playnotes.c

// playnotes.c - Plays a string of notes given on the command line.
// Created by flarn2006 - http://flarn2006.blogspot.com/
// Licensed under Creative Commons Attribution-ShareAlike 3.0 Unported
// Requires libao (http://xiph.org/ao/) - Compile with "-lao"

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#include <string.h>
#include <ao/ao.h>
#define SAMPLE_RATE 44100
#define NOTE_LENGTH 0.180

double tofreq(char note);

void play_note(ao_device *device, double freq, double duration)
{
    unsigned long i;
    size_t length = SAMPLE_RATE * duration;
    int16_t *audio = malloc(length*2);

    for (i=0; i<length; i++)
    {
        double value = sin(i * 2 * M_PI * (freq / (double)SAMPLE_RATE));
        audio[i] = (int16_t)(value * 0x7FFF);
    }

    ao_play(device, (char*)audio, length*2);

    free(audio);
}

int main(int argc, char *argv[])
{
    ao_device *device;
    ao_sample_format fmt;
    double duration = NOTE_LENGTH;
    double octave_mult = 1.0;

    if (argc == 2);  // do nothing
    else if (argc == 3)
    {
        sscanf(argv[2], "%lf", &duration);
        if (duration < 0)
        {
            printf("Note length can't be negative!\n");
            return 1;
        }
    }
    else
    {
        printf("Usage: %s notes [length]\n", argv[0]);
        return 2;
    }

    fmt.bits = 16;
    fmt.rate = SAMPLE_RATE;
    fmt.channels = 1;
    fmt.byte_format = AO_FMT_NATIVE;
    fmt.matrix = NULL;

    ao_initialize();

    device = ao_open_live(ao_default_driver_id(), &fmt, NULL);

    int i; for (i=0; i<strlen(argv[1]); i++)
    {
        char ch = argv[1][i];
        switch (ch)
        {
            case '-': octave_mult *= 0.5; break;
            case '+': octave_mult *= 2.0; break;
            default: play_note(device, tofreq(ch) * octave_mult, duration);
        }
    }

    ao_close(device);
    ao_shutdown();

    return 0;
}

double tofreq(char note)
{
    switch (note)
    {
        case 'C': case 'c': return 261.63; break;
        case 'D': case 'd': return 293.66; break;
        case 'E': case 'e': return 329.63; break;
        case 'F': case 'f': return 349.23; break;
        case 'G': case 'g': return 392.00; break;
        case 'A': case 'a': return 440.00; break;
        case 'B': case 'b': return 493.88; break;
        default:  return 0.00;   break; //rest
    }
}