关于DirectSound的一个问题

[slimak]

我在用DirectSound做一个录音程序，我的问题是如何才能实时得到麦克风
的声音的声音强度。

[acptvc]

或许mixerGetControlDetails等函数可以提供您需要的帮助，mixXXX系列API函数可以监控声卡的输入和输出的系统音量。mixerGetControlDetails可以获得与一个audio line相联系的单个控制的信息，如扬声器的音量等。如果您愿意，可以参看以下的一个使用这些函数的例子：

步骤：
1打开mixer设备，与声卡联系起来；

2得到您想要监控的line的mixer的控制；

3获得控制的信息（包括系统音量信息）。

代码：（使用winmm.lib:）

#include <windows.h>
#include <mmsystem.h>

MMRESULT rc; // Return code.
HMIXER hMixer; // Mixer handle used in mixer API calls.
MIXERCONTROL mxc; // Holds the mixer control data.
MIXERLINE mxl; // Holds the mixer line data.
MIXERLINECONTROLS mxlc; // Obtains the mixer control.

// Open the mixer. This opens the mixer with a deviceID of 0. If you
// have a single sound card/mixer, then this will open it. If you have
// multiple sound cards/mixers, the deviceIDs will be 0, 1, 2, and
// so on.
rc = mixerOpen(&hMixer, 0,0,0,0);
if (MMSYSERR_NOERROR != rc) {
// Couldn't open the mixer.
}

// Initialize MIXERLINE structure.
ZeroMemory(&mxl,sizeof(mxl));
mxl.cbStruct = sizeof(mxl);

// Specify the line you want to get. You are getting the input line
// here. If you want to get the output line, you need to use
// MIXERLINE_COMPONENTTYPE_SRC_WAVEOUT.
mxl.dwComponentType = MIXERLINE_COMPONENTTYPE_DST_WAVEIN;

rc = mixerGetLineInfo((HMIXEROBJ)hMixer, &mxl,
MIXER_GETLINEINFOF_COMPONENTTYPE);
if (MMSYSERR_NOERROR == rc) {
// Couldn't get the mixer line.
}

// Get the control.
ZeroMemory(&mxlc, sizeof(mxlc));
mxlc.cbStruct = sizeof(mxlc);
mxlc.dwLineID = mxl.dwLineID;
mxlc.dwControlType = MIXERCONTROL_CONTROLTYPE_PEAKMETER;
mxlc.cControls = 1;
mxlc.cbmxctrl = sizeof(mxc);
mxlc.pamxctrl = &mxc;
ZeroMemory(&mxc, sizeof(mxc));
mxc.cbStruct = sizeof(mxc);
rc = mixerGetLineControls((HMIXEROBJ)hMixer,&mxlc,
MIXER_GETLINECONTROLSF_ONEBYTYPE);
if (MMSYSERR_NOERROR != rc) {
// Couldn't get the control.
}

// After successfully getting the peakmeter control, the volume range
// will be specified by mxc.Bounds.lMinimum to mxc.Bounds.lMaximum.

MIXERCONTROLDETAILS mxcd; // Gets the control values.
MIXERCONTROLDETAILS_SIGNED volStruct; // Gets the control values.
long volume; // Holds the final volume value.

// Initialize the MIXERCONTROLDETAILS structure
ZeroMemory(&mxcd, sizeof(mxcd));
mxcd.cbStruct = sizeof(mxcd);
mxcd.cbDetails = sizeof(volStruct);
mxcd.dwControlID = mxc.dwControlID;
mxcd.paDetails = &volStruct;
mxcd.cChannels = 1;

// Get the current value of the peakmeter control.
rc = mixerGetControlDetails((HMIXEROBJ)hMixer, &mxcd,
MIXER_GETCONTROLDETAILSF_VALUE);
if (MMSYSERR_NOERROR == rc) {
// Couldn't get the current volume.
}
volume = volStruct.lValue;

如果需要进一步的信息，您可以参看：
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/multimed/mmfunc_0icz.asp及MSDN上其他有关信息。


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[slimak]

谢谢回复！！