generic-library/webrtc
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

media_opt_util: Fixed an assert and some code cleanup for AvgRecoveryFEC function.

Browse Source 
Review URL: http://webrtc-codereview.appspot.com/139007

git-svn-id: http://webrtc.googlecode.com/svn/trunk@502 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
marpan@google.com 2011-08-31 22:14:52 +00:00
parent b15bfd32d7
commit 243db12616
1 changed files with 26 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
src/modules/video_coding/main/source/media_opt_util.cc
View File

@ -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;
}