操作 Wave 文件(6): 获取 Wave 文件的波形数据

读取函数及测试代码:

---

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses MMSystem;

function GetWaveData(FilePath: string; var stream: TMemoryStream): Boolean;
var
  hFile: HMMIO;
  ckiRIFF,ckiData: TMMCKInfo;
begin
  Result := False;
  hFile := mmioOpen(PChar(FilePath), nil, MMIO_READ);
  if hFile = 0 then Exit;

  ZeroMemory(@ckiRIFF, SizeOf(TMMCKInfo));
  ZeroMemory(@ckiData, SizeOf(TMMCKInfo));
  ckiData.ckid := mmioStringToFOURCC('data', 0);

  //先获取主块的信息
  mmioDescend(hFile, @ckiRIFF, nil, MMIO_FINDRIFF);

  //再获取 data 块的信息后, 指针将自动指向 data 数据的起点; 然后读出数据
  if (ckiRIFF.ckid = FOURCC_RIFF) and
     (ckiRIFF.fccType = mmioStringToFOURCC('WAVE',0)) and
     (mmioDescend(hFile, @ckiData, @ckiRIFF, MMIO_FINDCHUNK) = MMSYSERR_NOERROR) then
    begin
      stream.Size := ckiData.cksize;
      Result := (mmioRead(hFile, stream.Memory, ckiData.cksize) = ckiData.cksize);
    end;
  mmioClose(hFile, 0);
end;

//调用测试
procedure TForm1.Button1Click(Sender: TObject);
const
  FilePath = 'C:\WINDOWS\Media\Windows XP 启动.wav';
var
  stream: TMemoryStream;
begin
  stream := TMemoryStream.Create;

  if GetWaveData(FilePath, stream) then
    ShowMessageFmt('读出的数据大小是: %d', [stream.Size]); {424600}

  stream.Free;
end;

end.