webrtc/modules/video_coding/main/source/media_opt_util.cc

/*
 *  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 "video_coding_defines.h"
#include "fec_tables_xor.h"
#include "er_tables_xor.h"
#include "nack_fec_tables.h"
#include "qm_select_data.h"
#include "media_opt_util.h"

#include <math.h>
#include <float.h>
#include <limits.h>
#include <stdio.h>

namespace webrtc {

bool
VCMProtectionMethod::BetterThan(VCMProtectionMethod *pm)
{
    if (pm == NULL)
    {
        return true;
    }
    return pm->_score > _score;
}

bool
VCMNackFecMethod::ProtectionFactor(const VCMProtectionParameters* /*parameters*/)
{

   //use FEC model with modification with RTT for now

    return true;
}

bool
VCMNackFecMethod::EffectivePacketLoss(const VCMProtectionParameters* /*parameters*/)
{
  //use FEC model with modification with RTT for now

  return true;
}


bool
VCMNackFecMethod::UpdateParameters(const VCMProtectionParameters* parameters)
{

     VCMFecMethod fecMethod;
     VCMNackMethod nackMethod;

    const WebRtc_UWord8 plossMax = 129;
     WebRtc_UWord16 rttMax = nackMethod.MaxRttNack();

    // We should reduce the NACK threshold for NackFec protection method,
    // with FEC and ER, we should only use NACK for small RTT, to avoid delay
     //But this parameter change should be shared with RTP and JB
     //rttMax  = (WebRtc_UWord16) 0.5*rttMax;

     //Compute the protection factor
     fecMethod.ProtectionFactor(parameters);

     //Compute the effective packet loss
     fecMethod.EffectivePacketLoss(parameters);

     WebRtc_UWord8 protFactorK = fecMethod._protectionFactorK;
     WebRtc_UWord8 protFactorD = fecMethod._protectionFactorD;
     WebRtc_UWord8 effPacketLoss = fecMethod._effectivePacketLoss;
     float resPacketLoss = fecMethod._residualPacketLoss;

    WebRtc_Word16 rttIndex= (WebRtc_UWord16) parameters->rtt;
    float softnessRtt = 1.0;
    if (parameters->rtt < rttMax)
    {
         softnessRtt = (float)VCMNackFecTable[rttIndex]/(float)4096.0;

         //soften ER with NACK on
        //table depends on roundtrip time relative to rttMax (NACK Threshold)
        _effectivePacketLoss = (WebRtc_UWord8)(effPacketLoss*softnessRtt);

        //soften FEC with NACK on
        //table depends on roundtrip time relative to rttMax (NACK Threshold)
        _protectionFactorK = (WebRtc_UWord8) (protFactorK * softnessRtt);
        _protectionFactorD = (WebRtc_UWord8) (protFactorD * softnessRtt);
    }


    //make sure I frame protection is at least larger than P frame protection, and at least as high as received loss
    WebRtc_UWord8 packetLoss = (WebRtc_UWord8)(255* parameters->lossPr);
     _protectionFactorK = static_cast<WebRtc_UWord8>(VCM_MAX(packetLoss,VCM_MAX(_scaleProtKey*protFactorD,protFactorK)));

    //check limit on amount of protection for I frame: 50% is max
    if (_protectionFactorK  >= plossMax) _protectionFactorK  = plossMax - 1;

    //Bit cost for NackFec

     // NACK cost: based on residual packet loss (since we should only NACK packet not recovered by FEC)
    _efficiency = 0.0f;
    if (parameters->rtt < rttMax)
        _efficiency = parameters->bitRate * resPacketLoss / (1.0f + resPacketLoss);

    //add FEC cost: ignore I frames for now
    float fecRate = static_cast<float>(_protectionFactorD) / 255.0f;
    if (fecRate >= 0.0f)
         _efficiency += parameters->bitRate * fecRate;

    _score = _efficiency;

    //Protection/fec rates obtained above is defined relative to total number of packets (total rate: source+fec)
    //FEC in RTP module assumes protection factor is defined relative to source number of packets
    //so we should convert the factor to reduce mismatch between mediaOpt suggested rate and the actual rate
    WebRtc_UWord8 codeRate = protFactorK;
    _protectionFactorK = fecMethod.ConvertFECRate(codeRate);
    codeRate = protFactorD;
    _protectionFactorD = fecMethod.ConvertFECRate(codeRate);

    return true;
}


bool
VCMNackMethod::EffectivePacketLoss(WebRtc_UWord8 effPacketLoss, WebRtc_UWord16 rttTime)
{

