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alsa: Restart PCM devices after recovery from an overrun/underrun.

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snd_pcm_recover() puts the device back in SND_PCM_STATE_PREPARED state; you
have to explicitly restart the device afterwards with snd_pcm_start().

Fixes #13761.
This commit is contained in:
Ryan C. Gordon
2025-09-05 13:50:06 -04:00
parent 197bfab0b5
commit 937bf4d789
1 changed files with 19 additions and 3 deletions
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22
src/audio/alsa/SDL_alsa_audio.c
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@@ -82,6 +82,7 @@ static int (*ALSA_snd_pcm_nonblock)(snd_pcm_t *, int);
static int (*ALSA_snd_pcm_wait)(snd_pcm_t *, int);
static int (*ALSA_snd_pcm_sw_params_set_avail_min)(snd_pcm_t *, snd_pcm_sw_params_t *, snd_pcm_uframes_t);
static int (*ALSA_snd_pcm_reset)(snd_pcm_t *);
static snd_pcm_state_t (*ALSA_snd_pcm_state)(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 **);
@@ -171,6 +172,7 @@ static bool load_alsa_syms(void)
SDL_ALSA_SYM(snd_pcm_wait);
SDL_ALSA_SYM(snd_pcm_sw_params_set_avail_min);
SDL_ALSA_SYM(snd_pcm_reset);
SDL_ALSA_SYM(snd_pcm_state);
SDL_ALSA_SYM(snd_device_name_hint);
SDL_ALSA_SYM(snd_device_name_get_hint);
SDL_ALSA_SYM(snd_device_name_free_hint);
@@ -352,6 +354,20 @@ static char *get_pcm_str(void *handle)
return pcm_str;
}
static int RecoverALSADevice(snd_pcm_t *pcm, int errnum)
{
const snd_pcm_state_t prerecovery = ALSA_snd_pcm_state(pcm);
const int status = ALSA_snd_pcm_recover(pcm, errnum, 0); // !!! FIXME: third parameter is non-zero to prevent libasound from printing error messages. Should we do that?
if (status == 0) {
const snd_pcm_state_t postrecovery = ALSA_snd_pcm_state(pcm);
if ((prerecovery == SND_PCM_STATE_XRUN) && (postrecovery == SND_PCM_STATE_PREPARED)) {
ALSA_snd_pcm_start(pcm); // restart the device if it stopped due to an overrun or underrun.
}
}
return status;
}
// This function waits until it is possible to write a full sound buffer
static bool ALSA_WaitDevice(SDL_AudioDevice *device)
{
@@ -362,7 +378,7 @@ static bool ALSA_WaitDevice(SDL_AudioDevice *device)
while (!SDL_GetAtomicInt(&device->shutdown)) {
const int rc = ALSA_snd_pcm_avail(device->hidden->pcm);
if (rc < 0) {
const int status = ALSA_snd_pcm_recover(device->hidden->pcm, rc, 0);
const int status = RecoverALSADevice(device->hidden->pcm, rc);
if (status < 0) {
// Hmm, not much we can do - abort
SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA wait failed (unrecoverable): %s", ALSA_snd_strerror(rc));
@@ -390,7 +406,7 @@ static bool ALSA_PlayDevice(SDL_AudioDevice *device, const Uint8 *buffer, int bu
SDL_assert(rc != 0); // assuming this can't happen if we used snd_pcm_wait and queried for available space.
if (rc < 0) {
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!
const int status = ALSA_snd_pcm_recover(device->hidden->pcm, rc, 0);
const int status = RecoverALSADevice(device->hidden->pcm, rc);
if (status < 0) {
// Hmm, not much we can do - abort
SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA write failed (unrecoverable): %s", ALSA_snd_strerror(rc));
@@ -445,7 +461,7 @@ static int ALSA_RecordDevice(SDL_AudioDevice *device, void *buffer, int buflen)
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!
if (rc < 0) {
const int status = ALSA_snd_pcm_recover(device->hidden->pcm, rc, 0);
const int status = RecoverALSADevice(device->hidden->pcm, rc);
if (status < 0) {
// Hmm, not much we can do - abort
SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA read failed (unrecoverable): %s", ALSA_snd_strerror(rc));