This message provides support for setting and retrieving system-wide audio control settings.

ulParam1 (ULONG)

This parameter can contain any of the following flags:

Note: The MCI_NOTIFY flag is not valid for this message.

MCI_WAIT

Control is not to be returned until the action indicated by this message is completed or an error occurs.
MCI_QUERYCURRENTSETTING
This flag queries the current setting of the indicated audio attribute.
MCI_QUERYSAVEDSETTING
This flag queries the saved setting of the indicated audio attribute.
MCI_SAVESETTING
This flag saves the current setting of the indicated audio attribute to the INI file.
MCI_MASTERVOL
This flag sets the system master volume level as a percentage. If a number greater than 100 is given then 100 will be used as the master volume setting and no error will be returned.
MCI_SPEAKERS
This flag sets the output to speakers.
MCI_HEADPHONES
This flag sets the output to headphones.
MCI_ON
This flag sets the output on or enabled. This flag must be used in conjunction with the MCI_SPEAKERS or MCI_HEADPHONES flag.
MCI_OFF
This flag sets output off or disabled. This flag must be used in conjunction with the MCI_SPEAKERS or MCI_HEADPHONES flag.

pParam2 (PMCI_MASTERAUDIO_PARMS)

A pointer to the MCI_MASTERAUDIO_PARMS data structure.

rc (ULONG)

Return codes indicating success or type of failure:

MCIERR_SUCCESS

If the function succeeds, 0 is returned.
MCIERR_MISSING_FLAG
A required flag is missing.
MCIERR_INVALID_FLAG
Flag (ulParam1) is invalid.
MCIERR_FLAGS_NOT_COMPATIBLE
Flags cannot be used together.
MCIERR_MISSING_PARAMETER
Required parameter is missing.

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