Win32 MCI API for playing media

Question

Hi all
We often see questions in here regarding how do I play so and so media. Very often I recommend the WIn32 MCI API. The following declarations for SendString etc. can play most media in Windows - you send it the device type, then the name of the file, then send the command to open the file, then the command to play the file etc.
Below in an example for playing two or more audio files (waves) simultaneously. I might add more about the Win32 MCI API later.
Allan


In a code module put the Win32 API declarations (such as):

Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

Public Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal dwError As Integer, ByVal lpstrBuffer As String, ByVal uLength As Integer) As Integer

Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Integer, ByVal hwndCallback As Integer) As Integer

Then in your program, you can play as many sounds as you like simulataneously using API calls such as:

ret = mciSendString("Open " & Chr(34) & FileName & Chr(34) & " alias audio", CStr(0), 0, 0)

ret = mciSendString("play audio", CStr(0), 0, 0)

ret = mciSendString("pause audio", CStr(0), 0, 0)

ret = mciSendString("resume audio", CStr(0), 0, 0)

ret = mciSendString("stop audio", CStr(0), 0, 0)

ret = mciSendString("close audio", CStr(0), 0, 0)

etc.etc.,
Points:
1) 'ret' is an integer (long in vb6) holding the return code: - 0 means success, non-zero is an appropriate MCI error code.
2) Use a different alias in mciSendString for each sound file - e.g. alias audio1, alias audio2, alias audio3, etc. - if you are playing multiple files on the same form (as it avoids clashes).
3) The MCI command set is a very rich one - see the MSDN documentation of the 100's of commands and permutations possible.
4) There are numerous Get and Set MCI commands for querying and setting various things - such as volume, balance, position in the file, status (i.e. playing, paused, stopped), etc.
5) You will be stepping out of the .Net environment and will be using the Win32 MCI API instead.

Answer 1

Win32 MCI API Device Types (taken from MSDN documentation):

Devices are considered to be of two types: simple and compound. Simple multimedia devices do not require a data file for playback. For example, when Videodisc and CD audio players are opened, you play, rewind, or forward through 'tracks'. Compound devices, however, require a data file for playback.

The following table lists some of the devices supported by the Multimedia control and the string required by the DeviceType 'property' to use the device. Those listing an accompanying file type are compound devices.

Device type                 String          File Type     Description
CD audio                  CDAudio                           CD audio player
Digital Audio Tape    DAT                                  Digital audio tape player
Digital video             DigitalVideo                      Digital video in a window (not GDI-based)
Other                       Other                               Undefined MCI device
Overlay                    Overlay                            Overlay device 
Scanner                   Scanner                            Image scanner
Sequencer               Sequencer     .mid            Musical Instrument Digital Interface  (MIDI) sequencer
Vcr                           VCR                                  Video cassette recorder or player
AVI                          AVIVideo        .avi             Audio Visual Interleaved video. 
Mpeg Video               MPEGVideo   .mpg          MPEG Video in its own window
Videodisc                Videodisc                          Videodisc player
Wave audio           Waveaudio      .wav           Wave device that plays digitized waveform files.

Answer 2

Typical MCI commands are:

Command		Description
Open		Opens a MCI device.
Close		Closes a MCI device.
Play		Plays a MCI device.
Pause	PAUSE or  RESUME	Pauses playing or recording.
Stop		Stops a MCI device.
Back		Steps backward through available tracks.
Step		Steps forward through available tracks.
Prev		Goes to the beginning of the current track using the Seek command. If executed within three seconds of the previous Prev command, goes to the beginning of the previous track or to the beginning of the first track if at the first track.
Next		Goes to the beginning of the next track (if at last track, goes to the beginning of the last track) using the Seek command.
Seek		Seeks track forward or backward.
Record		Records MCI device input.
Eject		Ejects Audio CD from CD drive (opens/closes door)
Save		Saves an open file.

Answer 3

Congratulations! The code you provided is very interesting...

---

Thank you!

