(Android) Supply device-optimal audio defaults through the intent

The launch intent carries AUDIO_RATE and AUDIO_FRAMES extras with the
AudioManager-reported optimal sample rate and buffer size.  The
frontend stores them in g_defaults and config_set_defaults applies
them as the audio_out_rate and audio_block_frames defaults, so a value
saved in the config file still overrides them on load.

configuration.c

@@ -5487,6 +5487,17 @@ void config_set_defaults(void *data)
    if (!g_defaults.settings_in_latency)
       g_defaults.settings_in_latency          = DEFAULT_IN_LATENCY;
 
+   /* Device-optimal audio parameters supplied by the frontend.
+    * Values saved in the config file still override these on
+    * load. */
+   if (g_defaults.settings_out_sample_rate > 0)
+      settings->uints.audio_output_sample_rate =
+            (unsigned)g_defaults.settings_out_sample_rate;
+
+   if (g_defaults.settings_out_block_frames > 0)
+      settings->uints.audio_block_frames       =
+            (unsigned)g_defaults.settings_out_block_frames;
+
 
    audio_set_float(AUDIO_ACTION_VOLUME_GAIN, settings->floats.audio_volume);
 #ifdef HAVE_AUDIOMIXER

defaults.h

@@ -81,6 +81,11 @@ struct defaults
 #endif
    int settings_out_latency;
    int settings_in_latency;
+   /* Device-optimal audio output parameters supplied by the
+    * frontend; 0 means the frontend has no opinion and the
+    * built-in defaults apply. */
+   int settings_out_sample_rate;
+   int settings_out_block_frames;
 #ifdef HAVE_MENU
    unsigned menu_materialui_menu_color_theme;
 #endif

frontend/drivers/platform_unix.c

@@ -1989,6 +1989,49 @@ static void frontend_unix_get_env(int *argc,
       }
    }
 
+   /* Device-optimal audio output parameters, queried from
+    * AudioManager on the Java side.  These become the defaults;
+    * values saved in the config file still win. */
+   CALL_OBJ_METHOD_PARAM(env, jstr, obj, android_app->getStringExtra,
+         (*env)->NewStringUTF(env, "AUDIO_RATE"));
+
+   if (android_app->getStringExtra && jstr)
+   {
+      const char *argv = (*env)->GetStringUTFChars(env, jstr, 0);
+      int rate         = 0;
+
+      if (argv && *argv)
+         rate = atoi(argv);
+      (*env)->ReleaseStringUTFChars(env, jstr, argv);
+
+      if (rate > 0)
+      {
+         g_defaults.settings_out_sample_rate = rate;
+         __android_log_print(ANDROID_LOG_INFO,
+            "RetroArch", "[ENV] Device sample rate: %d Hz.\n", rate);
+      }
+   }
+
+   CALL_OBJ_METHOD_PARAM(env, jstr, obj, android_app->getStringExtra,
+         (*env)->NewStringUTF(env, "AUDIO_FRAMES"));
+
+   if (android_app->getStringExtra && jstr)
+   {
+      const char *argv = (*env)->GetStringUTFChars(env, jstr, 0);
+      int frames       = 0;
+
+      if (argv && *argv)
+         frames = atoi(argv);
+      (*env)->ReleaseStringUTFChars(env, jstr, argv);
+
+      if (frames > 0)
+      {
+         g_defaults.settings_out_block_frames = frames;
+         __android_log_print(ANDROID_LOG_INFO,
+            "RetroArch", "[ENV] Device audio block frames: %d.\n", frames);
+      }
+   }
+
    /* Content. */
    CALL_OBJ_METHOD_PARAM(env, jstr, obj, android_app->getStringExtra,
          (*env)->NewStringUTF(env, "DATADIR"));