Workaround for jack sample rate mismatch (#607)

During the creation of a jack audio driver, it is checked whether the sample-rate of the settings object matches jack's rate. If not, it was adjusted previously via fluid_synth_set_sample_rate(). Due to the deprecation of that function and removal of real-time capability of the synth.sample-rate setting, a regression was introduced in 5fbddcecc3 causing the synth's sample-rate to be not updated.

This workaround obtains the synth via the settings instance and for now calls the deprecated sample-rate set function.

src/drivers/fluid_adriver.c

@@ -294,7 +294,9 @@ find_fluid_audio_driver(fluid_settings_t *settings)
  * @return The new audio driver instance.
  *
  * Creates a new audio driver for a given \p synth instance with a defined set
- * of configuration \p settings.
+ * of configuration \p settings. The \p settings instance must be the same that
+ * you have passed to new_fluid_synth() when creating the \p synth instance.
+ * Otherwise the behaviour is undefined.
  *
  * @note As soon as an audio driver is created, the \p synth starts rendering audio.
  * This means that all necessary sound-setup should be completed after this point,
@@ -331,8 +333,10 @@ new_fluid_audio_driver(fluid_settings_t *settings, fluid_synth_t *synth)
  * @return The new audio driver instance.
  *
  * Like new_fluid_audio_driver() but allows for custom audio processing before
- * audio is sent to audio driver.  It is the responsibility of the callback
- * \p func to render the audio into the buffers.
+ * audio is sent to audio driver. It is the responsibility of the callback
+ * \p func to render the audio into the buffers. If \p func uses a fluid_synth_t \p synth,
+ * the \p settings instance must be the same that you have passed to new_fluid_synth()
+ * when creating the \p synth instance. Otherwise the behaviour is undefined.
  *
  * @note Not as efficient as new_fluid_audio_driver().
  *

src/drivers/fluid_adriver.h

@@ -119,6 +119,7 @@ fluid_audio_driver_t *new_fluid_jack_audio_driver2(fluid_settings_t *settings,
         fluid_audio_func_t func, void *data);
 void delete_fluid_jack_audio_driver(fluid_audio_driver_t *p);
 void fluid_jack_audio_driver_settings(fluid_settings_t *settings);
+int fluid_jack_obtain_synth(fluid_settings_t *settings, fluid_synth_t **synth);
 #endif
 
 #if SNDMAN_SUPPORT

src/drivers/fluid_jack.c

@@ -484,7 +484,6 @@ fluid_jack_client_register_ports(void *driver, int isaudio, jack_client_t *clien
         }
     }
 
-
     /* Adjust sample rate to match JACK's */
     jack_srate = jack_get_sample_rate(client);
     FLUID_LOG(FLUID_DBG, "Jack engine sample rate: %lu", jack_srate);
@@ -493,15 +492,21 @@ fluid_jack_client_register_ports(void *driver, int isaudio, jack_client_t *clien
 
     if((unsigned long)sample_rate != jack_srate)
     {
-        FLUID_LOG(FLUID_INFO, "Jack sample rate mismatch, adjusting."
+        fluid_synth_t* synth;
+        if(fluid_jack_obtain_synth(settings, &synth) == FLUID_OK)
+        {
+            FLUID_LOG(FLUID_INFO, "Jack sample rate mismatch, adjusting."
                   " (synth.sample-rate=%lu, jackd=%lu)", (unsigned long)sample_rate, jack_srate);
-        fluid_settings_setnum(settings, "synth.sample-rate", jack_srate);
-    }
-
-    /* Changing sample rate is non RT, so make sure we process it and/or other things now */
-    if(dev->callback == NULL)
-    {
-        fluid_synth_process_event_queue(dev->data);
+            fluid_synth_set_sample_rate(synth, jack_srate);
+            /* Changing sample rate is non RT, so make sure we process it and/or other things now */
+            fluid_synth_process_event_queue(synth);
+        }
+        else
+        {
+            FLUID_LOG(FLUID_WARN, "Jack sample rate mismatch (synth.sample-rate=%lu, jackd=%lu)"
+            " impossible to adjust, because the settings object provided to new_fluid_audio_driver2() was not used to create a synth."
+            , (unsigned long)sample_rate, jack_srate);
+        }
     }
 
     return FLUID_OK;
@@ -865,7 +870,7 @@ new_fluid_jack_midi_driver(fluid_settings_t *settings,
     }
 
     return (fluid_midi_driver_t *)dev;
-    
+
 error_recovery:
     delete_fluid_jack_midi_driver((fluid_midi_driver_t *)dev);
     return NULL;
@@ -887,4 +892,18 @@ delete_fluid_jack_midi_driver(fluid_midi_driver_t *p)
     FLUID_FREE(dev);
 }
 
