Sound Effect Implementation Question?

The following is a simple sound example for a basic shooter when you fire a weapon:

-----------------------------------
Method Fire()

Local pTMissileFiringSound:TSound


pTMissileFiringSound = LoadSound("Sounds/Firing/Shot.wav")
pTMissileFiringSound.Play()

End Method
-------------------------

Couple of questions:

1) When the pTMissileFiringSound pointer goes out of scope at the end of the method why does the sound continue to play?

2) Is there anything wrong with this implementation; should I be using a TList to queue the sounds to avoid memory allocation issues? For example, what if the instance of the Type/Class that created the sound was detroyed before the sound finished?

3) If I want units in the distance to sound further away sould I use SetPan and SetDepth?

4) Is there a limit to the number of sound channels and are they automatically cleaned up at the end of the sound?

Thanks

Hi Sean,

I hope this code helps, its a multi-channel sound system I developed for BMax that allows queing, overlapping, no-overlapping. It will support as many channels as you want and any queue depth. It will also clean up after itself.

This code is based on something done for Blitz3D some years ago by someone else - no idea who.

' And Indiepath Production by Tim Fisher (c)2005 Indiepath LTd
DebugLog "MOD_SFX_Engine.bmx"

Const CH_ANY 	= -1
Const CH_1		= 1				'Brick Sounds 
Const CH_2		= 2				'Score Sounds
Const CH_3		= 3				'Powerup Sounds
Const CH_4		= 4				'Incidential Sounds
Const CH_5		= 5				
Const CH_6		= 6				' Diamond Sounds
Const CH_7		= 7				' Chords
Const CH_8		= 8				' Vox
Const CH_9		= 9				' GUI Sounds
Const CH_10		= 10			' BG Music
Const CH_11		= 11			' Score Sounds

' ---------------------------------------------------------------------

Global ChannelTList:TList = New TList

Type ActiveChannel
	Field SampleID	:Int
	Field Address	:TChannel
	Field FadeTime	:Double
	Field FadeStart	:Double
	Field CreateTime:Int
	Field Volume	:Double
	Field VolumeS	:Double
	Field Queue		:TSound[8]
	Field VolQ		:Double[8]
	Field Qcount	:Double
	
		Method New ()
            	If ChannelTList = Null Then ChannelTList = New TList
            	ChannelTList.AddLast Self
    	End Method		

		'----------------------------------------------------------------
		
		Function Destroy (a:ActiveChannel)
				Local b:Int
				a.Address = Null
				For b = 0 To 7
					a.Queue[b] = Null
				Next
				ChannelTList.Remove a
				a = Null
				FlushMem
        End Function

		'----------------------------------------------------------------
		
		Function MusicQueueState(ID:Int)
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					If c.SampleID = ID Then Return Int(c.QCount)
				Next
		End Function

		'----------------------------------------------------------------
	
		Function PlaySample(add:TSound,ID:Int=-1,Vol:Double=1,Queue:Byte=False,overlap:Byte=False,rate:Double=1)
		
				Local Channel:ActiveChannel
				Local Simultaneous:Byte = False
				Local Playing:Byte = False
				
				If ID <0 Then Simultaneous = True
				
				For Channel:ActiveChannel = EachIn ChannelTList
				
					If Channel.SampleID = ID
						If Queue = True
							Channel.Qcount = Channel.Qcount + 1
							If Channel.Qcount > 1 Then 
								Channel.QCount = 1
								DebugLog "**SFX Queue Overload!"
								Return
							EndIf
							Channel.Queue[Channel.Qcount] = add
							Channel.VolQ[Channel.Qcount] = vol
							Playing = True

						Else
							Playing = True
						EndIf
						
						If overlap And (MilliSecs() - Channel.Createtime > 100) Then Playing = False
									
					EndIf
					
					If Not ChannelPlaying(Channel.Address) Then 
						StopChannel(Channel.Address)
						Destroy(Channel)
					EndIf
				
				Next
				
				If Not (Simultaneous = False And Playing = True)
				
					Channel:ActiveChannel = New ActiveChannel
					Channel.SampleID = ID
					Channel.Address = AllocChannel()
					Channel.Volume = Vol
					Channel.VolumeS = Vol
					SetChannelVolume(Channel.Address,Channel.Volume)
					PlaySound(Add,Channel.Address)
					Channel.FadeTime = 0
					Channel.CreateTime = MilliSecs()
					SetChannelRate(Channel.Address,rate)
					
