From 5fb9905186ba3ce1042ec7ae67cb50211df119b0 Mon Sep 17 00:00:00 2001
From: Andrzej Kapolka <drzej.k@gmail.com>
Date: Tue, 9 Dec 2014 12:14:21 -0800
Subject: [PATCH] Rather than reducing rate on first drop, wait until three
 consecutive packets have been dropped.

---
 .../metavoxels/src/DatagramSequencer.cpp      | 20 +++++++++++++------
 libraries/metavoxels/src/DatagramSequencer.h  |  2 ++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/libraries/metavoxels/src/DatagramSequencer.cpp b/libraries/metavoxels/src/DatagramSequencer.cpp
index 1aeef8e450..65d548ba1c 100644
--- a/libraries/metavoxels/src/DatagramSequencer.cpp
+++ b/libraries/metavoxels/src/DatagramSequencer.cpp
@@ -45,7 +45,8 @@ DatagramSequencer::DatagramSequencer(const QByteArray& datagramHeader, QObject*
     _packetsToWrite(0.0f),
     _slowStartThreshold(DEFAULT_SLOW_START_THRESHOLD),
     _packetRateIncreasePacketNumber(0),
-    _packetRateDecreasePacketNumber(0) {
+    _packetRateDecreasePacketNumber(0),
+    _packetDropCount(0) {
 
     _outgoingPacketStream.setByteOrder(QDataStream::LittleEndian);
     _incomingDatagramStream.setByteOrder(QDataStream::LittleEndian);
@@ -348,11 +349,18 @@ void DatagramSequencer::sendRecordLost(const SendRecord& record) {
         }
     }
     
-    // halve the rate and remember as threshold
-    if (record.packetNumber >= _packetRateDecreasePacketNumber) {
-        _packetsPerGroup = qMax(_packetsPerGroup * 0.5f, 1.0f);
-        _slowStartThreshold = _packetsPerGroup;
-        _packetRateDecreasePacketNumber = _outgoingPacketNumber + 1;
+    // if we've lost three in a row, halve the rate and remember as threshold
+    if (_packetDropCount == 0 || record.packetNumber == _lastPacketDropped + 1) {
+        _packetDropCount++;
+        _lastPacketDropped = record.packetNumber;
+        const int CONSECUTIVE_DROPS_BEFORE_REDUCTION = 3;
+        if (_packetDropCount >= CONSECUTIVE_DROPS_BEFORE_REDUCTION && record.packetNumber >= _packetRateDecreasePacketNumber) {
+            _packetsPerGroup = qMax(_packetsPerGroup * 0.5f, 1.0f);
+            _slowStartThreshold = _packetsPerGroup;
+            _packetRateDecreasePacketNumber = _outgoingPacketNumber + 1;
+        }
+    } else {
+        _packetDropCount = 0;
     }
 }
 
diff --git a/libraries/metavoxels/src/DatagramSequencer.h b/libraries/metavoxels/src/DatagramSequencer.h
index 02fbd0f365..d3d37f2621 100644
--- a/libraries/metavoxels/src/DatagramSequencer.h
+++ b/libraries/metavoxels/src/DatagramSequencer.h
@@ -238,6 +238,8 @@ private:
     float _slowStartThreshold;
     int _packetRateIncreasePacketNumber;
     int _packetRateDecreasePacketNumber;
+    int _packetDropCount;
+    int _lastPacketDropped;
     
     QHash<int, ReliableChannel*> _reliableOutputChannels;
     QHash<int, ReliableChannel*> _reliableInputChannels;