Playing a sound or a piece of music.

Both soundelements are loaded from the application script to illustrate the usage of a soundelement loaded in the script from code. Here is the script snippet that loads the MP3 'background.mp3' for the background music and 'lightning.wav' as sample FX soundelement.

# Load an MP3 before application execution and assign
# ElementScriptID 'MP3_1' to it
-10;_SOUNDSYSTEM;LOADMP3;background.mp3;MP3_1;0;

# Load a Sample before application execution and assign
# ElementScriptID 'SMPL_1' to it
-9;_SOUNDSYSTEM;LOADSMPL;lightning.wav;SMPL_1;0;

Both soundelements are not marked for 3D sound usage so normal panning will have effect. When the sound elements were marked for 3D usage, to have decent panning and volume settings also 3D positioning and a 3D listener position should be set. The script snippet above loads both the soundelements before application execution, since the timespots are negative.

The background music should start when the application starts, and the best way to do that is from a TLE, since the TLE's get executed at pre-defined timespots. The soundFX will be started when the fading of the splash effect (see Creating an effectclass) is completed. Now the flexibility of this system shows: in the early days designers had to mix in the soundeffects with the background music and tune and tweak the application so it would play the visual effects at the same time as the background music was playing the soundeffect. That's not needed anymore: the designer can change the soundFX at any time and doesn't have to worry if the soundFX are played at the right time.

Below is the TLE definition of the start of the backgroundmusic.

# Start the MP3_1 soundelement with volume 100, normal panning
# from startposition 0 (is the start) and loop playback
# and start it on channel with ChannelScriptID CHAN_MP3_1 
0;_SOUNDSYSTEM;PLAYMP3;MP3_1;0;100;0;1;CHAN_MP3_1;

Because it's background music, it should run forever, so the playback is looped. The playback is started using channel CHAN_MP3_1, at timespot 0, which is the start of the application execution.

The background music is playing from the beginning and the soundeffect should be started when the fading is done. The code knows when the fading is done, so we'll play the soundeffect from code. In this example the ElementScriptID of the soundFX soundelement is known by the programmer and is hardcoded. This also could have been send to the effectobject using a TLE:

-8;SPLASH;SENDSTRING;SoundFxElementScriptID;SMPL_1;0;

The effectobject registered with the name 'SPLASH' will receive the string 'SMPL_1', assigned to the name 'SoundFxElementScriptID' in the method ReceiveString(). In this example, this method is not implemented in CSplash, so it doesn't have any effect.

To start the soundeffect when the fading is completely done, we add some code to the DrawLogo() method of the CSplash class. This code will determine when the fading is over, and then start the sound element. The new DrawLogo() method looks something like this:

// Purpose: draws the actual splashscreen.
void
CSplash::DrawLogo(long lNow)
{
	float	fPassedSeconds;
	long	iElementCodeID

	fPassedSeconds = ((float)(lNow - m_lTimeStart))/1000.f;
	
	if(fPassedSeconds <= 10.0f) 
	{ 
		// we will fade up in 10 seconds. So we will go from 0 
		// to 1.0 in 10 seconds. 
		glColor4f(1.0f,1.0f,1.0f, fPassedSeconds/10.0f); 
	}
	else 
	{
		// fading is over, test if we're here for the first time 
		if(!m_bSoundFXStarted) 
		{
			// yes. start soundfx 
			// Get iElementCodeID 
			iElementCodeID=DEMOGL_SoundSystemElementScriptID2ElementCodeID("SMPL_1");
			m_lChannelScriptID=DEMOGL_SoundSystemStartElement(
				iElementCodeID, // The ElementCodeID to start 
				DGL_SS_SAMPLEELEMENT, // Element type 
				0, // Startposition 
				false, // Loop 
				100, // Volume 
				0, // Panning 
				-1, // Frequency (-1== left untouched) 
				NULL, // 3D position structure. No 3D used 
				CHAN_SMPL_1 // ChannelScriptID 
				); 
			m_bSoundFXStarted=true;
		} 
	}
	// start drawing a quad. 
	glBegin(GL_QUADS); 
		glTexCoord2f(0.0f,0.0f);glVertex3f(0.2f,0.125f,-0.45f); 
		glTexCoord2f(1.0f,0.0f);glVertex3f(0.8f,0.125f,-0.45f); 
		glTexCoord2f(1.0f,1.0f);glVertex3f(0.8f,0.875f,-0.45f); 
		glTexCoord2f(0.0f,1.0f);glVertex3f(0.2f,0.875f,-0.45f); 
	glEnd(); 
	
	// draw white background 
	glDisable(GL_TEXTURE_2D); 
	glBegin(GL_QUADS); 
		glVertex3f(0.0f,0.0f,-0.5f); 
		glVertex3f(1.0f,0.0f,-0.5f); 
		glVertex3f(1.0f,1.0f,-0.5f); 
		glVertex3f(0.0f,1.0f,-0.5f); 
	glEnd(); 
}

Two new membervariables are introduced here, m_lChannelScriptID and m_bSoundFXStarted. The have to be added to the private member section of the CSplash class defintion in CSplash.h:

	// ... CSplash public and private method declaration
	
	// Private members
	private:
		long	m_lChannelCodeID;
		bool	m_bSoundFXStarted;
		
		// ... rest of private member declarations

The Init() method of CSplash has to be altered to initialize the member variables just added:

// Purpose: implementation of init()
int
CSplash::Init(int iWidth, int iHeight)
{
	m_bSoundFXStarted=false;
	m_lChannelCodeID=0;
	
	// ... rest of Init() code

DemoGL will clean up every soundelement and every channel playing when the application exits, since this can happen at any time when the user presses ALT-F4, hits ESC or clicks the close window button. It's however a clean coding practice to at least add some sort of cleaning up code when possible.