Improve code

MediaBrowser.MediaEncoding/Attachments/AttachmentExtractor.cs

@@ -88,13 +88,13 @@ namespace MediaBrowser.MediaEncoding.Attachments
             MediaSourceInfo mediaSource,
             string outputPath,
             CancellationToken cancellationToken)
-        {
-            if (!Directory.Exists(outputPath))
         {
             var semaphore = _semaphoreLocks.GetOrAdd(outputPath, key => new SemaphoreSlim(1, 1));
 
             await semaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
 
+            if (!Directory.Exists(outputPath))
+            {
                 try
                 {
                     await ExtractAllAttachmentsInternal(
@@ -115,13 +115,13 @@ namespace MediaBrowser.MediaEncoding.Attachments
             string id,
             string outputPath,
             CancellationToken cancellationToken)
-        {
-            if (!File.Exists(Path.Join(outputPath, id)))
         {
             var semaphore = _semaphoreLocks.GetOrAdd(outputPath, key => new SemaphoreSlim(1, 1));
 
             await semaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
 
+            if (!File.Exists(Path.Join(outputPath, id)))
+            {
                 try
                 {
                     await ExtractAllAttachmentsInternal(
@@ -158,10 +158,7 @@ namespace MediaBrowser.MediaEncoding.Attachments
                 throw new ArgumentNullException(nameof(outputPath));
             }
 
-            if (!Directory.Exists(outputPath))
-            {
             Directory.CreateDirectory(outputPath);
-            }
 
             var processArgs = string.Format(
                 CultureInfo.InvariantCulture,