user- defined function retrieves the Control Panel settings in the registry by first using the RegOpenKeyExA function to open the WaveFormats registry key. The RegQueryValueStringA and the RegQueryValueExA functions are used to retrieve the registry key values. The RegCloseKey is used to close the registry key.

REFERENCES

For more information about sound cards or using the multimedia API functions, please see the following topics:

The Multimedia Reference in the Platform SDK Product Documentation

Multimedia MCI Control in the Visual Basic Reference

The following Windows API functions were used in this sample. For more information on these functions, please see the Platform SDK Product Documentation:

mciGetErrorStringA

mciSendCommandA

RegOpenKeyExA

RegQueryValueExA

RegCloseKey

waveOutGetDevCapsA

waveInGetDevCapsA

For additional information, please see the following article in the Microsoft Knowledge Base:

Q147811 : HOWTO: Detect If Computer Has Sound Card That Plays Wave Audio

Additional query words: kbwin32sdk kbapi kbVBp kbdsd kbDSupport kbVBp500 kbVBp600

Keywords : kbfile kbGrpVB
Version : WINDOWS:5.0,6.0
Platform : WINDOWS
Issue type : kbinfo