+int fluid_jack_obtain_synth(fluid_settings_t *settings, fluid_synth_t **synth)
+{
+    void *data;
+
+    if(!fluid_settings_is_realtime(settings, "synth.gain") ||
+       (data = fluid_settings_get_user_data(settings, "synth.gain")) == NULL)
+    {
+        return FLUID_FAILED;
+    }
+
+    *synth = data;
+    return FLUID_OK;
+}
+
 #endif /* JACK_SUPPORT */

src/utils/fluid_settings.c

@@ -791,6 +791,40 @@ int fluid_settings_callback_int(fluid_settings_t *settings, const char *name,
     return FLUID_OK;
 }
 
+void* fluid_settings_get_user_data(fluid_settings_t * settings, const char *name)
+{
+    fluid_setting_node_t *node;
+    void* retval = NULL;
+
+    fluid_return_val_if_fail(settings != NULL, NULL);
+    fluid_return_val_if_fail(name != NULL, NULL);
+    fluid_return_val_if_fail(name[0] != '\0', NULL);
+
+    fluid_rec_mutex_lock(settings->mutex);
+
+    if(fluid_settings_get(settings, name, &node) == FLUID_OK)
+    {
+        if(node->type == FLUID_NUM_TYPE)
+        {
+            fluid_num_setting_t *setting = &node->num;
+            retval = setting->data;
+        }
+        else if(node->type == FLUID_STR_TYPE)
+        {
+            fluid_str_setting_t *setting = &node->str;
+            retval = setting->data;
+        }
+        else if(node->type == FLUID_INT_TYPE)
+        {
+            fluid_int_setting_t *setting = &node->i;
+            retval = setting->data;
+        }
+    }
+
+    fluid_rec_mutex_unlock(settings->mutex);
+    return retval;
+}
+
 /**
  * Get the type of the setting with the given name
  *

src/utils/fluid_settings.h

@@ -52,4 +52,6 @@ int fluid_settings_callback_int(fluid_settings_t *settings, const char *name,
 
 int fluid_settings_split_csv(const char *str, int *buf, int buf_len);
 
+void* fluid_settings_get_user_data(fluid_settings_t * settings, const char *name);
+
 #endif /* _FLUID_SETTINGS_H */

test/CMakeLists.txt

@@ -19,6 +19,7 @@ ADD_FLUID_TEST(test_synth_process)
 ADD_FLUID_TEST(test_ct2hz)
 ADD_FLUID_TEST(test_seq_event_queue_sort)
 ADD_FLUID_TEST(test_seq_scale)
+ADD_FLUID_TEST(test_jack_obtaining_synth)
 
 # if ( LIBSNDFILE_HASVORBIS )
 #     ADD_FLUID_TEST(test_sf3_sfont_loading)

test/test_jack_obtaining_synth.c

@@ -0,0 +1,34 @@
+
+#include "test.h"
+#include "fluidsynth.h"
+#include "fluid_adriver.h"
+
+// The jack driver may need the synth instance to adjust the sample-rate in case it mismatches with
+// the sample-rate of the jack driver. However, new_fluid_audio_driver2() does not receive a synth pointer.
+// Thus looking up the synth instance must be done via the settings object.
+int main(void)
+{
+#if JACK_SUPPORT
+    fluid_synth_t *obtained_synth;
+    fluid_synth_t *expected_synth;
+    fluid_settings_t *settings = new_fluid_settings();
+    TEST_ASSERT(settings != NULL);
+
+    expected_synth = new_fluid_synth(settings);
+    TEST_ASSERT(expected_synth != NULL);
+
+    TEST_SUCCESS(fluid_jack_obtain_synth(settings, &obtained_synth));
+    TEST_ASSERT(obtained_synth == expected_synth);
+
+    delete_fluid_synth(obtained_synth);
+    delete_fluid_settings(settings);
+
+    obtained_synth = expected_synth = NULL;
+
+    settings = new_fluid_settings();
+    TEST_ASSERT(settings != NULL);
+    TEST_ASSERT(fluid_jack_obtain_synth(settings, &obtained_synth) == FLUID_FAILED);
+    delete_fluid_settings(settings);
+#endif
+    return EXIT_SUCCESS;
+}