ao_avfoundation: sleep on zero sample

audio/out/ao_avfoundation.m

@@ -96,12 +96,10 @@ static void feed(struct ao *ao)
 
     int real_sample_count = ao_read_data_nonblocking(ao, data, request_sample_count, p->end_time_mp);
     if (real_sample_count == 0) {
-        // in this case, we must satisfy renderer to avoid spining
-        real_sample_count = ao_read_data(ao, data, request_sample_count, p->end_time_mp);
-        if (real_sample_count == 0) {
-            // ao_read_data may still return zero?
-            real_sample_count = request_sample_count;
-        }
+        CFRelease(block_buffer);
+        block_buffer = NULL;
+        mp_sleep_ns(1000000); // avoid spinning
+        return;
     }
 
     CMSampleTimingInfo sample_timing_into[] = {(CMSampleTimingInfo) {
@@ -159,9 +157,11 @@ static void stop(struct ao *ao)
 {
     struct priv *p = ao->priv;
 
-    [p->renderer stopRequestingMediaData];
-    [p->renderer flush];
-    [p->synchronizer setRate:0];
+    dispatch_sync(p->queue, ^{
+        [p->renderer stopRequestingMediaData];
+        [p->renderer flush];
+        [p->synchronizer setRate:0];
+    });
 }
 
 static int control(struct ao *ao, enum aocontrol cmd, void *arg)
@@ -326,6 +326,8 @@ static void uninit(struct ao *ao)
 {
     struct priv *p = ao->priv;
 
+    stop(ao);
+
     [p->renderer release];
     [p->synchronizer release];
     dispatch_release(p->queue);