Don't send blocks from qtcapture Demux that we have already sent before. Avoid...

Don't send blocks from qtcapture Demux that we have already sent before. Avoid excessive CPU usage while there are no new blocks.

modules/access/qtcapture.m

@@ -68,6 +68,7 @@ vlc_module_end();
 {
     CVImageBufferRef currentImageBuffer;
     mtime_t currentPts;
+    mtime_t previousPts;
 }
 - (id)init;
 - (void)outputVideoFrame:(CVImageBufferRef)videoFrame withSampleBuffer:(QTSampleBuffer *)sampleBuffer fromConnection:(QTCaptureConnection *)connection;
@@ -82,6 +83,7 @@ vlc_module_end();
     {
         currentImageBuffer = nil;
         currentPts = 0;
+        previousPts = 0;
     }
     return self;
 }
@@ -117,13 +119,13 @@ vlc_module_end();
     CVImageBufferRef imageBuffer;
     mtime_t pts;
 
-    if(!currentImageBuffer)
+    if(!currentImageBuffer || currentPts == previousPts )
         return 0;
 
     @synchronized (self)
     {
         imageBuffer = CVBufferRetain(currentImageBuffer);
-        pts = currentPts;
+        pts = previousPts = currentPts;
 
         CVPixelBufferLockBaseAddress(imageBuffer, 0);
         void * pixels = CVPixelBufferGetBaseAddress(imageBuffer);
@@ -353,6 +355,7 @@ static int Demux( demux_t *p_demux )
         /* Nothing to display yet, just forget */
         block_Release( p_block );
         [pool release];
+        msleep( 10000 );
         return 1;
     }