diff --git a/app.py b/app.py
index 5d1965e..31c7b56 100755
--- a/app.py
+++ b/app.py
@@ -172,7 +172,8 @@ def list_media_files(folder):
 def generate_thumbnails():
     media_files = list_media_files(upload_folder)
     for media in media_files:
-        subprocess.call(['ffmpeg', '-i', os.path.join(upload_folder, media), '-q:v', '30', '-s', '160x120', '-vf', 'boxblur=2', '-ss', '00:00:01.000', '-vframes', '1', os.path.join(thumbnails_folder, media) + ".jpg", "-y"])
+        if not os.path.exists(os.path.join(thumbnails_folder, media["filename"]) + ".jpg"):
+            subprocess.call(['ffmpeg', '-i', os.path.join(upload_folder, media["filename"]), '-q:v', '30', '-s', '160x120', '-vf', 'boxblur=2', '-ss', '00:00:01.000', '-vframes', '1', os.path.join(thumbnails_folder, media["filename"]) + ".jpg", "-y"])
         
 
 def value_in_dict_list(value, dict_list, key):