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Code cleanup for residual packet loss function in media_opt_util.cc.

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Review URL: http://webrtc-codereview.appspot.com/89004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@256 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
marpan@google.com 2011-07-26 16:47:11 +00:00
parent 694019b9aa
commit 13955743b0
1 changed files with 41 additions and 39 deletions
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80
src/modules/video_coding/main/source/media_opt_util.cc
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@ -199,8 +199,9 @@ VCMFecMethod::ConvertFECRate(WebRtc_UWord8 codeRateRTP) const
(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
// AvgRecoveryFEC: computes the residual packet loss 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
VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
{
@ -209,40 +210,41 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
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);
// Total (average) number of packets per frame (source and fec):
const WebRtc_UWord8 avgTotPackets = 1 + static_cast<WebRtc_UWord8>
(static_cast<float> (bitRatePerFrame * 1000.0) /
static_cast<float> (8.0 * _maxPayloadSize) + 0.5);
// parameters for tables
// 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);
const float protectionFactor = static_cast<float>(_protectionFactorD) /
255.0;
WebRtc_UWord8 fecPacketsPerFrame = static_cast<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
// No protection, so average recovery from FEC == 0.
return 0.0;
}
// table defined up to codeSizexcodeSize code
// 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");
}
// Check: protection factor is maxed at 50%, so this should never happen
assert(sourcePacketsPerFrame >= 1);
// index for ER tables: up to codeSizexcodeSize mask
// Index for ER tables: up to codeSizexcodeSize mask
WebRtc_UWord16 codeIndexTable[codeSize * codeSize];
WebRtc_UWord16 k = 0;
for (WebRtc_UWord8 i = 1; i <= codeSize; i++)
@ -254,25 +256,23 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
}
}
const WebRtc_UWord8 lossRate = (WebRtc_UWord8) (255.0 *
parameters->lossPr + 0.5f);
const WebRtc_UWord8 lossRate = static_cast<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 codeIndex = (fecPacketsPerFrame - 1) * codeSize +
(sourcePacketsPerFrame - 1);
const WebRtc_UWord16 codeIndex2 = (fecPacketsPerFrame) * codeSize
+ (sourcePacketsPerFrame);
WebRtc_UWord16 indexTable2 = codeIndexTable[codeIndex2] * plossMax
+ lossRate;
const WebRtc_UWord16 indexTable = codeIndexTable[codeIndex] * plossMax +
lossRate;
// checks on table index
if (indexTable >= maxErTableSize)
{
assert("ER table index too large\n");
}
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;
@ -282,7 +282,7 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
// this is from tables, computed using random loss model
WebRtc_UWord8 avgFecRecov1 = 0;
WebRtc_UWord8 avgFecRecov2 = 0;
float avgFecRecov = 0;
float avgFecRecov = 0.0f;
if (fecPacketsPerFrame > 0)
{
@ -290,11 +290,13 @@ VCMFecMethod::AvgRecoveryFEC(const VCMProtectionParameters* parameters) const
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;
// 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);
return avgFecRecov;
}