robert@533: /*
robert@533:  ____  _____ _        _    
robert@533: | __ )| ____| |      / \   
robert@533: |  _ \|  _| | |     / _ \  
robert@533: | |_) | |___| |___ / ___ \ 
robert@533: |____/|_____|_____/_/   \_\
robert@533: 
robert@533: The platform for ultra-low latency audio and sensor processing
robert@533: 
robert@533: http://bela.io
robert@533: 
robert@533: A project of the Augmented Instruments Laboratory within the
robert@533: Centre for Digital Music at Queen Mary University of London.
robert@533: http://www.eecs.qmul.ac.uk/~andrewm
robert@533: 
robert@533: (c) 2016 Augmented Instruments Laboratory: Andrew McPherson,
robert@533: 	Astrid Bin, Liam Donovan, Christian Heinrichs, Robert Jack,
robert@533: 	Giulio Moro, Laurel Pardue, Victor Zappi. All rights reserved.
robert@533: 
robert@533: The Bela software is distributed under the GNU Lesser General Public License
robert@533: (LGPL 3.0), available here: https://www.gnu.org/licenses/lgpl-3.0.txt
robert@533: */
robert@533: 
robert@533: #include <Bela.h>
robert@533: #include <cmath>
robert@533: 
robert@533: float gFrequency = 4.0;
robert@533: float gPhase;
robert@533: float gInverseSampleRate;
robert@533: 
robert@533: bool setup(BelaContext *context, void *userData)
robert@533: {
robert@533: 
robert@533: 	gInverseSampleRate = 1.0 / context->audioSampleRate;
robert@533: 	gPhase = 0.0;
robert@533: 
robert@533: 	return true;
robert@533: }
robert@533: 
robert@533: void render(BelaContext *context, void *userData)
robert@533: {
robert@533: 	// Nested for loops for audio channels
robert@533: 	for(unsigned int n = 0; n < context->audioFrames; n++) {
robert@533: 	
robert@533: 		// Generate a sinewave with frequency set by gFrequency
robert@533: 		// and amplitude from -0.5 to 0.5
robert@533: 		float lfo = sinf(gPhase) * 0.5;
robert@533: 		// Keep track and wrap the phase of the sinewave
robert@533: 		gPhase += 2.0 * M_PI * gFrequency * gInverseSampleRate;
robert@533: 		if(gPhase > 2.0 * M_PI)
robert@533: 			gPhase -= 2.0 * M_PI;
robert@533: 
robert@533: 		for(unsigned int channel = 0; channel < context->audioChannels; channel++) {
robert@533: 		    // Read the audio input and half the amplitude
robert@533: 		    float input = audioRead(context, n, channel) * 0.5;
robert@533: 			// Write to audio output the audio input multiplied by the sinewave
robert@533: 			audioWrite(context, n, channel, (input*lfo));
robert@533: 			
robert@533: 		}
robert@533: 	}
robert@533: 	
robert@533: 	// Nested for loops for analog channels
robert@533: 	for(unsigned int n = 0; n < context->analogFrames; n++) {
robert@533: 		for(unsigned int ch = 0; ch < context->analogChannels; ch++) {
robert@533: 			// Read analog channel 0 and map the range from 0-1 to 0.25-20
robert@533: 			// use this to set the value of gFrequency
robert@533: 			gFrequency = map(analogRead(context, n, 0), 0.0, 1.0, 0.25, 20.0);
robert@533: 		
robert@533: 		}
robert@533: 	}
robert@533: 	
robert@533: }
robert@533: 
robert@533: void cleanup(BelaContext *context, void *userData)
robert@533: {
robert@533: 
robert@533: }
robert@533: 
robert@533: 
robert@533: /**
robert@533: \example tremolo/render.cpp
robert@533: 
robert@533: A simple tremolo effect
robert@533: -----------------------
robert@533: 
robert@533: This sketch demonstrates how to make a simple tremolo effect with one potiometer to
robert@533: control the rate of the effect. A tremolo effect is a simple type of amplitude modulation
robert@533: where the amplitude of one signal is continuous modulated by the amplitude of another.
robert@533: This is achieved by multiplying to signals together.
robert@533: 
robert@533: In this example we want to create a tremolo effect like that you would find in a guitar
robert@533: effects box so our first signal will be our audio input into which we could plug a guitar
robert@533: or external sound source. This will be our 'carrier' signal.
robert@533: 
robert@533: The second signal that we will use, the 'modulator', will be a low freqeuncy oscillator (LFO),
robert@533: in this case a sinetone which we will generate in the same way as the 01-Basic/sinetone example. 
robert@533: The frequency of this sinetone is determined by a global variable, `gFrequency`. Again, the 
robert@533: sinetone is produced by incrementing the phase of a sine function on every audio frame.
robert@533: 
robert@533: In `render()` you'll see two nested for loop structures, one for audio and the other for the 
robert@533: analogs. You should be pretty familiar with this structure by now. In the first of these for loops
robert@533: we deal with all the audio -- in the second with reading the analog input channels. We read the 
robert@533: value of analog input 0 and map it to an appropriate range for controlling the frequency
robert@533: of the sine tone.
robert@533: 
robert@533: The lfo is then mulitplied together with the audio input and sent to the audio output.
robert@533: */