一个函数实现调节录音麦克风输入音量

头文件包含：

#include "mmsystem.h"
#pragma comment(lib, "winmm.lib")

BOOL SetMicrPhoneVolume(DWORD dwVolume)
{
 BOOL bResult = FALSE;
 try
 {
  int mixerNum = (int)mixerGetNumDevs();
  for(int i = 0; i < mixerNum; i ++)
  {
   DWORD dwSource = 0;
   HMIXER m_hMixer = NULL;   
   MMRESULT mr = NULL;
   //打开Mixer设备   
   if(mixerOpen(&m_hMixer, i, 0, 0, MIXER_OBJECTF_MIXER) != MMSYSERR_NOERROR)
    continue; 
   MIXERLINE MixerLine;   
   //结构体的大小   
   MixerLine.cbStruct = sizeof(MixerLine);   
   //录制设备总线   
   MixerLine.dwComponentType   =   MIXERLINE_COMPONENTTYPE_DST_WAVEIN;   
   //得到录制总线中的连接数   
   if(mixerGetLineInfo((HMIXEROBJ)m_hMixer, &MixerLine,
    MIXER_OBJECTF_HMIXER | MIXER_GETLINEINFOF_COMPONENTTYPE) != MMSYSERR_NOERROR)
    continue; 
   //将连接数保存   
   DWORD dwConnections = MixerLine.cConnections;   
   //准备获取麦克风设备的ID   
   DWORD dwLineID = 0;   
   for(DWORD i = 0; i < dwConnections; i++ )   
   {   
    //枚举每一个设备，当Source的ID等于当前的迭代记数   
    MixerLine.dwSource = i;   
    //根据SourceID获得连接的信息   
    if(mixerGetLineInfo((HMIXEROBJ)m_hMixer, &MixerLine,   
     MIXER_OBJECTF_HMIXER | MIXER_GETLINEINFOF_SOURCE) != MMSYSERR_NOERROR) 
     //判断函数执行错误   
     break;  
    //如果当前设备类型是麦克风，则跳出循环。   
    if(MixerLine.dwComponentType == MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE)   
    {   
     dwLineID = MixerLine.dwLineID;
     dwSource = MixerLine.dwSource;
     break;   
    }   
   }
   //如果没有找到，返回失败。   
   if(dwLineID == 0)   
    continue;   
   //get line id of destination line   
   MIXERLINE lineinfo_Dest;   
   ::ZeroMemory(&lineinfo_Dest, sizeof(MIXERLINE));   
   lineinfo_Dest.cbStruct = sizeof(MIXERLINE);   
   lineinfo_Dest.dwComponentType = MIXERLINE_COMPONENTTYPE_DST_WAVEIN;   
   if(::mixerGetLineInfo(   
    (HMIXEROBJ)m_hMixer,   
    &lineinfo_Dest,   
    MIXER_OBJECTF_HMIXER   |     
    MIXER_GETLINEINFOF_COMPONENTTYPE) != MMSYSERR_NOERROR)
    continue;  
   //get id of specified connector   
   MIXERLINE lineinfo_Connector;   
   ::ZeroMemory(&lineinfo_Connector, sizeof(MIXERLINE));  
   lineinfo_Connector.cbStruct = sizeof(MIXERLINE);   
   lineinfo_Connector.dwDestination = lineinfo_Dest.dwLineID;   
   lineinfo_Connector.dwSource = dwSource;   
   if(::mixerGetLineInfo(   
    (HMIXEROBJ)m_hMixer,   
    &lineinfo_Connector,     
    MIXER_GETLINEINFOF_SOURCE) != MMSYSERR_NOERROR)
    continue;  
   MIXERCONTROL mxc;   
   MIXERLINECONTROLS mxlc;   
   mxlc.cbStruct = sizeof(MIXERLINECONTROLS);   
   mxlc.dwLineID = lineinfo_Connector.dwLineID;   
   mxlc.dwControlType = MIXERCONTROL_CONTROLTYPE_VOLUME;   
   mxlc.cControls = 1;   
   mxlc.cbmxctrl = sizeof(MIXERCONTROL);   
   mxlc.pamxctrl = &mxc;   
   if(::mixerGetLineControls(   
    reinterpret_cast<HMIXEROBJ>(m_hMixer),   
    &mxlc,   
    MIXER_OBJECTF_HMIXER|MIXER_GETLINECONTROLSF_ONEBYTYPE)!= MMSYSERR_NOERROR)
    continue;  
   //get volume value range now   
   MIXERCONTROLDETAILS_UNSIGNED mxcdVolume;   
   MIXERCONTROLDETAILS mxcd;   
   mxcd.cbStruct = sizeof(MIXERCONTROLDETAILS);   
   mxcd.dwControlID = mxc.dwControlID;   
   mxcd.cChannels = 1;   
   mxcd.cMultipleItems = 0;   
   mxcd.cbDetails = sizeof(MIXERCONTROLDETAILS_UNSIGNED);   
   mxcd.paDetails = &mxcdVolume;   
   if(mixerGetControlDetails(   
    reinterpret_cast<HMIXEROBJ>(m_hMixer),   
    &mxcd,   
    MIXER_GETCONTROLDETAILSF_VALUE)!= MMSYSERR_NOERROR)
    continue;  
   //set volume   
   MIXERCONTROLDETAILS_UNSIGNED mxcdVolume_Set = { mxc.Bounds.dwMaximum * dwVolume / 100 };   
   MIXERCONTROLDETAILS mxcd_Set;   
   mxcd_Set.cbStruct = sizeof(MIXERCONTROLDETAILS);   
   mxcd_Set.dwControlID = mxc.dwControlID;   
   mxcd_Set.cChannels = 1;   
   mxcd_Set.cMultipleItems = 0;   
   mxcd_Set.cbDetails = sizeof(MIXERCONTROLDETAILS_UNSIGNED);   
   mxcd_Set.paDetails = &mxcdVolume_Set;   
   if(mixerSetControlDetails(reinterpret_cast<HMIXEROBJ>(m_hMixer),   
    &mxcd_Set,   
    MIXER_OBJECTF_HMIXER | MIXER_SETCONTROLDETAILSF_VALUE) != MMSYSERR_NOERROR)
    continue;   
   ::mixerClose(m_hMixer);
   m_hMixer = NULL;
   bResult = TRUE;;
  }
 }
 catch(...){ return FALSE; }
 return bResult;
}