update subtitle conversion

MediaBrowser.Server.Implementations/Library/MediaSourceManager.cs

@@ -72,6 +72,12 @@ namespace MediaBrowser.Server.Implementations.Library
 
         private bool InternalTextStreamSupportsExternalStream(MediaStream stream)
         {
+            // These usually have styles and fonts that won't convert to text very well
+            if (string.Equals(stream.Codec, "ass", StringComparison.OrdinalIgnoreCase))
+            {
+                return false;
+            }
+
             return true;
         }