[bb] Simple Channel Fading by _PJ_ [ 1+ years ago ]

[BlitzBot]

Title : Simple Channel Fading
Author : _PJ_
Posted : 1+ years ago

Description : This is a very simple example only. Intended to outline the concept behind fading from one channel to another. There's a lot that this example does NOT deal with such as checking for the end of the sound being played (ChannelPlaying()=False) or any validation of the sound files themselves.

However, it should serve it purpose as a basis for understanding how to maximise the use of sound channel handles to manipulate the playback of various sounds.

The variables of particular interest are OVERLAP#  which is the total duration in milliseconds that the cross-fade from
one channel to the other should take.

Also A_PATH$ and B_PATH$ need to be populated with full filepaths to the music for each channel.

Code :

Code (blitzbasic) Select Expand

; THESE ARE REEQUIRED!
Global CHANNEL_PLAYING
Global CHANNEL_HIDDEN

Global PLAYING_VOLUME#=1.00
Global HIDDEN_VOLUME#=0.00

Global nb_Fading=False
Global FADE_START_TIME=0


;EXAMPLE:

Graphics 800,600,32,2
SetBuffer BackBuffer()

Const OVERLAP#=5850.0

Const A_PATH$="[INSERT FILEPATH HERE]"
Const B_PATH$="[INSERT FILEPATH HERE]"

Global SOUND_A=LoadSound(A_PATH)
Global SOUND_B=LoadSound(B_PATH)

InitialiseChannels(SOUND_A,SOUND_B)

While (Not KeyDown(1))
Cls

If (nb_Fading)

UpdateFade

Else
Text 0,0,"Press Space Bar to Begin Fade In/Out"

If (KeyHit(57))

BeginFade

End If

End If

Flip

Wend



Function InitialiseChannels(SOUNDHandle_A,SOUNDHandle_B)
CHANNEL_PLAYING=PlaySound(SOUNDHandle_A)
CHANNEL_HIDDEN=PlaySound(SOUNDHandle_B)

ChannelVolume CHANNEL_PLAYING,PLAYING_VOLUME#
ChannelVolume CHANNEL_HIDDEN,HIDDEN_VOLUME#

PauseChannel CHANNEL_HIDDEN

ResumeChannel CHANNEL_PLAYING
End Function

Function BeginFade()
FADE_START_TIME=MilliSecs()
nb_Fading=True
ResumeChannel CHANNEL_HIDDEN
End Function

Function UpdateFade()

Local Elapsed=(MilliSecs()-FADE_START_TIME)

Text 0,20,"Fading..."

If (Elapsed>OVERLAP)
; It's been too long = swap over channels

Local spare=CHANNEL_PLAYING
CHANNEL_PLAYING=CHANNEL_HIDDEN
CHANNEL_HIDDEN=spare

PLAYING_VOLUME#=1.0
HIDDEN_VOLUME#=0.0

;we're donw with the faded-out channel
PauseChannel CHANNEL_HIDDEN

; No longer fading because we've all faded out ;)
nb_Fading=False

Else

Local f_VolumeDrop#=Float(Elapsed/OVERLAP)

PLAYING_VOLUME#=1.0-(f_VolumeDrop#)
HIDDEN_VOLUME#=(f_VolumeDrop#)
End If

;Update Volume on channels

ChannelVolume CHANNEL_PLAYING,PLAYING_VOLUME
ChannelVolume CHANNEL_HIDDEN,HIDDEN_VOLUME


Text 0,40,Str(PLAYING_VOLUME)
End Function

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