Avoids irregular OnMoreData callbacks on Windows using Core Audio

media/audio/win/core_audio_util_win_unittest.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 "base/memory/scoped_ptr.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/win/scoped_com_initializer.h"
 #include "base/win/scoped_handle.h"
 #include "media/audio/win/core_audio_util_win.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ skipping 366 matching lines @@
       // Do a proper initialization and verify that it works this time.
       CoreAudioUtil::SharedModeInitialize(client, &format, NULL,
                                           &endpoint_buffer_size);
       capture_client = CoreAudioUtil::CreateCaptureClient(client);
       EXPECT_TRUE(capture_client);
       EXPECT_GT(endpoint_buffer_size, 0u);
     }
   }
 }
 
+TEST_F(CoreAudioUtilWinTest, FillRenderEndpointBufferWithSilence) {
+  if (!CanRunAudioTest())
+    return;
+
+  // Create default clients using the default mixing format for shared mode.
+  ScopedComPtr<IAudioClient> client(
+      CoreAudioUtil::CreateDefaultClient(eRender, eConsole));
+  EXPECT_TRUE(client);
+
+  WAVEFORMATPCMEX format;
+  size_t endpoint_buffer_size = 0;
+  EXPECT_TRUE(SUCCEEDED(CoreAudioUtil::GetSharedModeMixFormat(client,
+                                                              &format)));
+  CoreAudioUtil::SharedModeInitialize(client, &format, NULL,
+                                      &endpoint_buffer_size);
+  EXPECT_GT(endpoint_buffer_size, 0u);
+
+  ScopedComPtr<IAudioRenderClient> render_client(
+      CoreAudioUtil::CreateRenderClient(client));
+  EXPECT_TRUE(render_client);
+
+  // The endpoint audio buffer should not be filled up by default after being
+  // created.
+  UINT32 num_queued_frames = 0;
+  client->GetCurrentPadding(&num_queued_frames);
+  EXPECT_EQ(num_queued_frames, 0u);
+
+  // Fill it up with zeros and verify that the buffer is full.
+  // It is not possible to verify that the actual data consists of zeros
+  // since we can't access data that has already been sent to the endpoint
+  // buffer.
+  EXPECT_TRUE(CoreAudioUtil::FillRenderEndpointBufferWithSilence(
+                  client, render_client));
+  client->GetCurrentPadding(&num_queued_frames);
+  EXPECT_EQ(num_queued_frames, endpoint_buffer_size);
+}
+
 //
 
 }  // namespace media