Reduce code duplication in renderers

app/streaming/video/ffmpeg-renderers/renderer.h

@@ -20,10 +20,26 @@ public:
     virtual bool initialize(PDECODER_PARAMETERS params) = 0;
     virtual bool prepareDecoderContext(AVCodecContext* context) = 0;
     virtual void renderFrame(AVFrame* frame) = 0;
-    virtual bool needsTestFrame() = 0;
-    virtual int getDecoderCapabilities() = 0;
-    virtual FramePacingConstraint getFramePacingConstraint() = 0;
-    virtual bool isRenderThreadSupported() = 0;
+
+    virtual bool needsTestFrame() {
+        // No test frame required by default
+        return false;
+    }
+
+    virtual int getDecoderCapabilities() {
+        // No special capabilities by default
+        return 0;
+    }
+
+    virtual FramePacingConstraint getFramePacingConstraint() {
+        // No pacing preference
+        return PACING_ANY;
+    }
+
+    virtual bool isRenderThreadSupported() {
+        // Render thread is supported by default
+        return true;
+    }
 
     // IOverlayRenderer
     virtual void notifyOverlayUpdated(Overlay::OverlayType) override {