microphone.c

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#include <sndfile.h>
#include <sys/syslog.h>
#include <sys/wait.h>
#include "../inc/microphone.h"
 
#define THRESHOLD -35 // Audio threshold [dB]
#define LIMIT 3
 
int startRecording()
{
    int ret = 0;
 
    ret = system("ffmpeg \
    -f alsa -ac 1 -ar 44100 -i plughw:0,0 \
    -c:a copy \
    -t 2 -y \
    /etc/audiorecord.wav");
 
    // return value from the command on the upper 8-bits of the return value
    //  0 on sucess, 1 on failure
    return WEXITSTATUS(ret);
}
 
double calculateLoudness()
{
    char *inFileName;
    SNDFILE *inFile;
    SF_INFO inFileInfo;
    double sum = 0;
    int i;
 
    inFileName = "/etc/audiorecord.wav"; // Audio file name
 
    inFile = sf_open(inFileName, SFM_READ, &inFileInfo); // Open the .wav file with read permissions
    if (inFile == NULL)
        return ERR_OPEN;
 
    int samples = inFileInfo.frames * inFileInfo.channels; // Get the size of the audio file in samples
    double buffer[samples];
 
    if (sf_read_double(inFile, buffer, samples) != samples) // Read the audio file values to the buffer
        return ERR_READ;
 
    sf_close(inFile);
 
    // Calculate the RMS value of the audio sample
    for (i = 0; i < samples; i++)
    {
        sum += buffer[i] * buffer[i];
    }
    double ms = sqrt(sum) / (double)samples;
 
    return 10 * log10(ms); // Returns in dB
}
 
int processAudio(double *loudness)
{
    double ret = 0;
    static u_int8_t crying_counter = 0;
 
    ret = calculateLoudness();
 
    if ((int)ret == ERR_OPEN || (int)ret == ERR_READ)
        return (int)ret;
 
    *loudness = ret;
 
    if (ret >= THRESHOLD)
    {
        ret = 0;
        if (++crying_counter >= LIMIT)
        {
            crying_counter = 0;
            ret = 1;
        }
        return ret;
    }
 
    if (crying_counter > 0)
        crying_counter--;
 
    return 0;
}