Raspberry Pi + MPD + KissFFT Spectrum Analyser

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <math.h>
#include "kiss_fft.h"

float hanningWindow(short in, size_t i, size_t s) {
    return in*0.5f*(1.0f-cos(2.0f*M_PI*(float)(i)/(float)(s-1.0f)));
}

void drawBar(kiss_fft_cpx *fin, int start, int range) {
    unsigned int i, barlen, barval;
    kiss_fft_cpx ffto;

    barlen = 0;
    for(i=0;i<range;i++) {
        ffto = fin[start + i];

        // sqrt(i*i + r*r)
        barval = sqrt(ffto.i * ffto.i + ffto.r * ffto.r);

        // 20 * log10(2^16) should max at 96(db), but i get values over 150?
        barval = (unsigned int)(20.0f * (float)log10(barval));

        // Record the maximum bin value over this range
        if(barval > barlen)
            barlen = barval;
    }

    // Generate bars 150 chars long, pad with spaces
    for(i=0;i<barlen;i++)
        printf("*");

    for(;i<150;i++)
        printf(" ");

    printf("\n");
}

int main() {
    kiss_fft_cpx *fin = malloc(sizeof(kiss_fft_cpx)*1024);
    kiss_fft_cpx *fout = malloc(sizeof(kiss_fft_cpx)*1024);
    unsigned int barlen, barval;
    int16_t buf[1024];
    int fd;
    int i;


    fd = open("/tmp/mpd.fifo", O_RDONLY);   // 44100:16:1
    kiss_fft_cfg mycfg = kiss_fft_alloc(1024,0,NULL,NULL);  // 1024 bins = 48kHz
    printf("\033[2J");  // Clear screen

    while(read(fd, buf, sizeof(buf)) > 0) { // Keep looping while we have samples
        for(i=0;i<1024;i++) {   // Populate sample buffer
            fin[i].r = hanningWindow(buf[i],i,1024);    // Apply Hanning Window
            fin[i].i = 0;
        }

        kiss_fft(mycfg, fin, fout); // Perform FFT

        printf("\033[H");   // Return cursor to 0,0

        // Ignore the first 5 bins (DC + <200Hz)
        for(i=5;i<=37;i++) {    // Pull the next 32 bins into bars
            drawBar(fout, i, 1);    // Draw bars of 1 bin width
        }

        for(i=3;i<24;i++) { // Generate 21 more bars from the remaining 336 bins
            drawBar(fout, i*16, 16);    // Draw bars of 16 bin widths
        }
    }

    close(fd);
}