diff examples/04-Audio/filter-IIR/render.cpp @ 464:8fcfbfb32aa0 prerelease

Examples reorder with subdirectories. Added header to each project. Moved Doxygen to bottom of render.cpp.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/04-Audio/filter-IIR/render.cpp	Mon Jun 20 16:20:38 2016 +0100
@@ -0,0 +1,230 @@
+/*
+ ____  _____ _        _    
+| __ )| ____| |      / \   
+|  _ \|  _| | |     / _ \  
+| |_) | |___| |___ / ___ \ 
+|____/|_____|_____/_/   \_\
+
+The platform for ultra-low latency audio and sensor processing
+
+http://bela.io
+
+A project of the Augmented Instruments Laboratory within the
+Centre for Digital Music at Queen Mary University of London.
+http://www.eecs.qmul.ac.uk/~andrewm
+
+(c) 2016 Augmented Instruments Laboratory: Andrew McPherson,
+  Astrid Bin, Liam Donovan, Christian Heinrichs, Robert Jack,
+  Giulio Moro, Laurel Pardue, Victor Zappi. All rights reserved.
+
+The Bela software is distributed under the GNU Lesser General Public License
+(LGPL 3.0), available here: https://www.gnu.org/licenses/lgpl-3.0.txt
+*/
+
+
+#include <Bela.h>	// to schedule lower prio parallel process
+#include <rtdk.h>
+#include <cmath>
+#include <stdio.h>
+#include "SampleData.h"
+
+SampleData gSampleData;	// User defined structure to get complex data from main
+int gReadPtr;			// Position of last read sample from file
+
+// filter vars
+float gLastX[2];
+float gLastY[2];
+double lb0, lb1, lb2, la1, la2 = 0.0;
+
+// communication vars between the 2 auxiliary tasks
+int gChangeCoeff = 0;
+int gFreqDelta = 0;
+
+void initialise_filter(float freq);
+
+void calculate_coeff(float cutFreq);
+
+bool initialise_aux_tasks();
+
+// Task for handling the update of the frequencies using the matrix
+AuxiliaryTask gChangeCoeffTask;
+
+void check_coeff();
+
+// Task for handling the update of the frequencies using the matrix
+AuxiliaryTask gInputTask;
+
+void read_input();
+
+
+extern float gCutFreq;
+
+
+bool setup(BelaContext *context, void *userData)
+{
+
+	// Retrieve a parameter passed in from the initAudio() call
+	gSampleData = *(SampleData *)userData;
+
+	gReadPtr = -1;
+
+	initialise_filter(200);
+
+	// Initialise auxiliary tasks
+	if(!initialise_aux_tasks())
+		return false;
+
+	return true;
+}
+
+void render(BelaContext *context, void *userData)
+{
+	for(unsigned int n = 0; n < context->audioFrames; n++) {
+		float sample = 0;
+		float out = 0;
+
+		// If triggered...
+		if(gReadPtr != -1)
+			sample += gSampleData.samples[gReadPtr++];	// ...read each sample...
+
+		if(gReadPtr >= gSampleData.sampleLen)
+			gReadPtr = -1;
+
+		out = lb0*sample+lb1*gLastX[0]+lb2*gLastX[1]-la1*gLastY[0]-la2*gLastY[1];
+
+		gLastX[1] = gLastX[0];
+		gLastX[0] = out;
+		gLastY[1] = gLastY[0];
+		gLastY[0] = out;
+
+		for(unsigned int channel = 0; channel < context->audioChannels; channel++)
+			context->audioOut[n * context->audioChannels + channel] = out;	// ...and put it in both left and right channel
+
+	}
+
+	// Request that the lower-priority tasks run at next opportunity
+	Bela_scheduleAuxiliaryTask(gChangeCoeffTask);
+	Bela_scheduleAuxiliaryTask(gInputTask);
+}
+
+// First calculation of coefficients
+
+void initialise_filter(float freq)
+{
+	calculate_coeff(freq);
+}
+
+
+// Calculate the filter coefficients
+// second order low pass butterworth filter
+
+void calculate_coeff(float cutFreq)
+{
+	// Initialise any previous state (clearing buffers etc.)
+	// to prepare for calls to render()
+	float sampleRate = 44100;
+	double f = 2*M_PI*cutFreq/sampleRate;
+	double denom = 4+2*sqrt(2)*f+f*f;
+	lb0 = f*f/denom;
+	lb1 = 2*lb0;
+	lb2 = lb0;
+	la1 = (2*f*f-8)/denom;
+	la2 = (f*f+4-2*sqrt(2)*f)/denom;
+	gLastX[0] = gLastX [1] = 0;
+	gLastY[0] = gLastY[1] = 0;
+
+}
+
+
+// Initialise the auxiliary tasks
+// and print info
+
+bool initialise_aux_tasks()
+{
+	if((gChangeCoeffTask = Bela_createAuxiliaryTask(&check_coeff, 90, "bela-check-coeff")) == 0)
+		return false;
+
+	if((gInputTask = Bela_createAuxiliaryTask(&read_input, 50, "bela-read-input")) == 0)
+		return false;
+
+	rt_printf("Press 'a' to trigger sample, 's' to stop\n");
+	rt_printf("Press 'z' to low down cut-off freq of 100 Hz, 'x' to raise it up\n");
+	rt_printf("Press 'q' to quit\n");
+
+	return true;
+}
+
+// Check if cut-off freq has been changed
+// and new coefficients are needed
+
+void check_coeff()
+{
+	if(gChangeCoeff == 1)
+	{
+		gCutFreq += gFreqDelta;
+		gCutFreq = gCutFreq < 0 ? 0 : gCutFreq;
+		gCutFreq = gCutFreq > 22050 ? 22050 : gCutFreq;
+
+		rt_printf("Cut-off frequency: %f\n", gCutFreq);
+
+		calculate_coeff(gCutFreq);
+		gChangeCoeff = 0;
+	}
+}
+
+// This is a lower-priority call to periodically read keyboard input
+// and trigger samples. By placing it at a lower priority,
+// it has minimal effect on the audio performance but it will take longer to
+// complete if the system is under heavy audio load.
+
+void read_input()
+{
+	// This is not a real-time task!
+	// Cos getchar is a system call, not handled by Xenomai.
+	// This task will be automatically down graded.
+
+	char keyStroke = '.';
+
+	keyStroke =	getchar();
+	while(getchar()!='\n'); // to read the first stroke
+
+	switch (keyStroke)
+	{
+		case 'a':
+			gReadPtr = 0;
+			break;
+		case 's':
+			gReadPtr = -1;
+			break;
+		case 'z':
+			gChangeCoeff = 1;
+			gFreqDelta = -100;
+			break;
+		case 'x':
+			gChangeCoeff = 1;
+			gFreqDelta = 100;
+			break;
+		case 'q':
+			gShouldStop = true;
+			break;
+		default:
+			break;
+	}
+}
+
+
+void cleanup(BelaContext *context, void *userData)
+{
+	delete[] gSampleData.samples;
+}
+
+/* ------------ Project Explantation ------------ */
+
+/**
+\example 04-filter-IIR
+
+Infinite Impulse Response Filter
+------------------------------
+
+This is an example of a infinite impulse response filter implementation.
+*/