    WebRtc_UWord16 rttMax = MaxRttNack();

    //For large RTT, we should rely on some Error Resilience, so we set packetLossEnc = 0
    //for RTT less than the NACK threshold
    if (rttTime < rttMax )
        effPacketLoss =  0;   //may want a softer transition here

     _effectivePacketLoss = effPacketLoss;

    return true;

}
bool
VCMNackMethod::UpdateParameters(const VCMProtectionParameters* parameters)
{

    //Compute the effective packet loss for ER
    WebRtc_UWord8 effPacketLoss = (WebRtc_UWord8)(255* parameters->lossPr);
    WebRtc_UWord16 rttTime = (WebRtc_UWord16) parameters->rtt;
    EffectivePacketLoss(effPacketLoss, rttTime);
    //

    //Compute the NACK bit cost
    _efficiency = parameters->bitRate * parameters->lossPr / (1.0f + parameters->lossPr);
    _score = _efficiency;
    if (parameters->rtt > _NACK_MAX_RTT)
    {
        _score = 0.0f;
        return false;
    }

    return true;
}


WebRtc_UWord8
VCMFecMethod::BoostCodeRateKey(WebRtc_UWord8 packetFrameDelta, WebRtc_UWord8 packetFrameKey) const
{

    WebRtc_UWord8 boostRateKey = 2;
    //default: ratio scales the FEC protection up for I frames
    WebRtc_UWord8 ratio = 1;

    if (packetFrameDelta > 0)
        ratio = (WebRtc_Word8)( packetFrameKey / packetFrameDelta );

    ratio = VCM_MAX(boostRateKey, ratio);

    return ratio;

}

WebRtc_UWord8
VCMFecMethod::ConvertFECRate(WebRtc_UWord8 codeRateRTP) const
{
    return static_cast<WebRtc_UWord8>(VCM_MIN(255,(0.5 + 255.0*codeRateRTP/(float)(255 - codeRateRTP))));
}

//AvgRecoveryFEC: average recovery from FEC, assuming random packet loss model
//Computed offline for a range of FEC code parameters and loss rates
float
VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
{

    //Total (avg) bits available per frame: total rate over actual/sent frame rate
    //units are kbits/frame
    const WebRtc_UWord16 bitRatePerFrame = static_cast<WebRtc_UWord16>(parameters->bitRate/(parameters->frameRate));

    //Total (avg) number of packets per frame (source and fec):
    const WebRtc_UWord8 avgTotPackets  = 1 + (WebRtc_UWord8)((float)bitRatePerFrame*1000.0/(float)(8.0*_maxPayloadSize) + 0.5);

    //parameters for tables
    const WebRtc_UWord8 codeSize = 24;
    const WebRtc_UWord8 plossMax = 129;
    const WebRtc_UWord16 maxErTableSize = 38700;
    //

    //
    //Get index for table
    const float protectionFactor = (float)_protectionFactorD/(float)255;
    WebRtc_UWord8 fecPacketsPerFrame =  (WebRtc_UWord8)(0.5 + protectionFactor*avgTotPackets);
    WebRtc_UWord8 sourcePacketsPerFrame = avgTotPackets - fecPacketsPerFrame;

    if (fecPacketsPerFrame == 0)
    {
        return 0.0; //no protection, so avg. recov from FEC == 0
    }

    //table defined up to codeSizexcodeSize code
    if (sourcePacketsPerFrame > codeSize)
    {
        sourcePacketsPerFrame = codeSize;
    }

    //check: protection factor is maxed at 50%, so this should never happen
    if (sourcePacketsPerFrame < 1)
    {
        assert("average number of source packets below 1\n");
    }

