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audio/sdlaudio: Allow audio playback with SDL2

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When compiling with SDL2, the semaphore trick used in sdlaudio.c
does not work - QEMU locks up completely in this case. To avoid
the hang and get at least some audio playback up and running (it's
a little bit crackling, but better than nothing), we can use the
SDL locking functions SDL_LockAudio() and SDL_UnlockAudio() to sync
with the sound playback thread instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1485852398-2327-1-git-send-email-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Thomas Huth 2017-01-31 09:46:38 +01:00 committed by Gerd Hoffmann
parent 1ffc266539
commit bcf19777df
1 changed files with 48 additions and 0 deletions
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48
audio/sdlaudio.c
View file

@ -38,10 +38,14 @@
#define AUDIO_CAP "sdl"
#include "audio_int.h"
#define USE_SEMAPHORE (SDL_MAJOR_VERSION < 2)
typedef struct SDLVoiceOut {
HWVoiceOut hw;
int live;
#if USE_SEMAPHORE
int rpos;
#endif
int decr;
} SDLVoiceOut;
@ -53,8 +57,10 @@ static struct {
static struct SDLAudioState {
int exit;
#if USE_SEMAPHORE
SDL_mutex *mutex;
SDL_sem *sem;
#endif
int initialized;
bool driver_created;
} glob_sdl;
@ -73,31 +79,45 @@ static void GCC_FMT_ATTR (1, 2) sdl_logerr (const char *fmt, ...)
static int sdl_lock (SDLAudioState *s, const char *forfn)
{
#if USE_SEMAPHORE
if (SDL_LockMutex (s->mutex)) {
sdl_logerr ("SDL_LockMutex for %s failed\n", forfn);
return -1;
}
#else
SDL_LockAudio();
#endif
return 0;
}
static int sdl_unlock (SDLAudioState *s, const char *forfn)
{
#if USE_SEMAPHORE
if (SDL_UnlockMutex (s->mutex)) {
sdl_logerr ("SDL_UnlockMutex for %s failed\n", forfn);
return -1;
}
#else
SDL_UnlockAudio();
#endif
return 0;
}
static int sdl_post (SDLAudioState *s, const char *forfn)
{
#if USE_SEMAPHORE
if (SDL_SemPost (s->sem)) {
sdl_logerr ("SDL_SemPost for %s failed\n", forfn);
return -1;
}
#endif
return 0;
}
#if USE_SEMAPHORE
static int sdl_wait (SDLAudioState *s, const char *forfn)
{
if (SDL_SemWait (s->sem)) {
@ -106,6 +126,7 @@ static int sdl_wait (SDLAudioState *s, const char *forfn)
}
return 0;
}
#endif
static int sdl_unlock_and_post (SDLAudioState *s, const char *forfn)
{
@ -246,6 +267,7 @@ static void sdl_callback (void *opaque, Uint8 *buf, int len)
int to_mix, decr;
/* dolog ("in callback samples=%d\n", samples); */
#if USE_SEMAPHORE
sdl_wait (s, "sdl_callback");
if (s->exit) {
return;
@ -264,6 +286,11 @@ static void sdl_callback (void *opaque, Uint8 *buf, int len)
if (!sdl->live) {
goto again;
}
#else
if (s->exit || !sdl->live) {
break;
}
#endif
/* dolog ("in callback live=%d\n", live); */
to_mix = audio_MIN (samples, sdl->live);
@ -274,7 +301,11 @@ static void sdl_callback (void *opaque, Uint8 *buf, int len)
/* dolog ("in callback to_mix %d, chunk %d\n", to_mix, chunk); */
hw->clip (buf, src, chunk);
#if USE_SEMAPHORE
sdl->rpos = (sdl->rpos + chunk) % hw->samples;
#else
hw->rpos = (hw->rpos + chunk) % hw->samples;
#endif
to_mix -= chunk;
buf += chunk << hw->info.shift;
}
@ -282,12 +313,21 @@ static void sdl_callback (void *opaque, Uint8 *buf, int len)
sdl->live -= decr;
sdl->decr += decr;
#if USE_SEMAPHORE
again:
if (sdl_unlock (s, "sdl_callback")) {
return;
}
#endif
}
/* dolog ("done len=%d\n", len); */
#if (SDL_MAJOR_VERSION >= 2)
/* SDL2 does not clear the remaining buffer for us, so do it on our own */
if (samples) {
memset(buf, 0, samples << hw->info.shift);
}
#endif
}
static int sdl_write_out (SWVoiceOut *sw, void *buf, int len)
@ -315,8 +355,12 @@ static int sdl_run_out (HWVoiceOut *hw, int live)
decr = audio_MIN (sdl->decr, live);
sdl->decr -= decr;
#if USE_SEMAPHORE
sdl->live = live - decr;
hw->rpos = sdl->rpos;
#else
sdl->live = live;
#endif
if (sdl->live > 0) {
sdl_unlock_and_post (s, "sdl_run_out");
@ -405,6 +449,7 @@ static void *sdl_audio_init (void)
return NULL;
}
#if USE_SEMAPHORE
s->mutex = SDL_CreateMutex ();
if (!s->mutex) {
sdl_logerr ("Failed to create SDL mutex\n");
@ -419,6 +464,7 @@ static void *sdl_audio_init (void)
SDL_QuitSubSystem (SDL_INIT_AUDIO);
return NULL;
}
#endif
s->driver_created = true;
return s;
@ -428,8 +474,10 @@ static void sdl_audio_fini (void *opaque)
{
SDLAudioState *s = opaque;
sdl_close (s);
#if USE_SEMAPHORE
SDL_DestroySemaphore (s->sem);
SDL_DestroyMutex (s->mutex);
#endif
SDL_QuitSubSystem (SDL_INIT_AUDIO);
s->driver_created = false;
}