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...play sound through a sound card?
Autor: Alan Lloyd
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Tip Rating (61):  
     


uses
  
MMSystem;

type
  
TVolumeLevel = 0..127;

procedure MakeSound(Frequency{Hz}, Duration{mSec}: Integer; Volume: TVolumeLevel);
  {writes tone to memory and plays it}
var
  
WaveFormatEx: TWaveFormatEx;
  MS: TMemoryStream;
  i, TempInt, DataCount, RiffCount: integer;
  SoundValue: byte;
  w: double; // omega ( 2 * pi * frequency)
const
  
Mono: Word = $0001;
  SampleRate: Integer = 11025; // 8000, 11025, 22050, or 44100
  
RiffId: string = 'RIFF';
  WaveId: string = 'WAVE';
  FmtId: string = 'fmt ';
  DataId: string = 'data';
begin
  if 
Frequency > (0.6 * SampleRate) then
  begin
    
ShowMessage(Format('Sample rate of %d is too Low to play a tone of %dHz',
      [SampleRate, Frequency]));
    Exit;
  end;
  with WaveFormatEx do
  begin
    
wFormatTag := WAVE_FORMAT_PCM;
    nChannels := Mono;
    nSamplesPerSec := SampleRate;
    wBitsPerSample := $0008;
    nBlockAlign := (nChannels * wBitsPerSample) div 8;
    nAvgBytesPerSec := nSamplesPerSec * nBlockAlign;
    cbSize := 0;
  end;
  MS := TMemoryStream.Create;
  with MS do
  begin
    
{Calculate length of sound data and of file data}
    
DataCount := (Duration * SampleRate) div 1000; // sound data
    
RiffCount := Length(WaveId) + Length(FmtId) + SizeOf(DWORD) +
      SizeOf(TWaveFormatEx) + Length(DataId) + SizeOf(DWORD) + DataCount; // file data
    {write out the wave header}
    
Write(RiffId[1], 4); // 'RIFF'
    
Write(RiffCount, SizeOf(DWORD)); // file data size
    
Write(WaveId[1], Length(WaveId)); // 'WAVE'
    
Write(FmtId[1], Length(FmtId)); // 'fmt '
    
TempInt := SizeOf(TWaveFormatEx);
    Write(TempInt, SizeOf(DWORD)); // TWaveFormat data size
    
Write(WaveFormatEx, SizeOf(TWaveFormatEx)); // WaveFormatEx record
    
Write(DataId[1], Length(DataId)); // 'data'
    
Write(DataCount, SizeOf(DWORD)); // sound data size
    {calculate and write out the tone signal} // now the data values
    
w := 2 * Pi * Frequency; // omega
    
for i := 0 to DataCount - 1 do
    begin
      
SoundValue := 127 + trunc(Volume * sin(i * w / SampleRate)); // wt = w * i / SampleRate
      
Write(SoundValue, SizeOf(Byte));
    end;
    {now play the sound}
    
sndPlaySound(MS.Memory, SND_MEMORY or SND_SYNC);
    MS.Free;
  end;
end;

// How to call the function:

procedure TForm1.Button1Click(Sender: TObject);
begin
  
MakeSound(1200, 1000, 60);
end;


 

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