Important:
This is retired content. This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This content may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist.
A version of this page is also available for
4/8/2010

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 WAVEHDRstructure 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 WAVEHDRstructure.

Return Value

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

Value Description

MMSYSERR_NOERROR

Success.

MMSYSERR_INVALHANDLE

Specified device handle is invalid.

MMSYSERR_INVALPARAM

The buffer's base address is not aligned with the sample size.

MMSYSERR_NODRIVER

No device driver is present.

MMSYSERR_NOMEM

Unable to allocate or lock memory.

Remarks

The lpData, dwBufferLength, and dwFlagsmembers of the WAVEHDRstructure must be set before calling this function ( dwFlagsmust be zero).

Once prepared, the application may not change the lpDatafield.

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 waveInPrepareHeaderon one and waveOutPrepareHeaderon the other as appropriate.

Requirements

Header mmsystem.h
Library coredll.lib
Windows Embedded CE Windows CE 2.0 and later
Windows Mobile Windows Mobile Version 5.0 and later

See Also