Answer 4

Some examples (taken from a VB6 program I wote):

ret = mciSendString(ByVal "C:\Media\mymovie.avi type AVIVideo alias media", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "play media wait", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "stop media ", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "close media ", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)

-----------------------------------------------------------

ret = mciSendString(ByVal "open CDAudio alias media ", ByVal lpszReturnString,ByVal lstrlen(lpszReturnString), ByVal 0)
ret = mciSendString(ByVal "set media time format tmsf", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "play media from 1 to 2 wait", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "stop media ", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "close media ", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)

-----------------------------------------------------------
ret = mciSendString(ByVal "open C:\Media\halsorry.wav type WaveAudio alias media", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "play media wait", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)
ret = mciSendString(ByVal "close media", ByVal lpstrReturnString, ByVal Len(lpstrReturnString), ByVal 0)

-----------------------------------------------------------

Should be enough to start people off.
Allan

Note:
I defined lpstrReturnString as a fixed length of 128 chars in the vb6 prog.
In vb.Net you'd just do:

Dim lpstrReturnString As String = Space(128) 'or something like that

Answer 5

Angelos Sfakianakis said:

Congratulations! The code you provided is very interesting...

---

Thank you!

Your welcome - I'm surprised that .Net seemingly has no substitute for the MCI API declarations.
Allan

Answer 6

A quick example (took about 20 minutes to write) of using the WIn32 MCI API from vb.net to play mp3 files.

Create a new project, and double-click the blank form and paste the following code into the form, modify the path in the code to your Mp3s, and run it.
Select an mp3 file from the drop-down combo, click the Open button, then the play button. Note the file has to be closed beore the Exit button is active.
Please note it's just a bit of quick and ready code to play mp3s to illustrate playing Mp3s using the Win32 MCI API. A lot of work would be needed to make it a really useful and robust Mp3 player.
Allan

Imports System.Windows.Forms

Public Class Form1

Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

Public Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal dwError As Integer, ByVal lpstrBuffer As String, ByVal uLength As Integer) As Integer

Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Integer, ByVal hwndCallback As Integer) As Integer

Dim btnExit As New Button

Dim cmbMP3 As New ComboBox

Dim lblMP3 As New Label

Dim btnOpen As New Button

Dim btnPlay As New Button

Dim btnStop As New Button

Dim btnClose As New Button

Dim Opened As Boolean = False

Dim Status As Boolean = False

Dim whatdir As String

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Me.DoubleBuffered = True

Me.Text = "Media Player"

Me.Width = 800

Me.Height = 480

Me.StartPosition = FormStartPosition.CenterScreen

btnExit = New Button With {.Text = "E&xit", .Width = 34, .Height = 29, .Top = Me.Height - 75, .Left = Me.Width - 65, .Anchor = AnchorStyles.Right + AnchorStyles.Bottom}

cmbMP3 = New ComboBox With {.Text = "", .Width = 600, .Height = 100, .Top = 100, .Left = 50}

lblMP3 = New Label With {.Text = "", .Width = 600, .Height = 100, .Top = 70, .Left = 50}

btnOpen = New Button With {.Text = "&Open", .Width = 50, .Height = 29, .Top = 200, .Left = 50, .Enabled = False}

btnPlay = New Button With {.Text = "&Play", .Width = 50, .Height = 29, .Top = 200, .Left = 100, .Enabled = False}

btnStop = New Button With {.Text = "&Stop", .Width = 50, .Height = 29, .Top = 200, .Left = 150, .Enabled = False}

btnClose = New Button With {.Text = "&Close", .Width = 50, .Height = 29, .Top = 200, .Left = 200, .Enabled = False}

Me.Controls.Add(btnExit)

AddHandler btnExit.Click, AddressOf btnExit_Click

Me.Controls.Add(btnOpen)

AddHandler btnOpen.Click, AddressOf btnOpen_Click

Me.Controls.Add(btnPlay)

AddHandler btnPlay.Click, AddressOf btnPlay_Click

Me.Controls.Add(btnStop)

AddHandler btnStop.Click, AddressOf btnStop_Click

Me.Controls.Add(btnClose)

