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Using DirectSound to Play Audio Stream Data

, 9 Mar 2005
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An article on how to play audio stream data with DirectSound.


This article with its code shows how to play audio stream data with DirectSound. It gives a more flexible method to control the stream data. The demo shows how to play, pause, stop, seek a small or a big WAV file.


Before you read the code, you should know something about DirectSound. You can find the related material in:

MSDN\Graphics and Multimedia\DirectX\SDK Documentation\DiretX8.1(C++)\DirectX Audio

Using the code

The CMyDirectSound has the following public method:

                                                      LPBYTE lpDesBuf,
                                                      const DWORD dwRequiredSamples, 
                                                      DWORD &dwRetSamples, 
                                                      LPVOID lpData);
void Play();
void Pause();
void Stop();
void Release();
DWORD GetSamplesPlayed();

First, you should give the information of the audio data you want to play, with "SetFormat":

m_pWavFile->Open((LPTSTR)(LPCTSTR)m_strFileName, &formatWav, WAVEFILE_READ);
formatWav = *m_pWavFile->GetFormat();

if (NULL == m_pDYDS) {

  m_pDYDS = new CDYDirectSound;

Second, set the callback function which is to get the audio stream data:

m_pMyDS->SetCallback(GetSamples, this);

Certainly, the body of the callback function should be written by yourself. Then you can play, pause, stop the audio data.

The "GetSamplesPlayed" method will give the number of audio samples played after you begin play. You can use this method to give the playing position.

Points of Interest

I think there're two key points in this class.

1. How to control the DirectSound buffer circle?

I create a second DirectSound buffer with two seconds duration:

//Create Second Sound Buffer
dsbd.dwBufferBytes = 2*m_WFE.nAvgBytesPerSec; //2-Second Buffer 
dsbd.lpwfxFormat = &m_WFE;

if ( FAILED(m_lpDS->CreateSoundBuffer(&dsbd, &m_lpDSB, NULL)) ) {

  OutputDebugString(_T("Create Second Sound Buffer Failed!"));
  m_strLastError = _T("MyDirectSound SetFormat Failed!");

And I set two DirectSound notify at 0.5 second and 1.5 second:

               (1st Notify)                          (2nd Notify)
0              0.5Second        1Second              1.5Second         2Second
|                  |               |                     |                 |
|                                  |                                       |
//Set Direct Sound Buffer Notify Position
pPosNotify[0].dwOffset = m_WFE.nAvgBytesPerSec/2 - 1;
pPosNotify[1].dwOffset = 3*m_WFE.nAvgBytesPerSec/2 - 1;  
pPosNotify[0].hEventNotify = m_pHEvent[0];
pPosNotify[1].hEventNotify = m_pHEvent[1];

if ( FAILED(lpDSBNotify->SetNotificationPositions(2, pPosNotify)) ) {

  OutputDebugString(_T("Set NotificationPosition Failed!"));
  m_strLastError = _T("MyDirectSound SetFormat Failed!");

When you call the Play method, a timer will be triggered. The "TimerProcess" function will be called every 300 milliseconds.

//Beging Play
m_lpDSB->Play(0, 0, DSBPLAY_LOOPING);

m_timerID = timeSetEvent(300, 100, TimerProcess, 

In the "TimerProcess" function, the next second audio stream data will be gotten when the current play cursor arrives the 1st or 2nd notify point.

void CALLBACK TimerProcess(UINT uTimerID, UINT uMsg, 
                           DWORD dwUser, DWORD dw1, DWORD dw2)
  CMyDirectSound *pDDS = (CMyDirectSound *)dwUser;

void CMyDirectSound::TimerCallback()
  LPVOID lpvAudio1 = NULL, lpvAudio2 = NULL;
  DWORD dwBytesAudio1 = 0, dwBytesAudio2 = 0;
  DWORD dwRetSamples = 0, dwRetBytes = 0;

  HRESULT hr = WaitForMultipleObjects(2, m_pHEvent, FALSE, 0);
  if(WAIT_OBJECT_0 == hr) {


    //Lock DirectSoundBuffer Second Part
    HRESULT hr = m_lpDSB->Lock(m_WFE.nAvgBytesPerSec, m_WFE.nAvgBytesPerSec,
    &lpvAudio1, &dwBytesAudio1,&lpvAudio2, &dwBytesAudio2, 0);
    if ( FAILED(hr) ) {

      m_strLastError = _T("Lock DirectSoundBuffer Failed!");
  else if (WAIT_OBJECT_0 + 1 == hr) {    


    //Lock DirectSoundBuffer First Part
    HRESULT hr = m_lpDSB->Lock(0, m_WFE.nAvgBytesPerSec, 
    &lpvAudio1, &dwBytesAudio1, &lpvAudio2, &dwBytesAudio2, 0);
    if ( FAILED(hr) ) {

      m_strLastError = _T("Lock DirectSoundBuffer Failed!");
  else {


  //Get 1 Second Audio Buffer 
  m_lpGETAUDIOSAMPLES(m_lpAudioBuf, m_WFE.nSamplesPerSec, dwRetSamples, m_lpData);
  dwRetBytes = dwRetSamples*m_WFE.nBlockAlign;
  //If near the end of the audio data
  if (dwRetSamples < m_WFE.nSamplesPerSec) {

    DWORD dwRetBytes = dwRetSamples*m_WFE.nBlockAlign;
    memset(m_lpAudioBuf+dwRetBytes, 0, m_WFE.nAvgBytesPerSec - dwRetBytes);        
  //Copy AudioBuffer to DirectSoundBuffer
  if (NULL == lpvAudio2) {

    memcpy(lpvAudio1, m_lpAudioBuf, dwBytesAudio1);
  else {

    memcpy(lpvAudio1, m_lpAudioBuf, dwBytesAudio1);
    memcpy(lpvAudio2, m_lpAudioBuf + dwBytesAudio1, dwBytesAudio2);
  //Unlock DirectSoundBuffer
  m_lpDSB->Unlock(lpvAudio1, dwBytesAudio1, lpvAudio2, dwBytesAudio2);

