我编写了一个非常简单的应用程序，用于在Windows 7上运行的Delphi 2007中播放音乐收藏。我为Windows Media Player掏腰包，以避免Delphi Media Player组件拒绝播放某些曲目，我扔给它。我现在想从应用程序控制扬声器的音量。
此时，我说的是“扬声器音量”而不是“ WMP音量”，因为我想控制WMP的音量比控制所有应用程序的整体扬声器/主音量要困难得多。
我确信这在过去非常简单，但是OS变得更加复杂，我发现并尝试过的所有代码段都不适用于控制扬声器的主/核心音量。
是否有可能通过Windows 7上运行的Delphi 2007控制此主卷？
如果是这样，那么我将非常喜欢使用诸如GetVolume和SetVolume之类的几个函数来完成这样的基本任务。
我看过过去问过的类似问题，但我没有希望。
布鲁斯。
尝试使用SetMasterVolumeLevelScalar方法的此代码。
{$APPTYPE CONSOLE}
uses
SysUtils,
Windows,
ActiveX,
ComObj;
const
CLASS_IMMDeviceEnumerator : TGUID = '{BCDE0395-E52F-467C-8E3D-C4579291692E}';
IID_IMMDeviceEnumerator : TGUID = '{A95664D2-9614-4F35-A746-DE8DB63617E6}';
IID_IAudioEndpointVolume : TGUID = '{5CDF2C82-841E-4546-9722-0CF74078229A}';
type
IAudioEndpointVolumeCallback = interface(IUnknown)
['{657804FA-D6AD-4496-8A60-352752AF4F89}']
end;
IAudioEndpointVolume = interface(IUnknown)
['{5CDF2C82-841E-4546-9722-0CF74078229A}']
function RegisterControlChangeNotify(AudioEndPtVol: IAudioEndpointVolumeCallback): HRESULT; stdcall;
function UnregisterControlChangeNotify(AudioEndPtVol: IAudioEndpointVolumeCallback): HRESULT; stdcall;
function GetChannelCount(out PInteger): HRESULT; stdcall;
function SetMasterVolumeLevel(fLevelDB: single; pguidEventContext: PGUID): HRESULT; stdcall;
function SetMasterVolumeLevelScalar(fLevelDB: single; pguidEventContext: PGUID): HRESULT; stdcall;
function GetMasterVolumeLevel(out fLevelDB: single): HRESULT; stdcall;
function GetMasterVolumeLevelScaler(out fLevelDB: single): HRESULT; stdcall;
function SetChannelVolumeLevel(nChannel: Integer; fLevelDB: double; pguidEventContext: PGUID): HRESULT; stdcall;
function SetChannelVolumeLevelScalar(nChannel: Integer; fLevelDB: double; pguidEventContext: PGUID): HRESULT; stdcall;
function GetChannelVolumeLevel(nChannel: Integer; out fLevelDB: double): HRESULT; stdcall;
function GetChannelVolumeLevelScalar(nChannel: Integer; out fLevel: double): HRESULT; stdcall;
function SetMute(bMute: Boolean; pguidEventContext: PGUID): HRESULT; stdcall;
function GetMute(out bMute: Boolean): HRESULT; stdcall;
function GetVolumeStepInfo(pnStep: Integer; out pnStepCount: Integer): HRESULT; stdcall;
function VolumeStepUp(pguidEventContext: PGUID): HRESULT; stdcall;
function VolumeStepDown(pguidEventContext: PGUID): HRESULT; stdcall;
function QueryHardwareSupport(out pdwHardwareSupportMask): HRESULT; stdcall;
function GetVolumeRange(out pflVolumeMindB: double; out pflVolumeMaxdB: double; out pflVolumeIncrementdB: double): HRESULT; stdcall;
end;
IAudioMeterInformation = interface(IUnknown)
['{C02216F6-8C67-4B5B-9D00-D008E73E0064}']
end;
IPropertyStore = interface(IUnknown)
end;
IMMDevice = interface(IUnknown)
['{D666063F-1587-4E43-81F1-B948E807363F}']
function Activate(const refId: TGUID; dwClsCtx: DWORD; pActivationParams: PInteger; out pEndpointVolume: IAudioEndpointVolume): HRESULT; stdCall;
function OpenPropertyStore(stgmAccess: DWORD; out ppProperties: IPropertyStore): HRESULT; stdcall;
function GetId(out ppstrId: PLPWSTR): HRESULT; stdcall;
function GetState(out State: Integer): HRESULT; stdcall;
end;
IMMDeviceCollection = interface(IUnknown)
['{0BD7A1BE-7A1A-44DB-8397-CC5392387B5E}']
end;
IMMNotificationClient = interface(IUnknown)
['{7991EEC9-7E89-4D85-8390-6C703CEC60C0}']
end;
IMMDeviceEnumerator = interface(IUnknown)
['{A95664D2-9614-4F35-A746-DE8DB63617E6}']
function EnumAudioEndpoints(dataFlow: TOleEnum; deviceState: SYSUINT; DevCollection: IMMDeviceCollection): HRESULT; stdcall;
function GetDefaultAudioEndpoint(EDF: SYSUINT; ER: SYSUINT; out Dev :IMMDevice ): HRESULT; stdcall;
function GetDevice(pwstrId: pointer; out Dev: IMMDevice): HRESULT; stdcall;
function RegisterEndpointNotificationCallback(pClient: IMMNotificationClient): HRESULT; stdcall;
end;
procedure SetMasterVolume(fLevelDB: single);
var
pEndpointVolume: IAudioEndpointVolume;
LDeviceEnumerator: IMMDeviceEnumerator;
Dev: IMMDevice;
begin
if not Succeeded(CoCreateInstance(CLASS_IMMDeviceEnumerator, nil, CLSCTX_INPROC_SERVER, IID_IMMDeviceEnumerator, LDeviceEnumerator)) then
RaiseLastOSError;
if not Succeeded(LDeviceEnumerator.GetDefaultAudioEndpoint($00000000, $00000000, Dev)) then
RaiseLastOSError;
if not Succeeded( Dev.Activate(IID_IAudioEndpointVolume, CLSCTX_INPROC_SERVER, nil, pEndpointVolume)) then
RaiseLastOSError;
if not Succeeded(pEndpointVolume.SetMasterVolumeLevelScalar(fLevelDB, nil)) then
RaiseLastOSError;
end;
begin
try
CoInitialize(nil);
try
SetMasterVolume(1.0); //set the volume to the max
Sleep(2000);
SetMasterVolume(0.5); //set the volume to the 50 %
Sleep(2000);
SetMasterVolume(0.1); //set the volume to the 10 %
Sleep(2000);
finally
CoUninitialize;
end;
except
on E:Exception do
Writeln(E.Classname, ':', E.Message);
end;
Writeln('Press Enter to exit');
Readln;
end.