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

media_opt_util: Update robustness settings for Hybrid mode. Updated table for the computation of the adjustment factor.

Browse Source 
Review URL: http://webrtc-codereview.appspot.com/93013

git-svn-id: http://webrtc.googlecode.com/svn/trunk@286 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
mikhal@google.com
2011-08-01 22:14:58 +00:00
parent 5fc2dcd64a
commit 679450f4a6
3 changed files with 125 additions and 227 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
src/modules/video_coding/main/source/media_opt_util.cc
View File

@@ -43,19 +43,12 @@ VCMNackFecMethod::ProtectionFactor(const
VCMProtectionParameters* parameters)
{
// Hybrid Nack FEC has three operational modes:
// 1. Low RTT - Nack only (Set FEC rates to zero)
// 2. High RTT - FEC Only
// 3. Medium RTT values - Hybrid ; in hybrid mode, we will only nack the
// residual following the decoding of the FEC (refer to JB logic)
// Low RTT - NACK only mode
if (parameters->rtt < kLowRttNackMs)
{
// Set the FEC parameters to 0
_protectionFactorK = 0;
_protectionFactorD = 0;
return true;
}
// 1. Low RTT (below kLowRttNackMs) - Nack only: Set FEC rate
// (_protectionFactorD) to zero.
// 2. High RTT (above kHighRttNackMs) - FEC Only: Keep FEC factors.
// 3. Medium RTT values - Hybrid mode: We will only nack the
// residual following the decoding of the FEC (refer to JB logic). FEC
// delta protection factor will be adjusted based on the RTT.
// Otherwise: we count on FEC; if the RTT is below a threshold, then we
// nack the residual, based on a decision made in the JB.
@@ -66,18 +59,22 @@ VCMNackFecMethod::ProtectionFactor(const
_protectionFactorK = _fecMethod->_protectionFactorK;
_protectionFactorD = _fecMethod->_protectionFactorD;
// When in Hybrid mode, correct FEC rates based on the
// RTT (NACK effectiveness)
// When in Hybrid mode (RTT range), adjust FEC rates based on the
// RTT (NACK effectiveness) - adjustment factor is in the range [0,1].
if (parameters->rtt < kHighRttNackMs)
{
WebRtc_UWord16 rttIndex = (WebRtc_UWord16) parameters->rtt;
// TODO(mikhal): update table
float softnessRtt = (float)VCMNackFecTable[rttIndex] / (float)4096.0;
float adjustRtt = (float)VCMNackFecTable[rttIndex] / 100.0f;
// Soften FEC with NACK on (for delta frame only)
// Adjust FEC with NACK on (for delta frame only)
// table depends on RTT relative to rttMax (NACK Threshold)
_protectionFactorD *= static_cast<WebRtc_UWord8> (softnessRtt);
_protectionFactorD = static_cast<WebRtc_UWord8>
(adjustRtt *
static_cast<float>(_protectionFactorD));
// update FEC rates after applyingadjustment softness parameter
_fecMethod->UpdateProtectionFactorD(_protectionFactorD);
}
return true;
}
@@ -85,16 +82,6 @@ bool
VCMNackFecMethod::EffectivePacketLoss(const
VCMProtectionParameters* parameters)
{
// NACK only mode
if (parameters->rtt < kLowRttNackMs)
{
// Effective Packet Loss, NA in current version.
_effectivePacketLoss = 0;
// No FEC applied.
_residualPacketLossFec = parameters->lossPr;
return true;
}
// Set the effective packet loss for encoder (based on FEC code).
// Compute the effective packet loss and residual packet loss due to FEC.
_fecMethod->EffectivePacketLoss(parameters);
@@ -180,6 +167,14 @@ VCMFecMethod::ConvertFECRate(WebRtc_UWord8 codeRateRTP) const
(float)(255 - codeRateRTP))));
}
// Update FEC with protectionFactorD
void
VCMFecMethod::UpdateProtectionFactorD(WebRtc_UWord8 protectionFactorD)
{
_protectionFactorD = protectionFactorD;
}
// 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.