From 8aa9ac82d4eae895753d1854fbcd4795aff92312 Mon Sep 17 00:00:00 2001
From: Fey <fey@imail.yo3explorer.moe>
Date: Wed, 28 Jan 2026 18:04:51 +0100
Subject: [PATCH] Added a entropy-calculating filter.

---
 .../Math/EntropyCalculatorStream.cs           | 27 ++++++-----
 .../Math/PidEntryCalculatorFilter.cs          | 45 +++++++++++++++++++
 2 files changed, 60 insertions(+), 12 deletions(-)
 create mode 100644 skyscraper8/Skyscraper/Math/PidEntryCalculatorFilter.cs

diff --git a/skyscraper8/Skyscraper/Math/EntropyCalculatorStream.cs b/skyscraper8/Skyscraper/Math/EntropyCalculatorStream.cs
index 0b8d80c..df05e48 100644
--- a/skyscraper8/Skyscraper/Math/EntropyCalculatorStream.cs
+++ b/skyscraper8/Skyscraper/Math/EntropyCalculatorStream.cs
@@ -54,18 +54,21 @@ namespace skyscraper8.Skyscraper.Math
 				double p_i = (double)freq[i] / (double)internalPosition;
 				if (p_i > 0)
 					newEntropy -= p_i * System.Math.Log2(p_i);
-			}
-
-			//Raise events if we feel like it
-			if (newEntropy != Entropy)
-			{
-				double oldEntropy = Entropy;
-				double oldPercentage = Percentage;
-				double newPercentage = (newEntropy / 8.0) * 100.0;
-				if (newEntropy > Entropy)
-					EntropyRising?.Invoke(oldEntropy, newEntropy, oldPercentage, newPercentage);
-				else if (newEntropy < Entropy)
-					EntropyFalling?.Invoke(oldEntropy, newEntropy, oldPercentage, newPercentage);
+			}
+
+			//Raise events if we feel like it
+			if (EntropyRising != null || EntropyFalling != null)
+			{
+				if (newEntropy != Entropy)
+				{
+					double oldEntropy = Entropy;
+					double oldPercentage = Percentage;
+					double newPercentage = (newEntropy / 8.0) * 100.0;
+					if (newEntropy > Entropy)
+						EntropyRising?.Invoke(oldEntropy, newEntropy, oldPercentage, newPercentage);
+					else if (newEntropy < Entropy)
+						EntropyFalling?.Invoke(oldEntropy, newEntropy, oldPercentage, newPercentage);
+				}
 			}
 
 			_entropy = newEntropy;
diff --git a/skyscraper8/Skyscraper/Math/PidEntryCalculatorFilter.cs b/skyscraper8/Skyscraper/Math/PidEntryCalculatorFilter.cs
new file mode 100644
index 0000000..58d7817
--- /dev/null
+++ b/skyscraper8/Skyscraper/Math/PidEntryCalculatorFilter.cs
@@ -0,0 +1,45 @@
+using skyscraper5.Mpeg2;
+using skyscraper5.src.Mpeg2.PacketFilter;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace skyscraper8.Skyscraper.Math
+{
+    public class PidEntryCalculatorFilter : IPacketFilter
+    {
+        public bool PassPacket(TsPacket packet)
+        {
+            if (entropyCalculatorStreams == null)
+                entropyCalculatorStreams = new EntropyCalculatorStream[0x1fff];
+
+            if (packet.PayloadFlagSet)
+            {
+                uint pid = packet.PID;
+                if (entropyCalculatorStreams[pid] == null)
+                    entropyCalculatorStreams[pid] = new EntropyCalculatorStream();
+                entropyCalculatorStreams[pid].Write(packet.Payload);
+            }
+            return true;
+        }
+
+        private EntropyCalculatorStream[] entropyCalculatorStreams;
+
+        public double GetEntropy(int pid)
+        {
+            if (pid < 0)
+                throw new ArgumentOutOfRangeException(nameof(pid));
+
+            if (pid > entropyCalculatorStreams.Length)
+                throw new ArgumentOutOfRangeException(nameof(pid));
+
+            EntropyCalculatorStream stream = entropyCalculatorStreams[pid];
+            if (stream == null)
+                return double.NaN;
+
+            return stream.Entropy;
+        }
+    }
+}