blob: aaef4b1b2763729a7c2dbb5478304a0124190671 [file] [log] [blame]
/*
* Copyright (c) 2012 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.
*/
#include "system_wrappers/include/rtp_to_ntp_estimator.h"
#include <stddef.h>
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
// Number of RTCP SR reports to use to map between RTP and NTP.
const size_t kNumRtcpReportsToUse = 2;
// Number of parameters samples used to smooth.
const size_t kNumSamplesToSmooth = 20;
// Calculates the RTP timestamp frequency from two pairs of NTP/RTP timestamps.
bool CalculateFrequency(int64_t ntp_ms1,
uint32_t rtp_timestamp1,
int64_t ntp_ms2,
uint32_t rtp_timestamp2,
double* frequency_khz) {
if (ntp_ms1 <= ntp_ms2)
return false;
*frequency_khz = static_cast<double>(rtp_timestamp1 - rtp_timestamp2) /
static_cast<double>(ntp_ms1 - ntp_ms2);
return true;
}
bool Contains(const std::list<RtpToNtpEstimator::RtcpMeasurement>& measurements,
const RtpToNtpEstimator::RtcpMeasurement& other) {
for (const auto& measurement : measurements) {
if (measurement.IsEqual(other))
return true;
}
return false;
}
} // namespace
bool RtpToNtpEstimator::Parameters::operator<(const Parameters& other) const {
if (frequency_khz < other.frequency_khz - 1e-6) {
return true;
} else if (frequency_khz > other.frequency_khz + 1e-6) {
return false;
} else {
return offset_ms < other.offset_ms - 1e-6;
}
}
bool RtpToNtpEstimator::Parameters::operator==(const Parameters& other) const {
return !(other < *this || *this < other);
}
bool RtpToNtpEstimator::Parameters::operator!=(const Parameters& other) const {
return other < *this || *this < other;
}
bool RtpToNtpEstimator::Parameters::operator<=(const Parameters& other) const {
return !(other < *this);
}
RtpToNtpEstimator::RtcpMeasurement::RtcpMeasurement(uint32_t ntp_secs,
uint32_t ntp_frac,
int64_t unwrapped_timestamp)
: ntp_time(ntp_secs, ntp_frac),
unwrapped_rtp_timestamp(unwrapped_timestamp) {}
bool RtpToNtpEstimator::RtcpMeasurement::IsEqual(
const RtcpMeasurement& other) const {
// Use || since two equal timestamps will result in zero frequency and in
// RtpToNtpMs, |rtp_timestamp_ms| is estimated by dividing by the frequency.
return (ntp_time == other.ntp_time) ||
(unwrapped_rtp_timestamp == other.unwrapped_rtp_timestamp);
}
// Class for converting an RTP timestamp to the NTP domain.
RtpToNtpEstimator::RtpToNtpEstimator()
: consecutive_invalid_samples_(0),
smoothing_filter_(kNumSamplesToSmooth),
params_calculated_(false) {}
RtpToNtpEstimator::~RtpToNtpEstimator() {}
void RtpToNtpEstimator::UpdateParameters() {
if (measurements_.size() != kNumRtcpReportsToUse)
return;
Parameters params;
int64_t timestamp_new = measurements_.front().unwrapped_rtp_timestamp;
int64_t timestamp_old = measurements_.back().unwrapped_rtp_timestamp;
int64_t ntp_ms_new = measurements_.front().ntp_time.ToMs();
int64_t ntp_ms_old = measurements_.back().ntp_time.ToMs();
if (!CalculateFrequency(ntp_ms_new, timestamp_new, ntp_ms_old, timestamp_old,
&params.frequency_khz)) {
return;
}
params.offset_ms = timestamp_new - params.frequency_khz * ntp_ms_new;
params_calculated_ = true;
smoothing_filter_.Insert(params);
}
bool RtpToNtpEstimator::UpdateMeasurements(uint32_t ntp_secs,
uint32_t ntp_frac,
uint32_t rtp_timestamp,
bool* new_rtcp_sr) {
*new_rtcp_sr = false;
int64_t unwrapped_rtp_timestamp = unwrapper_.Unwrap(rtp_timestamp);
RtcpMeasurement new_measurement(ntp_secs, ntp_frac, unwrapped_rtp_timestamp);
if (Contains(measurements_, new_measurement)) {
// RTCP SR report already added.
return true;
}
if (!new_measurement.ntp_time.Valid())
return false;
int64_t ntp_ms_new = new_measurement.ntp_time.ToMs();
bool invalid_sample = false;
if (!measurements_.empty()) {
int64_t old_rtp_timestamp = measurements_.front().unwrapped_rtp_timestamp;
int64_t old_ntp_ms = measurements_.front().ntp_time.ToMs();
if (ntp_ms_new <= old_ntp_ms) {
invalid_sample = true;
} else if (unwrapped_rtp_timestamp <= old_rtp_timestamp) {
RTC_LOG(LS_WARNING)
<< "Newer RTCP SR report with older RTP timestamp, dropping";
invalid_sample = true;
} else if (unwrapped_rtp_timestamp - old_rtp_timestamp > (1 << 25)) {
// Sanity check. No jumps too far into the future in rtp.
invalid_sample = true;
}
}
if (invalid_sample) {
++consecutive_invalid_samples_;
if (consecutive_invalid_samples_ < kMaxInvalidSamples) {
return false;
}
RTC_LOG(LS_WARNING) << "Multiple consecutively invalid RTCP SR reports, "
"clearing measurements.";
measurements_.clear();
smoothing_filter_.Reset();
params_calculated_ = false;
}
consecutive_invalid_samples_ = 0;
// Insert new RTCP SR report.
if (measurements_.size() == kNumRtcpReportsToUse)
measurements_.pop_back();
measurements_.push_front(new_measurement);
*new_rtcp_sr = true;
// List updated, calculate new parameters.
UpdateParameters();
return true;
}
bool RtpToNtpEstimator::Estimate(int64_t rtp_timestamp,
int64_t* rtp_timestamp_ms) const {
if (!params_calculated_)
return false;
int64_t rtp_timestamp_unwrapped = unwrapper_.Unwrap(rtp_timestamp);
Parameters params = smoothing_filter_.GetFilteredValue();
// params_calculated_ should not be true unless ms params.frequency_khz has
// been calculated to something non zero.
RTC_DCHECK_NE(params.frequency_khz, 0.0);
double rtp_ms =
(static_cast<double>(rtp_timestamp_unwrapped) - params.offset_ms) /
params.frequency_khz +
0.5f;
if (rtp_ms < 0)
return false;
*rtp_timestamp_ms = rtp_ms;
return true;
}
const absl::optional<RtpToNtpEstimator::Parameters> RtpToNtpEstimator::params()
const {
absl::optional<Parameters> res;
if (params_calculated_) {
res.emplace(smoothing_filter_.GetFilteredValue());
}
return res;
}
} // namespace webrtc