AddHandler btnClose.Click, AddressOf btnClose_Click

Me.Controls.Add(cmbMP3)

AddHandler cmbMP3.Click, AddressOf cmbMP3_click

AddHandler cmbMP3.TextChanged, AddressOf cmbMP3_TextChanged

Call populateCmbMp3("C:\mp3s")

Me.Controls.Add(lblMP3)

End Sub

Private Sub btnExit_Click()

Me.Close()

Application.Exit()

End Sub

Private Sub cmbMP3_click()

Dim itemtext As String

itemtext = cmbMP3.Text

lblMP3.Text = itemtext

lblMP3.Refresh()

End Sub

Private Sub cmbMP3_TextChanged()

Dim itemtext As String

itemtext = cmbMP3.Text

lblMP3.Text = itemtext

lblMP3.Refresh()

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

End Sub

Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize

If Me.Width < 600 Then

Me.Width = 600

End If

If Me.Height < 400 Then

Me.Height = 400

End If

Me.Refresh()

End Sub

Private Sub populateCmbMp3(ByVal Filepath)

Dim FoundFile As String

Dim FileName As String

' Clear the list box.

Me.cmbMP3.Items.Clear()

' Add each file in the Documents folder to list box.

For Each FoundFile In My.Computer.FileSystem.GetFiles( _

Filepath, FileIO.SearchOption.SearchAllSubDirectories)

'Get directory

FileName = My.Computer.FileSystem.GetDirectoryInfo(FoundFile).ToString 'Add full path to the combo box

' Note: if you want to add only the name of each found file to the combo box, uncomment next line ad modify open

' FileName = My.Computer.FileSystem.GetName(FoundFile)

If FileName.Substring(Len(FileName) - 4) = ".mp3" Then

Me.cmbMP3.Items.Add(FileName)

End If

Next

If Me.cmbMP3.Items.Count > 0 Then

Me.cmbMP3.SelectedIndex = 0

End If

End Sub

Private Sub btnOpen_Click()

Dim ret As Integer

If lblMP3.Text = "" Then

Exit Sub

End If

ret = mciSendString("Open " & Chr(34) & lblMP3.Text & Chr(34) & " alias audio", CStr(0), 0, 0)

If ret = 0 Then

Opened = True

btnOpen.Enabled = False

btnClose.Enabled = True

btnPlay.Enabled = True

btnStop.Enabled = True

cmbMP3.Enabled = False

btnExit.Enabled = False

Else

MsgBox("Error opening file")

Opened = False

btnOpen.Enabled = False

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

End If

End Sub

Private Sub btnPlay_Click()

Dim ret As Integer

If lblMP3.Text = "" Or Opened = False Then

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = True

Exit Sub

End If

ret = mciSendString("play audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error playing file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = False

End If

End Sub

Private Sub btnStop_Click()

Dim ret As Integer

If lblMP3.Text = "" And Opened = True Then

Exit Sub

End If

ret = mciSendString("stop audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error stopping file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = False

End If

End Sub

Private Sub btnClose_Click()

Dim ret As Integer

ret = mciSendString("close audio", CStr(0), 0, 0)

Opened = False

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

cmbMP3.Enabled = True

If ret <> 0 Then

MsgBox("Error closing file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = False

cmbMP3.Enabled = False

End If

End Sub

End Class

Answer 7

Hi all
I've just spent the last couple of hours tidying up the Win32 MCI API mp3 player - added some more controls and a bit more functionality and made it a lot better. It should suffice now as a kind of blueprint for using the Win32 MCI API from vb.net.
Just copy and paste the following code into a blank form on a new project. Change the path in the code to where your MP3s are and run the program. Everything is done for you - it will create the controls etc.
Allan

Dam the listing is now too big - just a sec while I post it in a separate post or two.

