Updated comments for SwapChainProcessor (#522)

Update comments for SwapChainProcessor in IndirectDisplay driver sample

Co-authored-by: Shantanu Gupta <shagu@microsoft.com>

video/IndirectDisplay/IddSampleDriver/Driver.cpp

@@ -422,6 +422,7 @@ void SwapChainProcessor::RunCore()
         }
         else if (SUCCEEDED(hr))
         {
+            // We have new frame to process, the surface has a reference on it that the driver has to release
             AcquiredBuffer.Attach(Buffer.MetaData.pSurface);
 
             // ==============================
@@ -435,7 +436,17 @@ void SwapChainProcessor::RunCore()
             //  * a GPU custom compute shader encode operation
             // ==============================
 
+            // We have finished processing this frame hence we release the reference on it.
+            // If the driver forgets to release the reference to the surface, it will be leaked which results in the
+            // surfaces being left around after swapchain is destroyed.
+            // NOTE: Although in this sample we release reference to the surface here; the driver still
+            // owns the Buffer.MetaData.pSurface surface until IddCxSwapChainReleaseAndAcquireBuffer returns
+            // S_OK and gives us a new frame, a driver may want to use the surface in future to re-encode the desktop 
+            // for better quality if there is no new frame for a while
             AcquiredBuffer.Reset();
+
+            // Indicate to OS that we have finished inital processing of the frame, it is a hint that
+            // OS could start preparing another frame
             hr = IddCxSwapChainFinishedProcessingFrame(m_hSwapChain);
             if (FAILED(hr))
             {