From ceebc28d4b56f4721c3e47af912a4c60dc1bfdf2 Mon Sep 17 00:00:00 2001
From: Nikolaj Olsson <nikse.dk@gmail.com>
Date: Sun, 30 May 2021 08:30:48 +0200
Subject: [PATCH] Improve picking best image w PGS/fading - thx peter-qgd  :)
 Fix #5066

---
 src/libse/BluRaySup/BluRaySupParser.cs | 42 ++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/src/libse/BluRaySup/BluRaySupParser.cs b/src/libse/BluRaySup/BluRaySupParser.cs
index 8e300212e..8f5a7a5c8 100644
--- a/src/libse/BluRaySup/BluRaySupParser.cs
+++ b/src/libse/BluRaySup/BluRaySupParser.cs
@@ -844,7 +844,10 @@ namespace Nikse.SubtitleEdit.Core.BluRaySup
                 }
             }
 
-            // merge images that are the same (probably due to fade)
+            // Merge images that are the same (probably due to fade)
+            // First we find groups with same pixels
+            var removeIndices = new List<DeleteIndex>();
+            int deleteNo = 0;
             for (int pcsIndex = pcsList.Count - 1; pcsIndex > 0; pcsIndex--)
             {
                 var cur = pcsList[pcsIndex];
@@ -879,11 +882,38 @@ namespace Nikse.SubtitleEdit.Core.BluRaySup
 
                         if (remove)
                         {
-                            prev.EndTime = cur.EndTime;
-                            pcsList.RemoveAt(pcsIndex);
+                            if (!removeIndices.Any(p => p.Number == deleteNo && p.Index == pcsIndex - 1))
+                            {
+                                removeIndices.Add(new DeleteIndex { Number = deleteNo, Index = pcsIndex - 1 });
+                            }
+                            if (!removeIndices.Any(p => p.Number == deleteNo && p.Index == pcsIndex))
+                            {
+                                removeIndices.Add(new DeleteIndex { Number = deleteNo, Index = pcsIndex });
+                            }
                         }
                     }
                 }
+                else
+                {
+                    deleteNo++;
+                }
+            }
+
+            // Use the middle image of each group with same pixels
+            foreach (var group in removeIndices.GroupBy(p => p.Number).OrderBy(p => p.Key))
+            {
+                var arr = group.OrderByDescending(p => p.Index).ToArray();
+                var middle = (int)Math.Round(group.Count() / 2.0);
+                var middleElement = arr[middle];
+                pcsList[middleElement.Index].StartTime = pcsList[arr.Last().Index].StartTime;
+                pcsList[middleElement.Index].EndTime = pcsList[arr.First().Index].EndTime;
+                foreach (var deleteIndex in group.OrderByDescending(p => p.Index))
+                {
+                    if (deleteIndex != middleElement)
+                    {
+                        pcsList.RemoveAt(deleteIndex.Index);
+                    }
+                }
             }
 
             // save last palette
@@ -899,6 +929,12 @@ namespace Nikse.SubtitleEdit.Core.BluRaySup
             return pcsList;
         }
 
+        public class DeleteIndex
+        {
+            public int Number { get; set; }
+            public int Index { get; set; }
+        }
+
         private static bool ByteArraysEqual(byte[] b1, byte[] b2)
         {
             if (b1 == b2)