在 Delphi 下使用 DirectSound (4): 设置音量、相位、播放频率和播放位置

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:

---

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 

---

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:

---

{实现 TReadWaveFile 类的单元}

unit ReadWaveFile;



interface



uses Windows, Classes, SysUtils, MMSystem;



type

TReadWaveFile = class

private

  FFileHandle: HMMIO;

  FFormat: TWaveFormatEx;

  FSize: DWORD;

public

  constructor 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;

begin

  inherited;



end;



destructor TReadWaveFile.Destroy;

begin

  if FFileHandle > 0 then mmioClose(FFileHandle, 0);

  inherited;

end;



function TReadWaveFile.Open(FileName: string): Boolean;

var

  ckiRIFF,ckiFmt,ckiData: TMMCKInfo;

begin

  Result := 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) then

    mmioRead(FFileHandle, @FFormat, SizeOf(TWaveFormatEx));



  mmioAscend(FFileHandle, @ckiFmt, 0);



  if (mmioDescend(FFileHandle, @ckiData, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) then

    FSize := ckiData.cksize;



  Result := FFormat.wFormatTag = WAVE_FORMAT_PCM;

end;



function TReadWaveFile.Read(pDest: Pointer; Size: DWORD): Boolean;

begin

  Result := mmioRead(FFileHandle, pDest, Size) = Size;

end;



end.

---

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

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, ComCtrls;



type

  TForm1 = 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;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses DirectSound, ReadWaveFile; // ReadWaveFile 是 TReadWaveFile 类所在的单元



var

  myDSound: IDirectSound8;

  buf: IDirectSoundBuffer;



procedure TForm1.FormCreate(Sender: TObject);

begin

  TrackBar1.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);

var

  bufDesc: TDSBufferDesc;

  p1: Pointer;

  n1: DWORD;

  wavPath: string;

  wav: TReadWaveFile; //

begin

  buf := nil;

  myDSound := nil;

  with TOpenDialog.Create(nil) do begin

    Filter := 'Wave File(*.wav)|*.wav';

    if Execute then wavPath := FileName;

    Free;

  end;



  wav := TReadWaveFile.Create;

  if not wav.Open(wavPath) then

  begin

    ShowMessage('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);

begin

  if buf <> nil then buf.Play(0, 0, DSBPLAY_LOOPING);

end;



procedure TForm1.Button3Click(Sender: TObject);

begin

  if buf <> nil then buf.Stop;

end;



{从头播放}

procedure TForm1.Button4Click(Sender: TObject);

begin

  if buf = nil then Exit;

  buf.Stop;

  buf.SetCurrentPosition(0);

  buf.Play(0, 0, 0);

end;



{音量调节}

procedure TForm1.TrackBar1Change(Sender: TObject);

begin

  if buf <> nil then buf.SetVolume(TTrackBar(Sender).Position);

end;



{相位调节}

procedure TForm1.TrackBar2Change(Sender: TObject);

begin

  if buf <> nil then buf.SetPan(TTrackBar(Sender).Position);

end;



{频率调节}

procedure TForm1.TrackBar3Change(Sender: TObject);

begin

  if buf <> nil then buf.SetFrequency(TTrackBar(Sender).Position);

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  buf := nil;

  myDSound := nil;

end;



end.

---