The monitor command specifies the presentation source. (The default presentation source is the workspace.) Switching the presentation source switches all audio and video streams in the source. Digital-video devices recognize this command.

To send this command, call the mciSendString function with the lpszCommand parameter set as follows.

  TEXT("monitor %s %s %s"), 



Identifier of an MCI device. This identifier or alias is assigned when the device is opened.


One or more of the following flags.

Value Meaning
file Specifies that the workspace is the presentation source. This is the default source.
input Specifies that the external input is the presentation source. If a play command is in progress, it is first paused. If setvideo is "on", this flag displays a default hidden window. Devices might limit what other device instances can do while monitoring input.
method method When used with monitor "input", this flag selects the method of monitoring. The method is either "pre", "post", or "direct". Direct monitoring requests that the device be configured for optimum display quality during monitoring. The direct monitoring method might be incompatible with motion video recording.

Pre- and post-monitoring allow motion video recording. Pre-monitoring shows the external input prior to compression, while post-monitoring shows the external input after compression. Typically, different monitoring methods have different hardware implications. The default monitoring method is selected by the device.


Can be "wait", "notify", "test", or a combination of these. For more information about these flags, see The Wait, Notify, and Test Flags.

Return Values

Returns zero if successful or an error otherwise.


The presentation source automatically switches to the workspace after a play, step, pause, cue "output", or seek command. The record command does not automatically switch presentation sources, which gives your application the option of not showing video while it is being recorded.


  Windows NT/2000/XP: Included in Windows NT 3.1 and later.
  Windows 95/98/Me: Included in Windows 95 and later.

See Also

MCI, MCI Command Strings, cue, pause, play, record, seek, step