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git-svn-id: http://webrtc.googlecode.com/svn/trunk@4 4adac7df-926f-26a2-2b94-8c16560cd09d

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niklase@google.com
2011-05-30 11:22:19 +00:00
parent 01813fe945
commit 77ae29bc81
1153 changed files with 404089 additions and 0 deletions
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259
modules/video_coding/main/source/timestamp_extrapolator.cc Normal file
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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.
*/
#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;
}
}