学步园

左右声道的音量是单调的; 表示音量的 32 位整数的低 16 位是左声道、高 16 位是右声道.

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    ScrollBar1: TScrollBar;
    ScrollBar2: TScrollBar;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure ScrollBar1Change(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses MMSystem;

function GetWaveFmtData(path: string; var fmt: TWaveFormatEx; var buf: TBytes): Boolean;
var
  hFile: HMMIO;
  ckiRIFF,ckiFmt,ckiData: TMMCKInfo;
begin
  Result := False;
  hFile := mmioOpen(PChar(path), nil, MMIO_READ);
  if hFile = 0 then Exit;

  ZeroMemory(@ckiRIFF, SizeOf(TMMCKInfo));
  ZeroMemory(@ckiFmt, SizeOf(TMMCKInfo));
  ZeroMemory(@ckiData, SizeOf(TMMCKInfo));

  ckiRIFF.fccType := mmioStringToFOURCC('WAVE', 0);
  ckiFmt.ckid := mmioStringToFOURCC('fmt', 0);
  ckiData.ckid := mmioStringToFOURCC('data', 0);

  ZeroMemory(@fmt, SizeOf(TWaveFormatEx));

  mmioDescend(hFile, @ckiRIFF, nil, MMIO_FINDRIFF);

  if (ckiRIFF.ckid = FOURCC_RIFF) and (ckiRIFF.fccType = mmioStringToFOURCC('WAVE',0)) and
     (mmioDescend(hFile, @ckiFmt, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) and
     (mmioRead(hFile, @fmt, ckiFmt.cksize) = ckiFmt.cksize) and
     (mmioAscend(hFile, @ckiFmt, 0) = MMSYSERR_NOERROR) and
     (mmioDescend(hFile, @ckiData, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) then
  begin
    SetLength(buf, ckiData.cksize);
    Result := (mmioRead(hFile, PAnsiChar(buf), ckiData.cksize) = ckiData.cksize);
  end;

  mmioClose(hFile, 0);
end;

//------------------------------------------------------------------------------
var
  wh: TWaveHdr;
  hWaveOut: HWAVE;
  fmt: TWaveFormatEx;
  buf: TBytes;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Button1.Caption := '打开并播放';
  Button2.Caption := '暂停';
  Button3.Caption := '继续';

  ScrollBar1.Min := 0;
  ScrollBar1.Max := 100;
  ScrollBar2.Min := 0;
  ScrollBar2.Max := 100;

  ScrollBar2.OnChange := ScrollBar1.OnChange;
end;

procedure TForm1.ScrollBar1Change(Sender: TObject);
var
  L,R: Word;
begin
  if hWaveOut = 0 then Exit;
  L := Trunc(ScrollBar1.Position / 100 * MAXWORD);
  R := Trunc(ScrollBar2.Position / 100 * MAXWORD);
  waveOutSetVolume(hWaveOut, MakeLong(L, R));
end;

procedure WaveProc(hWave: HWAVE; uMsg, dwInstance, dwParam1, dwParam2: DWORD); stdcall;
begin
  case uMsg of
    MM_WOM_DONE: waveOutUnprepareHeader(hWave, PWaveHdr(dwParam1), SizeOf(TWaveHdr));
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
const
  path = 'C:\WINDOWS\Media\Windows XP 启动.wav';
var
  volume: DWORD;
begin
  GetWaveFmtData(path, fmt, buf);

  wh.lpData := PAnsiChar(buf);
  wh.dwBufferLength := Length(buf);
  wh.dwBytesRecorded := 0;
  wh.dwUser := 0;
  wh.dwFlags := WHDR_BEGINLOOP or WHDR_ENDLOOP;
  wh.dwLoops := 3;
  wh.lpNext := nil;
  wh.reserved := 0;

  waveOutOpen(@hWaveOut, WAVE_MAPPER, @fmt, DWORD(@WaveProc), 0, CALLBACK_FUNCTION);
  waveOutGetVolume(hWaveOut, @volume);

  ScrollBar1.Position := Trunc(LoWord(volume) / MAXWORD * 100);
  ScrollBar2.Position := Trunc(HiWord(volume) / MAXWORD * 100);

  waveOutPrepareHeader(hWaveOut, @wh, SizeOf(TWaveHdr));
  waveOutWrite(hWaveOut, @wh, SizeOf(TWaveHdr));
end;

//暂停
procedure TForm1.Button2Click(Sender: TObject);
begin
  waveOutPause(hWaveOut);
end;

//继续
procedure TForm1.Button3Click(Sender: TObject);
begin
  waveOutRestart(hWaveOut);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  if hWaveOut  0 then waveOutClose(hWaveOut);
end;

end.

窗体文件:

---

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 182
  ClientWidth = 342
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 32
    Top = 24
    Width = 75
    Height = 25
    Caption = #25171#24320#24182#25773#25918
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 136
    Top = 24
    Width = 75
    Height = 25
    Caption = #26242#20572
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 240
    Top = 24
    Width = 75
    Height = 25
    Caption = #32487#32493
    TabOrder = 2
    OnClick = Button3Click
  end
  object ScrollBar1: TScrollBar
    Left = 32
    Top = 80
    Width = 283
    Height = 17
    PageSize = 0
    TabOrder = 3
    OnChange = ScrollBar1Change
  end
  object ScrollBar2: TScrollBar
    Left = 32
    Top = 120
    Width = 283
    Height = 17
    PageSize = 0
    TabOrder = 4
  end
end