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/*
* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef CALL_RECEIVE_TIME_CALCULATOR_H_
#define CALL_RECEIVE_TIME_CALCULATOR_H_
#include <stdint.h>
#include <memory>
#include "api/optional.h"
namespace webrtc {
// The receive time calculator serves the purpose of combining packet time
// stamps with a safely incremental clock. This assumes that the packet time
// stamps are based on lower layer timestamps that have more accurate time
// increments since they are based on the exact receive time. They might
// however, have large jumps due to clock resets in the system. To compensate
// this they are combined with a safe clock source that is guaranteed to be
// consistent, but it will not be able to measure the exact time when a packet
// is received.
class ReceiveTimeCalculator {
public:
static std::unique_ptr<ReceiveTimeCalculator> CreateFromFieldTrial();
// The min delta is used to correct for jumps backwards in time, to allow some
// packet reordering a small negative value is appropriate to use. The max
// delta difference is used as margin when detecting when packet time
// increases more than the safe clock. This should be larger than the largest
// expected sysmtem induced delay in the safe clock timestamp.
ReceiveTimeCalculator(int64_t min_delta_ms, int64_t max_delta_diff_ms);
int64_t ReconcileReceiveTimes(int64_t packet_time_us_, int64_t safe_time_us_);
private:
const int64_t min_delta_us_;
const int64_t max_delta_diff_us_;
rtc::Optional<int64_t> receive_time_offset_us_;
int64_t last_packet_time_us_ = 0;
int64_t last_safe_time_us_ = 0;
};
} // namespace webrtc
#endif // CALL_RECEIVE_TIME_CALCULATOR_H_