This message is sent to begin playback.

ulParam1 (ULONG)

This parameter can contain any of the following flags:

MCI_NOTIFY

A notification message will be posted to the window specified in the hwndCallback parameter of the data structure pointed to by the pParam2 parameter. The notification will be posted when the action indicated by this message is completed or when an error occurs.
MCI_WAIT
Control is not to be returned until the action indicated by this message is completed or an error occurs.
MCI_FROM
This flag indicates that the ulFrom field of the play data structure is to be used as the starting position for the play operation. If this flag is not set, the current position is assumed.
MCI_TO
This flag indicates that the ulTo field of the play data structure is to be used as the ending position of the play operation. If this flag is not set, playback continues to the end of the media or segment, as defined by the device. If the to position is beyond the end of the media or segment, an MCIERR_OUTOFRANGE error is returned.
Digital Video Extensions

The following additional flags apply to digital video devices:

MCI_DGV_PLAY_SPEED

This flag adds a speed parameter. The units are specified by the currently set speed format. The speed value is in the ulSpeed field in the play data structure.
MCI_DGV_PLAY_REVERSE
This flag specifies to play in reverse.
MCI_DGV_PLAY_FAST
This flag specifies to play at the fast rate (twice the normal recorded playback rate).
MCI_DGV_PLAY_SCAN
Specifies to scan. Scan usually means to play as quickly as possible, with audio disabled.
MCI_DGV_PLAY_SLOW
This flag specifies to play at the slow rate (half the normal recorded playback rate).
MCI_DGV_PLAY_REPEAT
This flag specifies that the play operation be repeated until the command is superseded by another command or aborted.

This flag is not supported by the digital video MCD.

Videodisc Extensions

The following additional flags apply to videodisc devices. MCI_VD_PLAY_REVERSE and MCI_VD_PLAY_SCAN are mutually exclusive. Only one of the other flags is allowed with this message.

MCI_VD_PLAY_REVERSE

This flag specifies to play in reverse.
MCI_VD_PLAY_FAST
This flag specifies to play at the fast rate.
MCI_VD_PLAY_SCAN
This flag specifies to scan. Scan usually means to play as fast as possible, with audio disabled.
MCI_VD_PLAY_SPEED
This flag adds a speed parameter. The units are specified by the currently set speed format. The speed value is in the ulSpeed field of the play data structure.
MCI_VD_PLAY_SLOW
This flag specifies to play at the slow rate.

pParam2 (PMCI_PLAY_PARMS)

A pointer to an MCI_PLAY_PARMS data structure. Devices with extended command sets might replace this pointer with a pointer to a device-specific data structure as follows:

PMCI_DGV_PLAY_PARMS

A pointer to an MCI_DGV_PLAY_PARMS data structure.
PMCI_VD_PLAY_PARMS
A pointer to an MCI_VD_PLAY_PARMS data structure.

rc (ULONG)

Return codes indicating success or type of failure:

MCIERR_SUCCESS

If the function succeeds, 0 is returned.
MCIERR_MEDIA_CHANGED
The required media has changed.
MCIERR_DEVICE_NOT_READY
The device is not ready.
MCIERR_INVALID_DEVICE_ID
The device id is not VALID.
MCIERR_INSTANCE_INACTIVE
The device is currently inactive. Issue MCI_ACQUIREDEVICE to make device context active.
MCIERR_MISSING_FLAG
A required flag is missing.
MCIERR_UNSUPPORTED_FLAG
Given flag is unsupported for this device.
MCIERR_INVALID_CALLBACK_HANDLE
Given callback handle is invalid.
MCIERR_UNSUPPORTED_FUNCTION
Unsupported function.
MCIERR_INVALID_FLAG
Flag (ulParam1) is invalid.
MCIERR_FLAGS_NOT_COMPATIBLE
Flags cannot be used together.
MCIERR_OUTOFRANGE
Units are out of range.
MCIERR_MISSING_PARAMETER
Required parameter is missing.
MCIERR_CHANNEL_OFF
Primary channel is off.

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