    //index for ER tables: up to codeSizexcodeSize mask
    WebRtc_UWord16 codeIndexTable[codeSize*codeSize];
    WebRtc_UWord16 k = -1;
    for(WebRtc_UWord8 i=1;i<=codeSize;i++)
    {
        for(WebRtc_UWord8 j=1;j<=i;j++)
        {
            k += 1;
            codeIndexTable[(j-1)*codeSize + i - 1] = k;
        }
    }

    const WebRtc_UWord8 lossRate = (WebRtc_UWord8) (255.0*parameters->lossPr + 0.5f);

    const WebRtc_UWord16 codeIndex = (fecPacketsPerFrame - 1)*codeSize + (sourcePacketsPerFrame - 1);
    const WebRtc_UWord16 indexTable = codeIndexTable[codeIndex] * plossMax + lossRate;

    const WebRtc_UWord16 codeIndex2 = (fecPacketsPerFrame)*codeSize + (sourcePacketsPerFrame);
    WebRtc_UWord16 indexTable2 =  codeIndexTable[codeIndex2] * plossMax + lossRate;

    //checks on table index
    if (indexTable >= maxErTableSize)
    {
        assert("ER table index too large\n");
    }

    if (indexTable2 >= maxErTableSize)
    {
        indexTable2 = indexTable;
    }
    //

    //Get the average effective packet loss recovery from FEC
    //this is from tables, computed using random loss model
    WebRtc_UWord8 avgFecRecov1 = 0;
    WebRtc_UWord8 avgFecRecov2 = 0;
    float avgFecRecov = 0;

    if (fecPacketsPerFrame > 0)
    {
        avgFecRecov1 = VCMAvgFECRecoveryXOR[indexTable];
        avgFecRecov2 = VCMAvgFECRecoveryXOR[indexTable2];
    }

    //interpolate over two FEC codes
    const float weightRpl = (float)(0.5 + protectionFactor*avgTotPackets) - (float)fecPacketsPerFrame;
    avgFecRecov = (float)weightRpl * (float)avgFecRecov2 + (float)(1.0 - weightRpl) * (float)avgFecRecov1;


    return avgFecRecov;

}

bool
VCMFecMethod::ProtectionFactor(const VCMProtectionParameters* parameters)
{

    //FEC PROTECTION SETTINGS: varies with packet loss and bitrate

    const float bitRate = parameters->bitRate;
    WebRtc_UWord8 packetLoss = (WebRtc_UWord8)(255* parameters->lossPr);


    //Size of tables
    const WebRtc_UWord16 maxFecTableSize =  6450;
    //Parameters for range of rate and packet loss for tables
    const WebRtc_UWord8 ratePar1 = 5;
    const WebRtc_UWord8 ratePar2 = 49;
    const WebRtc_UWord8 plossMax = 129;

    //
    //Just for testing: for the case where we randomly lose slices instead of RTP packets and use SingleMode packetization in RTP module
    //const WebRtc_UWord16 slice_size = 3000/6; //corresponds to rate=1000k with 4 cores

    //float slice_mtu = (float)_maxPayloadSize/(float)slice_size;
    const float slice_mtu = 1.0;
    //

    //Total (avg) bits available per frame: total rate over actual/sent frame rate
    //units are kbits/frame
    const WebRtc_UWord16 bitRatePerFrame = static_cast<WebRtc_UWord16>(slice_mtu*bitRate/(parameters->frameRate));

    //Total (avg) number of packets per frame (source and fec):
    const WebRtc_UWord8 avgTotPackets  = 1 + (WebRtc_UWord8)((float)bitRatePerFrame*1000.0/(float)(8.0*_maxPayloadSize) + 0.5);

    //TODO(marpan): Tune model for FEC Protection.
    //Better modulation of protection with available bits/frame (or avgTotpackets) using weight factors
    //FEC Tables include this effect already, but need to tune model off-line
    float weight1 = 0.5;
    float weight2 = 0.5;
    if (avgTotPackets > 4)
    {
        weight1 = 1.0;
        weight2 = 0.;
    }
    if (avgTotPackets > 6)
    {
        weight1 = 1.5;
        weight2 = 0.;
    }
   //

    //Fec rate parameters: for P and I frame
    WebRtc_UWord8 codeRateDelta = 0;
    WebRtc_UWord8 codeRateKey = 0;