Answer 8

The listing part one:

Option Strict On

Option Explicit On

Option Infer On

Imports System.Windows.Forms

Public Class Form1

Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

Public Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal dwError As Integer, ByVal lpstrBuffer As String, ByVal uLength As Integer) As Integer

Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Integer, ByVal hwndCallback As Integer) As Integer

Dim btnExit As New Button

Dim cmbMP3 As New ComboBox

Dim lblMP3 As New Label

Dim btnOpen As New Button

Dim btnPlay As New Button

Dim btnPause As New Button

Dim btnResume As New Button

Dim btnMute As New Button

Dim btnStop As New Button

Dim btnClose As New Button

Dim playlist As New ListBox

Dim lblmutelight As New Label

Dim lblMute As New Label

Dim lblVolume As New Label

Dim lblVolumeValue As New Label

Dim sldVolume As New HScrollBar

Dim Opened As Boolean = False

Dim Status As Boolean = False

Dim muted As Boolean = False

Dim whatdir As String

Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing

Dim reply As Integer, ret As Integer

reply = MsgBox("Are you sure that you want to quit?", MsgBoxStyle.YesNoCancel Or MsgBoxStyle.Question)

If reply = vbYes Then

'Note: - we are not really concerned if the file is already stopped and/or closed or not (i.e. if ret = true or false on on return)

'since we are telling the MCI API to do it anyways so it's safe to exit

ret = mciSendString("stop audio", CStr(0), 0, 0) 'Just to be on the safe side

ret = mciSendString("close audio", CStr(0), 0, 0) 'Just to be on the safe side

sldVolume.Enabled = False 'Just to be safe

muted = False 'Just to be safe

lblmutelight.BackColor = Color.Black 'Just to be safe

e.Cancel = False 'Application should now end gracefully here

Else

e.Cancel = True

End If

End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim ret As Integer

Me.DoubleBuffered = True

Me.Text = "Media Player"

Me.Width = 800

Me.Height = 480

Me.StartPosition = FormStartPosition.CenterScreen

btnExit = New Button With {.Text = "E&xit", .Width = 34, .Height = 29, .Top = 400, .Left = Me.Width - 65, .Anchor = AnchorStyles.Right Or AnchorStyles.Bottom, .Enabled = True}

cmbMP3 = New ComboBox With {.Text = "", .Width = 600, .Height = 20, .Top = 50, .Left = 50}

lblMP3 = New Label With {.Text = "", .Width = 600, .Height = 20, .Top = 30, .Left = 50}

btnOpen = New Button With {.Text = "&Open", .Width = 70, .Height = 29, .Top = 400, .Left = 50, .Enabled = False}

btnPlay = New Button With {.Text = "&Play", .Width = 70, .Height = 29, .Top = 400, .Left = 120, .Enabled = False}

btnPause = New Button With {.Text = "P&ause", .Width = 70, .Height = 29, .Top = 400, .Left = 190, .Enabled = False}

btnResume = New Button With {.Text = "&Resume", .Width = 70, .Height = 29, .Top = 400, .Left = 260, .Enabled = False}

btnStop = New Button With {.Text = "&Stop", .Width = 70, .Height = 29, .Top = 400, .Left = 330, .Enabled = False}

btnMute = New Button With {.Text = "&Mute", .Width = 70, .Height = 29, .Top = 400, .Left = 400, .Enabled = False}

btnClose = New Button With {.Text = "&Close", .Width = 70, .Height = 29, .Top = 400, .Left = 480, .Enabled = False}

playlist = New ListBox With {.Text = "", .Width = 600, .Height = 300, .Top = 90, .Left = 50}

lblmutelight = New Label With {.Text = "", .Width = 10, .Height = 10, .Top = 410, .Left = 560, .BorderStyle = BorderStyle.Fixed3D, .BackColor = Color.Black}

lblMute = New Label With {.Text = "Muted:", .Width = 40, .Height = 20, .Top = 390, .Left = 550, .BorderStyle = BorderStyle.None}

sldVolume = New HScrollBar With {.Width = 125, .Height = 20, .Top = 410, .Left = 600, .Minimum = 0, .Maximum = 1000, .Value = 500, .Enabled = False}

lblVolume = New Label With {.Text = "Volume:", .Width = 50, .Height = 20, .Top = 390, .Left = 600, .BorderStyle = BorderStyle.None}

lblVolumeValue = New Label With {.Text = "500", .Width = 35, .Height = 20, .Top = 390, .Left = 650, .BorderStyle = BorderStyle.FixedSingle, .TextAlign = ContentAlignment.MiddleRight}

