From 243db1261610680f42559c5b168815df015c3de7 Mon Sep 17 00:00:00 2001 From: "marpan@google.com" <marpan@google.com@4adac7df-926f-26a2-2b94-8c16560cd09d> Date: Wed, 31 Aug 2011 22:14:52 +0000 Subject: [PATCH] media_opt_util: Fixed an assert and some code cleanup for AvgRecoveryFEC function. Review URL: http://webrtc-codereview.appspot.com/139007 git-svn-id: http://webrtc.googlecode.com/svn/trunk@502 4adac7df-926f-26a2-2b94-8c16560cd09d --- .../main/source/media_opt_util.cc | 74 +++++++------------ 1 file changed, 26 insertions(+), 48 deletions(-) diff --git a/src/modules/video_coding/main/source/media_opt_util.cc b/src/modules/video_coding/main/source/media_opt_util.cc index 1050596f1..f01fb5040 100644 --- a/src/modules/video_coding/main/source/media_opt_util.cc +++ b/src/modules/video_coding/main/source/media_opt_util.cc @@ -209,7 +209,7 @@ VCMFecMethod::UpdateProtectionFactorD(WebRtc_UWord8 protectionFactorD) _protectionFactorD = protectionFactorD; } -// AvgRecoveryFEC: computes the residual packet loss function. +// AvgRecoveryFEC: computes the residual packet loss (RPL) function. // This is the average recovery from the FEC, assuming random packet loss model. // Computed off-line for a range of FEC code parameters and loss rates. float @@ -226,11 +226,16 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const static_cast<float> (8.0 * _maxPayloadSize) + 0.5); // Parameters for tables - const WebRtc_UWord8 codeSize = 24; + // Maximum number of source packets in off-line model + const WebRtc_UWord8 maxNumPackets = 24; + // Max value of loss rates in off-line model const WebRtc_UWord8 plossMax = 129; + + // Table size for model is: plossMax * numberOfFecCodes = 38700 + // numberOfFecCodes is determined as: + // {(1,1), (2,1), (2,2),...(n,1),..(n,n-1), (n,n)} = n*(n+1)/2; for n=24. const WebRtc_UWord16 maxErTableSize = 38700; - // Get index for table const float protectionFactor = static_cast<float>(_protectionFactorD) / 255.0; @@ -245,76 +250,49 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const return 0.0; } - // Table defined up to codeSizexcodeSize code - if (sourcePacketsPerFrame > codeSize) + // Table defined up to maxNumPackets + if (sourcePacketsPerFrame > maxNumPackets) { - sourcePacketsPerFrame = codeSize; + sourcePacketsPerFrame = maxNumPackets; } - // Table defined up to codeSizexcodeSize code - if (fecPacketsPerFrame > codeSize) + // Table defined up to maxNumPackets + if (fecPacketsPerFrame > maxNumPackets) { - fecPacketsPerFrame = codeSize; + fecPacketsPerFrame = maxNumPackets; } - // Check: protection factor is maxed at 50%, so this should never happen - assert(sourcePacketsPerFrame >= 1); - - // Index for ER tables: up to codeSizexcodeSize mask - WebRtc_UWord16 codeIndexTable[codeSize * codeSize]; + // Code index for tables: up to (maxNumPackets * maxNumPackets) + WebRtc_UWord16 codeIndexTable[maxNumPackets * maxNumPackets]; WebRtc_UWord16 k = 0; - for (WebRtc_UWord8 i = 1; i <= codeSize; i++) + for (WebRtc_UWord8 i = 1; i <= maxNumPackets; i++) { for (WebRtc_UWord8 j = 1; j <= i; j++) { - codeIndexTable[(j - 1) * codeSize + i - 1] = k; + codeIndexTable[(j - 1) * maxNumPackets + i - 1] = k; k += 1; } } WebRtc_UWord8 lossRate = static_cast<WebRtc_UWord8> (255.0 * parameters->lossPr + 0.5f); - // Constrain lossRate to 129 (50% protection) - // TODO (marpan): Verify table values - const WebRtc_UWord16 codeIndex = (fecPacketsPerFrame - 1) * codeSize + + // Constrain lossRate to 50%: tables defined up to 50% + if (lossRate >= plossMax) + { + lossRate = plossMax - 1; + } + + const WebRtc_UWord16 codeIndex = (fecPacketsPerFrame - 1) * maxNumPackets + (sourcePacketsPerFrame - 1); const WebRtc_UWord16 indexTable = codeIndexTable[codeIndex] * plossMax + lossRate; - const WebRtc_UWord16 codeIndex2 = (fecPacketsPerFrame) * codeSize + - (sourcePacketsPerFrame); - - WebRtc_UWord16 indexTable2 = codeIndexTable[codeIndex2] * plossMax + - lossRate; - // Check on table index assert (indexTable < maxErTableSize); - 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 = 0.0f; - - if (fecPacketsPerFrame > 0) - { - avgFecRecov1 = VCMAvgFECRecoveryXOR[indexTable]; - avgFecRecov2 = VCMAvgFECRecoveryXOR[indexTable2]; - } - - // Interpolate over two FEC codes - const float weightRpl = static_cast<float> - (0.5 + protectionFactor * avgTotPackets) - - (float) fecPacketsPerFrame; - - avgFecRecov = weightRpl * static_cast<float> (avgFecRecov2) + - (1.0 - weightRpl) * static_cast<float> (avgFecRecov1); + float avgFecRecov = static_cast<float> (VCMAvgFECRecoveryXOR[indexTable]); return avgFecRecov; }