Example of Writing Waveform Data - Win32 Multimedia Programmer's Reference

Custom Search

Example of Writing Waveform Data

The following example illustrates the steps required to allocate and set up a WAVEHDR structure and write a block of data to a waveform output device.

// Global variables.

HANDLE hData = NULL; // handle of waveform data memory

HPSTR lpData = NULL; // pointer to waveform data memory

oid WriteWaveData(void)

{

HWAVEOUT hWaveOut;

HGLOBAL hWaveHdr;

LPWAVEHDR lpWaveHdr;

HMMIO hmmio;

UINT wResult;

HANDLE hFormat;

WAVEFORMAT *pFormat;

DWORD dwDataSize;

// Open a waveform device for output using window callback.

if (waveOutOpen((LPHWAVEOUT)&hWaveOut, WAVE_MAPPER,

(LPWAVEFORMAT)pFormat,

(LONG)hwndApp, 0L, CALLBACK_WINDOW))

{

MessageBox(hwndApp,

"Failed to open waveform output device.",

NULL, MB_OK | MB_ICONEXCLAMATION);

LocalUnlock(hFormat);

LocalFree(hFormat);

mmioClose(hmmio, 0);

return;

}

// Allocate and lock memory for the waveform data.

hData = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE, dwDataSize );

if (!hData)

{

MessageBox(hwndApp, "Out of memory.",

NULL, MB_OK | MB_ICONEXCLAMATION);

mmioClose(hmmio, 0);

return;

}

if ((lpData = GlobalLock(hData)) == NULL)

{

MessageBox(hwndApp, "Failed to lock memory for data chunk.",

NULL, MB_OK | MB_ICONEXCLAMATION);

GlobalFree(hData);

mmioClose(hmmio, 0);

return;

}

// Read the waveform data subchunk.

if(mmioRead(hmmio, (HPSTR) lpData, dwDataSize) != (LRESULT)dwDataSize)

{

MessageBox(hwndApp, "Failed to read data chunk.",

NULL, MB_OK | MB_ICONEXCLAMATION);

GlobalUnlock(hData);

GlobalFree(hData);

mmioClose(hmmio, 0);

return;

}

// Allocate and lock memory for the header.

hWaveHdr = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE,

(DWORD) sizeof(WAVEHDR));

if (hWaveHdr == NULL)

{

GlobalUnlock(hData);

GlobalFree(hData);

MessageBox(hwndApp, "Not enough memory for header.",

NULL, MB_OK | MB_ICONEXCLAMATION);

return;

}

lpWaveHdr = (LPWAVEHDR) GlobalLock(hWaveHdr);

if (lpWaveHdr == NULL)

{

GlobalUnlock(hData);

GlobalFree(hData);

MessageBox(hwndApp,

"Failed to lock memory for header.",

NULL, MB_OK | MB_ICONEXCLAMATION);

return;

}

// After allocation, set up and prepare header.

lpWaveHdr->lpData = lpData;

lpWaveHdr->dwBufferLength = dwDataSize;

lpWaveHdr->dwFlags = 0L;

lpWaveHdr->dwLoops = 0L;

waveOutPrepareHeader(hWaveOut, lpWaveHdr, sizeof(WAVEHDR));

// Now the data block can be sent to the output device. The

// waveOutWrite function returns immediately and waveform

// data is sent to the output device in the background.

wResult = waveOutWrite(hWaveOut, lpWaveHdr, sizeof(WAVEHDR));

if (wResult != 0)

{

waveOutUnprepareHeader(hWaveOut, lpWaveHdr,

sizeof(WAVEHDR));

GlobalUnlock( hData);

GlobalFree(hData);

MessageBox(hwndApp, "Failed to write block to device",

NULL, MB_OK | MB_ICONEXCLAMATION);

return;

}

Last news from Greatis Software

    Nostalgia .Net     .Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More »

Recommended software for developers

    Ultimate Pack     Component pack for Delphi and C++ Builder that contains runtime form designer, runtime object inspector, print suite and much more for the very special price. More »

    Form Designer .Net     Unique runtime form design solution that allows to edit any form in .Net WinForms application at runtime with full source codes for only 300 euro! More »

    Print Suite .Net     Print Suite .Net is a set of components for easy printing texts, images and grids from your WinForms applications. Full C# source codes are available More »

    Gradient Controls .Net     Gradient Controls .Net offers controls with gradient background feature. Labels, panels and so on... Full C# source codes are available More »

    Greatis iGrid     iGrid plots drawing grid right over your desktop, so you can use it everywhere, with any drawing application without any special plugins for different graphic editors. More »

All the contacts and projects

Dmitry Vasiliev (just.dmitry)

More Online Helps

Win32 Programmer's Reference
Win32 Multimedia Programmer's Reference
OLE Programmer's Reference
Microsoft Windows Pen API Programmer's Reference
Microsoft Windows Sockets 2 Reference
Microsoft Windows Telephony API (TAPI) Programmer's Reference
Unix Manual Pages

greatis just4fun network