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SDL
Simple Directmedia Layer Forums
Rewind Audio SDL.
Samohtvii
Joined: 02 May 2010
Posts: 1
Posted: Mon May 03, 2010 2:18 am
I am trying to write a program that plays an audio file but on the event that 'r' is pressed the audio will skip back to the start and play again.
Here is what i have so far but it doesn't change the audio at all it just keep playing through.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include "SDL/SDL_config.h"
#include "SDL/SDL.h"
#include "SDL/SDL_audio.h"
struct {
SDL_AudioSpec spec; /* SDL Audio Spec Structure */
Uint8 *sound; /* Pointer to wave data */
Uint32 soundlen; /* Length of wave data */
int soundpos; /* Current play position */
} wave;
static int done = 0;
void poked(int sig)
{
done = 1;
}
/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
static void quit(int rc)
{
SDL_Quit();
exit(rc);
}
/**
* This is a call-back function that will be automatically called by SDL
* @param
*/
void SDLCALL fillerup(void *unused, Uint8 *stream, int len)
{
Uint8 *waveptr;
int waveleft;
/* Set up the pointers */
waveptr = wave.sound + wave.soundpos;
waveleft = wave.soundlen - wave.soundpos;
/* Go! */
while ( waveleft <= len )
{
/* Process samples */
Uint8 process_buf[waveleft];
SDL_memcpy(process_buf, waveptr, waveleft);
/* do processing here, e.g. */
/* processing the audio samples in process_buf[*] */
// play the processed audio samples
SDL_memcpy(stream, process_buf, waveleft);
stream += waveleft;
len -= waveleft;
// ready to repeat play the audio
waveptr = wave.sound;
waveleft = wave.soundlen;
wave.soundpos = 0;
}
/* Process samples */
Uint8 process_buf[len];
SDL_memcpy(process_buf, waveptr, len);
/* do processing here, e.g. */
/* processing the audio samples in process_buf[*] */
// play the processed samples
SDL_memcpy(stream, process_buf, len);
wave.soundpos += len;
}
static const int SCR_WIDTH = 240;
static const int SCR_HEIGHT = 180;
void playAudio(char argv[], int argc)
{
char name[32];
SDL_Surface *screen;
/* Load the SDL library */
if ( SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) < 0 )
{
fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
return;
}
if ( argc <=1 )
{
fprintf(stderr, "Usage %s <input wav file>\n", argv[0]);
return;
}
/* Make a screen for visual information & for accepting keyboard events*/
#ifndef __DARWIN__
screen = SDL_SetVideoMode(SCR_WIDTH, SCR_HEIGHT, 0, 0);
#else
screen = SDL_SetVideoMode(SCR_WIDTH, SCR_HEIGHT, 24, 0);
#endif
if (!screen)
{
fprintf(stderr, "SDL: could not set video mode - exiting\n");
quit(1);
}
/* Load the wave file into memory */
if ( SDL_LoadWAV(argv,&wave.spec, &wave.sound, &wave.soundlen) == NULL )
{
fprintf(stderr, "Couldn't load %s: %s\n", argv[1], SDL_GetError());
quit(1);
}
// set up the callback function
wave.spec.callback = fillerup;
#if HAVE_SIGNAL_H
/* Set the signals */
#ifdef SIGHUP
signal(SIGHUP, poked);
#endif
signal(SIGINT, poked);
#ifdef SIGQUIT
signal(SIGQUIT, poked);
#endif
signal(SIGTERM, poked);
#endif /* HAVE_SIGNAL_H */
/* Initialize fillerup() variables */
if (SDL_OpenAudio(&wave.spec, NULL) < 0 )
{
fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
SDL_FreeWAV(wave.sound);
quit(2);
}
// start playing
SDL_PauseAudio(0);
/* Let the audio run */
printf("Using audio driver: %s\n", SDL_AudioDriverName(name, 32));
}
int main(int argc, char *argv[])
{
playAudio(argv[1], argc);
Uint8 *keys;
SDL_Event event;
while ( ! done && (SDL_GetAudioStatus() == SDL_AUDIO_PLAYING) )
{
// Poll input queue, run keyboard loop
while ( SDL_PollEvent(&event) )
{
if ( event.type == SDL_QUIT )
done = 1;
}
keys = SDL_GetKeyState(NULL);
if (keys[SDLK_q])
{
done = 1;
}
else if(keys[SDLK_r])
{
playAudio(argv[1], argc);
}
SDL_Delay(100);
}
/* Clean up on signal */
SDL_CloseAudio();
SDL_FreeWAV(wave.sound);
SDL_Quit();
return(0);
}
Thanks for the help. SDL is really doing my head in.