260 lines
7.7 KiB
C++
260 lines
7.7 KiB
C++
/*
|
|
* 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.
|
|
*/
|
|
|
|
#include "internal_defines.h"
|
|
#include "timestamp_extrapolator.h"
|
|
#include "tick_time.h"
|
|
#include "trace.h"
|
|
|
|
namespace webrtc {
|
|
|
|
VCMTimestampExtrapolator::VCMTimestampExtrapolator(WebRtc_Word32 vcmId, WebRtc_Word32 id)
|
|
:
|
|
_rwLock(*RWLockWrapper::CreateRWLock()),
|
|
_vcmId(vcmId),
|
|
_id(id),
|
|
_startMs(0),
|
|
_firstTimestamp(0),
|
|
_wrapArounds(0),
|
|
_prevTs90khz(0),
|
|
_lambda(1),
|
|
_firstAfterReset(true),
|
|
_packetCount(0),
|
|
_startUpFilterDelayInPackets(2),
|
|
_detectorAccumulatorPos(0),
|
|
_detectorAccumulatorNeg(0),
|
|
_alarmThreshold(60e3),
|
|
_accDrift(6600), // in timestamp ticks, i.e. 15 ms
|
|
_accMaxError(7000),
|
|
_P11(1e10)
|
|
{
|
|
Reset(VCMTickTime::MillisecondTimestamp());
|
|
}
|
|
|
|
VCMTimestampExtrapolator::~VCMTimestampExtrapolator()
|
|
{
|
|
delete &_rwLock;
|
|
}
|
|
|
|
void
|
|
VCMTimestampExtrapolator::Reset(const WebRtc_Word64 nowMs /* = -1 */)
|
|
{
|
|
WriteLockScoped wl(_rwLock);
|
|
if (nowMs > -1)
|
|
{
|
|
_startMs = nowMs;
|
|
}
|
|
else
|
|
{
|
|
_startMs = VCMTickTime::MillisecondTimestamp();
|
|
}
|
|
_prevMs = _startMs;
|
|
_firstTimestamp = 0;
|
|
_w[0] = 90.0;
|
|
_w[1] = 0;
|
|
_P[0][0] = 1;
|
|
_P[1][1] = _P11;
|
|
_P[0][1] = _P[1][0] = 0;
|
|
_firstAfterReset = true;
|
|
_prevTs90khz = 0;
|
|
_wrapArounds = 0;
|
|
_packetCount = 0;
|
|
_detectorAccumulatorPos = 0;
|
|
_detectorAccumulatorNeg = 0;
|
|
}
|
|
|
|
void
|
|
VCMTimestampExtrapolator::Update(WebRtc_Word64 tMs, WebRtc_UWord32 ts90khz, bool trace)
|
|
{
|
|
|
|
_rwLock.AcquireLockExclusive();
|
|
if (tMs - _prevMs > 10e3)
|
|
{
|
|
// Ten seconds without a complete frame.
|
|
// Reset the extrapolator
|
|
_rwLock.ReleaseLockExclusive();
|
|
Reset();
|
|
_rwLock.AcquireLockExclusive();
|
|
}
|
|
else
|
|
{
|
|
_prevMs = tMs;
|
|
}
|
|
|
|
// Remove offset to prevent badly scaled matrices
|
|
tMs -= _startMs;
|
|
|
|
WebRtc_Word32 prevWrapArounds = _wrapArounds;
|
|
CheckForWrapArounds(ts90khz);
|
|
WebRtc_Word32 wrapAroundsSincePrev = _wrapArounds - prevWrapArounds;
|
|
|
|
if (wrapAroundsSincePrev == 0 && ts90khz < _prevTs90khz)
|
|
{
|
|
_rwLock.ReleaseLockExclusive();
|
|
return;
|
|
}
|
|
|
|
if (_firstAfterReset)
|
|
{
|
|
// Make an initial guess of the offset,
|
|
// should be almost correct since tMs - _startMs
|
|
// should about zero at this time.
