rendering_helper - Warm up the rendering.

content/common/gpu/media/rendering_helper.cc

 // Copyright 2013 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/rendering_helper.h"
 
 #include <algorithm>
 #include <numeric>
 #include <vector>
 
@@ skipping 284 matching lines @@
   if (tex_external != -1) {
     glUniform1i(tex_external, 1);
   }
   int pos_location = glGetAttribLocation(program_, "in_pos");
   glEnableVertexAttribArray(pos_location);
   glVertexAttribPointer(pos_location, 2, GL_FLOAT, GL_FALSE, 0, kVertices);
   int tc_location = glGetAttribLocation(program_, "in_tc");
   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;
+  std::vector<GLubyte> emptyData(screen_size_.GetArea() * 2);

[piman, 2014/10/14 17:26:43]

nit: scoped_ptr<GLubyte[]> empty_data(new GLubyte[screen_size_.GetArea() * 2]);

std::vector doesn't guarantee contiguous storage (before c++11 STL, which we
don't use consistenly yet).

+  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[0]);
+  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_);
 
   render_task_.Cancel();
 
   if (render_as_thumbnails_) {
     glDeleteTextures(1, &thumbnails_texture_id_);
     glDeleteFramebuffersEXT(1, &thumbnails_fbo_id_);
   }
 
@@ skipping 286 matching lines @@
     scale = std::min(1.0f, scale);
 
     size_t w = scale * size.width();
     size_t h = scale * size.height();
     size_t x = offset_x[i % cols] + (widths[i % cols] - w) / 2;
     size_t y = offset_y[i / cols] + (heights[i / cols] - h) / 2;
     videos_[i].render_area = gfx::Rect(x, y, w, h);
   }
 }
 }  // namespace content