Add a buffering controller for Chromecast.

chromecast/media/cma/base/buffering_controller.h

+// Copyright 2014 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_BASE_BUFFERING_CONTROLLER_H
+#define CHROMECAST_MEDIA_CMA_BASE_BUFFERING_CONTROLLER_H
+
+#include <list>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+
+namespace media {
+namespace cma {
+class BufferingConfig;
+class BufferingState;
+
+class BufferingController {
+ public:
+  typedef base::Callback<void(bool)> BufferingNotificationCb;

[xhwang, 2014/08/28 20:44:43]

nit: in media code, we use FooCB for callback type. Note it's CB instead of Cb.

[damienv1, 2014/08/29 15:09:06]

Done.

+
+  // Create a buffering controller where the conditions to trigger re-buffering
+  // are given by |config|. The whole point of the buffering controller is to
+  // derive a single buffering state from the buffering state of various
+  // streams.
+  // |buffering_notification_cb| is a callback invoked to inform about possible
+  // changes of the buffering state.
+  BufferingController(
+      const scoped_refptr<BufferingConfig>& config,
+      const BufferingNotificationCb& buffering_notification_cb);
+  ~BufferingController();
+
+  // Create a buffering state for one stream. This state is added to the list
+  // of streams monitored by the buffering controller.
+  scoped_refptr<BufferingState> AddStream();
+
+  // Set the playback time.
+  void SetMediaTime(base::TimeDelta time);
+
+  // Return the maximum media time available for rendering.
+  // Return kNoTimestamp() if unknown.
+  base::TimeDelta GetMaxRenderingTime() const;
+
+  // Return whether there is an active buffering phase.
+  bool IsBuffering() const { return is_buffering_; }
+
+  // Reset the buffering controller. This includes removing all the buffering
+  // states that were previously added.
+  void Reset();
+
+ private:
+  // Invoked each time the buffering state of one of the streams has changed.
+  // If |force_notification| is set, |buffering_notification_cb_| is invoked
+  // regardless whether the buffering state has changed or not.
+  // If |buffering_timeout| is set, then the condition to leave the buffering
+  // state is relaxed (we don't want to wait more).
+  void OnBufferingStateChanged(bool force_notification,
+                               bool buffering_timeout);
+
+  // Update the high buffer level threshold to |high_level_threshold|
+  // if needed.
+  // This condition is triggered when one of the stream reached its maximum
+  // capacity. In that case, to avoid possible race condition (the buffering
+  // controller waits for more data to come but the buffer is to small to
+  // accomodate additional data), the thresholds in |config_| are adjusted
+  // accordingly.
+  void UpdateHighLevelThreshold(base::TimeDelta high_level_threshold);
+
+  // Determine the overall buffer level based on the buffer level of each
+  // stream.
+  bool IsHighBufferLevel();
+  bool IsLowBufferLevel();
+
+  // Log the state of the buffering controller.
+  void DumpState() const;
+
+  base::ThreadChecker thread_checker_;
+
+  // Settings used to determine when to start/stop buffering.
+  scoped_refptr<BufferingConfig> config_;
+
+  // Callback invoked to inform the stream about the buffering state.
+  BufferingNotificationCb buffering_notification_cb_;
+
+  // State of the buffering controller.
+  bool is_buffering_;
+
+  // Buffering state for metrics reporting.
+  base::Time begin_buffering_time_;
+
+  // Buffering level for each individual stream.
+  typedef std::list<scoped_refptr<BufferingState> > StreamList;
+  StreamList stream_list_;
+
+  base::WeakPtrFactory<BufferingController> weak_factory_;
+  base::WeakPtr<BufferingController> weak_this_;
+
+  DISALLOW_COPY_AND_ASSIGN(BufferingController);
+};
+
+}  // namespace cma
+}  // namespace media
+
+#endif  // CHROMECAST_MEDIA_CMA_BASE_BUFFERING_CONTROLLER_H