media/cast/logging/receiver_time_offset_estimator_impl.h

   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_