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/*
* Copyright (c) 2011 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 MODULES_VIDEO_CODING_TIMING_TIMESTAMP_EXTRAPOLATOR_H_
#define MODULES_VIDEO_CODING_TIMING_TIMESTAMP_EXTRAPOLATOR_H_
#include <stdint.h>
#include <memory>
#include <optional>
#include "absl/strings/string_view.h"
#include "api/field_trials_view.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "rtc_base/experiments/struct_parameters_parser.h"
#include "rtc_base/numerics/sequence_number_unwrapper.h"
namespace webrtc {
// Not thread safe.
class TimestampExtrapolator {
public:
// Configuration struct for overriding some constants and behaviour,
// configurable through field trials.
struct Config {
inline static constexpr absl::string_view kFieldTrialsKey =
"WebRTC-TimestampExtrapolatorConfig";
// Factory function that parses the field trials and returns a `Config`
// with validated values.
static Config ParseAndValidate(const FieldTrialsView& field_trials);
std::unique_ptr<StructParametersParser> Parser() {
// clang-format off
return StructParametersParser::Create(
"hard_reset_timeout", &hard_reset_timeout,
"alarm_threshold", &alarm_threshold,
"acc_drift", &acc_drift,
"acc_max_error", &acc_max_error,
"reset_full_cov_on_alarm", &reset_full_cov_on_alarm);
// clang-format on
}
// If a frame has not been received within this timeout, do a full reset.
TimeDelta hard_reset_timeout = TimeDelta::Seconds(10);
// Alarm on sudden delay change if the (filtered; see below) accumulated
// residuals are larger than this number of RTP ticks. After the
// startup period, an alarm will result in a full or partial reset of the
// uncertainty covariance (see `reset_full_cov_on_alarm` below).
int alarm_threshold = 60000; // 666 ms <=> 20 frames@30fps.
// Acceptable level of per-frame drift in the detector (in RTP ticks).
int acc_drift = 6600; // 73 ms <=> 2.2 frames@30fps.
// Max limit on residuals in the detector (in RTP ticks).
// TODO(brandtr): Increase from this unreasonably low value.
int acc_max_error = 7000; // 77 ms <=> 2.3 frames@30fps.
// If true, reset the entire uncertainty covariance matrix on alarms.
// If false, only reset the offset variance term.
// TODO(brandtr): Flip so that the frequency term won't get hit tpp badly
// when a large delay spike happens.
bool reset_full_cov_on_alarm = false;
};
TimestampExtrapolator(Timestamp start, const FieldTrialsView& field_trials);
~TimestampExtrapolator();
void Update(Timestamp now, uint32_t ts90khz);
std::optional<Timestamp> ExtrapolateLocalTime(uint32_t timestamp90khz) const;
void Reset(Timestamp start);
Config GetConfigForTest() const { return config_; }
private:
void CheckForWrapArounds(uint32_t ts90khz);
bool DelayChangeDetection(double error);
const Config config_;
double w_[2];
double p_[2][2];
Timestamp start_;
Timestamp prev_;
std::optional<int64_t> first_unwrapped_timestamp_;
RtpTimestampUnwrapper unwrapper_;
std::optional<int64_t> prev_unwrapped_timestamp_;
int packet_count_;
double detector_accumulator_pos_;
double detector_accumulator_neg_;
};
} // namespace webrtc
#endif // MODULES_VIDEO_CODING_TIMING_TIMESTAMP_EXTRAPOLATOR_H_
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