From dbd7be091d802a788e520809fe55c9063a9cdaf4 Mon Sep 17 00:00:00 2001
From: Bond_009 <bond.009@outlook.com>
Date: Mon, 14 Feb 2022 15:03:08 +0100
Subject: [PATCH] Fix MediaStreamSelector

---
 .../Library/MediaStreamSelector.cs            |  7 ++++-
 .../Library/MediaStreamSelectorTests.cs       | 30 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 tests/Jellyfin.Server.Implementations.Tests/Library/MediaStreamSelectorTests.cs

diff --git a/Emby.Server.Implementations/Library/MediaStreamSelector.cs b/Emby.Server.Implementations/Library/MediaStreamSelector.cs
index 13f0999b35..6ba9b29fa3 100644
--- a/Emby.Server.Implementations/Library/MediaStreamSelector.cs
+++ b/Emby.Server.Implementations/Library/MediaStreamSelector.cs
@@ -17,7 +17,12 @@ namespace Emby.Server.Implementations.Library
 
             if (preferDefaultTrack)
             {
-                return sortedStreams.FirstOrDefault(i => i.IsDefault)?.Index;
+                var defaultStream = streams.FirstOrDefault(i => i.IsDefault);
+
+                if (defaultStream != null)
+                {
+                    return defaultStream.Index;
+                }
             }
 
             return sortedStreams.FirstOrDefault()?.Index;
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Library/MediaStreamSelectorTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Library/MediaStreamSelectorTests.cs
new file mode 100644
index 0000000000..d59f2f4e51
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Library/MediaStreamSelectorTests.cs
@@ -0,0 +1,30 @@
+using System;
+using Emby.Server.Implementations.Library;
+using MediaBrowser.Model.Entities;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.Library;
+
+public class MediaStreamSelectorTests
+{
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GetDefaultAudioStreamIndex_EmptyStreams_Null(bool preferDefaultTrack)
+    {
+        Assert.Null(MediaStreamSelector.GetDefaultAudioStreamIndex(Array.Empty<MediaStream>(), Array.Empty<string>(), preferDefaultTrack));
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GetDefaultAudioStreamIndex_WithoutDefault_NotNull(bool preferDefaultTrack)
+    {
+        var streams = new[]
+        {
+            new MediaStream()
+        };
+
+        Assert.NotNull(MediaStreamSelector.GetDefaultAudioStreamIndex(streams, Array.Empty<string>(), preferDefaultTrack));
+    }
+}