Fixes a dealock in the Windows Audio Session API (WASAPI) backend. Reported by Ingo Bauersachs.

src/org/jitsi/impl/neomedia/jmfext/media/protocol/wasapi/WASAPIStream.java

@@ -1169,7 +1169,12 @@ private AudioFormat doConnectInSourceMode(
     @Override
     protected Format doGetFormat()
     {
-        return (format == null) ? super.doGetFormat() : format;
+        synchronized (this)
+        {
+            if (format != null)
+                return format;
+        }
+        return super.doGetFormat();
     }
 
     /**
@@ -1342,6 +1347,30 @@ private AudioFormat findClosestMatchCaptureSupportedFormat(
                     NativelySupportedAudioFormat.class);
     }
 
+    /**
+     * {@inheritDoc}
+     *
+     * Overrides the super implementation to avoid a deadlock with
+     * {@link #stop()}. The <tt>stop()</tt> method is generally invoked with a
+     * certain synchronization root locked, the implementation of
+     * <tt>WASAPIStream</tt> waits for {@link #processThread} to quit but
+     * <tt>processThread</tt> indirectly invokes
+     * {@link AbstractPushBufferStream#getFormat()} which in turn results in an
+     * attempt to lock the mentioned synchronization root i.e. the thread
+     * invoking the <tt>stop()</tt> method and <tt>processThread</tt> fall into
+     * a deadlock.
+     */
+    @Override
+    public Format getFormat()
+    {
+        synchronized (this)
+        {
+            if (format != null)
+                return format;
+        }
+        return super.getFormat();
+    }
+
     /**
      * Gets the <tt>MediaLocator</tt> of this instance which identifies the
      * audio endpoint device this <tt>SourceStream</tt> is to capture data from.