Ok, firstly, I apollogise if this is my code, although various people have looked at this (including people on the SDL mailing list) and no-one can find fault with it, and it works elsewhere. The following code produces a nice sine wave sound on my friend's debian system, but makes clicking noises every other buffer swap on all of my gentoo boxes. I have the following configuration: (gentoo-sources) kernel 2.6.15 ALSA (tried on VIA inteli8x0 and audigy), with: realtime-lsm installed (although i don't believe I'm calling it) RTC Timer support enabled SDL: media-libs/libsdl-1.2.9-r1 Here's the program. Compile with "gcc sdlsound.c -lSDL". : #include <SDL/SDL.h> #include <SDL/SDL_audio.h> #include <math.h> #include <string.h> #define sinf __builtin_sinf #define printf __builtin_printf #define exit __builtin_exit #define M_PI 3.14159265358979323846 #define AUDIO_FREQ 48000 float sine_pos = 0; float sine_speed = M_PI * 2.0 * 440.0 / (float) AUDIO_FREQ; void mix(void* data, Uint8* stream, int len) { Uint8* s_ptr; Uint8* stream_end = stream + len; for (s_ptr = stream; s_ptr < stream_end; s_ptr+= sizeof(Sint16)) { *((Sint16*) s_ptr) = (Sint16) (10000.0f * sinf(sine_pos)); sine_pos += sine_speed; if (sine_pos >= 2*M_PI) sine_pos -= 2*M_PI; // Fix FP accuracy. } } int main(int argc, char* argv[]) { SDL_AudioSpec desired; SDL_AudioSpec obtained; memset(&desired, 0, sizeof(desired)); memset(&obtained, 0, sizeof(obtained)); desired.freq = AUDIO_FREQ; desired.format = AUDIO_S16SYS; desired.channels = 1; desired.samples = 16384; desired.callback = mix; desired.userdata = NULL; if (SDL_Init(SDL_INIT_AUDIO)) { printf("Couldn't initialise SDL\n"); exit(1); } if (SDL_OpenAudio(&desired, &obtained) < 0) { printf("Failed to open audio: %s\n", SDL_GetError()); exit(1); } else if (obtained.format != AUDIO_S16SYS) { printf("Failed to open correct audio format\n"); exit(1); } else if (obtained.freq != AUDIO_FREQ) { printf("Failed to open correct audio format\n"); exit(1); } SDL_PauseAudio(0); SDL_Delay(10000); SDL_PauseAudio(1); SDL_CloseAudio(); return 0; }
does it work correctly with libsdl-1.2.8-r1 ?
Sorry - should've updated this - it's a bug in the snd-hda-intel driver! Both my laptop and my work machine have the same chipset. I now have a creative audigy notebook ZS plugged into the laptop and the problem has gone away. I was mistaken - I didn't have intel-8x0, it was hda-intel. Zynaddsubfx (the softsynth) suffered from the same problem with this chipset.
