c/sampler/synth.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <math.h>
   5 #include "SDL.h"
   6 #include "SDL_mixer.h"
   7
   8 #define PI 3.1415
   9 #define deg2rad(a) (((a)/180)*PI)
  10
  11
  12 SDL_AudioSpec *desired, *obtained;
  13 SDL_AudioSpec *hardware_spec;
  14
  15
  16 void my_audio_callback(void *userdata, Uint8 *stream, int len) {
  17         int sampl_freq = desired->freq;
  18         sampl_freq = 44100;
  19
  20         double sine_freq = 50;
  21         static double i,j; // = 0;
  22
  23         short int *u; u = (short int *)stream;
  24         //for(;len>0;len--) *(u++) = random();
  25         while( (void *)u<(void *)(stream+len) ) {
  26                 // *(u++) = 0;
  27                 *(u++) = sin(
  28                         i += (2*PI*sine_freq)/sampl_freq
  29                 )*128000;
  30                 // *(u++) = sin(deg2rad(j+=8))*1280000;
  31                 // *(u++) = 0;
  32                 *(u++) = *(u-1);
  33         }
  34         //if(i>=2*PI) i=0;
  35         //if(j>=2*PI) j=0;
  36 }
  37
  38
  39 int main(int argc, char *argv[]) {
  40
  41        /* Allocate a desired SDL_AudioSpec */
  42        desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
  43
  44        /* Allocate space for the obtained SDL_AudioSpec */
  45        obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
  46
  47        /* 22050Hz - FM Radio quality */
  48        desired->freq=22050;
  49        desired->freq=44100;
  50
  51        /* 16-bit signed audio */
  52        desired->format=AUDIO_S16LSB;
  53        //desired->format=AUDIO_S8;
  54
  55        desired->channels=2; //0,1,2 = autodetect,mono,stereo
  56
  57        /* Large audio buffer reduces risk of dropouts but increases response time */
  58        desired->samples=65530;
  59
  60        /* Our callback function */
  61        desired->callback=my_audio_callback;
  62
  63        desired->userdata=NULL;
  64        desired->userdata=&desired->freq;
  65
  66        /* Open the audio device */
  67        if ( SDL_OpenAudio(desired, obtained) < 0 ){
  68          fprintf(stderr, "Couldn't open audio: %s", SDL_GetError());
  69          exit(-1);
  70        }
  71        /* desired spec is no longer needed */
  72        free(desired);
  73        hardware_spec=obtained;
  74
  75        /* Prepare callback for playing */
  76
  77        /* Start playing */
  78        SDL_PauseAudio(0);
  79                          sleep(100);
  80 }