Me.Controls.Add(btnExit)

AddHandler btnExit.Click, AddressOf btnExit_Click

Me.Controls.Add(btnOpen)

AddHandler btnOpen.Click, AddressOf btnOpen_Click

Me.Controls.Add(btnPlay)

AddHandler btnPlay.Click, AddressOf btnPlay_Click

Me.Controls.Add(btnPause)

AddHandler btnPause.Click, AddressOf btnPause_Click

Me.Controls.Add(btnResume)

AddHandler btnResume.Click, AddressOf btnResume_click

Me.Controls.Add(btnMute)

AddHandler btnMute.Click, AddressOf btnMute_click

Me.Controls.Add(btnStop)

AddHandler btnStop.Click, AddressOf btnStop_Click

Me.Controls.Add(btnClose)

AddHandler btnClose.Click, AddressOf btnClose_Click

Me.Controls.Add(cmbMP3)

AddHandler cmbMP3.Click, AddressOf cmbMP3_click

AddHandler cmbMP3.TextChanged, AddressOf cmbMP3_TextChanged

Call populateCmbMp3("C:\mp3s")

Me.Controls.Add(lblMP3)

Me.Controls.Add(lblmutelight)

Me.Controls.Add(lblMute)

Me.Controls.Add(playlist)

AddHandler playlist.Click, AddressOf playlist_click

AddHandler playlist.TextChanged, AddressOf playlist_TextChanged

Me.Controls.Add(sldVolume)

Me.Controls.Add(lblVolume)

Me.Controls.Add(lblVolumeValue)

AddHandler sldVolume.Scroll, AddressOf sldVolume_Scroll

muted = False

lblmutelight.BackColor = Color.Black

ret = mciSendString("setaudio audio volume to " & CStr(sldVolume.Value), CStr(0), 0, 0) 'We assume that this ret will be zero

End Sub

Private Sub sldVolume_Scroll(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If Opened = False Then

Exit Sub 'Nothing open

End If

ret = mciSendString("setaudio audio volume to " & CStr(sldVolume.Value), CStr(0), 0, 0) 'We assume that this ret will be zero

If ret <> 0 Then

MsgBox("Unable to set volume")

Else

lblVolumeValue.Text = CStr(sldVolume.Value)

End If

End Sub

Answer 9

The listing part two:

Private Sub btnExit_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Application.Exit()

End Sub

Private Sub cmbMP3_click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim itemtext As String

Dim ret As Integer

'Note: - we are not really concerned if the file is already stopped and/or closed or not (i.e. if ret = true or false on on return)

'since we are telling the MCI API to do it anyways so it's safe to exit

ret = mciSendString("stop audio", CStr(0), 0, 0) 'Just to be on the safe side

ret = mciSendString("close audio", CStr(0), 0, 0) 'Just to be on the safe side

muted = False

lblmutelight.BackColor = Color.Black

itemtext = cmbMP3.Text

lblMP3.Text = itemtext

lblMP3.Refresh()

playlist.Text = itemtext

playlist.Refresh()

End Sub

Private Sub cmbMP3_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs)

Dim itemtext As String

Dim ret As Integer

'Note: - we are not really concerned if the file is already stopped and/or closed or not (i.e. if ret = true or false on on return)

'since we are telling the MCI API to do it anyways so it's safe to exit

ret = mciSendString("stop audio", CStr(0), 0, 0) 'Just to be on the safe side

ret = mciSendString("close audio", CStr(0), 0, 0) 'Just to be on the safe side

muted = False

lblmutelight.BackColor = Color.Black

itemtext = cmbMP3.Text

lblMP3.Text = itemtext

lblMP3.Refresh()

playlist.Text = itemtext

playlist.Refresh()

btnOpen.Enabled = True

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnClose.Enabled = False

End Sub

Private Sub playlist_click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim itemtext As String

