Added dynamic tic stabilization

Attempts to balance periods of rough traffic by putting in an artificial delay, smoothing playback but further increasing input delay. This can be disabled with net_ticbalance.

src/common/engine/i_net.h

@@ -11,6 +11,7 @@ enum ENetConstants
 	BACKUPTICS = 35 * 5,	// Remember up to 5 seconds of data.
 	MAXTICDUP = 3,
 	MAXSENDTICS = 35 * 1,	// Only send up to 1 second of data at a time.
+	STABILITYTICS = 12,
 	LOCALCMDTICS = (BACKUPTICS * MAXTICDUP),
 	MAX_MSGLEN = 14000,
 };

src/d_net.cpp

@@ -116,6 +116,14 @@ int					LastSentConsistency = 0;		// Last consistency we sent out. If < CurrentC
 int					CurrentConsistency = 0;			// Last consistency we generated.
 FClientNetState		ClientStates[MAXPLAYERS] = {};
 
+// Try and stabilize uneven connections by checking for spikes in available
+// sequences. If they're found, try and average out a buffer to prioritize
+// making the experience smoother over very stop and go heavy.
+static int			StabilityBuffer = 0;
+static int			PrevAvailableDiff = 0;
+static size_t		CurStabilityTic = 0u;
+static int			StabilityTics[STABILITYTICS] = {};
+
 // If we're sending a packet to ourselves, store it here instead. This is the simplest way to execute
 // playback as it means in the world running code itself all player commands are built the exact same way
 // instead of having to rely on pulling from the correct local buffers. It also ensures all commands are
@@ -157,7 +165,7 @@ extern	bool	 advancedemo;
 CVAR(Bool, vid_dontdowait, false, CVAR_ARCHIVE|CVAR_GLOBALCONFIG)
 CVAR(Bool, vid_lowerinbackground, true, CVAR_ARCHIVE|CVAR_GLOBALCONFIG)
 
-CVAR(Bool, net_ticbalance, false, CVAR_SERVERINFO | CVAR_NOSAVE) // Currently deprecated, but may be brought back later.
+CVAR(Bool, net_ticbalance, true, CVAR_SERVERINFO | CVAR_NOSAVE)
 CVAR(Bool, net_extratic, false, CVAR_SERVERINFO | CVAR_NOSAVE)
 CVAR(Bool, net_limitsaves, true, CVAR_SERVERINFO | CVAR_NOSAVE)
 CVAR(Bool, net_repeatableactioncooldown, true, CVAR_SERVERINFO | CVAR_NOSAVE)
@@ -395,6 +403,9 @@ void Net_ClearBuffers()
 	LastEnterTic = LastGameUpdate = EnterTic;
 	gametic = ClientTic = 0;
 	SkipCommandTimer = SkipCommandAmount = CommandsAhead = 0;
+	StabilityBuffer = PrevAvailableDiff = 0;
+	CurStabilityTic = 0u;
+	memset(StabilityTics, 0, sizeof(StabilityTics));
 	NetEvents.ResetStream();
 	
 	CutsceneReady = 0u;
@@ -502,6 +513,9 @@ void Net_ResetCommands(bool midTic)
 	bCommandsReset = midTic;
 	++CurrentLobbyID;
 	SkipCommandTimer = SkipCommandAmount = CommandsAhead = 0;
+	StabilityBuffer = PrevAvailableDiff = 0;
+	CurStabilityTic = 0u;
+	memset(StabilityTics, 0, sizeof(StabilityTics));
 
 	int tic = gametic / TicDup;
 	if (midTic)
@@ -1292,6 +1306,7 @@ static bool Net_UpdateStatus()
 
 	if (updated)
 	{
+		lowestDiff -= StabilityBuffer;
 		if (lowestDiff > 0)
 		{
 			if (SkipCommandTimer++ > TICRATE / 2)
@@ -2090,6 +2105,47 @@ static bool ShouldStabilizeTick()
 			&& gameaction != ga_worlddone && gameaction != ga_completed && gameaction != ga_screenshot && gameaction != ga_fullconsole;
 }
 
+// If the connection has been unstable then let the game lag behind for a little bit
+// while we wait for it to stabilize, otherwise everything will appear to jitter around.
+static void CalculateNetStabilityBuffer(int diff)
+{
+	if (!netgame || demoplayback)
+	{
+		StabilityBuffer = 0;
+		return;
+	}
+
+	if (diff < 0)
+		diff = 0;
+
+	if (!(gametic % TicDup))
+	{
+		StabilityTics[CurStabilityTic++ % STABILITYTICS] = diff > PrevAvailableDiff ? diff : 0;
+		PrevAvailableDiff = diff;
+	}
+
+	// If we're not balancing latency, just give an extra tic for padding
+	// and nothing else.
+	if (!net_ticbalance)
+	{
+		StabilityBuffer = 1;
+		return;
+	}
+
+	double total = 0.0;
+	int unstableCount = 0;
+	for (int t : StabilityTics)
+	{
+		if (t > 0)
+		{
+			++unstableCount;
+			total += t;
+		}
+	}
+
+	StabilityBuffer = unstableCount > 0 ? static_cast<int>(ceil(total / unstableCount)) : 0;
+}
+
 //
 // TryRunTics
 //
@@ -2148,8 +2204,12 @@ void TryRunTics()
 	// If the amount of tics to run is falling behind the amount of available tics,
 	// speed the playsim up a bit to help catch up.
 	int runTics = min<int>(totalTics, availableTics);
-	if (totalTics > 0 && totalTics < availableTics && !singletics)
-		++runTics;
+	if (!singletics && totalTics > 0)
+	{
+		CalculateNetStabilityBuffer(availableTics - totalTics);
+		if (totalTics < availableTics - StabilityBuffer)
+			++runTics;
+	}
 
 	// Test player prediction code in singleplayer
 	// by running the gametic behind the ClientTic

wadsrc/static/menudef.txt

@@ -2440,6 +2440,7 @@ OptionMenu NetworkOptions protected
 	StaticText " "
 	StaticText "$NETMNU_HOSTOPTIONS", 1
 	Option "$NETMNU_EXTRATICS",				"net_extratic", "OnOff"
+	Option "$NETMNU_BALANCETICS",			"net_ticbalance", "OnOff"
 	Option "$NETMNU_LIMITCONVO",			"net_limitconversations", "OnOff"
 	Option "$NETMNU_REPEATCOOLDOWN",		"net_repeatableactioncooldown", "OnOff"
 	Option "$NETMNU_DISABLEPAUSE",			"net_disablepause", "PauseTypes"