Sound & Games

The Next Level

DirectSound with EasySound^TM

Though the WaveMix32.dll allowed us to play multiple sounds, it is somewhat cumbersome to use both in initialization and playback. So to use it effectively you most likely need a good wrapper class to make the interface to the dll a bit easier. It is also not quite perfect when it comes to playback, since you might experience minor delays when you start to playback and until the sound is actually heard.

So the only option you really have to efficiently apply sounds in your games, is to use the de facto standard of playing sounds, namely DirectSound. But it is always easier to name a tool to use, than it is to actually be using it. This statement is also fitting for DirectSound in Visual Basic. Since DirectSound is, as of yet, still not supported in Visual Basic you only have two choices; either get an ActiveX control or some other third party tool, which will let you access DirectSound or get a Type Library which will let you access the DirectSound interface in Visual Basic. The first option of getting a third party control could prove quite expensive, and the second option of getting a Type Library would require an in-depth knowledge of DirectSound.

So what can you do? Well you can start to feel lucky, because this is were the nice authors of this compendium steps in and presents the EasySound control. This control wraps around the DirectSound interface and provides you with a very ‘easy’ way of playing sounds and applying some special effect to the sounds. And best of all it is royalty free.

NOTE: You need DirectX version 5.0 or later to use the control.

You can locate the zipped program on the ToolBox page. Run the setup program and install the control.

There are, as with the WaveMix32.dll, certain initializing steps, which must be handled before we can start playing sounds with the control. Also, as with the WaveMix32.dll, you have to pre-load the wave sounds and obtain, not a handle, but an index to the sounds, before you can play them. The process of initialization and playback is illustrated in the following figure:

As you can see from the illustration you can set special features of a wave sound through the control. These features include Frequency, Pan, Volume, PlayPosition and more.

Initializing the control

The first thing you should when using the control, is to set the .Window property of the control instance that you are using. The control will not initialize if you have not set this property. The Window property should be set with the .hWnd property of you main window:

EasySound.Window = MainWindow.hWnd

After this you initialize the control by calling the ControlName.InitializeSound(). You should check the return value from this call, since it is the only way you can be certain that the control is properly initialized. If you do not check the value, and the control is not properly initialized, you will get run time errors if you try to load or play any sounds with the control. The reason that you will get these errors is that the control is optimized for speed, and thus does not check to see if the thing has been properly initialized.

Loading and Playing

After proper initialization you can start to load and play some wave sounds. The control supports two types of sounds, Static and Streaming sounds. Static sounds are short sounds, which should not have a playtime longer than 4 seconds. Streaming sounds are sounds longer than 4 seconds. The difference lies in the way that the control plays the sounds. Static sounds are completely loaded into memory on either the soundcard or in the system, and are played directly from there. Streaming sounds are loaded into memory in chunks of data. The data is then played from the buffer, while the control continuously feed the buffer more data, and thus saves system resources. So it is quite obvious that you use the Static sounds to the small quick sounds, and the Streaming sounds as the background music, speech or whatever sounds.

To load a static sound you use the CreateStaticSound method of the control:

CreateStaticSound(FileName As String) As Long

The function returns an index to the sound, which is used in playback or in setting special settings of the particular wave sound. A very similar function is used to load a Streaming sound:

CreateStreamingSound(FileName As String) As Long

This function also returns an index to the Streaming sound, which is used in playback or functions relevant to the particular sound. To play a loaded sound either call the PlayStaticSound or PlayStreamingSound depending on the type of sound you wish to play.

PlayStreamingSound(Index As Long, Loop As Long) As Long

Or

PlayStaticSound(Index As Long, Loop As Long) As Long

Each of these functions must be supplied with the Index of the sound that must be played. The index is, as stated above, returned from Loading the sound with either the CreateStaticSound() or the CreateStreamingSound() function. The sample project EASYSOUND demonstrates the use of some of the methods the control provides for playback of sounds.

NOTE: you must install the control before using this project.

The project uses three sounds, one streaming sound and two static sounds. The control is initialized and the sound files re loaded in the load event of the form:

Private Sub Form_Load()
Dim rt As Long
Dim AppPath As String

'don´t forget this
ESound.Window = Me.hWnd

'Initialize the sound machine
rt = ESound.InitializeSound()

  If rt <> EX_OK Then 
    MsgBox "Could Not initialize sound", vbOKOnly, "Failure"
    Exit Sub
  End If

  AppPath = App.Path & "\"

  StaticMachineGun = ESound.CreateStaticSound(AppPath & "machine.wav")

  If StaticMachineGun < 0 Then 
     MsgBox "Could not load machine gun sound", vbOKOnly, "Failure" 
     cmdMachine.Enabled="False" 
  End If 

  StaticBoink="ESound.CreateStaticSound(AppPath" & "boink.wav") 

  If StaticBoink < 0 Then 
     MsgBox "Could not load boink sound", vbOKOnly, "Failure" 
     cmdBoink.Enabled="False" 
  End If 

  StreamCount="ESound.CreateStreamingSound(AppPath" & "countdown.wav") 

  If StreamCount < 0 Then 
     MsgBox "Could not load count sound", vbOKOnly, "Failure" 
     cmdStream.Enabled="False" 
     cmdStop.Enabled="False" 
End If 
End Sub

The first thing to do is to set the Window property of the control. It is set to the hWnd property of the form. The control is then initialized by a call to the InitializeSound() function. The return value from this function is verified to be ok by comparing it to the EX_OK constant. The three sounds are then loaded, and the return value from each load of a sound is stored in a public variable, to ensure that we do not lose it.

The form is now loaded and shown. As you can see then you can play the three sounds by clicking the top row of buttons on the form. They each play indifferently to the other sounds running. But the same sound can not be played over itself, meaning that you have to wait for a sound to stop before it can be played again. This is not very lucky since many times you will have the need to play the same sound on itself many times. You could of course just load it again in a new sound index, but this would waste unnecessary resources. Instead you would want to use DirectSound’s Duplicate Sound feature. This feature enables you to play the same loaded sound buffer on itself over and over again, without creating a new wasteful sound buffer. The EasySound control wraps around this feature of DirectSound with the DuplicateStaticSound() function:

DuplicateStaticSound(Index As Long ) As Long

This function will return a new index to the duplicated sound, which can be played independently from the original sound. The same function, which played an original static sound, is also used to play a duplicated static sound in the same manner.

The sample project also demonstrates how to get and set the frequency of static sound, for more information on this and other special function you should look in the Sound Appendix where the complete documentation on the EasySound control is located.

You might now be thinking where the catch on this control is, it plays multiple sounds simultaneously, it is easy to use, it cleans up after itself, it is free etc… Well beside the point that the user of the control must have DirectSound version 5.0 or later, the catch is that DirectSound (even version 6.0) can only play regular PCM sound formats, and so the control can also only play regular PCM sound formats. Beside that and perhaps a bug or two there is no catch with this control.

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These tutorials were originally developed by Soren Christensen and Burt Abreu as part of a book which we were working on. The book idea didn't come to fruition and so we decided to post the completed chapters here in the hopes that you would find them useful. We retain copyright to this material and you may not reproduce it, post it, or otherwise disseminate it in any fashion without our express written consent with the exception of making copies for your personal use.