Dim ret As Integer

'Note: - we are not really concerned if the file is already stopped and/or closed or not (i.e. if ret = true or false on on return)

'since we are telling the MCI API to do it anyways so it's safe to exit

ret = mciSendString("stop audio", CStr(0), 0, 0) 'Just to be on the safe side

ret = mciSendString("close audio", CStr(0), 0, 0) 'Just to be on the safe side

muted = False

lblmutelight.BackColor = Color.Black

itemtext = playlist.Text

playlist.Text = itemtext

playlist.Refresh()

lblMP3.Text = itemtext

lblMP3.Refresh()

cmbMP3.Text = itemtext

cmbMP3.Refresh()

End Sub

Private Sub playlist_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs)

Dim itemtext As String

Dim ret As Integer

'Note: - we are not really concerned if the file is already stopped and/or closed or not (i.e. if ret = true or false on on return)

'since we are telling the MCI API to do it anyways so it's safe to exit

ret = mciSendString("stop audio", CStr(0), 0, 0) 'Just to be on the safe side

ret = mciSendString("close audio", CStr(0), 0, 0) 'Just to be on the safe side

muted = False

lblmutelight.BackColor = Color.Black

itemtext = playlist.Text

playlist.Text = itemtext

playlist.Refresh()

lblMP3.Text = itemtext

lblMP3.Refresh()

cmbMP3.Text = itemtext

cmbMP3.Refresh()

btnOpen.Enabled = True

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnClose.Enabled = False

End Sub

Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize

If Me.Width < 600 Then

Me.Width = 600

End If

If Me.Height < 400 Then

Me.Height = 400

End If

Me.Refresh()

End Sub

Private Sub populateCmbMp3(ByVal Filepath As String)

Dim FoundFile As String

Dim FileName As String

' Clear the list box.

Me.cmbMP3.Items.Clear()

Me.playlist.Items.Clear()

Me.playlist.BeginUpdate()

' Add each file in the Documents folder to list box.

For Each FoundFile In My.Computer.FileSystem.GetFiles(Filepath.ToString, FileIO.SearchOption.SearchAllSubDirectories)

'Get directory

FileName = My.Computer.FileSystem.GetDirectoryInfo(FoundFile).ToString 'Add full path to the combo box

' Note: if you want to add only the name of each found file to the combo box, uncomment the next line and modify the open routine

' FileName = My.Computer.FileSystem.GetName(FoundFile)

If FileName.Substring(Len(FileName) - 4) = ".mp3" Then

Me.cmbMP3.Items.Add(FileName)

Me.playlist.Items.Add(FileName)

End If

Next

Me.playlist.EndUpdate()

If Me.cmbMP3.Items.Count > 0 Then

Me.cmbMP3.SelectedIndex = 0

Me.playlist.SelectedIndex = 0

End If

End Sub

Private Sub btnOpen_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" Then

Exit Sub

End If

ret = mciSendString("Open " & Chr(34) & lblMP3.Text & Chr(34) & " alias audio", CStr(0), 0, 0)

If ret = 0 Then

Opened = True

btnOpen.Enabled = False

btnPlay.Enabled = True

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnClose.Enabled = True

sldVolume.Enabled = True

Else

MsgBox("Error opening file")

Opened = False

btnOpen.Enabled = False

btnClose.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

sldVolume.Enabled = False

End If

End Sub

Private Sub btnPlay_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" Or Opened = False Then

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnMute.Enabled = False

lblmutelight.BackColor = Color.Black

btnStop.Enabled = True

Exit Sub

End If

ret = mciSendString("play audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error playing file")

btnOpen.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnMute.Enabled = False

btnStop.Enabled = False

btnClose.Enabled = True

btnExit.Enabled = True

Else

'Playing ok

btnOpen.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = True

btnResume.Enabled = False

btnMute.Enabled = True

btnStop.Enabled = True

btnClose.Enabled = True

btnExit.Enabled = True

End If

End Sub

Private Sub btnPause_click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" Or Opened = False Then

