Merge pull request #11495 from smoogipoo/more-accurate-most-common-bpm

Make most common BPM more accurate

osu.Game/Beatmaps/Beatmap.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osu.Game.Beatmaps.Timing;
 using osu.Game.Rulesets.Objects;
 using System.Collections.Generic;
@@ -48,6 +49,31 @@ namespace osu.Game.Beatmaps
 
         public virtual IEnumerable<BeatmapStatistic> GetStatistics() => Enumerable.Empty<BeatmapStatistic>();
 
+        public double GetMostCommonBeatLength()
+        {
+            // The last playable time in the beatmap - the last timing point extends to this time.
+            // Note: This is more accurate and may present different results because osu-stable didn't have the ability to calculate slider durations in this context.
+            double lastTime = HitObjects.LastOrDefault()?.GetEndTime() ?? ControlPointInfo.TimingPoints.LastOrDefault()?.Time ?? 0;
+
+            var mostCommon =
+                // Construct a set of (beatLength, duration) tuples for each individual timing point.
+                ControlPointInfo.TimingPoints.Select((t, i) =>
+                                {
+                                    if (t.Time > lastTime)
+                                        return (beatLength: t.BeatLength, 0);
+
+                                    var nextTime = i == ControlPointInfo.TimingPoints.Count - 1 ? lastTime : ControlPointInfo.TimingPoints[i + 1].Time;
+                                    return (beatLength: t.BeatLength, duration: nextTime - t.Time);
+                                })
+                                // Aggregate durations into a set of (beatLength, duration) tuples for each beat length
+                                .GroupBy(t => Math.Round(t.beatLength * 1000) / 1000)
+                                .Select(g => (beatLength: g.Key, duration: g.Sum(t => t.duration)))
+                                // Get the most common one, or 0 as a suitable default
+                                .OrderByDescending(i => i.duration).FirstOrDefault();
+
+            return mostCommon.beatLength;
+        }
+
         IBeatmap IBeatmap.Clone() => Clone();
 
         public Beatmap<T> Clone() => (Beatmap<T>)MemberwiseClone();

osu.Game/Beatmaps/BeatmapManager.cs

@@ -451,7 +451,7 @@ namespace osu.Game.Beatmaps
                     // TODO: this should be done in a better place once we actually need to dynamically update it.
                     beatmap.BeatmapInfo.StarDifficulty = ruleset?.CreateInstance().CreateDifficultyCalculator(new DummyConversionBeatmap(beatmap)).Calculate().StarRating ?? 0;
                     beatmap.BeatmapInfo.Length = calculateLength(beatmap);
-                    beatmap.BeatmapInfo.BPM = beatmap.ControlPointInfo.BPMMode;
+                    beatmap.BeatmapInfo.BPM = 60000 / beatmap.GetMostCommonBeatLength();
 
                     beatmapInfos.Add(beatmap.BeatmapInfo);
                 }

osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs

@@ -101,13 +101,6 @@ namespace osu.Game.Beatmaps.ControlPoints
         public double BPMMinimum =>
             60000 / (TimingPoints.OrderByDescending(c => c.BeatLength).FirstOrDefault() ?? TimingControlPoint.DEFAULT).BeatLength;
 
-        /// <summary>
-        /// Finds the mode BPM (most common BPM) represented by the control points.
-        /// </summary>
-        [JsonIgnore]
-        public double BPMMode =>
-            60000 / (TimingPoints.GroupBy(c => c.BeatLength).OrderByDescending(grp => grp.Count()).FirstOrDefault()?.FirstOrDefault() ?? TimingControlPoint.DEFAULT).BeatLength;
-
         /// <summary>
         /// Remove all <see cref="ControlPointGroup"/>s and return to a pristine state.
         /// </summary>

osu.Game/Beatmaps/IBeatmap.cs

@@ -47,6 +47,11 @@ namespace osu.Game.Beatmaps
         /// <returns></returns>
         IEnumerable<BeatmapStatistic> GetStatistics();
 
+        /// <summary>
+        /// Finds the most common beat length represented by the control points in this beatmap.
+        /// </summary>
+        double GetMostCommonBeatLength();
+
         /// <summary>
         /// Creates a shallow-clone of this beatmap and returns it.
         /// </summary>

osu.Game/Screens/Edit/EditorBeatmap.cs

@@ -88,6 +88,8 @@ namespace osu.Game.Screens.Edit
 
         public IEnumerable<BeatmapStatistic> GetStatistics() => PlayableBeatmap.GetStatistics();
 
+        public double GetMostCommonBeatLength() => PlayableBeatmap.GetMostCommonBeatLength();
+
         public IBeatmap Clone() => (EditorBeatmap)MemberwiseClone();
 
         private IList mutableHitObjects => (IList)PlayableBeatmap.HitObjects;

osu.Game/Screens/Play/GameplayBeatmap.cs

@@ -43,6 +43,8 @@ namespace osu.Game.Screens.Play
 
         public IEnumerable<BeatmapStatistic> GetStatistics() => PlayableBeatmap.GetStatistics();
 
+        public double GetMostCommonBeatLength() => PlayableBeatmap.GetMostCommonBeatLength();
+
         public IBeatmap Clone() => PlayableBeatmap.Clone();
 
         private readonly Bindable<JudgementResult> lastJudgementResult = new Bindable<JudgementResult>();

osu.Game/Screens/Select/BeatmapInfoWedge.cs

@@ -391,7 +391,7 @@ namespace osu.Game.Screens.Select
                 if (Precision.AlmostEquals(bpmMin, bpmMax))
                     return $"{bpmMin:0}";
 
-                return $"{bpmMin:0}-{bpmMax:0} (mostly {beatmap.ControlPointInfo.BPMMode:0})";
+                return $"{bpmMin:0}-{bpmMax:0} (mostly {60000 / beatmap.GetMostCommonBeatLength():0})";
             }
 
             private OsuSpriteText[] getMapper(BeatmapMetadata metadata)