I just want to produce a beep at 1200hz for 1 second.

This unit loads WaveAPI at start, should play a beep for 1 second, and close WaveAPI at end.

But when running, I can only hear a little noise.

Nothing to say in particular, should be stereo channels, and coded as 2 SmallInt (short in C++) for Left and Right.

The volume is not integrated but is considered as 100% for both channels.

This is my Delphi 6 code:

unit C4Audio;

interface

uses Windows;

type
  TAudioBits  = SHORT;
  TAudioDelay = WORD;
  TAudioHerz  = WORD;

  TAudioByte = record
                     Left, Right : TAudioBits;
               end;

  TAudioStereo = record
                       Left, Right : 0..100;
                 end;
implementation

uses Forms,
     mmsystem;

var
  AudioAPI    : hWaveOut;
  AudioBuffer : array of TAudioByte;
  AudioHeader : TWaveHdr;
  AudioStyle  : TWaveFormatEx;

var _alpha   : Real;
    _cursor  : Integer;
    _high    : Integer;

initialization
               with AudioStyle
                    do begin
                            wFormatTag      := WAVE_FORMAT_PCM;
                            nChannels       := 2;
                            nSamplesPerSec  := 44100;
                            wBitsPerSample  := SizeOf(TAudioBits) * 8;
                            nBlockAlign     := (wBitsPerSample div 8) * nChannels;
                            nAvgBytesPerSec := nBlockAlign * nSamplesPerSec;
                            cbSize          := 0;
                       end;

               if waveOutOpen(@AudioAPI, WAVE_MAPPER, @AudioStyle, 0, 0, CALLBACK_NULL) = MMSYSERR_NOERROR
                  then begin
                            SetLength(AudioBuffer, 1000);

                            with AudioHeader
                                 do begin
                                         dwBufferLength := Length(AudioBuffer) * SizeOf(TAudioByte);
                                         dwFlags        := 0;
                                         dwLoops        := $FFFF;
                                         lpData         := @AudioBuffer;
                                    end;

                            _alpha := 0;
                            _high  := High(TAudioBits);

                            for _cursor := Low(AudioBuffer) to High(AudioBuffer)
                                do begin
                                        AudioBuffer[_cursor].Left  := Round(_high * Sin(_alpha));
                                        AudioBuffer[_cursor].Right := Round(_high * Sin(_alpha));

                                        _alpha := _alpha  + 2 * PI * 1200 / AudioStyle.nSamplesPerSec;
                                   end;

                            if (waveOutPrepareHeader(AudioAPI, @AudioHeader, SizeOf(TWaveHdr)) = MMSYSERR_NOERROR)
                               and
                               (waveOutWrite(AudioAPI, @AudioHeader, sizeof(TWaveHdr)) = MMSYSERR_NOERROR)
                               then Sleep(1000);
                      end
                  else
                    AudioAPI := 0;

finalization
            if AudioAPI <> 0
              then begin
                        while waveOutUnprepareHeader(AudioAPI, @AudioHeader, SizeOf(TWaveHdr)) = WAVERR_STILLPLAYING
                              do Application.ProcessMessages;

                        if waveOutClose(AudioAPI) = MMSYSERR_NOERROR
                           then begin
                                end;
                   end;
end.