waveOutPrepareHeader (Compact 2013)

3/26/2014

This function prepares a waveform data block for playback. This function allows both the audio driver and the operating system (OS) to do time consuming processing of the header and/or buffer once at initialization. The application can use the buffer repeatedly without additional processing by the driver or the OS.

Syntax

MMRESULT waveOutPrepareHeader(
  HWAVEOUT hwo,
  LPWAVEHDR pwh,
  UINT cbwh
); 

Parameters

• hwo
  Handle to the waveform-audio output device.

• pwh
  Pointer to a WAVEHDR structure that identifies the data block to be prepared. The buffer's base address must be aligned with the respect to the sample size.

• cbwh
  Size, in bytes, of the WAVEHDR structure.

Return Value

One of the values described in the following table is returned.

Remarks

The lpData, dwBufferLength, and dwFlags members of the WAVEHDR structure must be set before calling this function (dwFlags must be zero).

Once prepared, the application may not change the lpData field.

Preparing a header that has already been prepared has no effect, and the function returns zero.

An application should not attempt to prepare the same header on two different wave devices at the same time. If you want to record from one wave device and play back the same data to another wave device, but don't want to copy data between buffers, you can allocate two wave headers, point them both to the same data buffer, and then call waveInPrepareHeader on one and waveOutPrepareHeader on the other as appropriate.

Requirements

See Also

Reference

Waveform Audio Functions