comparison projects/filter_IIR/render.cpp @ 3:6810f166482f

_new IIR filter example

+/*
+ * render.cpp
+ *
+ *  Created on: Oct 24, 2014
+ *      Author: Andrew McPherson and Victor Zappi
+ */
+
+
+#include "../../include/render.h"
+#include "../../include/RTAudio.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
+int gNumChannels;
+
+// 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;
+
+
+// initialise_render() is called once before the audio rendering starts.
+// Use it to perform any initialisation and allocation which is dependent
+// on the period size or sample rate.
+//
+// userData holds an opaque pointer to a data structure that was passed
+// in from the call to initAudio().
+//
+// Return true on success; returning false halts the program.
+
+bool initialise_render(int numChannels, int numMatrixFramesPerPeriod,
+					   int numAudioFramesPerPeriod, float matrixSampleRate,
+					   float audioSampleRate, void *userData)
+{
+
+	// Retrieve a parameter passed in from the initAudio() call
+	gSampleData = *(SampleData *)userData;
+
+	gReadPtr = -1;
+	gNumChannels = numChannels;
+
+	initialise_filter(200);
+
+	// Initialise auxiliary tasks
+	if(!initialise_aux_tasks())
+		return false;
+
+	return true;
+}
+
+// render() is called regularly at the highest priority by the audio engine.
+// Input and output are given from the audio hardware and the other
+// ADCs and DACs (if available). If only audio is available, numMatrixFrames
+// will be 0.
+
+void render(int numMatrixFrames, int numAudioFrames, float *audioIn, float *audioOut,
+			uint16_t *matrixIn, uint16_t *matrixOut)
+{
+	for(int n = 0; n < numAudioFrames; 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(int channel = 0; channel < gNumChannels; channel++)
+			audioOut[n * gNumChannels + channel] = out;	// ...and put it in both left and right channel
+
+	}
+
+	// Request that the lower-priority tasks run at next opportunity
+	scheduleAuxiliaryTask(gChangeCoeffTask);
+	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 = createAuxiliaryTaskLoop(&check_coeff, 90, "beaglert-check-coeff")) == 0)
+		return false;
+
+	if((gInputTask = createAuxiliaryTaskLoop(&read_input, 50, "beaglert-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;
+	}
+}
+
+
+
+// cleanup_render() is called once at the end, after the audio has stopped.
+// Release any resources that were allocated in initialise_render().
+
+void cleanup_render()
+{
+	delete[] gSampleData.samples;
+}