From 7dc6544d3441187f73393dac54dc358b3ceb98ed Mon Sep 17 00:00:00 2001
From: klizas <klizas@users.noreply.github.com>
Date: Mon, 5 Oct 2026 19:18:45 -0400
Subject: Backport pull request #18186 from jellyfin/release-12.z

Fix segment cleaner deleting segments ahead of playback when remuxing MKV

Original-merge: 3acc9c8443d7ee445c4fe015f2977a47d4ea57ac

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Cody Robibero <cody@robibe.ro>
---
 .../MediaEncoding/TranscodingJob.cs                | 36 ++++++++++++++++++++++
 .../MediaEncoding/TranscodingSegmentCleaner.cs     |  8 ++---
 2 files changed, 39 insertions(+), 5 deletions(-)

(limited to 'MediaBrowser.Controller')

diff --git a/MediaBrowser.Controller/MediaEncoding/TranscodingJob.cs b/MediaBrowser.Controller/MediaEncoding/TranscodingJob.cs
index 5045030b9b..12600af384 100644
--- a/MediaBrowser.Controller/MediaEncoding/TranscodingJob.cs
+++ b/MediaBrowser.Controller/MediaEncoding/TranscodingJob.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.Threading;
 using MediaBrowser.Model.Dto;
@@ -14,6 +15,7 @@ public sealed class TranscodingJob : IDisposable
     private readonly ILogger<TranscodingJob> _logger;
     private readonly Lock _processLock = new();
     private readonly Lock _timerLock = new();
+    private readonly ConcurrentDictionary<int, long> _segmentEndPositionTicks = new();
 
     private int _activeRequestCount;
     private Timer? _killTimer;
@@ -156,6 +158,40 @@ public sealed class TranscodingJob : IDisposable
     /// </summary>
     public int PingTimeout { get; set; }
 
+    /// <summary>
+    /// Records the end position of a served segment.
+    /// </summary>
+    /// <param name="segmentIndex">The segment index.</param>
+    /// <param name="segmentEndPositionTicks">The segment end position ticks.</param>
+    public void ReportSegmentDownloaded(int segmentIndex, long segmentEndPositionTicks)
+    {
+        if (segmentIndex < 0)
+        {
+            return;
+        }
+
+        _segmentEndPositionTicks[segmentIndex] = segmentEndPositionTicks;
+    }
+
+    /// <summary>
+    /// Gets the highest index among served segments whose end position is at or before the given position.
+    /// </summary>
+    /// <param name="positionTicks">The position ticks.</param>
+    /// <returns>The segment index, or <c>null</c> if there is none.</returns>
+    public int? GetHighestServedSegmentIndexEndingAtOrBefore(long positionTicks)
+    {
+        int? result = null;
+        foreach (var (index, endPositionTicks) in _segmentEndPositionTicks)
+        {
+            if (endPositionTicks <= positionTicks && (result is null || index > result))
+            {
+                result = index;
+            }
+        }
+
+        return result;
+    }
+
     /// <summary>
     /// Increments the active request count.
     /// </summary>
diff --git a/MediaBrowser.Controller/MediaEncoding/TranscodingSegmentCleaner.cs b/MediaBrowser.Controller/MediaEncoding/TranscodingSegmentCleaner.cs
index 67bfcb02fd..924fc2e659 100644
--- a/MediaBrowser.Controller/MediaEncoding/TranscodingSegmentCleaner.cs
+++ b/MediaBrowser.Controller/MediaEncoding/TranscodingSegmentCleaner.cs
@@ -22,7 +22,6 @@ public class TranscodingSegmentCleaner : IDisposable
     private readonly IFileSystem _fileSystem;
     private readonly IMediaEncoder _mediaEncoder;
     private Timer? _timer;
-    private int _segmentLength;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="TranscodingSegmentCleaner"/> class.
@@ -32,7 +31,7 @@ public class TranscodingSegmentCleaner : IDisposable
     /// <param name="config">Instance of the <see cref="IConfigurationManager"/> interface.</param>
     /// <param name="fileSystem">Instance of the <see cref="IFileSystem"/> interface.</param>
     /// <param name="mediaEncoder">Instance of the <see cref="IMediaEncoder"/> interface.</param>
-    /// <param name="segmentLength">The segment length of this transcoding job.</param>
+    /// <param name="segmentLength">The segment length of this transcoding job. Unused.</param>
     public TranscodingSegmentCleaner(TranscodingJob job, ILogger<TranscodingSegmentCleaner> logger, IConfigurationManager config, IFileSystem fileSystem, IMediaEncoder mediaEncoder, int segmentLength)
     {
         _job = job;
@@ -40,7 +39,6 @@ public class TranscodingSegmentCleaner : IDisposable
         _config = config;
         _fileSystem = fileSystem;
         _mediaEncoder = mediaEncoder;
-        _segmentLength = segmentLength;
     }
 
     /// <summary>
@@ -104,11 +102,11 @@ public class TranscodingSegmentCleaner : IDisposable
 
             if (downloadPositionSeconds > 0 && segmentKeepSeconds > 0 && downloadPositionSeconds > segmentKeepSeconds)
             {
-                var idxMaxToDelete = (downloadPositionSeconds - segmentKeepSeconds) / _segmentLength;
+                var idxMaxToDelete = _job.GetHighestServedSegmentIndexEndingAtOrBefore(downloadPositionTicks - TimeSpan.FromSeconds(segmentKeepSeconds).Ticks);
 
                 if (idxMaxToDelete > 0)
                 {
-                    await DeleteSegmentFiles(_job, 0, idxMaxToDelete, 1500).ConfigureAwait(false);
+                    await DeleteSegmentFiles(_job, 0, idxMaxToDelete.Value, 1500).ConfigureAwait(false);
                 }
             }
         }
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