    //Get index for new table: the FEC protection depends on the (avergare) available bits/frame
    //the range on the rate index corresponds to rates (bps) from 200k to 8000k, for 30fps
    WebRtc_UWord8 rateIndexTable = (WebRtc_UWord8) VCM_MAX(VCM_MIN((bitRatePerFrame-ratePar1)/ratePar1,ratePar2),0);

    // Restrict packet loss range to 50 for now%: current tables defined only up to 50%
    if (packetLoss >= plossMax)
    {
        packetLoss = plossMax - 1;
    }
    WebRtc_UWord16 indexTable = rateIndexTable * plossMax + packetLoss;

    //check on table index
    if (indexTable >= maxFecTableSize)
    {
        assert("FEC table index too large\n");
    }
    //

    //For Key frame: effectively at a higher rate, so we scale/boost the rate index.
    //the boost factor may depend on several factors: ratio of packet number of I to P frames, how much protection placed on P frames, etc.
    //default is 2
    const WebRtc_UWord8 packetFrameDelta = (WebRtc_UWord8)(0.5 + parameters->packetsPerFrame);
    const WebRtc_UWord8 packetFrameKey = (WebRtc_UWord8) (0.5 + parameters->packetsPerFrameKey);
    const WebRtc_UWord8 boostKey = BoostCodeRateKey(packetFrameDelta, packetFrameKey);
    rateIndexTable = (WebRtc_UWord8) VCM_MAX(VCM_MIN(1+(boostKey*bitRatePerFrame-ratePar1)/ratePar1,ratePar2),0);
    WebRtc_UWord16 indexTableKey = rateIndexTable * plossMax + packetLoss;

    indexTableKey = VCM_MIN(indexTableKey, maxFecTableSize);

    codeRateDelta = VCMCodeRateXORTable[indexTable];  //protection factor for P fra
    codeRateKey = VCMCodeRateXORTable[indexTableKey]; //protection factor for I frame

    //average with minimum protection level given by (average) total number of packets
    if (packetLoss > 0)
    {
        codeRateDelta = static_cast<WebRtc_UWord8>((weight1*(float)codeRateDelta + weight2*255.0/(float)avgTotPackets));
    }

    //check limit on amount of protection for P frame; 50% is max
    if (codeRateDelta >= plossMax)
    {
        codeRateDelta = plossMax - 1;
    }

    //make sure I frame protection is at least larger than P frame protection, and at least as high as received loss
    codeRateKey = static_cast<WebRtc_UWord8>(VCM_MAX(packetLoss,VCM_MAX(_scaleProtKey*codeRateDelta, codeRateKey)));

    //check limit on amount of protection for I frame: 50% is max
    if (codeRateKey >= plossMax)
    {
        codeRateKey = plossMax - 1;
    }

    _protectionFactorK = codeRateKey;
    _protectionFactorD = codeRateDelta;

    // DONE WITH FEC PROTECTION SETTINGS


    return true;
}


bool
VCMFecMethod::EffectivePacketLoss(const VCMProtectionParameters* parameters)
{

    // ER SETTINGS:
    //Effective packet loss to encoder is based on RPL (residual packet loss)
    //this is a soft setting based on degree of FEC protection
    //RPL = received/input packet loss - average_FEC_recovery
    //note: received/input packet loss may be filtered according to FilteredLoss

    //The input packet loss:
    WebRtc_UWord8 effPacketLoss = (WebRtc_UWord8)(255*parameters->lossPr);

    float scaleErRS = 0.5;
    float scaleErXOR = 0.5;
    float minErLevel = (float) 0.025;
    //float scaleErRS = 1.0;
    //float scaleErXOR = 1.0;
    //float minErLevel = (float) 0.0;

    float avgFecRecov = 0.;
    //Effective packet loss for ER:
    float scaleEr = scaleErXOR;
    avgFecRecov = AvgRecoveryFEC(parameters);

    //Residual Packet Loss:
    _residualPacketLoss = (float)(effPacketLoss - avgFecRecov)/(float)255.0;


    //Effective Packet Loss for encoder:
    _effectivePacketLoss = 0;
    if (effPacketLoss > 0)
    {
        _effectivePacketLoss = VCM_MAX((effPacketLoss - (WebRtc_UWord8)(scaleEr*avgFecRecov)),static_cast<WebRtc_UWord8>(minErLevel*255));
    }


