[VBnet FAQ] mciSendString: Eject Media from a CD-ROM


	Visual Basic FAQ mciSendString: Eject Media from a CD-ROM

Posted:	Sunday June 21, 1998
Updated:	Monday December 26, 2011

Applies to:	VB4-32, VB5, VB6

Prerequisites

None.

mciSendString provides several commands via the mciSendString API. Perhaps one of the most frequently requested is ejecting (and loading) a CD automatically from code. Using a single line call, this is easily achieved.

BAS Module Code

None.

Form Code

Add a command button to a form along with the following code:

Option Explicit

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' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Private Declare Function mciSendString Lib "winmm.dll" _
   Alias "mciSendStringA" _
  (ByVal lpstrCommand As String, _
   ByVal lpstrReturnString As String, _
   ByVal uReturnLength As Long, _
   ByVal hwndCallback As Long) As Long
   
   
Private Sub Command1_Click()

   Call mciSendString("Set CDAudio Door Open Wait", 0&, 0&, 0&)

End Sub

Comments

Pretty simple. The API takes a pre-defined string, and executes it. The return value is 0 if successful, or an error code if not. And unlike its sister the mciSendCommand API, there is no need to obtain a handle to the device. However, on systems with multiple CD-ROMs installed, this may be the only method to assure the correct CD is ejected. But since I have only one here, I can't test this out.

The following table, from the MSDN reference, lists device types that recognize the set command and the flags used by each type:

cdaudio	audio all off audio all on audio left off audio left on audio right off audio right on	door closed door open time format milliseconds time format msf time format tmsf
digitalvideo	audio all off audio all on audio left off audio left on audio right off audio right on door closed door open	file format format seek exactly on seek exactly off speed factor still file format format time format frames time format milliseconds video off video on
overlay	audio all off audio all on audio left off audio left on audio right off	audio right on door closed door open video off video on
sequencer	audio all off audio all on audio left off audio left on audio right off audio right on door closed door open master MIDI master none master SMPTE offset time	port mapper port none port port_number slave file slave MIDI slave none slave SMPTE tempo tempo_value time format milliseconds time format SMPTE fps time format SMPTE 30 drop time format song pointer
vcr	assemble record on assemble record off audio all off audio all on audio left off audio left on audio right off audio right on clock time counter format counter value door closed door open index counter index date index time index timecode length duration pause timeout postroll duration - duration	power on power off preroll duration duration record format SP record format LP record format EP speed factor time format frames time format hms time format milliseconds time format msf time format SMPTE fps time format SMPTE 30 drop time format tmsf time mode counter time mode detect time mode timecode tracking plus tracking minus tracking reset
videodisc	audio all off audio all on audio left off audio left on audio right off audio right on door closed	door open time format frames time format hms time format milliseconds time format track video off video on
waveaudio	alignment integer any input any output audio all off audio all on audio left off audio left on audio right off audio right on bitspersample bit_count bytespersec byte_rate	channels channel_count door closed door open format tag pcm format tag tag input integer output integer samplespersec integer time format bytes time format milliseconds time format samples

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