media/cast/logging/receiver_time_offset_estimator.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_H_
   6 #define MEDIA_CAST_LOGGING_RECEIVER_TIME_OFFSET_ESTIMATOR_H_
   7
   8 #include "base/time/time.h"
   9 #include "media/cast/logging/raw_event_subscriber.h"
  10
  11 namespace media {
  12 namespace cast {
  13
  14 // Estimates receiver time offset based on raw events received.
  15 // In most cases, the sender and receiver run on different time lines.
  16 // In order to convert receiver time back to sender time (or vice versa)
  17 // a certain time offset has to be applied.
  18 // An implementation of this interface listens to raw events to figure out
  19 // the bounds for the offset value (assuming the true offset value is constant
  20 // over the lifetime of a cast session).
  21 // The offset values provided here should be used as follows:
  22 // - Convert from sender to receiver time: add offset value to sender timestamp.
  23 // - Convert from receiver to sender time: subtract offset value from receiver
  24 //   timestamp.
  25 class ReceiverTimeOffsetEstimator : public RawEventSubscriber {
  26  public:
  27   ~ReceiverTimeOffsetEstimator() override {}
  28
  29   // If bounds are known, assigns |lower_bound| and |upper_bound| with the
  30   // lower bound and upper bound for the offset value, respectively.
  31   // Returns true if bounds are known.
  32   virtual bool GetReceiverOffsetBounds(base::TimeDelta* lower_bound,
  33                                        base::TimeDelta* upper_bound) = 0;
  34 };
  35
  36 }  // namespace cast
  37 }  // namespace media
  38
  39 #endif  // MEDIA_CAST_LOGGING_RECEIVER_TIME_OFFSET_ESTIMATOR_H_