Avoids irregular OnMoreData callbacks on Windows using Core Audio

media/audio/win/core_audio_util_win.h

 // 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.
 
 // Utility methods for the Core Audio API on Windows.
 // Always ensure that Core Audio is supported before using these methods.
 // Use media::CoreAudioIsSupported() for this purpose.
 // Also, all methods must be called on a valid COM thread. This can be done
 // by using the base::win::ScopedCOMInitializer helper class.
 
@@ skipping 86 matching lines @@
   // |audio_device|. Flow direction and role is define by the |audio_device|.
   static ScopedComPtr<IAudioClient> CreateClient(IMMDevice* audio_device);
 
   // Get the mix format that the audio engine uses internally for processing
   // of shared-mode streams. This format is not necessarily a format that the
   // audio endpoint device supports. Thus, the caller might not succeed in
   // creating an exclusive-mode stream with a format obtained by this method.
   static HRESULT GetSharedModeMixFormat(IAudioClient* client,
                                         WAVEFORMATPCMEX* format);
 
+  // Get the mix format that the audio engine uses internally for processing
+  // of shared-mode streams using the default IMMDevice where flow direction
+  // and role is define by |data_flow| and |role|.
+  static HRESULT GetDefaultSharedModeMixFormat(EDataFlow data_flow,
+                                               ERole role,
+                                               WAVEFORMATPCMEX* format);
+
   // Returns true if the specified |client| supports the format in |format|
   // for the given |share_mode| (shared or exclusive).
   static bool IsFormatSupported(IAudioClient* client,
                                 AUDCLNT_SHAREMODE share_mode,
                                 const WAVEFORMATPCMEX* format);
 
   // For a shared-mode stream, the audio engine periodically processes the
   // data in the endpoint buffer at the period obtained in |device_period|.
   // For an exclusive mode stream, |device_period| corresponds to the minimum
   // time interval between successive processing by the endpoint device.
@@ skipping 32 matching lines @@
   // output data to a rendering endpoint buffer.
   static ScopedComPtr<IAudioRenderClient> CreateRenderClient(
       IAudioClient* client);
 
   // Create an IAudioCaptureClient client for an existing IAudioClient given by
   // |client|. The IAudioCaptureClient interface enables a client to read
   // input data from a capture endpoint buffer.
   static ScopedComPtr<IAudioCaptureClient> CreateCaptureClient(
       IAudioClient* client);
 
+  // Fills up the endpoint rendering buffer with silence for an existing
+  // IAudioClient given by |client| and a corresponding IAudioRenderClient
+  // given by |render_client|.
+  static bool FillRenderEndpointBufferWithSilence(
+      IAudioClient* client, IAudioRenderClient* render_client);
+
  private:
   CoreAudioUtil() {}
   ~CoreAudioUtil() {}
   DISALLOW_COPY_AND_ASSIGN(CoreAudioUtil);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_CORE_AUDIO_UTIL_WIN_H_