1 files changed, 20 insertions, 16 deletions
diff --git a/Jellyfin.Api/Controllers/DynamicHlsController.cs b/Jellyfin.Api/Controllers/DynamicHlsController.cs
index 4aa728b5bf..034a9dea55 100644
--- a/Jellyfin.Api/Controllers/DynamicHlsController.cs
+++ b/Jellyfin.Api/Controllers/DynamicHlsController.cs
@@ -20,7 +20,6 @@ using MediaBrowser.Controller.Configuration;
 using MediaBrowser.Controller.Library;
 using MediaBrowser.Controller.MediaEncoding;
 using MediaBrowser.Controller.Streaming;
-using MediaBrowser.MediaEncoding.Encoder;
 using MediaBrowser.Model.Configuration;
 using MediaBrowser.Model.Dlna;
 using MediaBrowser.Model.Entities;
@@ -1456,22 +1455,16 @@ public class DynamicHlsController : BaseJellyfinApiController
 
         var segmentExtension = EncodingHelper.GetSegmentFileExtension(state.Request.SegmentContainer);
 
-        TranscodingJob? job;
-
-        if (System.IO.File.Exists(segmentPath))
-        {
-            job = _transcodeManager.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
-            _logger.LogDebug("returning {0} [it exists, try 1]", segmentPath);
-            return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, segmentId, job, cancellationToken).ConfigureAwait(false);
-        }
-
+        // Keep segment selection and transcoding replacement under the same playlist lock.
+        // An out-of-order request must not replace a job while another request is using its output.
         using (await _transcodeManager.LockAsync(playlistPath, cancellationToken).ConfigureAwait(false))
         {
+            TranscodingJob? job;
             var startTranscoding = false;
             if (System.IO.File.Exists(segmentPath))
             {
                 job = _transcodeManager.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
-                _logger.LogDebug("returning {0} [it exists, try 2]", segmentPath);
+                _logger.LogDebug("returning {0} [it exists]", segmentPath);
                 return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, segmentId, job, cancellationToken).ConfigureAwait(false);
             }
 
@@ -1505,6 +1498,9 @@ public class DynamicHlsController : BaseJellyfinApiController
                 // If the playlist doesn't already exist, startup ffmpeg
                 try
                 {
+                    var currentJob = _transcodeManager.GetTranscodingJob(playlistPath, TranscodingJobType);
+                    await WaitForActiveTranscodingRequests(currentJob, cancellationToken).ConfigureAwait(false);
+
                     await _transcodeManager.KillTranscodingJobs(streamingRequest.DeviceId, streamingRequest.PlaySessionId, p => false)
                         .ConfigureAwait(false);
 
@@ -1540,11 +1536,19 @@ public class DynamicHlsController : BaseJellyfinApiController
                     await job.TranscodingThrottler.UnpauseTranscoding().ConfigureAwait(false);
                 }
             }
+
+            _logger.LogDebug("returning {0} [general case]", segmentPath);
+            job ??= _transcodeManager.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
+            return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, segmentId, job, cancellationToken).ConfigureAwait(false);
         }
+    }
 
-        _logger.LogDebug("returning {0} [general case]", segmentPath);
-        job ??= _transcodeManager.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
-        return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, segmentId, job, cancellationToken).ConfigureAwait(false);
+    internal static async Task WaitForActiveTranscodingRequests(TranscodingJob? job, CancellationToken cancellationToken)
+    {
+        while (job?.ActiveRequestCount > 0)
+        {
+            await Task.Delay(100, cancellationToken).ConfigureAwait(false);
+        }
     }
 
     private static double[] GetSegmentLengths(StreamState state)
@@ -1647,9 +1651,9 @@ public class DynamicHlsController : BaseJellyfinApiController
             segmentFormat,
             startNumber.ToString(CultureInfo.InvariantCulture),
             baseUrlParam,
-            EncodingUtils.NormalizePath(outputTsArg),
+            outputTsArg.EscapeProcessArgument(),
             hlsArguments,
-            EncodingUtils.NormalizePath(outputPath)).Trim();
+            outputPath.EscapeProcessArgument()).Trim();
     }
 
     /// <summary>