Adds Core Audio Utility methods for Windows

media/audio/win/core_audio_util_win.h

Index: media/audio/win/core_audio_util_win.h
diff --git a/media/audio/win/core_audio_util_win.h b/media/audio/win/core_audio_util_win.h
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+// 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.
+
+#ifndef MEDIA_AUDIO_WIN_CORE_AUDIO_UTIL_WIN_H_
+#define MEDIA_AUDIO_WIN_CORE_AUDIO_UTIL_WIN_H_
+
+#include <audioclient.h>
+#include <mmdeviceapi.h>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/win/scoped_comptr.h"
+#include "media/audio/audio_device_name.h"
+#include "media/base/media_export.h"
+
+using base::win::ScopedComPtr;
+
+namespace media {
+
+class MEDIA_EXPORT CoreAudioUtil {
+ public:
+  // Returns true if Windows Core Audio is supported.
+  static bool IsSupported();
+
+  // The Windows Multimedia Device (MMDevice) API enables audio clients to
+  // discover audio endpoint devices and determine their capabilities.
+
+  // Number of active audio devices in the specified flow data flow direction.
+  // Set |data_flow| to eAll to retrive the total number of active audio
+  // devices.
+  static int NumberOfActiveDevices(EDataFlow data_flow);
+
+  // Creates an IMMDeviceEnumerator interface which provides methods for
+  // enumerating audio endpoint devices.
+  static ScopedComPtr<IMMDeviceEnumerator> CreateDeviceEnumerator();
+
+  // Create a default endpoint device that is specified by a data-flow
+  // direction and role, e.g. default render device.
+  static ScopedComPtr<IMMDevice> CreateDefaultDevice(
+      EDataFlow data_flow, ERole role);
+
+  // Create an endpoint device that is specified by a unique endpoint device-
+  // identification string.
+  static ScopedComPtr<IMMDevice> CreateDevice(const std::string& device_id);
+
+  // Returns the unique ID and user-friendly name of a given endpoint device.
+  // Example: "{0.0.1.00000000}.{8db6020f-18e3-4f25-b6f5-7726c9122574}", and
+  //          "Microphone (Realtek High Definition Audio)".
+  static HRESULT GetDeviceName(IMMDevice* device, AudioDeviceName* name);
+
+  // Gets the user-friendly name of the endpoint devcice which is represented
+  // by a uniqe id in |device_id|.
+  static std::string GetFriendlyName(const std::string& device_id);
+
+  // Returns true if the provided uniqe |device_id| correspinds to the current
+  // default device for the specified by a data-flow direction and role.
+  static bool DeviceIsDefault(
+      EDataFlow flow, ERole role, std::string device_id);
+
+  // Query if the audio device is a rendering device or a capture device.
+  static EDataFlow GetDataFlow(IMMDevice* device);
+
+  // The Windows Audio Session API (WASAPI) enables client applications to
+  // manage the flow of audio data between the application and an audio endpoint
+  // device.
+
+  // Create an IAudioClient interface for an existing IMMDevice given by
+  // |audio_device|. Flow direction and role is define by the |audio_device|.
+  // The IAudioClient interface enables a client to create and initialize an
+  // audio stream between an audio application and the audio engine (for a
+  // shared-mode stream) or the hardware buffer of an audio endpoint device
+  // (for an exclusive-mode stream).
+  static ScopedComPtr<IAudioClient> CreateClient(IMMDevice* audio_device);
+
+ private:
+  CoreAudioUtil() {}
+  ~CoreAudioUtil() {}
+  DISALLOW_COPY_AND_ASSIGN(CoreAudioUtil);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_WIN_CORE_AUDIO_UTIL_WIN_H_