Backport pull request #18309 from jellyfin/release-12.z

Fix crash when a subtitle charset has no .NET encoding

Original-merge: 2f5be2df9b

Merged-by: Bond-009 <bond.009@outlook.com>

Backported-by: Bond_009 <bond.009@outlook.com>

CONTRIBUTORS.md

@@ -250,6 +250,7 @@
  - [TheDreadPirate](https://github.com/thedreaddpirate)
  - [Daniel Aquino](https://github.com/chino)
  - [klizas](https://github.com/klizas)
+ - [p27ZuH6CNAdzr](https://github.com/p27ZuH6CNAdzr)
 
 # Emby Contributors
 

MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs

@@ -188,6 +188,14 @@ namespace MediaBrowser.MediaEncoding.Subtitles
 
                 _logger.LogDebug("charset {CharSet} detected for {Path}", detected.EncodingName, fileInfo.Path);
 
+                // If encoding is not supported by .NET (e.g., ISO-8859-16), return stream as-is
+                // The charset name will be passed to ffmpeg via -sub_charenc if needed
+                if (detected.Encoding is null)
+                {
+                    _logger.LogWarning("Encoding {Encoding} is not supported by .NET for {Path}, returning stream as-is", detected.EncodingName, fileInfo.Path);
+                    return stream;
+                }
+
                 await using (stream.ConfigureAwait(false))
                 {
                     using var reader = new StreamReader(stream, detected.Encoding);

tests/Jellyfin.MediaEncoding.Tests/Subtitles/SubtitleEncoderTests.cs

@@ -269,6 +269,46 @@ namespace Jellyfin.MediaEncoding.Subtitles.Tests
             }
         }
 
+        [Fact]
+        public async Task GetSubtitleStream_UnsupportedEncoding_DoesNotThrow()
+        {
+            // Regression test for issue #2200
+            // When the charset detector identifies an encoding not supported by .NET (e.g., ISO-8859-16),
+            // GetSubtitleStream should handle it gracefully instead of throwing ArgumentNullException
+            var cancellationToken = TestContext.Current.CancellationToken;
+            var srt = BuildGreekSrt();
+            var path = Path.GetTempFileName();
+            try
+            {
+                // Write as ISO-8859-7 (Greek) to create a non-UTF-8 file
+                await File.WriteAllTextAsync(path, srt, Encoding.GetEncoding("iso-8859-7"), cancellationToken);
+
+                var fixture = new Fixture().Customize(new AutoMoqCustomization { ConfigureMembers = true });
+                var subtitleEncoder = fixture.Create<SubtitleEncoder>();
+
+                var fileInfo = new SubtitleEncoder.SubtitleInfo
+                {
+                    Path = path,
+                    Protocol = MediaProtocol.File,
+                    Format = "srt",
+                    IsExternal = true
+                };
+
+                // This should not throw even if the detected encoding was unsupported
+                using var stream = await subtitleEncoder.GetSubtitleStream(fileInfo, cancellationToken);
+                Assert.NotNull(stream);
+
+                // Verify we can read from the stream without error
+                using var reader = new StreamReader(stream);
+                var text = await reader.ReadToEndAsync(cancellationToken);
+                Assert.NotEmpty(text);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
+
         private static SubtitleEncoder CreateEncoder()
         {
             var fixture = new Fixture().Customize(new AutoMoqCustomization { ConfigureMembers = true });