Add a buffering controller for Chromecast.

chromecast/media/cma/base/buffering_state.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_STATE_H_
+#define CHROMECAST_MEDIA_CMA_BASE_BUFFERING_STATE_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/time/time.h"

[lcwu1, 2014/08/28 02:14:58]

We should also include ref_counted.h. (IWYU)

[gunsch, 2014/08/28 02:39:54]

also base/macros.h, here and in buffering_controller.h

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

Done.

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

Done.

+
+namespace media {
+namespace cma {
+
+class BufferingConfig : public base::RefCountedThreadSafe<BufferingConfig> {
+ public:
+  BufferingConfig(base::TimeDelta low_level_threshold,
+                  base::TimeDelta high_level_threshold);
+
+  base::TimeDelta low_level() const { return low_level_threshold_; }
+  base::TimeDelta high_level() const { return high_level_threshold_; }
+
+  void set_low_level(base::TimeDelta low_level) {
+    low_level_threshold_ = low_level;
+  }
+  void set_high_level(base::TimeDelta high_level) {
+    high_level_threshold_ = high_level;
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<BufferingConfig>;
+  virtual ~BufferingConfig();
+
+  base::TimeDelta low_level_threshold_;
+  base::TimeDelta high_level_threshold_;
+
+  DISALLOW_COPY_AND_ASSIGN(BufferingConfig);
+};
+
+class BufferingState
+    : public base::RefCountedThreadSafe<BufferingState> {
+ public:
+  typedef base::Callback<void(base::TimeDelta)> HighLevelBufferCb;
+
+  enum State {
+    kLowLevel,
+    kMediumLevel,
+    kHighLevel,
+    kEosReached,
+  };
+
+  // Create a new buffering state. The initial state is |kLowLevel|.

[gunsch, 2014/08/28 02:39:54]

style nit (throughout the CL): "Function comments should be descriptive ("Opens
the file") rather than imperative ("Open the file");"

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

Done.

+  // |state_changed_cb| is used to notify about possible state changes.
+  // |high_level_buffer_cb| is used to adjust the high buffer threshold
+  // when the underlying buffer is not large enough to accomodate
+  // the current high buffer level.
+  BufferingState(const scoped_refptr<BufferingConfig>& config,
+                 const base::Closure& state_changed_cb,
+                 const HighLevelBufferCb& high_level_buffer_cb);
+
+  // Return the buffering state.
+  State GetState() const { return state_; }
+
+  // Notify the buffering state that the buffering configuration
+  // has been changed.
+  // Update the state but do not trigger |state_changed_cb_|.
+  void OnConfigChanged();
+
+  // Set the current rendering time for that stream.

[gunsch, 2014/08/28 02:39:54]

"this" stream ? (here and below)

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

Done.

+  void SetMediaTime(base::TimeDelta media_time);
+
+  // Set/get the maximum rendering media time for that stream.
+  // The maximum rendering time is always lower than the buffered time.
+  void SetMaxRenderingTime(base::TimeDelta max_rendering_time);
+  base::TimeDelta GetMaxRenderingTime() const;
+
+  // Set the buffered time.
+  void SetBufferedTime(base::TimeDelta buffered_time);
+
+  // Notify the buffering state that all the frames for that stream have been
+  // buffer, i.e. the end of stream has been reached.
+  void NotifyEos();
+
+  // Notify the buffering has reached its maximum capacity.

[gunsch, 2014/08/28 02:39:54]

Clarify: who is being notified?

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

Done.

+  // The maximum frame timestamp in the buffer is given by |buffered_time|.
+  // Note: this timestamp can be different from the one provided through
+  // SetBufferedTime since SetBufferedTime takes the timestamp of a playable
+  // frame which is not necessarily the case here (e.g. missing key id).
+  void NotifyMaxCapacity(base::TimeDelta buffered_time);
+
+  // Human readable output operator, for debugging.
+  std::string ToString() const;
+
+ private:
+  friend class base::RefCountedThreadSafe<BufferingState>;
+  virtual ~BufferingState();
+
+  // Return the state solely based on the buffered time.
+  State GetBufferLevelState() const;
+
+  // Update the state to |new_state|.
+  void UpdateState(State new_state);
+
+  scoped_refptr<BufferingConfig> const config_;
+
+  // Callback invoked each time there is a change of state.
+  base::Closure state_changed_cb_;
+
+  // Callback invoked to adjust the high buffer level.
+  HighLevelBufferCb high_level_buffer_cb_;
+
+  // State.
+  State state_;
+
+  // Playback media time.
+  // Equal to kNoTimestamp() when not known.
+  base::TimeDelta media_time_;
+
+  // Maximum rendering media time.
+  // This corresponds to the timestamp of the last frame sent to the hardware
+  // decoder/renderer.
+  base::TimeDelta max_rendering_time_;
+
+  // Buffered media time.
+  // Equal to kNoTimestamp() when not known.
+  base::TimeDelta buffered_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(BufferingState);
+};
+
+}  // namespace cma
+}  // namespace media
+
+#endif  // CHROMECAST_MEDIA_CMA_BASE_BUFFERING_STATE_H_