2. How the following callback function works?

//Get Audio Buffer
  m_lpGETAUDIOSAMPLES(m_lpAudioBuf, m_WFE.nSamplesPerSec, dwRetSamples, m_lpData);

Do you remember what you have done when you set the callback function?

void CDYDirectSound::SetCallback(LPGETAUDIOSAMPLES_PROGRESS Function_Callback, 
                                 LPVOID lpData)
  m_lpGETAUDIOSAMPLES = Function_Callback;
  m_lpData = lpData;

Yes, you transfer the GETAUDIOSAMPLES_PROGRESS function's pointer to m_lpGETAUDIOSAMPLES.

m_pMyDS->SetCallback(GetSamples, this);

And the GetSamples is defined as:

                            const DWORD dwRequiredSamples, 
                            DWORD &dwRetSamples, 
                            LPVOID lpData)
  CDirectSoundTestDlg *pDlg = (CDirectSoundTestDlg *)lpData;
  pDlg->GetAudioSamples(lpDesBuf, dwRequiredSamples, dwRetSamples);
  return 0;

HRESULT CDirectSoundTestDlg::GetAudioSamples(LPBYTE lpDesBuf,
                                             const DWORD dwRequiredSamples,
                                             DWORD &dwRetSamples)
  DWORD dwRequiredBytes = 0, dwRetBytes = 0;
  WAVEFORMATEX *pWFE = m_pWavFile->GetFormat();
  dwRequiredBytes = dwRequiredSamples*pWFE->nBlockAlign;
  m_pWavFile->Read(lpDesBuf, dwRequiredBytes, &dwRetBytes);
  dwRetSamples = dwRetBytes/pWFE->nBlockAlign;
  return dwRetBytes;

You can write your own "GetAudioSamples" to get the audio stream data.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Cai Tao

China China
No Biography provided

Comments and Discussions

QuestionHow do handle block mode audio ? PinmemberMusong22-Aug-06 17:54 
QuestionCalculation error in GetSamplesPlayed() ? PinmemberAzonacun8-May-06 9:38 
AnswerRe: Calculation error in GetSamplesPlayed() ? PinmemberKedzo6-Jul-06 12:51 
Question'dmusici.h' missing! PinmemberWilliamZhou24-Mar-06 6:29 
AnswerRe: 'dmusici.h' missing! PinmemberSreekanth Muralidharan27-Apr-06 20:49 
GeneralMeasuring the sound level Pinmembermsorc24-Feb-06 7:08 
QuestionUsing a Stream in stead of of File ? PinmemberYossef1-Dec-05 0:07 
GeneralBug report and my fixes PinsussIKedzo25-Oct-05 2:54 
GeneralConflicts with other applications PinmemberStevenDorning6-Oct-05 23:19 
GeneralSomething wrong when load different BitsPerSample WAV file! Pinmemberikkiu20011-Jul-05 0:51 
Generalabout mfc42u.lib Pinmembercaoxiang31-May-05 19:10 
GeneralRe: about mfc42u.lib PinmemberYesterdayOncemore13-Feb-06 21:13 
GeneralRe: about mfc42u.lib PinmemberDuncan1234529-Mar-06 22:59 
GeneralAudio Format.. Pinmembermpallavi28-Apr-05 19:08 
GeneralRe: Audio Format.. PinmemberCai Tao28-Apr-05 22:27 
GeneralRe: Audio Format.. Pinmembermpallavi29-Apr-05 2:45 
GeneralRe: Audio Format.. PinsussAnonymous2-May-05 5:42 
GeneralRe: Audio Format.. Pinmembermpallavi4-May-05 19:21 
Generalits urgent! Pinmembermpallavi19-Apr-05 19:13 
GeneralRe: its urgent! PinmemberCai Tao20-Apr-05 21:48 
GeneralRe: its urgent! Pinmembermpallavi26-Apr-05 20:30 
GeneralRe: its urgent! PinmemberCai Tao28-Apr-05 22:15 
GeneralRe: its urgent! Pinmembermpallavi29-Apr-05 0:16 
Generalone more difficulty... Pinmembermpallavi27-Apr-05 21:55 
GeneralConfused..plz help Pinmembermpallavi21-Mar-05 23:06 
GeneralRe: Confused..plz help PinmemberCai Tao22-Mar-05 0:39 
GeneralRe: Confused..plz help Pinmembermpallavi22-Mar-05 18:25 
QuestionRe: Confused..plz help Pinmemberrajneshmalik30-Aug-07 20:44 
Questionhow to use PlaySound()? PinsussAnonymous20-Mar-05 22:09 
AnswerRe: how to use PlaySound()? Pinmembermpallavi21-Mar-05 19:25 
Generalquestion Pinmemberweirdyi1-Mar-05 0:45 
GeneralRe: question PinmemberCai Tao9-Mar-05 19:42 
GeneralA Jerky Sound at the end of playing Pinmemberoiholkljio11-Feb-05 6:34 
GeneralRe: A Jerky Sound at the end of playing PinmemberCai Tao9-Mar-05 19:38 
Generalquestion Pinmembersave20007-Nov-04 21:08 
GeneralRe: question PinsussAnonymous8-Nov-04 15:58 
Generalquestion Pinmembereuacela1-Oct-04 9:02 
GeneralRe: question PinsussAnonymous3-Oct-04 5:32 

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