| /* |
| * 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 "bandwidth_management.h" |
| #include "trace.h" |
| #include "rtp_utility.h" |
| #include "rtp_rtcp_config.h" |
| |
| #include <math.h> // sqrt() |
| |
| namespace webrtc { |
| |
| BandwidthManagement::BandwidthManagement(const WebRtc_Word32 id) : |
| _id(id), |
| _critsect(CriticalSectionWrapper::CreateCriticalSection()), |
| _lastPacketLossExtendedHighSeqNum(0), |
| _lastReportAllLost(false), |
| _lastLoss(0), |
| _accumulateLostPacketsQ8(0), |
| _accumulateExpectedPackets(0), |
| _bitRate(0), |
| _minBitRateConfigured(0), |
| _maxBitRateConfigured(0), |
| _last_fraction_loss(0), |
| _last_round_trip_time(0), |
| _bwEstimateIncoming(0), |
| _smoothedFractionLostQ4(-1), // indicate uninitialized |
| _sFLFactorQ4(14), // 0.875 in Q4 |
| _timeLastIncrease(0) |
| { |
| } |
| |
| BandwidthManagement::~BandwidthManagement() |
| { |
| delete _critsect; |
| } |
| |
| WebRtc_Word32 |
| BandwidthManagement::SetSendBitrate(const WebRtc_UWord32 startBitrate, |
| const WebRtc_UWord16 minBitrateKbit, |
| const WebRtc_UWord16 maxBitrateKbit) |
| { |
| CriticalSectionScoped cs(_critsect); |
| |
| _bitRate = startBitrate; |
| _minBitRateConfigured = minBitrateKbit*1000; |
| if(maxBitrateKbit == 0) |
| { |
| // no max configured use 1Gbit/s |
| _maxBitRateConfigured = 1000000000; |
| } else |
| { |
| _maxBitRateConfigured = maxBitrateKbit*1000; |
| } |
| return 0; |
| } |
| |
| WebRtc_Word32 |
| BandwidthManagement::MaxConfiguredBitrate(WebRtc_UWord16* maxBitrateKbit) |
| { |
| CriticalSectionScoped cs(_critsect); |
| |
| if(_maxBitRateConfigured == 0) |
| { |
| return -1; |
| } |
| *maxBitrateKbit = (WebRtc_UWord16)(_maxBitRateConfigured/1000); |
| return 0; |
| } |
| |
| WebRtc_Word32 |
| BandwidthManagement::UpdateBandwidthEstimate(const WebRtc_UWord16 bandWidthKbit, |
| WebRtc_UWord32* newBitrate, |
| WebRtc_UWord8* fractionLost, |
| WebRtc_UWord16* roundTripTime) |
| { |
| *newBitrate = 0; |
| CriticalSectionScoped cs(_critsect); |
| |
| _bwEstimateIncoming = bandWidthKbit*1000; |
| |
| if(_bitRate == 0) |
| { |
| // BandwidthManagement off |
| return -1; |
| } |
| if (_bwEstimateIncoming > 0 && _bitRate > _bwEstimateIncoming) |
| { |
| _bitRate = _bwEstimateIncoming; |
| } else |
| { |
| return -1; |
| } |
| *newBitrate = _bitRate; |
| *fractionLost = _last_fraction_loss; |
| *roundTripTime = _last_round_trip_time; |
| return 0; |
| } |
| |
| WebRtc_Word32 BandwidthManagement::UpdatePacketLoss( |
| const WebRtc_UWord32 lastReceivedExtendedHighSeqNum, |
| WebRtc_UWord32 sentBitrate, |
| const WebRtc_UWord16 rtt, |
| WebRtc_UWord8* loss, |
| WebRtc_UWord32* newBitrate, |
| WebRtc_Word64 nowMS) |
| { |
| CriticalSectionScoped cs(_critsect); |
| |
| _last_fraction_loss = *loss; |
| _last_round_trip_time = rtt; |
| |
| if(_bitRate == 0) |
| { |
| // BandwidthManagement off |
| return -1; |
| } |
| |
| // Check sequence number diff and weight loss report |
| if (_lastPacketLossExtendedHighSeqNum > 0 && |
| (lastReceivedExtendedHighSeqNum >= _lastPacketLossExtendedHighSeqNum)) |
| { |
| // This is not the first loss report and the sequence number is |
| // non-decreasing. Calculate sequence number diff. |
| WebRtc_UWord32 seqNumDiff = lastReceivedExtendedHighSeqNum |
| - _lastPacketLossExtendedHighSeqNum; |
| |
| // Check if this report and the last was 100% loss, then report |
| // 100% loss even though seqNumDiff is small. |
| // If not, go on with the checks. |
| if (!(_lastReportAllLost && *loss == 255)) |
| { |
| _lastReportAllLost = (*loss == 255); |
| |
| // Calculate number of lost packets. |
| // loss = 256 * numLostPackets / expectedPackets. |
| const int numLostPacketsQ8 = *loss * seqNumDiff; |
| |
| // Accumulate reports. |
| _accumulateLostPacketsQ8 += numLostPacketsQ8; |
| _accumulateExpectedPackets += seqNumDiff; |
| |
| // Report loss if the total report is based on sufficiently |
| // many packets. |
| const int limitNumPackets = 10; |
| if (_accumulateExpectedPackets >= limitNumPackets) |
| { |
| *loss = _accumulateLostPacketsQ8 / _accumulateExpectedPackets; |
| |
| // Reset accumulators |
| _accumulateLostPacketsQ8 = 0; |
| _accumulateExpectedPackets = 0; |
| } |
| else |
| { |
| // Report zero loss until we have enough data to estimate |