|
|
_w[1] = -_w[0] * tMs;
|
|
_firstTimestamp = ts90khz;
|
|
_firstAfterReset = false;
|
|
}
|
|
|
|
// Compensate for wraparounds by changing the line offset
|
|
_w[1] = _w[1] - wrapAroundsSincePrev * ((static_cast<WebRtc_Word64>(1)<<32) - 1);
|
|
|
|
double residual = (static_cast<double>(ts90khz) - _firstTimestamp) - static_cast<double>(tMs) * _w[0] - _w[1];
|
|
if (DelayChangeDetection(residual, trace) &&
|
|
_packetCount >= _startUpFilterDelayInPackets)
|
|
{
|
|
// A sudden change of average network delay has been detected.
|
|
// Force the filter to adjust its offset parameter by changing
|
|
// the offset uncertainty. Don't do this during startup.
|
|
_P[1][1] = _P11;
|
|
}
|
|
//T = [t(k) 1]';
|
|
//that = T'*w;
|
|
//K = P*T/(lambda + T'*P*T);
|
|
double K[2];
|
|
K[0] = _P[0][0] * tMs + _P[0][1];
|
|
K[1] = _P[1][0] * tMs + _P[1][1];
|
|
double TPT = _lambda + tMs * K[0] + K[1];
|
|
K[0] /= TPT;
|
|
K[1] /= TPT;
|
|
//w = w + K*(ts(k) - that);
|
|
_w[0] = _w[0] + K[0] * residual;
|
|
_w[1] = _w[1] + K[1] * residual;
|
|
//P = 1/lambda*(P - K*T'*P);
|
|
double p00 = 1 / _lambda * (_P[0][0] - (K[0] * tMs * _P[0][0] + K[0] * _P[1][0]));
|
|
double p01 = 1 / _lambda * (_P[0][1] - (K[0] * tMs * _P[0][1] + K[0] * _P[1][1]));
|
|
_P[1][0] = 1 / _lambda * (_P[1][0] - (K[1] * tMs * _P[0][0] + K[1] * _P[1][0]));
|
|
_P[1][1] = 1 / _lambda * (_P[1][1] - (K[1] * tMs * _P[0][1] + K[1] * _P[1][1]));
|
|
_P[0][0] = p00;
|
|
_P[0][1] = p01;
|
|
if (_packetCount < _startUpFilterDelayInPackets)
|
|
{
|
|
_packetCount++;
|
|
}
|
|
if (trace)
|
|
{
|
|
WEBRTC_TRACE(webrtc::kTraceDebug, webrtc::kTraceVideoCoding, VCMId(_vcmId, _id), "w[0]=%f w[1]=%f ts=%u tMs=%u", _w[0], _w[1], ts90khz, tMs);
|
|
}
|
|
_rwLock.ReleaseLockExclusive();
|
|
}
|
|
|
|
WebRtc_UWord32
|
|
VCMTimestampExtrapolator::ExtrapolateTimestamp(WebRtc_Word64 tMs) const
|
|
{
|
|
ReadLockScoped rl(_rwLock);
|
|
WebRtc_UWord32 timestamp = 0;
|
|
if (_packetCount == 0)
|
|
{
|
|
timestamp = 0;
|
|
}
|
|
else if (_packetCount < _startUpFilterDelayInPackets)
|
|
{
|
|
timestamp = static_cast<WebRtc_UWord32>(90.0 * (tMs - _prevMs) + _prevTs90khz + 0.5);
|
|
}
|
|
else
|
|
{
|
|
timestamp = static_cast<WebRtc_UWord32>(_w[0] * (tMs - _startMs) + _w[1] + _firstTimestamp + 0.5);
|
|
}
|
|
return timestamp;
|
|
}
|
|
|
|
WebRtc_Word64
|
|
VCMTimestampExtrapolator::ExtrapolateLocalTime(WebRtc_UWord32 timestamp90khz) const
|
|
{
|
|
ReadLockScoped rl(_rwLock);
|
|
WebRtc_Word64 localTimeMs = 0;
|
|
if (_packetCount == 0)
|
|
{
|
|
localTimeMs = -1;
|
|
}
|
|
else if (_packetCount < _startUpFilterDelayInPackets)
|
|
{
|
|
localTimeMs = _prevMs + static_cast<WebRtc_Word64>(static_cast<double>(timestamp90khz - _prevTs90khz) / 90.0 + 0.5);
|
|
}
|
|
else
|
|
{
|
|
if (_w[0] < 1e-3)
|
|
{
|
|
localTimeMs = _startMs;
|
|
}
|
|
else
|
|
{
|
|
double timestampDiff = static_cast<double>(timestamp90khz) - static_cast<double>(_firstTimestamp);
|
|
localTimeMs = static_cast<WebRtc_Word64>(static_cast<double>(_startMs) + (timestampDiff - _w[1]) / _w[0] + 0.5);
|
|
}
|
|
}
|
|
return localTimeMs;
|
|
}
|
|
|
|
// Investigates if the timestamp clock has overflowed since the last timestamp and
|
|
// keeps track of the number of wrap arounds since reset.
