exstream.c from Allegro game programming library at Krugle

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/*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program shows how to use the audio stream functions to transfer
 *    large blocks of sample data to the soundcard.
 */


#include "allegro.h"



#define BUFFER_SIZE  1024



int main()
{
   AL_AUDIOSTREAM *stream;
   int updates = 0;
   int pitch = 0;
   int val = 0;
   int i;

   allegro_init();
   al_install_keyboard(); 
   al_install_timer();
   if (al_set_gfx_mode(AL_GFX_SAFE, 320, 200, 0, 0) != 0) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Unable to set any graphic mode\n%s\n", al_error);
      return 1;
   }
   al_set_palette(al_desktop_palette);
   al_clear_to_color(al_screen, al_make_color(255, 255, 255));
   al_text_mode(al_make_color(255, 255, 255));

   /* install a digital sound driver */
   if (al_install_sound(DIGI_AUTODETECT, AL_MIDI_NONE, NULL) != 0) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Error initialising sound system\n%s\n", al_error);
      return 1;
   }

   /* create an audio stream */
   stream = al_play_audio_stream(BUFFER_SIZE, 8, FALSE, 22050, 255, 128);
   if (!stream) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Error creating audio stream!\n");
      return 1;
   }

   al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, AL_SCREEN_H/3, al_make_color(0, 0, 0), "Audio stream is now playing...");
   al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, AL_SCREEN_H/3+24, al_make_color(0, 0, 0), "Driver: %s", digi_driver->name);

   while (!al_key_pressed()) {
      /* does the stream need any more data yet? */
      unsigned char *p = al_get_audio_stream_buffer(stream);

      if (p) {
	 /* if so, generate a bit more of our waveform... */
	 al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, AL_SCREEN_H*2/3, al_make_color(0, 0, 0), "update #%d", updates++);

	 for (i=0; i<BUFFER_SIZE; i++) {
	    /* this is just a sawtooth wave that gradually increases in 
	     * pitch. Obviously you would want to do something a bit more
	     * interesting here, for example you could fread() the next
	     * buffer of data in from a disk file...
	     */
	    p[i] = (val >> 16) & 0xFF;
	    val += pitch;
	    pitch++;
	    if (pitch > 0x40000)
	       pitch = 0x10000;
	 }

	 al_free_audio_stream_buffer(stream);
      }
   }

   al_stop_audio_stream(stream);

   return 0;
}

AL_END_OF_MAIN();
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