rendering_helper - Warm up the rendering.

The rendering for the first few frames is much slower (As much as
100ms on Peach Pit). To get stable/correct numbers in performance
tests, we try to warm it up by rendering several frames in the
beginning.

BUG=411123
TEST=Run the vda_unittest on Peach pit.

Review URL: https://codereview.chromium.org/583503002

Cr-Commit-Position: refs/heads/master@{#299861}

content/common/gpu/media/rendering_helper.cc

@@ -58,7 +58,9 @@ static void CreateShader(GLuint program,
 
 namespace content {
 
-RenderingHelperParams::RenderingHelperParams() {}
+RenderingHelperParams::RenderingHelperParams()
+    : rendering_fps(0), warm_up_iterations(0), render_as_thumbnails(false) {
+}
 
 RenderingHelperParams::~RenderingHelperParams() {}
 
@@ -302,9 +304,36 @@ void RenderingHelper::Initialize(const RenderingHelperParams& params,
   glEnableVertexAttribArray(tc_location);
   glVertexAttribPointer(tc_location, 2, GL_FLOAT, GL_FALSE, 0, kTextureCoords);
 
+  if (frame_duration_ != base::TimeDelta())
+    WarmUpRendering(params.warm_up_iterations);
+
   done->Signal();
 }
 
+// The rendering for the first few frames is slow (e.g., 100ms on Peach Pit).
+// This affects the numbers measured in the performance test. We try to render
+// several frames here to warm up the rendering.
+void RenderingHelper::WarmUpRendering(int warm_up_iterations) {
+  unsigned int texture_id;
+  scoped_ptr<GLubyte[]> emptyData(new GLubyte[screen_size_.GetArea() * 2]);
+  glGenTextures(1, &texture_id);
+  glBindTexture(GL_TEXTURE_2D, texture_id);
+  glTexImage2D(GL_TEXTURE_2D,
+               0,
+               GL_RGB,
+               screen_size_.width(),
+               screen_size_.height(),
+               0,
+               GL_RGB,
+               GL_UNSIGNED_SHORT_5_6_5,
+               emptyData.get());
+  for (int i = 0; i < warm_up_iterations; ++i) {
+    RenderTexture(GL_TEXTURE_2D, texture_id);
+    gl_surface_->SwapBuffers();
+  }
+  glDeleteTextures(1, &texture_id);
+}
+
 void RenderingHelper::UnInitialize(base::WaitableEvent* done) {
   CHECK_EQ(base::MessageLoop::current(), message_loop_);
 

content/common/gpu/media/rendering_helper.h

@@ -52,6 +52,10 @@ struct RenderingHelperParams {
   // The rendering FPS.
   int rendering_fps;
 
+  // The number of empty frames rendered when the rendering helper is
+  // initialized.
+  int warm_up_iterations;
+
   // The desired size of each window. We play each stream in its own window
   // on the screen.
   std::vector<gfx::Size> window_sizes;
@@ -149,6 +153,8 @@ class RenderingHelper {
 
   void RenderContent();
 
+  void WarmUpRendering(int warm_up_iterations);
+
   void LayoutRenderingAreas(const std::vector<gfx::Size>& window_sizes);
 
   // Render |texture_id| to the current view port of the screen using target

content/common/gpu/media/video_decode_accelerator_unittest.cc

@@ -101,6 +101,9 @@ const base::FilePath::CharType* g_output_log = NULL;
 // The value is set by the switch "--rendering_fps".
 double g_rendering_fps = 60;
 
+// The value is set by the switch "--rendering_warm_up".
+int g_rendering_warm_up = 0;
+
 // Magic constants for differentiating the reasons for NotifyResetDone being
 // called.
 enum ResetPoint {
@@ -1070,6 +1073,7 @@ TEST_P(VideoDecodeAcceleratorParamTest, TestSimpleDecode) {
 
   RenderingHelperParams helper_params;
   helper_params.rendering_fps = g_rendering_fps;
+  helper_params.warm_up_iterations = g_rendering_warm_up;
   helper_params.render_as_thumbnails = render_as_thumbnails;
   if (render_as_thumbnails) {
     // Only one decoder is supported with thumbnail rendering
@@ -1341,6 +1345,7 @@ TEST_F(VideoDecodeAcceleratorTest, TestDecodeTimeMedian) {
 
   // Disable rendering by setting the rendering_fps = 0.
   helper_params.rendering_fps = 0;
+  helper_params.warm_up_iterations = 0;
   helper_params.render_as_thumbnails = false;
 
   ClientStateNotification<ClientState>* note =
@@ -1421,6 +1426,11 @@ int main(int argc, char **argv) {
       CHECK(base::StringToDouble(input, &content::g_rendering_fps));
       continue;
     }
+    if (it->first == "rendering_warm_up") {
+      std::string input(it->second.begin(), it->second.end());
+      CHECK(base::StringToInt(input, &content::g_rendering_warm_up));
+      continue;
+    }
     // TODO(owenlin): Remove this flag once it is not used in autotest.
     if (it->first == "disable_rendering") {
       content::g_rendering_fps = 0;