通过 IDirectSoundBuffer 的 SetVolume、SetPan、SetFrequency、SetCurrentPosition 方法可以简单进行这些设置.
同时 IDirectSoundBuffer 也有对应的 GetVolume、GetPan、GetFrequency、GetCurrentPosition 方法.

关键的一点是如果能让缓冲区接受音量、相位和频率的设置, 必须在建立缓冲区时指定相应的标志.

下面的常量说明了它们的取值范围:

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DSBVOLUME_MAX = 0;      //音量最大值, 保持在控制面板设置的音量
DSBVOLUME_MIN = -10000; //音量最小值DSBPAN_LEFT   = -10000; //左声道
DSBPAN_CENTER = 0;      //均衡
DSBPAN_RIGHT  = 10000;  //右声道DSBFREQUENCY_ORIGINAL = 0;      //使用默认
DSBFREQUENCY_MIN      = 100;    //频率最小值
DSBFREQUENCY_MAX      = 200000; //频率最大值, 在 DirectSound 9.0 之下的版本, 此值是 100000

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在上一个例子中, 最占篇幅的就是那两个函数; 为了更方便使用, 把它们做在了一个 TReadWaveFile 类里:

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{实现 TReadWaveFile 类的单元}
unit ReadWaveFile;interfaceuses Windows, Classes, SysUtils, MMSystem;type
TReadWaveFile = class
privateFFileHandle: HMMIO;FFormat: TWaveFormatEx;FSize: DWORD;
publicconstructor Create;destructor Destroy; override;function Open(FileName: string): Boolean;            //打开文件并读取信息function Read(pDest: Pointer; Size: DWORD): Boolean; //读出波形数据property Format: TWaveFormatEx read FFormat;         //读出格式数据property Size: DWORD read FSize;                     //读出波形数据的大小
end;implementation{ TReadWaveFile }constructor TReadWaveFile.Create;
begininherited;end;destructor TReadWaveFile.Destroy;
beginif FFileHandle > 0 then mmioClose(FFileHandle, 0);inherited;
end;function TReadWaveFile.Open(FileName: string): Boolean;
varckiRIFF,ckiFmt,ckiData: TMMCKInfo;
beginResult := False;if not FileExists(FileName) then Exit;FFileHandle := mmioOpen(PChar(FileName), nil, MMIO_READ);if FFileHandle = 0 then Exit;ZeroMemory(@ckiRIFF, SizeOf(TMMCKInfo));mmioDescend(FFileHandle, @ckiRIFF, nil, MMIO_FINDRIFF);if (ckiRIFF.ckid <> FOURCC_RIFF) or (ckiRIFF.fccType <> mmioStringToFOURCC('WAVE',0)) then Exit;ZeroMemory(@FFormat, SizeOf(TWaveFormatEx));ZeroMemory(@ckiFmt, SizeOf(TMMCKInfo));ckiFmt.ckid := mmioStringToFOURCC('fmt', 0);ZeroMemory(@ckiData, SizeOf(TMMCKInfo));ckiData.ckid := mmioStringToFOURCC('data', 0);if (mmioDescend(FFileHandle, @ckiFmt, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) thenmmioRead(FFileHandle, @FFormat, SizeOf(TWaveFormatEx));mmioAscend(FFileHandle, @ckiFmt, 0);if (mmioDescend(FFileHandle, @ckiData, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) thenFSize := ckiData.cksize;Result := FFormat.wFormatTag = WAVE_FORMAT_PCM;
end;function TReadWaveFile.Read(pDest: Pointer; Size: DWORD): Boolean;
beginResult := mmioRead(FFileHandle, pDest, Size) = Size;
end;end.

