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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/gpu/media/dxva_video_decode_accelerator.h"
 
 #if !defined(OS_WIN)
 #error This file should only be built on Windows.
 #endif   // !defined(OS_WIN)
 
@@ skipping 366 matching lines @@
   glGetIntegerv(GL_TEXTURE_BINDING_2D, &current_texture);
 
   glBindTexture(GL_TEXTURE_2D, picture_buffer_.texture_id());
 
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 
   if (device_supports_format_conversion) {
     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,
                               NULL,
                               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_,
         EGL_BACK_BUFFER);
   } else {
     scoped_array<char> bits;
     RETURN_ON_FAILURE(GetBitmapFromSurface(DXVAVideoDecodeAccelerator::device_,
                                            dest_surface, &bits),
                       "Failed to get bitmap from surface for rendering",
                       false);
@@ skipping 724 matching lines @@
       return;
   }
 
   MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
       &DXVAVideoDecodeAccelerator::NotifyFlushDone, base::AsWeakPtr(this)));
 
   state_ = kNormal;
 }
 
 }  // namespace content