Sound doesn't play instantly...but wait for next operation to complete!!

Jayme65

I've a big interrogation concerning sound playback (WMP.lib)! This code should play a sound, then compute...but it computes then play the sound!

Class MainWindow
Dim writingPath As String = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) & "\_UI Sounds\"
Dim uiPlayer As New WMPLib.WindowsMediaPlayer
Private Sub MainWindow_Loaded(sender As Object, e As System.Windows.RoutedEventArgs) Handles Me.Loaded
RunTest()
End Sub
Private Sub RunTest()
Debug.Print("Started!")
uiPlayer.URL = writingPath & "son1.wav"
uiPlayer.controls.play()
'
Dim a As Integer = 0
For i As Integer = 0 To 999999999
a = i
Next
Debug.Print("Done!")
End Sub
End Class

I thought that I perhaps should run the sound in a thread to be sure that it's played by its own!? But this gives the same result

Imports System.Threading
Class MainWindow
Dim writingPath As String = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) & "\_UI Sounds\"
Dim uiPlayer As New WMPLib.WindowsMediaPlayer
Dim uiThread As Thread = New Thread(AddressOf PlayFile)
Private Sub MainWindow_Loaded(sender As Object, e As System.Windows.RoutedEventArgs) Handles Me.Loaded
RunTest()
End Sub
Private Sub RunTest()
uiThread = New Thread(AddressOf PlayFile)
uiThread.Start()
'
Debug.Print("Started!")
Dim a As Integer = 0
For i As Integer = 0 To 999999999
a = i
Next
Debug.Print("Done!")
End Sub
Private Sub PlayFile()
uiPlayer.URL = writingPath & "son1.wav"
uiPlayer.controls.play()
End Sub
End Class

How should I please proceed to hear my sound 'instantly'? What's my mistake? Thanks for your help!!

Richard Deeming

You've moved the wrong bit to the background thread.

Dim computeThread As Thread

Private Sub RunTest()
uiPlayer.URL = writingPath & "son1.wav"
uiPlayer.controls.play()

computeThread = new Thread(AddressOf Compute)
computeThread.Start()

End Sub

Private Sub Compute()
Debug.Print("Started!")

Dim a As Integer = 0
For i As Integer = 0 To 999999999
    a = i
Next

Debug.Print("Done!")

End Sub

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Bernhard Hiller

There are two possibilities to handle audio playing: one involves the message pump, the other one involves callback methods. I guess the WMPLib.WindowsMediaPlayer uses the message pump, and runs in the GUI thread of your application (as you explicitly call it uiPlayer). In that case, the messages can only be dealt with when the GUI of your apllication is ready to handle them. You may test that hypotheses by adding an Application.DoEvents() to your for loop (do not do that for production code): playing should now be possible.

Jayme65

It doesn't work better. Well, I had posted a simple code, hoping that it would be more clear for users to help me...but I'm afraid that I'd better post something very similar to my actual code..if I want the problem to be clearly exposed...and help you to try to help me ;-) There's a sound class, called UISound:

Imports System.Threading
Public Class UISound
Dim writingPath As String = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) & "\_UI Sounds\"
Public Shared WithEvents uiPlayer As New WMPLib.WindowsMediaPlayer
Public Shared uiThread As Thread = New Thread(AddressOf ReceiveSound)
Public Shared Sub ReceiveSound(ByVal url As String)
uiThread = New Thread(AddressOf PlayFile)
uiThread.Start(url)
End Sub
Public Shared Sub PlayFile(ByVal url As String)
uiPlayer.URL = writingPath & url
uiPlayer.controls.play()
End Sub
End Class

The sound is called from a sub in the MainWindow...which itself fires other subs in cascade that involve a heavy compute time:

Sub one()
UISound.ReceiveSound("sound1.wav")
Dim a As Integer = 0
For i As Integer = 0 To 999999999
a = i
Next
Two()
End Sub
Sub two()
Dim a As Integer = 0
For i As Integer = 0 To 999999999
a = i
Next
Three()
End Sub
Sub Three()
Dim a As Integer = 0
For i As Integer = 0 To 999999999
a = i
Next
End Sub

It appears that the sound is played after the whole "cascade" is runned, so after Sub Three() End. If you try this code you will verify that inserting

System.Windows.Forms.Application.DoEvents()

after uiPlayer.controls.play()...doesn't work better Thanks for your help!!