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QA: How can I change sound volume from my program?

Vassili Philippov (vasja@spbteam.com), October 02, 2001.

Question

I need to change sound volume from my program. It could be changed in the Control Panel in Sounds & Reminders applet but I need to change sound from my program. How can I do it?

Answer

Although there is a registry key (HKEY_CURRENT_USER\ControlPanel\Volume\Volume) that is changed every time when sound volume setting in the Control Panel is changed it seems impossible to change sound volume by changing this settings. I suggest another way for changing sound volume. This way is using waveOutSetVolume function. If you change sound volume using this function then settings in the Control Panel will not be changed but actual sound volume will be changed.

Using waveOutSetVolume

waveOutSetVolume function sets volume of the certain waveform-audio output device. If we assume that there is only one audio output device in our Pocket PC then it is enough to find the first one and set sound volume for it. Volume can be in range between 0 and 0xFFFF.

void SetSoundVolume(DWORD dwVolume) { WAVEFORMATEX wf; wf.wFormatTag = WAVE_FORMAT_PCM; wf.nChannels = 1; wf.nSamplesPerSec = 8000 * 1000; wf.wBitsPerSample = 8; wf.nBlockAlign = wf.nChannels * wf.wBitsPerSample / 8; wf.nAvgBytesPerSec = wf.nSamplesPerSec * wf.nBlockAlign; wf.cbSize = 0; HWAVEOUT hwo; for (UINT id = 0; id < waveOutGetNumDevs(); id++) { if (waveOutOpen(&hwo, id, &wf, 0, 0, CALLBACK_NULL) == MMSYSERR_NOERROR) { waveOutSetVolume(hwo, dwVolume); waveOutClose(hwo); break; } } }

Sound volume in percents

If you want to sound volume in percents instead of number between 0 and 0xFFFF then you can use the following code for that:

DWORD dwSoundVolumePercents = 50; SetSoundVolume( (DWORD)(0xFFFF*1.0*dwSoundVolumePercents/100.0) );

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