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Add configurable latency (however, SDL will most likely ignore this

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anyways.)
This commit is contained in:
Themaister 2011-01-07 16:11:48 +01:00
parent a5bbc68a84
commit 3d20fe70cd
1 changed files with 27 additions and 1 deletions
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28
audio/sdl.c
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@ -51,8 +51,29 @@ static void sdl_audio_cb(void *data, Uint8 *stream, int len)
memset(stream + write_size, 0, len - write_size);
}
// Interesting hack from http://www-graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
static inline uint32_t next_pow2(uint32_t v)
{
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;
return v;
}
static inline int find_num_frames(int rate, int latency)
{
int frames = (rate * latency) / 1000;
// SDL only likes 2^n sized buffers.
return next_pow2(frames);
}
static void* sdl_audio_init(const char* device, int rate, int latency)
{
(void)device;
if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0)
return NULL;
@ -60,11 +81,14 @@ static void* sdl_audio_init(const char* device, int rate, int latency)
if (!sdl)
return NULL;
// We have to buffer up some data ourselves, so we let SDL carry approx half of the latency.
int frames = find_num_frames(rate, latency / 2);
SDL_AudioSpec spec = {
.freq = rate,
.format = AUDIO_S16SYS,
.channels = 2,
.samples = 512,
.samples = frames, // This is in audio frames, not samples ... :(
.callback = sdl_audio_cb,
.userdata = sdl
};
@ -82,6 +106,8 @@ static void* sdl_audio_init(const char* device, int rate, int latency)
sdl->lock = SDL_CreateMutex();
sdl->cond = SDL_CreateCond();
SSNES_LOG("SDL audio: Requested %d ms latency, got %d ms\n", latency, (int)(out.samples * 3 * 1000 / g_settings.audio.out_rate));
// Create a buffer twice as big as needed and prefill the buffer.
size_t bufsize = out.samples * 4 * sizeof(int16_t);
void *tmp = calloc(1, bufsize);