view projects/filter_IIR/render.cpp @ 45:579c86316008 newapi

Major API overhaul. Moved to a single data structure for handling render functions. Functionally, generally similar except for scheduling within PRU loop function, which now uses interrupts from the PRU rather than polling. This requires an updated kernel.

/*
 * 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

// 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 numMatrixChannels, int numAudioChannels,
					   int numMatrixFramesPerPeriod,
					   int numAudioFramesPerPeriod,
					   float matrixSampleRate, float audioSampleRate,
					   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;
}

// 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 < gNumAudioChannels; channel++)
			audioOut[n * gNumAudioChannels + 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;
}