ALSA driver improvements:
* alsa hotplug thread is low priority
* give a chance for other threads to catch up when audio playback is not progressing
* use nonblocking for alsa audio capture
There is a bug with SDL hanging when an audio capture USB device is removed, because poll never returns
diff --git a/src/audio/alsa/SDL_alsa_audio.c b/src/audio/alsa/SDL_alsa_audio.c
index b87a598..931cfde 100644
--- a/src/audio/alsa/SDL_alsa_audio.c
+++ b/src/audio/alsa/SDL_alsa_audio.c
@@ -364,6 +364,13 @@
}
continue;
}
+ else if (status == 0) {
+ /* No frames were written (no available space in pcm device).
+ Allow other threads to catch up. */
+ Uint32 delay = (frames_left / 2 * 1000) / this->spec.freq;
+ SDL_Delay(delay);
+ }
+
sample_buf += status * frame_size;
frames_left -= status;
}
@@ -383,23 +390,22 @@
this->spec.channels;
const int total_frames = buflen / frame_size;
snd_pcm_uframes_t frames_left = total_frames;
+ snd_pcm_uframes_t wait_time = frame_size / 2;
SDL_assert((buflen % frame_size) == 0);
while ( frames_left > 0 && SDL_AtomicGet(&this->enabled) ) {
- /* !!! FIXME: This works, but needs more testing before going live */
- /* ALSA_snd_pcm_wait(this->hidden->pcm_handle, -1); */
- int status = ALSA_snd_pcm_readi(this->hidden->pcm_handle,
+ int status;
+
+ status = ALSA_snd_pcm_readi(this->hidden->pcm_handle,
sample_buf, frames_left);
- if (status < 0) {
+ if (status == -EAGAIN) {
+ ALSA_snd_pcm_wait(this->hidden->pcm_handle, wait_time);
+ status = 0;
+ }
+ else if (status < 0) {
/*printf("ALSA: capture error %d\n", status);*/
- if (status == -EAGAIN) {
- /* Apparently snd_pcm_recover() doesn't handle this case -
- does it assume snd_pcm_wait() above? */
- SDL_Delay(1);
- continue;
- }
status = ALSA_snd_pcm_recover(this->hidden->pcm_handle, status, 0);
if (status < 0) {
/* Hmm, not much we can do - abort */
@@ -745,8 +751,9 @@
SDL_memset(this->hidden->mixbuf, this->spec.silence, this->hidden->mixlen);
}
- /* Switch to blocking mode for playback */
- ALSA_snd_pcm_nonblock(pcm_handle, 0);
+ if (!iscapture) {
+ ALSA_snd_pcm_nonblock(pcm_handle, 0);
+ }
/* We're ready to rock and roll. :-) */
return 0;
@@ -763,16 +770,26 @@
add_device(const int iscapture, const char *name, void *hint, ALSA_Device **pSeen)
{
ALSA_Device *dev = SDL_malloc(sizeof (ALSA_Device));
- char *desc = ALSA_snd_device_name_get_hint(hint, "DESC");
+ char *desc;
char *handle = NULL;
char *ptr;
- if (!desc) {
- SDL_free(dev);
+ if (!dev) {
return;
- } else if (!dev) {
- free(desc);
- return;
+ }
+
+ /* Not all alsa devices are enumerable via snd_device_name_get_hint
+ (i.e. bluetooth devices). Therefore if hint is passed in to this
+ function as NULL, assume name contains desc.
+ Make sure not to free the storage associated with desc in this case */
+ if (hint) {
+ desc = ALSA_snd_device_name_get_hint(hint, "DESC");
+ if (!desc) {
+ SDL_free(dev);
+ return;
+ }
+ } else {
+ desc = (char *) name;
}
SDL_assert(name != NULL);
@@ -788,14 +805,16 @@
handle = SDL_strdup(name);
if (!handle) {
- free(desc);
+ if (hint) {
+ free(desc);
+ }
SDL_free(dev);
return;
}
SDL_AddAudioDevice(iscapture, desc, handle);
- free(desc);
-
+ if (hint)
+ free(desc);
dev->name = handle;
dev->iscapture = iscapture;
dev->next = *pSeen;
@@ -815,12 +834,15 @@
ALSA_Device *dev;
Uint32 ticks;
+ SDL_SetThreadPriority(SDL_THREAD_PRIORITY_LOW);
+
while (!SDL_AtomicGet(&ALSA_hotplug_shutdown)) {
void **hints = NULL;
+ ALSA_Device *unseen;
+ ALSA_Device *seen;
+ ALSA_Device *prev;
+
if (ALSA_snd_device_name_hint(-1, "pcm", &hints) != -1) {
- ALSA_Device *unseen = devices;
- ALSA_Device *seen = NULL;
- ALSA_Device *prev;
int i, j;
const char *match = NULL;
int bestmatch = 0xFFFF;
@@ -830,6 +852,8 @@
"hw:", "sysdefault:", "default:", NULL
};
+ unseen = devices;
+ seen = NULL;
/* Apparently there are several different ways that ALSA lists
actual hardware. It could be prefixed with "hw:" or "default:"
or "sysdefault:" and maybe others. Go through the list and see
@@ -924,7 +948,7 @@
/* report anything still in unseen as removed. */
for (dev = unseen; dev; dev = next) {
- /*printf("ALSA: removing %s device '%s'\n", dev->iscapture ? "capture" : "output", dev->name);*/
+ /*printf("ALSA: removing usb %s device '%s'\n", dev->iscapture ? "capture" : "output", dev->name);*/
next = dev->next;
SDL_RemoveAudioDevice(dev->iscapture, dev->name);
SDL_free(dev->name);
