操作 Wave 文件(7): 建立一个空的 Wave 文件(三种方法)

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses MMSystem;

//chan: 1 单声道、2 立体声;
//freq: 频率, 取值: 11025, 22050, 44100
//bit : 每个样本的大小, 取值 8、16
function CreateWav1(chan, freq, bit: Word; const FilePath: string): Boolean;
var
  h: HMMIO;
  ckiRiff, ckiFmt, ckiData: TMMCKInfo;
  fmt: TPCMWaveFormat;
begin
  //此函数是使用 mmioCreateChunk 函数来分别建立 Wave 文件的每个块.

  {初识化相关结构}
  ZeroMemory(@ckiRiff, SizeOf(TMMCKInfo));
  ckiRiff.cksize := 36; {mmioCreateChunk 函数会自动写上 ckid, 但其 cksize 需要手动给}
  ckiRiff.fccType := mmioStringToFOURCC('WAVE', 0);

  ZeroMemory(@ckiFmt, SizeOf(TMMCKInfo));
  ckiFmt.ckid := mmioStringToFOURCC('fmt', 0);

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

  {指定 Wave 格式}
  fmt.wf.wFormatTag := WAVE_FORMAT_PCM;
  fmt.wf.nChannels := chan;
  fmt.wf.nSamplesPerSec := freq;
  fmt.wf.nAvgBytesPerSec := freq * chan * bit div 8;
  fmt.wf.nBlockAlign := chan * bit div 8;
  fmt.wBitsPerSample := bit;

  h := mmioOpen(PChar(FilePath), nil, MMIO_CREATE or MMIO_WRITE);
  if h = 0 then Exit(False);

  {分别建立 RIFF、fmt、data 块}
  if (mmioCreateChunk(h, @ckiRiff, MMIO_CREATERIFF) = MMSYSERR_NOERROR) and
    (mmioCreateChunk(h, @ckiFmt, 0) = MMSYSERR_NOERROR) and
    (mmioWrite(h, PAnsiChar(@fmt), SizeOf(TPCMWaveFormat)) = SizeOf(TPCMWaveFormat)) and
    (mmioAscend(h, @ckiFmt, 0) = MMSYSERR_NOERROR) and
    (mmioCreateChunk(h, @ckiData, 0) = MMSYSERR_NOERROR) then Result := True;

  mmioClose(h, 0);
end;

//把 PCM 编码的 WAVE 文件的前 44 个字节看成一个结构来操作:
function CreateWav2(chan, freq, bit: Word; const FilePath: string): Boolean;
type
  TWaveHeader = record
    Riff_ckid      : DWORD;
    Riff_cksize    : DWORD;
    Riff_fccType   : DWORD;
    fmt_ckid       : DWORD;
    fmt_cksize     : DWORD;
    wFormatTag     : Word;
    nChannels      : Word;
    nSamplesPerSec : DWORD;
    nAvgBytesPerSec: DWORD;
    nBlockAlign    : Word;
    wBitsPerSample : Word;
    data_ckid      : DWORD;
    data_cksize    : DWORD;
  end;
var
  wh: TWaveHeader;
  hFile: Integer;
begin
  wh.Riff_ckid := FOURCC_RIFF;
  wh.Riff_cksize := 36;
  wh.Riff_fccType := mmioStringToFOURCC('WAVE', 0);
  wh.fmt_ckid := mmioStringToFOURCC('fmt', 0);
  wh.fmt_cksize := 16;
  wh.wFormatTag := WAVE_FORMAT_PCM;
  wh.nChannels := chan;
  wh.nSamplesPerSec := freq;
  wh.nAvgBytesPerSec := freq * chan * bit div 8;
  wh.nBlockAlign := chan * bit div 8;
  wh.wBitsPerSample := bit;
  wh.data_ckid := mmioStringToFOURCC('data', 0);
  wh.data_cksize := 0;

  hFile := FileCreate(FilePath);
  Result := (FileWrite(hFile, wh, SizeOf(TWaveHeader)) <> -1);
  FileClose(hFile);
end;

//同上, 只是改用流来写文件
function CreateWav3(chan, freq, bit: Word; const FilePath: string): Boolean;
type
  TWaveHeader = record
    Riff_ckid      : DWORD;
    Riff_cksize    : DWORD;
    Riff_fccType   : DWORD;
    fmt_ckid       : DWORD;
    fmt_cksize     : DWORD;
    wFormatTag     : Word;
    nChannels      : Word;
    nSamplesPerSec : DWORD;
    nAvgBytesPerSec: DWORD;
    nBlockAlign    : Word;
    wBitsPerSample : Word;
    data_ckid      : DWORD;
    data_cksize    : DWORD;
  end;
var
  wh: TWaveHeader;
begin
  wh.Riff_ckid := FOURCC_RIFF;
  wh.Riff_cksize := 36;
  wh.Riff_fccType := mmioStringToFOURCC('WAVE', 0);
  wh.fmt_ckid := mmioStringToFOURCC('fmt', 0);
  wh.fmt_cksize := 16;
  wh.wFormatTag := WAVE_FORMAT_PCM;
  wh.nChannels := chan;
  wh.nSamplesPerSec := freq;
  wh.nAvgBytesPerSec := freq * chan * bit div 8;
  wh.nBlockAlign := chan * bit div 8;
  wh.wBitsPerSample := bit;
  wh.data_ckid := mmioStringToFOURCC('data', 0);
  wh.data_cksize := 0;

  with TFileStream.Create(FilePath, fmCreate) do begin
    Result := (Write(wh, SizeOf(TWaveHeader)) = SizeOf(TWaveHeader));
    Free;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  CreateWav1(1, 11025, 8,  'C:\Temp\X1.wav');
  CreateWav2(2, 22050, 16, 'C:\Temp\X2.wav');
  CreateWav3(2, 44100, 16, 'C:\Temp\X3.wav');
end;

end.