Classifications
of MCI Commands
MCI defines
four command classifications: system, required, basic, and extended. The
following list describes these command classifications:
System commands are
handled by MCI directly, rather than by the driver.
Required commands are
handled by the driver. All MCI drivers must support the required commands and
flags.
Basic commands (or
optional commands) are used by some devices. If a device supports a basic
command, it must support a defined set of flags for that command.
Extended commands are
specific to a device type or driver. Extended commands include commands, like
the put (MCI_PUT) and where (MCI_WHERE) commands for the digitalvideo
and overlay device types, and extensions to existing commands (like the
stretch flag of the status
(MCI_STATUS)
command for the overlay device type).
While system
and required commands are the minimum command set for any MCI driver, basic and
extended commands are not supported by all drivers. Your application can always
use system and required commands and their flags, but if it needs to use a
basic or extended command or flag, it should first query the driver by using
the capability
(MCI_GETDEVCAPS)
command. The following sections summarize the specific commands in each
category.
System Commands
MCI processes
the following system commands directly, rather than passing them to MCI
devices.
|
String |
Message |
Description |
|
break |
MCI_BREAK |
Sets a
break key for an MCI device. |
|
sysinfo |
MCI_SYSINFO |
Returns
information about MCI devices. |
Required Commands
All MCI
devices support the following required commands.
|
String |
Message |
Description |
|
capability |
MCI_GETDEVCAPS |
Obtains the
capabilities of a device. |
|
close |
MCI_CLOSE |
Closes the
device. |
|
info |
MCI_INFO |
Obtains
textual information from a device. |
|
open |
MCI_OPEN |
Initializes
the device. |
|
status |
MCI_STATUS |
Obtains
status information from the device. Some of this command s flags are not
required, so it is also a basic command. |
Devices must
also support a standard set of command flags for the required commands.
Basic Commands
The following
list summarizes the basic commands. The use of these commands by an MCI device
is optional.
|
String |
Message |
Description |
|
load |
MCI_LOAD |
Loads data
from a file. |
|
pause |
MCI_PAUSE |
Stops
playing. Playback or recording can be resumed at the current position. |
|
play |
MCI_PLAY |
Starts
transmitting output data. |
|
record |
MCI_RECORD |
Starts
recording input data. |
|
resume |
MCI_RESUME |
Resumes
playing or recording on a paused device. |
|
save |
MCI_SAVE |
Saves data
to a disk file. |
|
seek |
MCI_SEEK |
Seeks
forward or backward. |
|
set |
MCI_SET |
Sets the
operating state of the device. |
|
status |
MCI_STATUS |
Obtains
status information about the device. This is also a required command; since
some of its flags are not required, it is also listed here. (The optional
items support devices that use linear media with identifiable positions.) |
|
stop |
MCI_STOP |
Stops
playing. |
If a driver
supports a basic command, it must also support a standard set of flags for the
command.
Extended Commands
Some MCI
devices have additional commands, or they add flags to existing commands. While
some extended commands apply only to a specific device driver, most of them
apply to all drivers of a particular device type. For example, the command set
for the sequencer device type extends the set (MCI_SET) command to add time
formats that are needed by MIDI sequencers.
You should
not assume that the device supports the extended commands or flags. You can use
the capability
(MCI_GETDEVCAPS)
command to determine whether a specific feature is supported, and your
application should be ready to deal with unsupported command or unsupported
function return values.
The following
extended commands are available with the listed device types.
|
String |
Message |
Device
types |
Description |
|
configure |
MCI_CONFIGURE |
digitalvideo |
Displays a
configuration dialog box. |
|
cue |
MCI_CUE |
digitalvideo,
waveaudio |
Prepares
for playing or recording. |
|
delete |
MCI_DELETE |
waveaudio |
Deletes a
data segment from the media file. |
|
escape |
MCI_ESCAPE |
videodisc |
Sends
custom information to a device. |
|
freeze |
MCI_FREEZE |
overlay |
Disables
video acquisition to the frame buffer. |
|
put |
MCI_PUT |
digitalvideo,
overlay |
Defines the
source, destination, and frame windows. |
|
realize |
MCI_REALIZE |
digitalvideo |
Tells the
device to select and realize its palette into a device context of the
displayed window. |
|
setaudio |
MCI_SETAUDIO |
digitalvideo |
Sets audio
parameters for video. |
|
setvideo |
MCI_SETVIDEO |
digitalvideo |
Sets video
parameters. |
|
signal |
MCI_SIGNAL |
digitalvideo |
Identifies
a specified position with a signal. |
|
spin |
MCI_SPIN |
videodisc |
Starts the
disc spinning or stops the disc from spinning. |
|
step |
MCI_STEP |
digitalvideo,
videodisc |
Steps the
play one or more frames forward or reverse. |
|
unfreeze |
MCI_UNFREEZE |
overlay |
Enables the
frame buffer to acquire video data. |
|
update |
MCI_UPDATE |
digitalvideo |
Repaints
the current frame into the device context. |
|
where |
MCI_WHERE |
digitalvideo,
overlay |
Obtains the
rectangle specifying the source, destination, or frame area. |
|
window |
MCI_WINDOW |
digitalvideo,
overlay |
Controls
the display window. |