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = True

Exit Sub

End If

ret = mciSendString("pause audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error pausing file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

Else

'Paused ok

btnOpen.Enabled = False

btnPlay.Enabled = True

btnPause.Enabled = False

btnResume.Enabled = True

btnStop.Enabled = True

btnClose.Enabled = True

End If

End Sub

Private Sub btnResume_click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" Or Opened = False Then

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = True

Exit Sub

End If

ret = mciSendString("resume audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error resuming file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

Else

'Resumed ok

btnOpen.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = True

btnResume.Enabled = False

btnStop.Enabled = True

btnClose.Enabled = True

End If

End Sub

Answer 10

The listing part three (hopefully the last bit):
Allan

Private Sub btnMute_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" And Opened = True Then

Exit Sub

End If

If muted = False Then

ret = mciSendString("setaudio audio off", CStr(0), 0, 0)

lblmutelight.BackColor = Color.Green

muted = True

Else

ret = mciSendString("setaudio audio on", CStr(0), 0, 0)

lblmutelight.BackColor = Color.Black

5:          muted = False

End If

If ret <> 0 Then

MsgBox("Error muting file")

btnMute.Enabled = False

lblmutelight.BackColor = Color.Black

Else

'Muted/Unmuted ok

btnMute.Enabled = True

End If

End Sub

Private Sub btnStop_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

If lblMP3.Text = "" And Opened = True Then

Exit Sub

End If

ret = mciSendString("stop audio", CStr(0), 0, 0)

If ret <> 0 Then

MsgBox("Error stopping file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

Else

'Stopped ok

btnOpen.Enabled = False

btnPlay.Enabled = True

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnClose.Enabled = True

End If

End Sub

Private Sub btnClose_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Dim ret As Integer

ret = mciSendString("close audio", CStr(0), 0, 0)

Opened = False

btnOpen.Enabled = True

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnMute.Enabled = False

muted = False

lblmutelight.BackColor = Color.Black

btnStop.Enabled = False

btnClose.Enabled = False

btnExit.Enabled = True

cmbMP3.Enabled = True

sldVolume.Enabled = False

If ret <> 0 Then

MsgBox("Error closing file")

btnOpen.Enabled = True

btnClose.Enabled = False

btnPlay.Enabled = False

btnPause.Enabled = False

btnResume.Enabled = False

btnStop.Enabled = False

btnExit.Enabled = True

btnMute.Enabled = False

lblmutelight.BackColor = Color.Black

cmbMP3.Enabled = False

sldVolume.Enabled = False

End If

End Sub

End Class

Answer 11

Thank you so much for this, it's a great help.

I was using DirectX to play audio, but I now need to do much more complicated things, and I'd been struggling though MCI, so its good to see it clearly laid out here.

One thing that's foxing me at the moment though is:

Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

Because what I've been trying to do, is select which soundcard audio should be played though. True, I can do it with DirectSound, and select which one of the four (!) soundcards in my system with something like:

        SoundDevice = New Device(devList(ComboBox1.SelectedIndex).DriverGuid)
        SoundDevice.SetCooperativeLevel(Me.Handle, CooperativeLevel.Priority)
        Buff = New SecondaryBuffer(soundfile, BuffDesc, SoundDevice)
        Buff.Play(0, BufferPlayFlags.Default)

which all works fine, but I'm struggling to do it with mci in VB.NET.

Now http://support.microsoft.com/kb/180032 makes it clear how to use mciSendCommand to change the soundcard. Except, of course, things in the VB world have moved on. So it no longer works.