|
|
void
|
|
VCMTimestampExtrapolator::CheckForWrapArounds(WebRtc_UWord32 ts90khz)
|
|
{
|
|
if (_prevTs90khz == 0)
|
|
{
|
|
_prevTs90khz = ts90khz;
|
|
return;
|
|
}
|
|
if (ts90khz < _prevTs90khz)
|
|
{
|
|
// This difference will probably be less than -2^31 if we have had a wrap around
|
|
// (e.g. timestamp = 1, _previousTimestamp = 2^32 - 1). Since it is casted to a Word32,
|
|
// it should be positive.
|
|
if (static_cast<WebRtc_Word32>(ts90khz - _prevTs90khz) > 0)
|
|
{
|
|
// Forward wrap around
|
|
_wrapArounds++;
|
|
}
|
|
}
|
|
// This difference will probably be less than -2^31 if we have had a backward wrap around.
|
|
// Since it is casted to a Word32, it should be positive.
|
|
else if (static_cast<WebRtc_Word32>(_prevTs90khz - ts90khz) > 0)
|
|
{
|
|
// Backward wrap around
|
|
_wrapArounds--;
|
|
}
|
|
_prevTs90khz = ts90khz;
|
|
}
|
|
|
|
bool
|
|
VCMTimestampExtrapolator::DelayChangeDetection(double error, bool trace)
|
|
{
|
|
// CUSUM detection of sudden delay changes
|
|
error = (error > 0) ? VCM_MIN(error, _accMaxError) : VCM_MAX(error, -_accMaxError);
|
|
_detectorAccumulatorPos = VCM_MAX(_detectorAccumulatorPos + error - _accDrift, (double)0);
|
|
_detectorAccumulatorNeg = VCM_MIN(_detectorAccumulatorNeg + error + _accDrift, (double)0);
|
|
if (_detectorAccumulatorPos > _alarmThreshold || _detectorAccumulatorNeg < -_alarmThreshold)
|
|
{
|
|
// Alarm
|
|
if (trace)
|
|
{
|
|
WEBRTC_TRACE(webrtc::kTraceDebug, webrtc::kTraceVideoCoding, VCMId(_vcmId, _id), "g1=%f g2=%f alarm=1", _detectorAccumulatorPos, _detectorAccumulatorNeg);
|
|
}
|
|
_detectorAccumulatorPos = _detectorAccumulatorNeg = 0;
|
|
return true;
|
|
}
|
|
if (trace)
|
|
{
|
|
WEBRTC_TRACE(webrtc::kTraceDebug, webrtc::kTraceVideoCoding, VCMId(_vcmId, _id), "g1=%f g2=%f alarm=0", _detectorAccumulatorPos, _detectorAccumulatorNeg);
|
|
}
|
|
return false;
|
|
}
|
|
|
|
}
|