    // DONE WITH ER SETTING

     return true;
}


bool
VCMFecMethod::UpdateParameters(const VCMProtectionParameters* parameters)
{

    // Compute the protection factor
    ProtectionFactor(parameters);

    // Compute the effective packet loss
    EffectivePacketLoss(parameters);


    // Compute the bit cost
    // Ignore key frames for now.
    float fecRate = static_cast<float>(_protectionFactorD) / 255.0f;
    if (fecRate >= 0.0f)
    {
        // use this formula if the fecRate (protection factor) is defined relative to number of source packets
        // this is the case for the previous tables:
        // _efficiency = parameters->bitRate * ( 1.0 - 1.0 / (1.0 + fecRate));

        // in the new tables, the fecRate is defined relative to total number of packets (total rate),
        // so overhead cost is:
        _efficiency = parameters->bitRate * fecRate;
    }
    else
    {
        _efficiency = 0.0f;
    }
    _score = _efficiency;


    // Protection/fec rates obtained above is defined relative to total number of packets (total rate: source+fec)
    // FEC in RTP module assumes protection factor is defined relative to source number of packets
    // so we should convert the factor to reduce mismatch between mediaOpt suggested rate and the actual rate
    _protectionFactorK = ConvertFECRate(_protectionFactorK);
    _protectionFactorD = ConvertFECRate(_protectionFactorD);

    return true;
}

bool
VCMIntraReqMethod::UpdateParameters(const VCMProtectionParameters* parameters)
{
    float packetRate = parameters->packetsPerFrame * parameters->frameRate;
    // Assume that all lost packets cohere to different frames
    float lossRate = parameters->lossPr * packetRate;
    if (parameters->keyFrameSize <= 1e-3)
    {
        _score = FLT_MAX;
        return false;
    }
    _efficiency = lossRate * parameters->keyFrameSize;
    _score = _efficiency;
    if (parameters->lossPr >= 1.0f / parameters->keyFrameSize || parameters->rtt > _IREQ_MAX_RTT)
    {
        return false;
    }
    return true;
}

bool
VCMPeriodicIntraMethod::UpdateParameters(const VCMProtectionParameters* /*parameters*/)
{
    // Periodic I-frames. The last thing we want to use.
    _efficiency = 0.0f;
    _score = FLT_MAX;
    return true;
}

bool
VCMMbIntraRefreshMethod::UpdateParameters(const VCMProtectionParameters* parameters)
{
    // Assume optimal for now.
    _efficiency = parameters->bitRate * parameters->lossPr / (1.0f + parameters->lossPr);
    _score = _efficiency;
    if (parameters->bitRate < _MBREF_MIN_BITRATE)
    {
        return false;
    }
    return true;
}

WebRtc_UWord16
VCMNackMethod::MaxRttNack() const
{
    return _NACK_MAX_RTT;
}

VCMLossProtectionLogic::~VCMLossProtectionLogic()
{
    ClearLossProtections();
}

void
VCMLossProtectionLogic::ClearLossProtections()
{
    ListItem *item;
    while ((item = _availableMethods.First()) != 0)
    {
        VCMProtectionMethod *method = static_cast<VCMProtectionMethod*>(item->GetItem());
        if (method != NULL)
        {
            delete method;
        }
        _availableMethods.PopFront();
    }
    _selectedMethod = NULL;
}

 bool
VCMLossProtectionLogic::AddMethod(VCMProtectionMethod *newMethod)
{
    VCMProtectionMethod *method;
    ListItem *item;
    if (newMethod == NULL)
    {
        return false;
    }
    for (item = _availableMethods.First(); item != NULL; item = _availableMethods.Next(item))
    {
        method = static_cast<VCMProtectionMethod *>(item->GetItem());
        if (method != NULL && method->Type() == newMethod->Type())
        {
            return false;
        }
    }
    _availableMethods.PushBack(newMethod);
    return true;

}
bool
VCMLossProtectionLogic::RemoveMethod(VCMProtectionMethodEnum methodType)
{
    VCMProtectionMethod *method;
    ListItem *item;
    bool foundAndRemoved = false;
    for (item = _availableMethods.First(); item != NULL; item = _availableMethods.Next(item))
    {
        method = static_cast<VCMProtectionMethod *>(item->GetItem());
        if (method != NULL && method->Type() == methodType)
        {
            if (_selectedMethod != NULL && _selectedMethod->Type() == method->Type())
            {
                _selectedMethod = NULL;
            }
            _availableMethods.Erase(item);
            item = NULL;
            delete method;
            foundAndRemoved = true;
        }
    }
    return foundAndRemoved;
}

