Sound

Simple sample to show you how to enable/disable sound and sample a sinus wave.

Using library

GP2X minimal library by rlyeh, 2005

License

• Free for non-commercial projects (it would be nice receiving a mail from you).  Other cases, ask me first.
• GamePark Holdings is not allowed to use this library and/or use parts from it.

Source code

#include "minimal.h"

int main(int argc, char *argv[])
{
 unsigned long volumeL=100, volumeR=100;

 gp2x_init(1000, 16, 44100,16,1,60, 1);

 //resume playing (sound is paused by default)
 gp2x_sound_pause(0);

 while(1)
 {
  unsigned long  pad=gp2x_joystick_read();

  if(pad & GP2X_VOL_DOWN) if(pad & GP2X_START) exit(0);

  if(pad & GP2X_RIGHT) { if(volumeL>0)   volumeL--; volumeR=100-volumeL; gp2x_sound_volume(volumeL,volumeR); }
  if(pad & GP2X_LEFT)  { if(volumeL<100) volumeL++; volumeR=100-volumeL; gp2x_sound_volume(volumeL,volumeR); }

  if(pad & GP2X_B) gp2x_sound_pause(1);
  if(pad & GP2X_X) gp2x_sound_pause(0);
 }
}

#define PI2 (3.14159f*2.f)

void gp2x_sound_frame(void *blah, void *buffer, int samples)
{
 signed short *buffer16=buffer;
 static float sinpos=0.0;

 while(samples--)
 {
  int L, R;

  L=R=(signed short)16384.f * sin(sinpos);

  *buffer16++=L;
  *buffer16++=R;

  sinpos += (PI2 * 400.f) / 44100.f;
 }

 if(sinpos >= PI2) sinpos -= PI2;
}

Explanation

• Our gp2x_init line inits the whole library.  We set 1000 ticks per second, 16 bits video mode, 44100/16bits/stereo/60Hz sound mode, and solid font.
• Our gp2x_joystick_read line reads the joystick.  It is used to act properly to different button combinations.
• Our gp2x_sound_frame line fills our sound buffer with a 400 Hz sinus wave.
• Note that we just fill the given buffer with the amount of specified samples, and we fill data with the expected sample format type.

C Compilation

arm-linux-gcc minimal.c sound.c -static -lpthread -lm

C++ Compilation

arm-linux-g++ minimal.c sound.c -static -lpthread -lm

Output

• this program plays a sinus wave.
• press left or right to pan sound (stereo volume).
• press B to pause sound, and X to resume playing.
• press volume down and start buttons to exit.