Producing a Dialog Box for Selecting a Specific Type of Format

You might want an application to allow the user to select a format from a restricted list of formats in a dialog box. Restrictions might limit the number of channels, the sampling rate, the waveform-audio format tag, or the number of bits per sample. In all of these cases, you can generate the list by using the acmFormatChoose function, setting the fdwEnum and pwfxEnum members of the ACMFORMATCHOOSE structure. The following example illustrates this process.



WAVEFORMATEX wfxSelection;


// Initialize the ACMFORMATCHOOSE members.

memset(&afc, 0, sizeof(afc));

afc.cbStruct = sizeof(afc);

afc.fdwStyle = 0L; // no special style flags

afc.hwndOwner = hwnd; // hwnd of parent window

afc.pwfx = &wfxSelection; // wfx to receive selection

afc.cbwfx = sizeof(wfxSelection);

afc.pszTitle = TEXT("16 Bit PCM Selection");

// Request that all 16-bit PCM formats be displayed for the user

// to select from.

memset(&wfxEnum, 0, sizeof(wfxEnum));

wfxEnum.wFormatTag = WAVE_FORMAT_PCM;

wfxEnum.wBitsPerSample = 16;



afc.pwfxEnum = &wfxEnum;

mmr = acmFormatChoose(&afc);

if ((MMSYSERR_NOERROR != mmr) && (ACMERR_CANCELED != mmr))


// There was a fatal error in bringing up the list

// dialog box (probably invalid input parameters).


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