Add subrip to SubtitleFormat

MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs

@@ -294,7 +294,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
                 return true;
             }
 
-            if (string.Equals(format, SubtitleFormat.SRT, StringComparison.OrdinalIgnoreCase) || string.Equals(format, "subrip", StringComparison.OrdinalIgnoreCase))
+            if (string.Equals(format, SubtitleFormat.SRT, StringComparison.OrdinalIgnoreCase) || string.Equals(format,SubtitleFormat.SUBRIP, StringComparison.OrdinalIgnoreCase))
             {
                 value = new SrtWriter();
                 return true;

MediaBrowser.Model/MediaInfo/SubtitleFormat.cs

@@ -5,6 +5,7 @@ namespace MediaBrowser.Model.MediaInfo
     public static class SubtitleFormat
     {
         public const string SRT = "srt";
+        public const string SUBRIP = "subrip";
         public const string SSA = "ssa";
         public const string ASS = "ass";
         public const string VTT = "vtt";