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测试程序用到了四个 Button 和三个 TrackBar 还有它们的默认事件:

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unit Unit1;interfaceusesWindows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls, ComCtrls;typeTForm1 = class(TForm)Button1: TButton;     //打开并播放Button2: TButton;     //反复播放Button3: TButton;     //暂停Button4: TButton;     //从头播放TrackBar1: TTrackBar; //用于音量调节TrackBar2: TTrackBar; //用于相位调节TrackBar3: TTrackBar; //用于频率调节procedure FormCreate(Sender: TObject);procedure FormDestroy(Sender: TObject);procedure Button1Click(Sender: TObject);procedure Button2Click(Sender: TObject);procedure Button3Click(Sender: TObject);procedure Button4Click(Sender: TObject);procedure TrackBar1Change(Sender: TObject);procedure TrackBar2Change(Sender: TObject);procedure TrackBar3Change(Sender: TObject);end;varForm1: TForm1;implementation{$R *.dfm}uses DirectSound, ReadWaveFile; // ReadWaveFile 是 TReadWaveFile 类所在的单元varmyDSound: IDirectSound8;buf: IDirectSoundBuffer;procedure TForm1.FormCreate(Sender: TObject);
beginTrackBar1.Min := DSBVOLUME_MIN;TrackBar1.Max := DSBVOLUME_MAX;TrackBar2.Min := DSBPAN_LEFT;TrackBar2.Max := DSBPAN_RIGHT;TrackBar3.Min := 100;TrackBar3.Max := 100000;Button1.Caption := '打开并播放';Button2.Caption := '反复播放';Button3.Caption := '暂停';Button4.Caption := '从头播放';System.ReportMemoryLeaksOnShutdown := true;
end;procedure TForm1.Button1Click(Sender: TObject);
varbufDesc: TDSBufferDesc;p1: Pointer;n1: DWORD;wavPath: string;wav: TReadWaveFile; //
beginbuf := nil;myDSound := nil;with TOpenDialog.Create(nil) do beginFilter := 'Wave File(*.wav)|*.wav';if Execute then wavPath := FileName;Free;end;wav := TReadWaveFile.Create;if not wav.Open(wavPath) thenbeginShowMessage('只能是 PCM 格式的 WAVE 文件');wav.Free;Exit;end;DirectSoundCreate8(nil, myDSound, nil);myDSound.SetCooperativeLevel(Self.Handle, DSSCL_NORMAL);ZeroMemory(@bufDesc, SizeOf(TDSBufferDesc));bufDesc.dwSize := SizeOf(TDSBufferDesc);{指定缓冲区允许音量、相位和频率调节}bufDesc.dwFlags := DSBCAPS_STATIC or DSBCAPS_CTRLVOLUME or DSBCAPS_CTRLPAN or DSBCAPS_CTRLFREQUENCY;bufDesc.dwBufferBytes := wav.Size;bufDesc.lpwfxFormat := @wav.Format;myDSound.CreateSoundBuffer(bufDesc, buf, nil);buf.Lock(0, 0, @p1, @n1, nil, nil, DSBLOCK_ENTIREBUFFER);wav.Read(p1, n1);buf.Unlock(p1, n1, nil, 0);buf.Play(0, 0, 0);TrackBar1.Position := 0;TrackBar2.Position := 0;TrackBar3.Position := wav.Format.nSamplesPerSec;wav.Free;
end;procedure TForm1.Button2Click(Sender: TObject);
beginif buf <> nil then buf.Play(0, 0, DSBPLAY_LOOPING);
end;procedure TForm1.Button3Click(Sender: TObject);
beginif buf <> nil then buf.Stop;
end;{从头播放}
procedure TForm1.Button4Click(Sender: TObject);
beginif buf = nil then Exit;buf.Stop;buf.SetCurrentPosition(0);buf.Play(0, 0, 0);
end;{音量调节}
procedure TForm1.TrackBar1Change(Sender: TObject);
beginif buf <> nil then buf.SetVolume(TTrackBar(Sender).Position);
end;{相位调节}
procedure TForm1.TrackBar2Change(Sender: TObject);
beginif buf <> nil then buf.SetPan(TTrackBar(Sender).Position);
end;{频率调节}
procedure TForm1.TrackBar3Change(Sender: TObject);
beginif buf <> nil then buf.SetFrequency(TTrackBar(Sender).Position);
end;procedure TForm1.FormDestroy(Sender: TObject);
beginbuf := nil;myDSound := nil;
end;end.

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