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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef MEDIA_CAST_LOGGING_RECEIVER_TIME_OFFSET_ESTIMATOR_IMPL_H_
      6 #define MEDIA_CAST_LOGGING_RECEIVER_TIME_OFFSET_ESTIMATOR_IMPL_H_
      7 
      8 #include "base/time/time.h"
      9 #include "base/threading/thread_checker.h"
     10 #include "media/cast/logging/logging_defines.h"
     11 #include "media/cast/logging/receiver_time_offset_estimator.h"
     12 
     13 namespace media {
     14 namespace cast {
     15 
     16 // This implementation listens to three types of video events:
     17 // 1. FRAME_ENCODED (sender side)
     18 // 2. FRAME_ACK_SENT (receiver side)
     19 // 3. FRAME_ACK_RECEIVED (sender side)
     20 // There is a causal relationship between these events in that these events
     21 // must happen in order. This class obtains the lower and upper bounds for
     22 // the offset by taking the difference of timestamps (2) - (1) and (2) - (3),
     23 // respectively.
     24 // The bound will become better as the latency between the events decreases.
     25 class ReceiverTimeOffsetEstimatorImpl : public ReceiverTimeOffsetEstimator {
     26  public:
     27   ReceiverTimeOffsetEstimatorImpl();
     28 
     29   virtual ~ReceiverTimeOffsetEstimatorImpl();
     30 
     31   // RawEventSubscriber implementations.
     32   virtual void OnReceiveFrameEvent(const FrameEvent& frame_event) OVERRIDE;
     33   virtual void OnReceivePacketEvent(const PacketEvent& packet_event) OVERRIDE;
     34 
     35   // ReceiverTimeOffsetEstimator implementation.
     36   virtual bool GetReceiverOffsetBounds(base::TimeDelta* lower_bound,
     37                                        base::TimeDelta* upper_bound) OVERRIDE;
     38 
     39  private:
     40   struct EventTimes {
     41     base::TimeTicks event_a_time;
     42     base::TimeTicks event_b_time;
     43     base::TimeTicks event_c_time;
     44   };
     45 
     46   typedef std::map<RtpTimestamp, EventTimes> EventTimesMap;
     47 
     48   void UpdateOffsetBounds(const EventTimes& event);
     49 
     50   // Fixed size storage to store event times for recent frames.
     51   EventTimesMap event_times_map_;
     52 
     53   bool bounded_;
     54   base::TimeDelta offset_lower_bound_;
     55   base::TimeDelta offset_upper_bound_;
     56 
     57   base::ThreadChecker thread_checker_;
     58   DISALLOW_COPY_AND_ASSIGN(ReceiverTimeOffsetEstimatorImpl);
     59 };
     60 
     61 }  // namespace cast
     62 }  // namespace media
     63 
     64 #endif  // MEDIA_CAST_LOGGING_RECEIVER_TIME_OFFSET_ESTIMATOR_IMPL_H_
     65