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diff --git a/chromecast/media/cma/backend/media_pipeline_backend_manager.h b/chromecast/media/cma/backend/media_pipeline_backend_manager.h
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+// Copyright 2016 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.
+
+#ifndef CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_BACKEND_MANAGER_H_
+#define CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_BACKEND_MANAGER_H_
+
+#include <map>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "chromecast/public/media/media_pipeline_backend.h"
+#include "chromecast/public/media/media_pipeline_device_params.h"
+
+namespace base {
+template <typename T>
+struct DefaultLazyInstanceTraits;
+}  // namespace base
+
+namespace chromecast {
+namespace media {
+
+// This class manages created media pipelines, and provides volume control by
+// stream type.
+// All functions in this class should be called on the media thread.
+class MediaPipelineBackendManager {
+ public:
+  // Create media pipeline backend.
+  static MediaPipelineBackend* CreateMediaPipelineBackend(
+      const MediaPipelineDeviceParams& params);
+
+  // Create media pipeline backend with a specific stream_type.
+  static MediaPipelineBackend* CreateMediaPipelineBackend(
+      const MediaPipelineDeviceParams& params,
+      int stream_type);
+
+  // Internal clean up when a new media pipeline backend is destroyed.
+  static void OnMediaPipelineBackendDestroyed(
+      const MediaPipelineBackend* backend);
+
+  // Sets the relative volume for a specified stream type,
+  // with range [0.0, 1.0] inclusive. If |multiplier| is outside the
+  // range [0.0, 1.0], it is clamped to that range.
+  // TODO(tianyuwang): change stream_type to use a enum.
+  static void SetVolumeMultiplier(int stream_type, float volume);
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<MediaPipelineBackendManager>;
+
+  // Returns a pointer to a singleton instance of the
+  // MediaPipelineBackendManager.
+  static MediaPipelineBackendManager* Get();
+
+  MediaPipelineBackendManager();
+  ~MediaPipelineBackendManager();
+
+  float GetVolumeMultiplier(int stream_type);
+
+  // A vector that stores all of the existing media_pipeline_backends_.
+  std::vector<MediaPipelineBackend*> media_pipeline_backends_;
+
+  // Volume multiplier for each type of audio streams.
+  std::map<int, float> volume_by_stream_type_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaPipelineBackendManager);
+};
+
+}  // namespace media
+}  // namespace chromecast
+
+#endif  // CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_BACKEND_MANAGER_H_