How to make audio sound batter? (C + FFMpeg audio generation example)

Question

So I found this grate C FFMpeg official example which I simplefied:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#ifdef HAVE_AV_CONFIG_H
#undef HAVE_AV_CONFIG_H
#endif

#include "libavcodec/avcodec.h"
#include "libavutil/mathematics.h"

#define INBUF_SIZE 4096
#define AUDIO_INBUF_SIZE 20480
#define AUDIO_REFILL_THRESH 4096

/*
 * Audio encoding example
 */
static void audio_encode_example(const char *filename)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    int frame_size, i, j, out_size, outbuf_size;
    FILE *f;
    short *samples;
    float t, tincr;
    uint8_t *outbuf;

    printf("Audio encoding\n");

    /* find the MP2 encoder */
    codec = avcodec_find_encoder(CODEC_ID_MP2);
    if (!codec) {
        fprintf(stderr, "codec not found\n");
        exit(1);
    }

    c= avcodec_alloc_context();

    /* put sample parameters */
    c->bit_rate = 64000;
    c->sample_rate = 44100;
    c->channels = 2;

    /* open it */
    if (avcodec_open(c, codec) < 0) {
        fprintf(stderr, "could not open codec\n");
        exit(1);
    }

    /* the codec gives us the frame size, in samples */
    frame_size = c->frame_size;
    samples = malloc(frame_size * 2 * c->channels);
    outbuf_size = 10000;
    outbuf = malloc(outbuf_size);

    f = fopen(filename, "wb");
    if (!f) {
        fprintf(stderr, "could not open %s\n", filename);
        exit(1);
    }

    /* encode a single tone sound */
    t = 0;
    tincr = 2 * M_PI * 440.0 / c->sample_rate;
    for(i=0;i<200;i++) {
        for(j=0;j<frame_size;j++) {
            samples[2*j] = (int)(sin(t) * 10000);
            samples[2*j+1] = samples[2*j];
            t += tincr;
        }
        /* encode the samples */
        out_size = avcodec_encode_audio(c, outbuf, outbuf_size, samples);
        fwrite(outbuf, 1, out_size, f);
    }
    fclose(f);
    free(outbuf);
    free(samples);

    avcodec_close(c);
    av_free(c);
}

int main(int argc, char **argv)
{

    /* must be called before using avcodec lib */
    avcodec_init();

    /* register all the codecs */
    avcodec_register_all();

    audio_encode_example("test.mp2");

    return 0;
}

How should it sound like? May be I don't get something but it sounds awful =( how to make audio generation sound batter/ more interesting/ melodical in a wary shourt way (no special functions just how to change this code to make it sound batter)?

Answer 1

If I understand the code correctly, it should be a pure tone, or an ascending tone (I'm really not sure). Either way it probably won't sound very nice. We rarely hear pure sine wave tones in nature - they sound rather strident and harsh. Most things that we consider to sound "musical" tend to be composed of many different frequencies.

As for changing it, maybe you could look into various sound generation algorithms which you can use to make the pitch vary in terms of multiple sine waves.