| // the loss rate. |
| *loss = 0; |
| } |
| } |
| } |
| // Keep for next time. |
| _lastLoss = *loss; |
| |
| // Remember the sequence number until next time |
| _lastPacketLossExtendedHighSeqNum = lastReceivedExtendedHighSeqNum; |
| |
| WebRtc_UWord32 bitRate = ShapeSimple(*loss, rtt, sentBitrate, nowMS); |
| if (bitRate == 0) |
| { |
| // no change |
| return -1; |
| } |
| _bitRate = bitRate; |
| *newBitrate = bitRate; |
| return 0; |
| } |
| |
| /* Calculate the rate that TCP-Friendly Rate Control (TFRC) would apply. |
| * The formula in RFC 3448, Section 3.1, is used. |
| */ |
| |
| // protected |
| WebRtc_Word32 BandwidthManagement::CalcTFRCbps(WebRtc_Word16 avgPackSizeBytes, |
| WebRtc_Word32 rttMs, |
| WebRtc_Word32 packetLoss) |
| { |
| if (avgPackSizeBytes <= 0 || rttMs <= 0 || packetLoss <= 0) |
| { |
| // input variables out of range; return -1 |
| return -1; |
| } |
| |
| double R = static_cast<double>(rttMs)/1000; // RTT in seconds |
| int b = 1; // number of packets acknowledged by a single TCP acknowledgement; recommended = 1 |
| double t_RTO = 4.0 * R; // TCP retransmission timeout value in seconds; recommended = 4*R |
| double p = static_cast<double>(packetLoss)/255; // packet loss rate in [0, 1) |
| double s = static_cast<double>(avgPackSizeBytes); |
| |
| // calculate send rate in bytes/second |
| double X = s / (R * sqrt(2 * b * p / 3) + (t_RTO * (3 * sqrt( 3 * b * p / 8) * p * (1 + 32 * p * p)))); |
| |
| return (static_cast<WebRtc_Word32>(X*8)); // bits/second |
| } |
| |
| /* |
| * Simple bandwidth estimation. Depends a lot on bwEstimateIncoming and packetLoss. |
| */ |
| // protected |
| WebRtc_UWord32 BandwidthManagement::ShapeSimple(WebRtc_Word32 packetLoss, |
| WebRtc_Word32 rtt, |
| WebRtc_UWord32 sentBitrate, |
| WebRtc_Word64 nowMS) |
| { |
| WebRtc_UWord32 newBitRate = 0; |
| bool reducing = false; |
| |
| // Limit the rate increases to once a second. |
| if (packetLoss <= 5) |
| { |
| if ((nowMS - _timeLastIncrease) < |
| kBWEUpdateIntervalMs) |
| { |
| return _bitRate; |
| } |
| _timeLastIncrease = nowMS; |
| } |
| |
| if (packetLoss > 5 && packetLoss <= 26) |
| { |
| // 2% - 10% |
| newBitRate = _bitRate; |
| } |
| else if (packetLoss > 26) |
| { |
| // 26/256 ~= 10% |
| // reduce rate: newRate = rate * (1 - 0.5*lossRate) |
| // packetLoss = 256*lossRate |
| newBitRate = static_cast<WebRtc_UWord32>( |
| (sentBitrate * static_cast<double>(512 - packetLoss)) / 512.0); |
| reducing = true; |
| } |
| else |
| { |
| // increase rate by 8% |
| newBitRate = static_cast<WebRtc_UWord32>(_bitRate * 1.08 + 0.5); |
| |
| // add 1 kbps extra, just to make sure that we do not get stuck |
| // (gives a little extra increase at low rates, negligible at higher rates) |
| newBitRate += 1000; |
| } |
| |
| // Calculate smoothed loss number |
| if (_smoothedFractionLostQ4 < 0) |
| { |
| // startup |
| _smoothedFractionLostQ4 = static_cast<WebRtc_UWord16>(packetLoss); |
| } |
| else |
| { |
| _smoothedFractionLostQ4 = ((_sFLFactorQ4 * _smoothedFractionLostQ4 + 8) >> 4) // Q4*Q4 = Q8; down to Q4 again with proper rounding |
| + (16 - _sFLFactorQ4) * static_cast<WebRtc_UWord16>(packetLoss); // Q4 * Q0 = Q4 |
| } |
| |
| // Calculate what rate TFRC would apply in this situation |
| //WebRtc_Word32 tfrcRate = CalcTFRCbps(1000, rtt, _smoothedFractionLostQ4 >> 4); // scale loss to Q0 (back to [0, 255]) |
| WebRtc_Word32 tfrcRate = CalcTFRCbps(1000, rtt, packetLoss); // scale loss to Q0 (back to [0, 255]) |
| |
| if (reducing && |
| tfrcRate > 0 && |
| static_cast<WebRtc_UWord32>(tfrcRate) > newBitRate) |
| { |
| // do not reduce further if rate is below TFRC rate |
| newBitRate = _bitRate; |
| } |
| |
| if (_bwEstimateIncoming > 0 && newBitRate > _bwEstimateIncoming) |
| { |
| newBitRate = _bwEstimateIncoming; |
| } |
| if (newBitRate > _maxBitRateConfigured) |
| { |
| newBitRate = _maxBitRateConfigured; |
| } |
| if (newBitRate < _minBitRateConfigured) |
| { |
| WEBRTC_TRACE(kTraceWarning, |
| kTraceRtpRtcp, |
| _id, |
| "The configured min bitrate (%u kbps) is greater than the " |
| "estimated available bandwidth (%u kbps).\n", |
| _minBitRateConfigured / 1000, newBitRate / 1000); |
| newBitRate = _minBitRateConfigured; |
| } |
| return newBitRate; |
| } |
| } // namespace webrtc |
