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/*
* Copyright (c) 2014 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 "webrtc/modules/rtp_rtcp/interface/remote_ntp_time_estimator.h"
#include "webrtc/base/logging.h"
#include "webrtc/system_wrappers/include/clock.h"
#include "webrtc/system_wrappers/include/timestamp_extrapolator.h"
namespace webrtc {
static const int kTimingLogIntervalMs = 10000;
// TODO(wu): Refactor this class so that it can be shared with
// vie_sync_module.cc.
RemoteNtpTimeEstimator::RemoteNtpTimeEstimator(Clock* clock)
: clock_(clock),
ts_extrapolator_(new TimestampExtrapolator(clock_->TimeInMilliseconds())),
last_timing_log_ms_(-1) {
}
RemoteNtpTimeEstimator::~RemoteNtpTimeEstimator() {}
bool RemoteNtpTimeEstimator::UpdateRtcpTimestamp(int64_t rtt,
uint32_t ntp_secs,
uint32_t ntp_frac,
uint32_t rtcp_timestamp) {
bool new_rtcp_sr = false;
if (!UpdateRtcpList(
ntp_secs, ntp_frac, rtcp_timestamp, &rtcp_list_, &new_rtcp_sr)) {
return false;
}
if (!new_rtcp_sr) {
// No new RTCP SR since last time this function was called.
return true;
}
// Update extrapolator with the new arrival time.
// The extrapolator assumes the TimeInMilliseconds time.
int64_t receiver_arrival_time_ms = clock_->TimeInMilliseconds();
int64_t sender_send_time_ms = Clock::NtpToMs(ntp_secs, ntp_frac);
int64_t sender_arrival_time_90k = (sender_send_time_ms + rtt / 2) * 90;
ts_extrapolator_->Update(receiver_arrival_time_ms, sender_arrival_time_90k);
return true;
}
int64_t RemoteNtpTimeEstimator::Estimate(uint32_t rtp_timestamp) {
if (rtcp_list_.size() < 2) {
// We need two RTCP SR reports to calculate NTP.
return -1;
}
int64_t sender_capture_ntp_ms = 0;
if (!RtpToNtpMs(rtp_timestamp, rtcp_list_, &sender_capture_ntp_ms)) {
return -1;
}
uint32_t timestamp = sender_capture_ntp_ms * 90;
int64_t receiver_capture_ms =
ts_extrapolator_->ExtrapolateLocalTime(timestamp);
int64_t ntp_offset =
clock_->CurrentNtpInMilliseconds() - clock_->TimeInMilliseconds();
int64_t receiver_capture_ntp_ms = receiver_capture_ms + ntp_offset;
int64_t now_ms = clock_->TimeInMilliseconds();
if (now_ms - last_timing_log_ms_ > kTimingLogIntervalMs) {
LOG(LS_INFO) << "RTP timestamp: " << rtp_timestamp
<< " in NTP clock: " << sender_capture_ntp_ms
<< " estimated time in receiver clock: " << receiver_capture_ms
<< " converted to NTP clock: " << receiver_capture_ntp_ms;
last_timing_log_ms_ = now_ms;
}
return receiver_capture_ntp_ms;
}
} // namespace webrtc
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