decoder/renderer: use memory cache and single decoder to optimize frames for

cycles

app/render/backend/renderbackend.cpp

@@ -83,6 +83,8 @@ void RenderBackend::Close()
 
   threads_.clear();
   processors_.clear();
+
+  decoder_cache_.Clear();
 }
 
 const QString &RenderBackend::GetError() const
@@ -375,6 +377,11 @@ void RenderBackend::SetWorkerBusyState(RenderWorker *worker, bool busy)
   processor_busy_state_.replace(processors_.indexOf(worker), busy);
 }
 
+DecoderCache *RenderBackend::decoder_cache()
+{
+  return &decoder_cache_;
+}
+
 bool RenderBackend::AllProcessorsAreAvailable() const
 {
   foreach (bool busy, processor_busy_state_) {