diff --git a/src/libse/SubtitleFormats/CsvNuendo.cs b/src/libse/SubtitleFormats/CsvNuendo.cs
index 5905e31c7..6b60ded52 100644
--- a/src/libse/SubtitleFormats/CsvNuendo.cs
+++ b/src/libse/SubtitleFormats/CsvNuendo.cs
@@ -24,10 +24,16 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
             var fine = 0;
             var errors = 0;
             var sb = new StringBuilder();
-            foreach (var line in lines)
+            for (var index = 0; index < lines.Count; index++)
             {
+                var line = lines[index];
+                if (index == 0 && line.StartsWith("<tt xmlns"))
+                {
+                    return false;
+                }
+
                 sb.Append(line);
-                if (line.IndexOf(':') > 0 && 
+                if (line.IndexOf(':') > 0 &&
                     (CsvLine.IsMatch(line) ||
                      CsvLineNoQuotes.IsMatch(line) ||
                      CsvLineAllQuotes.IsMatch(line) ||
diff --git a/src/libse/SubtitleFormats/UnknownSubtitle65.cs b/src/libse/SubtitleFormats/UnknownSubtitle65.cs
index 8f6346fcc..f802976be 100644
--- a/src/libse/SubtitleFormats/UnknownSubtitle65.cs
+++ b/src/libse/SubtitleFormats/UnknownSubtitle65.cs
@@ -8,6 +8,9 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
 {
     public class UnknownSubtitle65 : SubtitleFormat
     {
+
+        private readonly Regex _regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d,\d\d:\d\d:\d\d$", RegexOptions.Compiled);
+
         private enum ExpectingLine
         {
             TimeCodes,
@@ -57,8 +60,6 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
 
         public override void LoadSubtitle(Subtitle subtitle, List<string> lines, string fileName)
         {
-            var regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d,\d\d:\d\d:\d\d$", RegexOptions.Compiled);
-
             var paragraph = new Paragraph();
             ExpectingLine expecting = ExpectingLine.TimeCodes;
             _errorCount = 0;
@@ -66,7 +67,7 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
             subtitle.Paragraphs.Clear();
             foreach (string line in lines)
             {
-                if (line.Length == 17 && regexTimeCodes.IsMatch(line))
+                if (line.Length == 17 && _regexTimeCodes.IsMatch(line))
                 {
                     string[] parts = line.Split(new[] { ':', ',', '.', ' ' }, StringSplitOptions.RemoveEmptyEntries);
                     if (parts.Length == 6)
diff --git a/src/libse/SubtitleFormats/UnknownSubtitle7.cs b/src/libse/SubtitleFormats/UnknownSubtitle7.cs
index 7243e1def..45cc08bf3 100644
--- a/src/libse/SubtitleFormats/UnknownSubtitle7.cs
+++ b/src/libse/SubtitleFormats/UnknownSubtitle7.cs
@@ -11,6 +11,9 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
     /// </summary>
     public class UnknownSubtitle7 : SubtitleFormat
     {
+        private readonly Regex _regexTimeCode = new Regex(@"^\d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
+        private readonly Regex _regexTimeCodeEnd = new Regex(@"^\d\d:\d\d:\d\d:\d\d\t$", RegexOptions.Compiled);
+
         private enum ExpectingLine
         {
             TimeStart,
@@ -42,9 +45,6 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
 
         public override void LoadSubtitle(Subtitle subtitle, List<string> lines, string fileName)
         {
-            var regexTimeCode = new Regex(@"^\d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
-            var regexTimeCodeEnd = new Regex(@"^\d\d:\d\d:\d\d:\d\d\t$", RegexOptions.Compiled);
-
             var paragraph = new Paragraph();
             var expecting = ExpectingLine.TimeStart;
             _errorCount = 0;
@@ -54,7 +54,7 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
             foreach (string line in lines)
             {
                 count++;
-                if (regexTimeCode.IsMatch(line))
+                if (_regexTimeCode.IsMatch(line))
                 {
                     string[] parts = line.Substring(0, 11).Split(SplitCharColon, StringSplitOptions.RemoveEmptyEntries);
                     if (parts.Length == 4)
@@ -81,7 +81,7 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
                         }
                     }
                 }
-                else if (regexTimeCodeEnd.IsMatch(line) || (count == lines.Count && regexTimeCodeEnd.IsMatch(line + "\t")))
+                else if (_regexTimeCodeEnd.IsMatch(line) || (count == lines.Count && _regexTimeCodeEnd.IsMatch(line + "\t")))
                 {
                     string[] parts = line.Substring(0, 11).Split(SplitCharColon, StringSplitOptions.RemoveEmptyEntries);
                     if (parts.Length == 4)