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alsa: Simplify ALSA_WaitDevice. 

- Check for specific availability instead of waiting for "device ready."
- Don't use snd_pcm_wait, just use a simple SDL_Delay (nothing to recover).
- Fixed SDL_max call that should have been SDL_min (now using SDL_clamp).
- ALSA_RecordDevice() now returns 0 if no availability, which kicks us back
  to WaitDevice to try again, as an extra safety check.
This commit is contained in:
Ryan C. Gordon 2025-06-17 20:40:00 -04:00
parent b4ac5f43f5
commit c04624972e
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GPG Key ID: FA148B892AB48044
1 changed files with 18 additions and 19 deletions
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33
src/audio/alsa/SDL_alsa_audio.c
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@ -348,26 +348,22 @@ static char *get_pcm_str(void *handle)
// This function waits until it is possible to write a full sound buffer
static bool ALSA_WaitDevice(SDL_AudioDevice *device)
{
const int fulldelay = (int) ((((Uint64) device->sample_frames) * 1000) / device->spec.freq);
const int delay = SDL_max(fulldelay, 10);
const int sample_frames = device->sample_frames;
const int fulldelay = (int) ((((Uint64) sample_frames) * 1000) / device->spec.freq);
const int delay = SDL_clamp(fulldelay, 1, 5);
int total_delays = 0;
while (!SDL_GetAtomicInt(&device->shutdown)) {
const int rc = ALSA_snd_pcm_wait(device->hidden->pcm, delay);
if (rc < 0 && (rc != -EAGAIN)) {
const int status = ALSA_snd_pcm_recover(device->hidden->pcm, rc, 0);
if (status < 0) {
SDL_assert(fulldelay > 0); // so the `fulldelay * 5` below produces a reasonable result.
while (!SDL_GetAtomicInt(&device->shutdown) && (ALSA_snd_pcm_avail(device->hidden->pcm) < sample_frames)) {
if (total_delays >= (fulldelay * 5)) {
// Hmm, not much we can do - abort
SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA: snd_pcm_wait failed (unrecoverable): %s", ALSA_snd_strerror(rc));
SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA: hardware seems to have frozen, giving up on it.");
return false;
} else {
SDL_Delay(delay);
total_delays += delay; // THIS IS NOT EXACT, but just so we don't wait forever on problems...
}
continue;
}
if (rc > 0) {
break; // ready to go!
}
// Timed out! Make sure we aren't shutting down and then wait again.
}
return true;
@ -431,8 +427,11 @@ static int ALSA_RecordDevice(SDL_AudioDevice *device, void *buffer, int buflen)
SDL_assert((buflen % frame_size) == 0);
const snd_pcm_sframes_t total_available = ALSA_snd_pcm_avail(device->hidden->pcm);
const int total_frames = SDL_min(buflen / frame_size, total_available);
if (total_available == 0) {
return 0; // go back to WaitDevice and try again.
}
const int total_frames = SDL_min(buflen / frame_size, total_available);
const int rc = ALSA_snd_pcm_readi(device->hidden->pcm, buffer, total_frames);
SDL_assert(rc != -EAGAIN); // assuming this can't happen if we used snd_pcm_wait and queried for available space. snd_pcm_recover won't handle it!