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alsa: optionally run entire pipeline non-blocking.

This commit is contained in:
Ryan C. Gordon 2018-08-07 16:49:18 -04:00
parent 56f44cfa0f
commit 623a6defd3
1 changed files with 26 additions and 1 deletions
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27
src/audio/alsa/SDL_alsa_audio.c
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@ -22,6 +22,10 @@
#if SDL_AUDIO_DRIVER_ALSA
#ifndef SDL_ALSA_NON_BLOCKING
#define SDL_ALSA_NON_BLOCKING 0
#endif
/* Allow access to a raw mixing buffer */
#include <sys/types.h>
@ -90,6 +94,7 @@ static int (*ALSA_snd_pcm_reset)(snd_pcm_t *);
static int (*ALSA_snd_device_name_hint) (int, const char *, void ***);
static char* (*ALSA_snd_device_name_get_hint) (const void *, const char *);
static int (*ALSA_snd_device_name_free_hint) (void **);
static snd_pcm_sframes_t (*ALSA_snd_pcm_avail)(snd_pcm_t *);
#ifdef SND_CHMAP_API_VERSION
static snd_pcm_chmap_t* (*ALSA_snd_pcm_get_chmap) (snd_pcm_t *);
static int (*ALSA_snd_pcm_chmap_print) (const snd_pcm_chmap_t *map, size_t maxlen, char *buf);
@ -158,6 +163,7 @@ load_alsa_syms(void)
SDL_ALSA_SYM(snd_device_name_hint);
SDL_ALSA_SYM(snd_device_name_get_hint);
SDL_ALSA_SYM(snd_device_name_free_hint);
SDL_ALSA_SYM(snd_pcm_avail);
#ifdef SND_CHMAP_API_VERSION
SDL_ALSA_SYM(snd_pcm_get_chmap);
SDL_ALSA_SYM(snd_pcm_chmap_print);
@ -243,7 +249,24 @@ get_audio_device(void *handle, const int channels)
static void
ALSA_WaitDevice(_THIS)
{
/* We're in blocking mode, so there's nothing to do here */
#if SDL_ALSA_NON_BLOCKING
const snd_pcm_sframes_t needed = (snd_pcm_sframes_t) this->spec.samples;
while (SDL_AtomicGet(&this->enabled)) {
const snd_pcm_sframes_t rc = ALSA_snd_pcm_avail(this->hidden->pcm_handle);
if ((rc < 0) && (rc != -EAGAIN)) {
/* Hmm, not much we can do - abort */
fprintf(stderr, "ALSA snd_pcm_avail failed (unrecoverable): %s\n",
ALSA_snd_strerror(rc));
SDL_OpenedAudioDeviceDisconnected(this);
return;
} else if (rc < needed) {
const Uint32 delay = ((needed - (SDL_max(rc, 0))) * 1000) / this->spec.freq;
SDL_Delay(SDL_max(delay, 10));
} else {
break; /* ready to go! */
}
}
#endif
}
@ -672,9 +695,11 @@ ALSA_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
SDL_memset(this->hidden->mixbuf, this->spec.silence, this->hidden->mixlen);
}
#if !SDL_ALSA_NON_BLOCKING
if (!iscapture) {
ALSA_snd_pcm_nonblock(pcm_handle, 0);
}
#endif
/* We're ready to rock and roll. :-) */
return 0;