/* clap.c
/* Simple demo to detect claps from the sound card and execute a given command */
/* 1/27/05 eric buehl; eric@thebuehls.com */

#include <fcntl.h>
#include <sys/soundcard.h>
#include <stdio.h>

/*#define DEBUG		/* uncomment to get some info about claps received */

/* in order to configure, uncomment the debug line.  commands
will not be executed in debug mode */

/* these values will very greatly depending on your setup, microphone used, etc */
#define BUF_SIZE 2048	/* amount of audio to record at a time*/
#define PEAK 160	/* what values are considered a peak */
#define BOTTOM  96	/* what values are considered a min */
#define FREQ_GAP 30	/* the maximum space between a peak */
#define MIN_GAP 5	/* the minumum number of peaks that make a clap */
#define MAX_GAP 1500	/* the max length of a clap */
#define MIN_FREQ 0.35	/* the minimum freq that we consider to be a clap */
#define MAX_FREQ 0.90	/* the maximum freq that we consider to be a clap */


int audio_fd;
unsigned char recBuffer[BUF_SIZE];
int peaks[1024];
int numPeaks=0;
int claps[5][2];	/* [clap#][start,end] */

int main(int argc, char *argv[])
{
	int i,j;
	int len;
	float freq;
	int vol;
	int max=0,min=256;
	int avg;
	char DEVICE_NAME[50];
	char COMMAND[200]={0};
	int start,finish;

	if(argc<3){
		printf("Usage: %s device_name command\nEXAMPLE: %s /dev/dsp echo clap received\\n\n\n",argv[0],argv[0]);
		return -1;
	}
	
	strcpy(DEVICE_NAME,argv[1]);
	for(i=2;i<argc;i++){
		strcat(COMMAND,argv[i]);
		strcat(COMMAND," ");
	}
	strcat(COMMAND," &");
	printf("Listening to device: %s\n",DEVICE_NAME);

	if ((audio_fd = open(DEVICE_NAME, /*O_RDWR*/ O_RDONLY, 0)) == -1)
	{ /* Opening device failed */
		perror(DEVICE_NAME);
		exit(-1);
	}
	while(1)
		{
		if ((len = read(audio_fd, recBuffer, BUF_SIZE)) == -1)
		{
			perror("audio read");
			exit(-2);
		}
	
		for(i=0;i<BUF_SIZE;i++)
		{
			if((recBuffer[i]<=BOTTOM)||(recBuffer[i]>=PEAK))
				peaks[numPeaks++]=i;
			
		}

		for(i=0;i<numPeaks;i++)
		{
			start=peaks[i];
			while((i < numPeaks-1) && ((peaks[i]+FREQ_GAP) > (peaks[++i])));
			finish=peaks[i];
			if(finish-start < MIN_GAP || finish-start > MAX_GAP) continue;
			
			/* compute avergae frequency of clap */
			/* if we find the number of samples over a certain value
			   per constant time, we get an abstract frequency */
			j=start;
			freq=0;
			vol=0;
			while(j<=finish)
			{
				if(recBuffer[j]>128) vol+=recBuffer[j];
				if(recBuffer[j++] > 128 /* PEAK */) freq++;
			}
			freq/=(finish-start);
			vol/=j;
			if(freq<MIN_FREQ || freq>MAX_FREQ) continue;
#ifdef DEBUG
			printf("start:  %d\n",start);
			printf("finish: %d\n",finish);
			printf("diff:   %d\n",finish-start);
			printf("vol:    %f\n",vol);
			printf("freq:   %f\n",freq);
			printf("COMMAND: %s\n\n",COMMAND);
#else
			system(COMMAND);
#endif
		}
		numPeaks=0;
#ifdef DEBUG
		printf("--new buffer--\n");
#endif
	}

	close(audio_fd);

	return 0;
}