VCMProtectionMethod*
VCMLossProtectionLogic::FindMethod(VCMProtectionMethodEnum methodType) const
{
    VCMProtectionMethod *method;
    ListItem *item;
    for (item = _availableMethods.First(); item != NULL; item = _availableMethods.Next(item))
    {
        method = static_cast<VCMProtectionMethod *>(item->GetItem());
        if (method != NULL && method->Type() == methodType)
        {
            return method;
        }
    }
    return NULL;
}

float
VCMLossProtectionLogic::HighestOverhead() const
{
    VCMProtectionMethod *method;
    ListItem *item;
    float highestOverhead = 0.0f;
    for (item = _availableMethods.First(); item != NULL; item = _availableMethods.Next(item))
    {
        method = static_cast<VCMProtectionMethod *>(item->GetItem());
        if (method != NULL && method->RequiredBitRate() > highestOverhead)
        {
            highestOverhead = method->RequiredBitRate();
        }
    }
    return highestOverhead;
}

void
VCMLossProtectionLogic::UpdateRtt(WebRtc_UWord32 rtt)
{
    _rtt = rtt;
}

void
VCMLossProtectionLogic::UpdateResidualPacketLoss(float residualPacketLoss)
{
    _residualPacketLoss = residualPacketLoss;
}

void
VCMLossProtectionLogic::UpdateFecType(VCMFecTypes fecType)
{
    _fecType = fecType;
}

void
VCMLossProtectionLogic::UpdateLossPr(WebRtc_UWord8 lossPr255)
{
    WebRtc_UWord32 now = static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp());
    UpdateMaxLossHistory(lossPr255, now);
    _lossPr255.Apply(static_cast<float>(now - _lastPrUpdateT), static_cast<float>(lossPr255));
    _lastPrUpdateT = now;
    _lossPr = _lossPr255.Value() / 255.0f;
}

void
VCMLossProtectionLogic::UpdateMaxLossHistory(WebRtc_UWord8 lossPr255, WebRtc_Word64 now)
{
    if (_lossPrHistory[0].timeMs >= 0 &&
        now - _lossPrHistory[0].timeMs < kLossPrShortFilterWinMs)
    {
        if (lossPr255 > _shortMaxLossPr255)
        {
            _shortMaxLossPr255 = lossPr255;
        }
    }
    else
    {
        // Only add a new value to the history once a second
        if(_lossPrHistory[0].timeMs == -1)
        {
            // First, no shift
            _shortMaxLossPr255 = lossPr255;
        }
        else
        {
            // Shift
            for(WebRtc_Word32 i = (kLossPrHistorySize - 2); i >= 0 ; i--)
            {
                _lossPrHistory[i+1].lossPr255 = _lossPrHistory[i].lossPr255;
                _lossPrHistory[i+1].timeMs = _lossPrHistory[i].timeMs;
            }
        }
        if (_shortMaxLossPr255 == 0)
        {
            _shortMaxLossPr255 = lossPr255;
        }

         _lossPrHistory[0].lossPr255 = _shortMaxLossPr255;
        _lossPrHistory[0].timeMs = now;
        _shortMaxLossPr255 = 0;

    }
}

WebRtc_UWord8
VCMLossProtectionLogic::MaxFilteredLossPr(WebRtc_Word64 nowMs) const
{
    WebRtc_UWord8 maxFound = _shortMaxLossPr255;
    if (_lossPrHistory[0].timeMs == -1)
    {
        return maxFound;
    }
    for (WebRtc_Word32 i=0; i < kLossPrHistorySize; i++)
    {
        if (_lossPrHistory[i].timeMs == -1)
        {
            break;
        }
        if (nowMs - _lossPrHistory[i].timeMs > kLossPrHistorySize * kLossPrShortFilterWinMs)
        {
            // This sample (and all samples after this) is too old
            break;
        }
        if (_lossPrHistory[i].lossPr255 > maxFound)
        {
            // This sample is the largest one this far into the history
            maxFound = _lossPrHistory[i].lossPr255;
        }
    }
    return maxFound;
}

