fix subtitle encoding in certain situations

MediaBrowser.Api/Subtitles/SubtitleService.cs

@@ -213,22 +213,24 @@ namespace MediaBrowser.Api.Subtitles
                 return await ResultFactory.GetStaticFileResult(Request, subtitleStream.Path).ConfigureAwait(false);
             }
 
+            if (string.Equals(request.Format, "vtt", StringComparison.OrdinalIgnoreCase) && request.AddVttTimeMap)
+            {
                 using (var stream = await GetSubtitles(request).ConfigureAwait(false))
                 {
                     using (var reader = new StreamReader(stream))
                     {
                         var text = reader.ReadToEnd();
 
-                    if (string.Equals(request.Format, "vtt", StringComparison.OrdinalIgnoreCase) && request.AddVttTimeMap)
-                    {
                         text = text.Replace("WEBVTT", "WEBVTT\nX-TIMESTAMP-MAP=MPEGTS:900000,LOCAL:00:00:00.000");
-                    }
 
                         return ResultFactory.GetResult(text, MimeTypes.GetMimeType("file." + request.Format));
                     }
                 }
             }
 
+            return ResultFactory.GetResult(await GetSubtitles(request).ConfigureAwait(false), MimeTypes.GetMimeType("file." + request.Format));
+        }
+
         private Task<Stream> GetSubtitles(GetSubtitle request)
         {
             return _subtitleEncoder.GetSubtitles(request.Id,