I've changed the types to Structures of course, as in:

    Public Const MCI_SET As Long = &H80D
    Public Const MCI_WAVE_OUTPUT As Long = &H800000

    Public Structure MCI_WAVE_SET_PARMS
        Public dwCallback As Integer
        Public dwTimeFormat As Integer
        Public dwAudio As Integer
        Public wInput As Integer
        Public wOutput As Integer
        Public wFormatTag As Integer
        Public wReserved2 As Integer
        Public nChannels As Integer
        Public wReserved3 As Integer
        Public nSamplesPerSec As Long
        Public nAvgBytesPerSec As Long
        Public nBlockAlign As Integer
        Public wReserved4 As Integer
        Public wBitsPerSample As Integer
        Public wReserved5 As Integer
    End Structure

But then when I try and change the soundcard with something simple like:

        fileName = "C:\PFM.wav"
        retVal = mciSendString("Open " & Chr(34) & fileName & Chr(34) & " alias oursong", CStr(0), 0, 0)
        wDeviceID = mciGetDeviceID("oursong")
        Dim parms As MCI_WAVE_SET_PARMS
        parms.wOutput = 1
        retVal = mciSendCommand(wDeviceID, MCI_SET, MCI_WAVE_OUTPUT, parms)

The whole thing falls over if I leave mciSendCommand as
Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

It does however run if I change it to:
Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As MCI_WAVE_SET_PARMS) As Integer

But then it doesn't change the soundcard.

So... could you help me... how does mciSendCommand work to achieve this?

Answer 12

Hi Lorks
You are right - selecting the soundcard appears to be a pain in the .... in vb.net

I tried thw following:

Public Class Form1

Public Declare Function waveOutGetNumDevs Lib "winmm" () As Integer

Public Declare Function mciSendCommand Lib "winmm.dll" Alias "mciSendCommandA" (ByVal wDeviceID As Integer, ByVal uMessage As String, ByVal dwParam1 As Integer, ByVal dwParam2 As Object) As Integer

Public Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal dwError As Integer, ByVal lpstrBuffer As String, ByVal uLength As Integer) As Integer

Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Integer, ByVal hwndCallback As Integer) As Integer

Public Declare Function mciGetDeviceID Lib "winmm.dll" Alias "mciGetDeviceIDA" (ByVal lpstrName As String) As Integer

Dim ofd As OpenFileDialog

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim i As Integer

i = waveOutGetNumDevs()

If i > 0 Then         ' There is at least one device.

MsgBox("You Can Play Wave Data - you have " & i & "Devices")

Else

MsgBox("Cannot Play Wave Data")

End If

End Sub

Public Const MMSYSERR_NOERROR = 0

Public Const MCI_SET = &H80D

Public Const MCI_WAVE_OUTPUT = &H800000

Public Structure MCI_WAVE_SET_PARMS

Dim dwCallback As Integer

Dim dwTimeFormat As Integer

Dim dwAudio As Integer

Dim wInput As Integer

Dim wOutput As Integer

Dim wFormatTag As Short

Dim wReserved2 As Short

Dim nChannels As Short

Dim wReserved3 As Short

Dim nSamplesPerSec As Integer

Dim nAvgBytesPerSec As Integer

Dim nBlockAlign As Short

Dim wReserved4 As Short

Dim wBitsPerSample As Short

Dim wReserved5 As Short

End Structure

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

Dim parms As MCI_WAVE_SET_PARMS

Dim wDeviceID As Integer

Dim ret As Integer

' Specify the soundcard. This specifies the soundcard with a deviceID

' of 0. If you have a single soundcard, then this will open it. If you

' have multiple soundcards, the deviceIDs will be 0, 1, 2, etc.

parms.wOutput = 0

wDeviceID = mciGetDeviceID("waveaudio") 'Can't use alias cos we not opened file yet

' Send the MCI command to set the output device.

ret = mciSendCommand(wDeviceID, MCI_SET, MCI_WAVE_OUTPUT, parms)

If (ret <> MMSYSERR_NOERROR) Then

' The command failed.

Stop

End If

If ofd.ShowDialog Then

ret = mciSendString("Open " & Chr(34) & ofd.FileName & Chr(34) & " alias audio", CStr(0), 0, 0)

ret = mciSendString("Open audio", CStr(0), 0, 0)

End If

End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

Dim ret As Integer

ret = mciSendString("Close audio", CStr(0), 0, 0)

Application.Exit()

End Sub

End Class

Ok it gets the number of devices ok - but trying to select one throws an error. I guess we're just going to have to stick with the default sound device using MCI under Net :(
Allan