WebRtc_UWord8
VCMLossProtectionLogic::FilteredLoss() const
{

    //take the average received loss
    //return static_cast<WebRtc_UWord8>(_lossPr255.Value() + 0.5f);

    //take the windowed max of the received loss
    if (_selectedMethod != NULL && _selectedMethod->Type() == kFEC)
    {
        return MaxFilteredLossPr(static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp()));
    }
    else
    {
        return static_cast<WebRtc_UWord8>(_lossPr255.Value() + 0.5);
    }

}

void
VCMLossProtectionLogic::UpdateFilteredLossPr(WebRtc_UWord8 packetLossEnc)
{
   _lossPr = (float)packetLossEnc/(float)255.0;
}

void
VCMLossProtectionLogic::UpdateBitRate(float bitRate)
{
    _bitRate = bitRate;
}

void
VCMLossProtectionLogic::UpdatePacketsPerFrame(float nPackets)
{
    WebRtc_UWord32 now = static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp());
    _packetsPerFrame.Apply(static_cast<float>(now - _lastPacketPerFrameUpdateT), nPackets);
    _lastPacketPerFrameUpdateT = now;
}

void
VCMLossProtectionLogic::UpdatePacketsPerFrameKey(float nPackets)
{
    WebRtc_UWord32 now = static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp());
    _packetsPerFrameKey.Apply(static_cast<float>(now - _lastPacketPerFrameUpdateTKey), nPackets);
    _lastPacketPerFrameUpdateTKey = now;
}

void
VCMLossProtectionLogic::UpdateKeyFrameSize(float keyFrameSize)
{
    _keyFrameSize = keyFrameSize;
}

bool
VCMLossProtectionLogic::UpdateMethod(VCMProtectionMethod *newMethod /*=NULL */)
{
    _currentParameters.rtt     = _rtt;
    _currentParameters.lossPr  = _lossPr;
    _currentParameters.bitRate = _bitRate;
    _currentParameters.frameRate    = _frameRate; //should this be named actual frame rate?
    _currentParameters.keyFrameSize = _keyFrameSize;
    _currentParameters.fecRateDelta = _fecRateDelta;
    _currentParameters.fecRateKey   = _fecRateKey;
    _currentParameters.packetsPerFrame = _packetsPerFrame.Value();
    _currentParameters.packetsPerFrameKey = _packetsPerFrameKey.Value();
    _currentParameters.residualPacketLoss = _residualPacketLoss;
    _currentParameters.fecType = _fecType;

    if (newMethod == NULL)
    {
        //_selectedMethod = _bestNotOkMethod = NULL;
        VCMProtectionMethod *method;
        ListItem *item;
        for (item = _availableMethods.First(); item != NULL; item = _availableMethods.Next(item))
        {
            method = static_cast<VCMProtectionMethod *>(item->GetItem());
            if (method != NULL)
            {
                if (method->Type() == kFEC)
                {
                    _selectedMethod = method;
                }
                method->UpdateParameters(&_currentParameters);
            }
        }
        if (_selectedMethod != NULL && _selectedMethod->Type() != kFEC)
        {
            _selectedMethod = method;
        }
    }
    else
    {
        _selectedMethod = newMethod;
        _selectedMethod->UpdateParameters(&_currentParameters);
    }
    return true;
}

VCMProtectionMethod*
VCMLossProtectionLogic::SelectedMethod() const
{
    return _selectedMethod;
}

void
VCMLossProtectionLogic::Reset()
{
    _lastPrUpdateT = static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp());
    _lastPacketPerFrameUpdateT = static_cast<WebRtc_UWord32>(VCMTickTime::MillisecondTimestamp());
    _lossPr255.Reset(0.9999f);
    _packetsPerFrame.Reset(0.9999f);
    _fecRateDelta = _fecRateKey = 0;
    for (WebRtc_Word32 i=0; i < kLossPrHistorySize; i++)
    {
        _lossPrHistory[i].lossPr255 = 0;
        _lossPrHistory[i].timeMs = -1;
    }
    _shortMaxLossPr255 = 0;
    ClearLossProtections();
}

}