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media_opt_util: Modification to correction factor in FEC overhead.

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Review URL: http://webrtc-codereview.appspot.com/133019

git-svn-id: http://webrtc.googlecode.com/svn/trunk@573 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
marpan@google.com 2011-09-09 16:39:40 +00:00
parent 955d0eed2f
commit 3f28061f3a
1 changed files with 8 additions and 4 deletions
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12
src/modules/video_coding/main/source/media_opt_util.cc
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@ -305,6 +305,10 @@ VCMFecMethod::ProtectionFactor(const VCMProtectionParameters* parameters)
// First partition protection: ~ 20%
WebRtc_UWord8 firstPartitionProt = (WebRtc_UWord8) (255 * 0.20);
// Minimum protection level needed to generate one FEC packet for one
// source packet/frame (in RTP sender)
WebRtc_UWord8 minProtLevelFec = 85;
// Threshold on packetLoss and bitRrate/frameRate (=average #packets),
// above which we allocate protection to cover at least first partition.
WebRtc_UWord8 lossThr = 0;
@ -437,17 +441,17 @@ VCMFecMethod::ProtectionFactor(const VCMProtectionParameters* parameters)
// in mediaOpt may generate 0 FEC packets in RTP sender (since actual #FEC
// is based on rounding off protectionFactor on actual source packet number).
// The correction factor (_corrFecCost) attempts to corrects this, at least
// for cases of low rates/low # of packets.
// for cases of low rates (small #packets) and low protection levels.
const float estNumFecGen = 0.5f + static_cast<float> (_protectionFactorD *
avgTotPackets / 255.0f);
// Note we reduce cost factor (which will reduce overhead for FEC and
// We reduce cost factor (which will reduce overhead for FEC and
// hybrid method) and not the protectionFactor.
_corrFecCost = 1.0f;
if (estNumFecGen < 1.5f)
if (estNumFecGen < 1.5f && _protectionFactorD < minProtLevelFec)
{
_corrFecCost = 0.5f;
}
if (estNumFecGen < 1.0f)
if (estNumFecGen < 0.9f && _protectionFactorD < minProtLevelFec)
{
_corrFecCost = 0.0f;
}