				EndIf	
		
		End Function
		
		'----------------------------------------------------------------

		Method Update()
		
				Local a:Int
		
				If Not ChannelPlaying(self.Address)
					If self.Qcount = 0
						StopChannel(self.address)
						Destroy(Self)
						Return
					Else
						SetChannelVolume(self.address,self.volQ[1])
						PlaySound(self.queue[1],self.address)
						For a = 1 To self.qCount - 1
							self.queue[a] = self.queue[a+1]
							self.volQ[a] = self.volQ[a+1]
						Next
						self.Queue[self.Qcount] = Null
						self.Qcount = self.Qcount - 1
					EndIf
				EndIf
				
				If Self.FadeTime
					If self.Volume <= 0 Then
						If self.Qcount = 0
							StopChannel(self.address)
							Destroy(Self)
						Else
							Self.FadeTime = 0
							Self.Volume = self.volQ[1]
							SetChannelVolume(self.address,self.volQ[1])
							PlaySound(self.queue[1],self.address)
							For a = 1 To self.qCount - 1
								self.queue[a] = self.queue[a+1]
								self.volQ[a] = self.volQ[a+1]
							Next
							self.Queue[self.Qcount] = Null
							self.Qcount = self.Qcount - 1
						EndIf
						
					Else
						Self.Volume = self.VolumeS - Float(MilliSecs() - self.FadeStart) / self.fadetime
						SetChannelVolume(self.address,self.volume)
					EndIf
				EndIf		
				
		End Method
		
		'----------------------------------------------------------------

		Function UpdateAll()
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					c.Update()
				Next
		End Function
		
		'----------------------------------------------------------------
		
		Function SoundOff()
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					StopChannel(c.address)
					Destroy(c)
				Next
		End Function
		
		'----------------------------------------------------------------
		
		Function SetVolume(ID:Int,Vol:Double)
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					If c.SampleID = ID Then SetChannelVolume(c.address,vol)
				Next
		End Function
		
		
		
		'----------------------------------------------------------------
		
		Function Playing(ID:Int)
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					If c.SampleID = ID And ChannelPlaying(c.address) Then Return True
				Next
				Return False
		End Function
		
		'----------------------------------------------------------------
		
		Function ReleaseSample(ID:Int,Timeout:Double)
				Local c:ActiveChannel
				For c:ActiveChannel = EachIn ChannelTList
					If Not c.FadeTime
						If c.SampleID = ID Then
							If Timeout
								c.FadeTime = Timeout
								c.FadeStart = MilliSecs()
							Else
								StopChannel(c.Address)
								destroy(c)
							EndIf
						EndIf
					EndIf
				Next
		End Function

Hey Indiepath,

Thanks for the code!

Questions: Is there anything wrong with the way I was doing it above? What advantage does this offer; just curious because I am new to Blitz Sound.

Hi Sean,

Your code looks sound (no pun intended), if you want maximum control over the sound then you really do need to go the channel route. Using Channels allows you to change pitch on the fly, volume on the fly etc.. You'll also find that with my code you can just chuck stuff at the channels and it'll decide what to do with the sound - no more overloading the soundcard when 20 explosions all happen simultaneously.

Cheers, Tim.

PS. How come you've not got my games on your site :P

I don't think you should be using loadsound each time you fire.
An attempt to answer some questions (some guessing going on here)...
1) The variables out of scope but 'play' has automatically created a TChannel which still exists.
2) Destroy method could check whether the channel is playing and stop using stopchannel.
3) Setpan, SetDepth *and* Setvolume. There's an example in the docs.
4) Don't think there's a limit as each channel is an TChannel Object. I guess, once these are out of scope, flushmem will remove them.
<edit> I reserve the right to be very wrong

Tim,

GameSlammers primary focus is action/arcade and shooters. Also, you are using esellerate where generally I target Plimus, RegNow, or Share-It games. Altough, there are games on the site without any affiliate program in play. That said, I may be changing the affilate program we use in the next few weeks.

tonyg,

I ran accross one null exception error when setting using the channel. At the time, I was thinking that there were not channels remaining. Also, I have had no luch with SetDepth? I set the depth to -1 and the sound still comes out the front speakers; reverse is true for +1.

Presently, I am using a singleton to load all my sounds then I just allocate the channel and set the volume of the sound based on the distance of the sound from the camera (center of the screen).

I have not really had a chance to look at Tim's code in detail as of yet.

Tim,

Looking at your code but I can't see how to use it? How do I setup/queue a new sound? Do you have a sample of how you are using it?

Sean