waveOutOpen function (mmeapi.h)
The waveOutOpen function opens the given waveform-audio output device for playback.
MMRESULT waveOutOpen( LPHWAVEOUT phwo, UINT uDeviceID, LPCWAVEFORMATEX pwfx, DWORD_PTR dwCallback, DWORD_PTR dwInstance, DWORD fdwOpen );
Pointer to a buffer that receives a handle identifying the open waveform-audio output device. Use the handle to identify the device when calling other waveform-audio output functions. This parameter might be NULL if the WAVE_FORMAT_QUERY flag is specified for fdwOpen.
Identifier of the waveform-audio output device to open. It can be either a device identifier or a handle of an open waveform-audio input device. You can also use the following flag instead of a device identifier:
|WAVE_MAPPER||The function selects a waveform-audio output device capable of playing the given format.|
Pointer to a WAVEFORMATEX structure that identifies the format of the waveform-audio data to be sent to the device. You can free this structure immediately after passing it to waveOutOpen.
Specifies the callback mechanism. The value must be one of the following:
- A pointer to a callback function. For the function signature, see waveOutProc.
- A handle to a window.
- A thread identifier.
- A handle to an event.
- The value NULL.
User-instance data passed to the callback mechanism. This parameter is not used with the window callback mechanism.
Flags for opening the device. The following values are defined.
|CALLBACK_EVENT||The dwCallback parameter is an event handle.|
|CALLBACK_FUNCTION||The dwCallback parameter is a callback procedure address.|
|CALLBACK_NULL||No callback mechanism. This is the default setting.|
|CALLBACK_THREAD||The dwCallback parameter is a thread identifier.|
|CALLBACK_WINDOW||The dwCallback parameter is a window handle.|
|WAVE_ALLOWSYNC||If this flag is specified, a synchronous waveform-audio device can be opened. If this flag is not specified while opening a synchronous driver, the device will fail to open.|
If this flag is specified and the uDeviceID parameter is WAVE_MAPPER, the function opens the default communication device.
This flag applies only when uDeviceID equals WAVE_MAPPER.
Note Requires Windows 7
|WAVE_FORMAT_DIRECT||If this flag is specified, the ACM driver does not perform conversions on the audio data.|
|WAVE_FORMAT_QUERY||If this flag is specified, waveOutOpen queries the device to determine if it supports the given format, but the device is not actually opened.|
|WAVE_MAPPED||If this flag is specified, the uDeviceID parameter specifies a waveform-audio device to be mapped to by the wave mapper.|
Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.
||Specified resource is already allocated.|
||Specified device identifier is out of range.|
||No device driver is present.|
||Unable to allocate or lock memory.|
||Attempted to open with an unsupported waveform-audio format.|
||The device is synchronous but waveOutOpen was called without using the WAVE_ALLOWSYNC flag.|
Use the waveOutGetNumDevs function to determine the number of waveform-audio output devices present in the system. If the value specified by the uDeviceID parameter is a device identifier, it can vary from zero to one less than the number of devices present. The WAVE_MAPPER constant can also be used as a device identifier.
The structure pointed to by pwfx can be extended to include type-specific information for certain data formats. For example, for PCM data, an extra UINT is added to specify the number of bits per sample. Use the PCMWAVEFORMAT structure in this case. For all other waveform-audio formats, use the WAVEFORMATEX structure to specify the length of the additional data.
If you choose to have a window or thread receive callback information, the following messages are sent to the window procedure function to indicate the progress of waveform-audio output: MM_WOM_OPEN, MM_WOM_CLOSE, and MM_WOM_DONE.
If fdwOpen contains the CALLBACK_FUNCTION flag, dwCallback is a pointer to a callback function. For the function signature, see waveOutProc. The uMsg parameter of the callback indicates the progress of the audio output:
If fdwOpen contains the CALLBACK_EVENT flag, dwCallback is a handle to an event. The event is signaled whenever the state of the waveform buffer changes. The application can use WaitForSingleObject or WaitForMultipleObjects to wait for the event. When the event is signaled, you can get the current state of the waveform buffer by checking the dwFlags member of the WAVEHDR structure. (See waveOutPrepareHeader.)
If fdwOpen contains the CALLBACK_NULL flag, dwCallback must be NULL. In that case, no callback mechanism is used.
|Minimum supported client||Windows 2000 Professional [desktop apps only]|
|Minimum supported server||Windows 2000 Server [desktop apps only]|
|Header||mmeapi.h (include Windows.h)|