VC中调节系统音量

// #include // link with winmm.lib

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.

          //   打开mixer.   单声卡的deviceID为0.
          rc   =   mixerOpen(&hMixer;,   0,0,0,0);
          if   (MMSYSERR_NOERROR   !=   rc)   {
                  //   Couldn't   open   the   mixer.
          }

          //   初始化MIXERLINE结构体.
          ZeroMemory(&mxl;,sizeof(mxl));
          mxl.cbStruct   =   sizeof(mxl);

          //   指出需要获取的通道，扬声器用MIXERLINE_COMPONENTTYPE_DST_SPEAKERS
          mxl.dwComponentType   =   MIXERLINE_COMPONENTTYPE_DST_SPEAKERS;

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

          //   取得控制器.
          ZeroMemory(&mxlc;,   sizeof(mxlc));
          mxlc.cbStruct   =   sizeof(mxlc);
          mxlc.dwLineID   =   mxl.dwLineID;
          mxlc.dwControlType   =   MIXERCONTROL_CONTROLTYPE_VOLUME;
          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.
          }

          //   获取控制器中的值的音量范围：mxc.Bounds.lMinimum到mxc.Bounds.lMaximum.

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

          //   初始化MIXERCONTROLDETAILS结构体
          ZeroMemory(&mxcd;,   sizeof(mxcd));
          mxcd.cbStruct   =   sizeof(mxcd);
          mxcd.cbDetails   =   sizeof(volStruct);
          mxcd.dwControlID   =   mxc.dwControlID;
          mxcd.paDetails   =   &volStruct;
          mxcd.cChannels   =   1;

          //   获得音量值
          rc   =   mixerGetControlDetails((HMIXEROBJ)hMixer,   &mxcd;,
                                                                    MIXER_GETCONTROLDETAILSF_VALUE);
          if   (MMSYSERR_NOERROR   ==   rc)   {
                  //   Couldn't   get   the   current   volume.
          }
          volume   =   volStruct.lValue;

  volStruct.lValue   =   25000; //想要设置的值
  rc   =   mixerSetControlDetails((HMIXEROBJ)hMixer,   &mxcd;,
  MIXER_SETCONTROLDETAILSF_VALUE);