Improve choice of where to start playback of multiplayer spectator

osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/MultiSpectatorScreen.cs

@@ -2,12 +2,13 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
-using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Logging;
 using osu.Game.Graphics;
 using osu.Game.Online.Multiplayer;
 using osu.Game.Online.Rooms;
@@ -198,15 +199,29 @@ private bool isCandidateAudioSource(SpectatorPlayerClock? clock)
 
         private void performInitialSeek()
         {
-            // Seek the master clock to the gameplay time.
-            // This is chosen as the first available frame in the players' replays, which matches the seek by each individual SpectatorPlayer.
-            double startTime = instances.Where(i => i.Score != null)
-                                        .SelectMany(i => i.Score.AsNonNull().Replay.Frames)
-                                        .Select(f => f.Time)
-                                        .DefaultIfEmpty(0)
-                                        .Min();
+            // We want to start showing gameplay as soon as possible.
+            // Each client may be in a different place in the beatmap, so we need to do our best to find a common
+            // starting point.
+            //
+            // Preferring a lower value ensures that we don't have some clients stuttering to keep up.
+            List<double> minFrameTimes = new List<double>();
+
+            foreach (var instance in instances)
+            {
+                if (instance.Score == null)
+                    continue;
+
+                minFrameTimes.Add(instance.Score.Replay.Frames.MinBy(f => f.Time)?.Time ?? 0);
+            }
+
+            // Remove any outliers (only need to worry about removing those lower than the mean since we will take a Min() after).
+            double mean = minFrameTimes.Average();
+            minFrameTimes.RemoveAll(t => mean - t > 1000);
+
+            double startTime = minFrameTimes.Min();
 
             masterClockContainer.Reset(startTime, true);
+            Logger.Log($"Multiplayer spectator seeking to initial time of {startTime}");
         }
 
         protected override void OnNewPlayingUserState(int userId, SpectatorState spectatorState)
@@ -245,6 +260,7 @@ public override bool OnBackButton()
                 return base.OnBackButton();
 
             // On a manual exit, set the player back to idle unless gameplay has finished.
+            // Of note, this doesn't cover exiting using alt-f4 or menu home option.
             if (multiplayerClient.Room.State != MultiplayerRoomState.Open)
                 multiplayerClient.ChangeState(MultiplayerUserState.Idle);
 

osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/SpectatorSyncManager.cs

@@ -182,7 +182,7 @@ private void updateMasterState()
                 return;
 
             masterState = newState;
-            Logger.Log($"{nameof(SpectatorSyncManager)}'s master clock become {masterState}");
+            Logger.Log($"{nameof(SpectatorSyncManager)}'s master clock became {masterState}");
 
             switch (masterState)
             {