Commit bcf19777 authored by Thomas Huth's avatar Thomas Huth Committed by Gerd Hoffmann
Browse files

audio/sdlaudio: Allow audio playback with SDL2 



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: default avatarThomas Huth <thuth@redhat.com>
Message-id: 1485852398-2327-1-git-send-email-thuth@redhat.com
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 1ffc2665

audio/sdlaudio.c

+48 −0
Original line number Diff line number Diff line
@@ -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;

}