Don't wait endlessly for flushing the batched queries sent to the GPU driver during H/W decode

content/common/gpu/media/dxva_video_decode_accelerator.cc

Index: content/common/gpu/media/dxva_video_decode_accelerator.cc
===================================================================
--- content/common/gpu/media/dxva_video_decode_accelerator.cc	(revision 167469)
+++ content/common/gpu/media/dxva_video_decode_accelerator.cc	(working copy)
@@ -384,7 +384,17 @@
     base::win::ScopedComPtr<IDirect3DSurface9> d3d_surface;
     HRESULT hr = decoding_texture_->GetSurfaceLevel(0, d3d_surface.Receive());
     RETURN_ON_HR_FAILURE(hr, "Failed to get surface from texture", false);
+    
+    // Ideally, this should be done immediately before the draw call that uses
+    // the texture. Flush it once here though.
+    hr = query_->Issue(D3DISSUE_END);

[ananta, 2012/11/14 03:06:48]

Issuing the query upfront causes the loop below to execute in most cases once.

+    RETURN_ON_HR_FAILURE(hr, "Failed to issue END", false);
 
+    // The BeginScene/EndScene calls below indicate the start/end of rendering.
+    // It is an effort to ensure that pending rendering operations are flushed.
+    hr = device_->BeginScene();
+    RETURN_ON_HR_FAILURE(hr, "BeginScene failed", false);
+
     hr = device_->StretchRect(dest_surface,
                               NULL,
                               d3d_surface,
@@ -392,15 +402,21 @@
                               D3DTEXF_NONE);
     RETURN_ON_HR_FAILURE(hr, "Colorspace conversion via StretchRect failed",
                          false);
-    // Ideally, this should be done immediately before the draw call that uses
-    // the texture. Flush it once here though.
-    hr = query_->Issue(D3DISSUE_END);
-    RETURN_ON_HR_FAILURE(hr, "Failed to issue END", false);
-    do {
-      hr = query_->GetData(NULL, 0, D3DGETDATA_FLUSH);
-      if (hr == S_FALSE)
-        Sleep(1);  // Poor-man's Yield().
-    } while (hr == S_FALSE);
+    
+    hr = device_->EndScene();
+    RETURN_ON_HR_FAILURE(hr, "EndScene failed", false);
+
+    // The DXVA decoder has its own device which it uses for decoding. ANGLE
+    // has its own device which we don't have access to.
+    // The above code attempts to copy the decoded picture into a surface
+    // which is owned by ANGLE. As there are multiple devices involved in
+    // this, the StretchRect call above is not synchronous.
+    // We attempt to flush the batched operations to ensure that the picture is
+    // copied to the surface owned by ANGLE.
+    // We need to do this in a loop and call flush multiple times.
+    while (query_->GetData(NULL, 0, D3DGETDATA_FLUSH) == S_FALSE) {
+      Sleep(1);  // Poor-man's Yield().
+    }
     eglBindTexImage(
         static_cast<EGLDisplay*>(eglGetDisplay(EGL_DEFAULT_DISPLAY)),
         decoding_surface_,