diff --git a/croppa/main.py b/croppa/main.py
index ad40cca..aed04eb 100644
--- a/croppa/main.py
+++ b/croppa/main.py
@@ -2880,38 +2880,67 @@ class VideoEditor:
         if display_frame is None:
             return
 
-        # Resize to fit window while maintaining aspect ratio
-        height, width = display_frame.shape[:2]
-        available_height = self.window_height - (0 if self.is_image_mode else self.TIMELINE_HEIGHT)
+        # Get actual window dimensions (important for fullscreen mode)
+        window_title = "Image Editor" if self.is_image_mode else "Video Editor"
+        try:
+            window_rect = cv2.getWindowImageRect(window_title)
+            if window_rect[2] > 0 and window_rect[3] > 0:  # width and height > 0
+                actual_width = window_rect[2]
+                actual_height = window_rect[3]
+            else:
+                # Fallback to stored dimensions
+                actual_width = self.window_width
+                actual_height = self.window_height
+        except:
+            # Fallback to stored dimensions
+            actual_width = self.window_width
+            actual_height = self.window_height
 
-        # Don't downscale - keep original video quality
-        # If video is larger than window, we'll handle it by resizing the window
-        scale = min(self.window_width / width, available_height / height)
-        if scale < 1.0:
-            # Resize window to fit video instead of downscaling video
-            new_window_width = int(width * 1.1)  # Add 10% padding
-            new_window_height = int(height * 1.1) + (0 if self.is_image_mode else self.TIMELINE_HEIGHT)
-            
-            # Update window size
-            self.window_width = new_window_width
-            self.window_height = new_window_height
-            
-            # Resize the OpenCV window
-            window_title = "Image Editor" if self.is_image_mode else "Video Editor"
-            cv2.resizeWindow(window_title, self.window_width, self.window_height)
+        # Calculate available space for video (accounting for timeline)
+        available_height = actual_height - (0 if self.is_image_mode else self.TIMELINE_HEIGHT)
+        
+        # Get original video dimensions to maintain aspect ratio
+        height, width = display_frame.shape[:2]
+        
+        # Calculate scale to fit video in available space while maintaining aspect ratio
+        scale_x = actual_width / width
+        scale_y = available_height / height
+        scale = min(scale_x, scale_y)  # Use the smaller scale to ensure video fits
+        
+        # Ensure scale is never greater than 1.0 to prevent upscaling beyond screen
+        scale = min(scale, 1.0)
+        
+        # Calculate scaled dimensions
+        scaled_width = int(width * scale)
+        scaled_height = int(height * scale)
+        
+        # Double-check that scaled dimensions fit within available space
+        if scaled_height > available_height:
+            scale = available_height / height
+            scaled_width = int(width * scale)
+            scaled_height = int(height * scale)
+        
+        if scaled_width > actual_width:
+            scale = actual_width / width
+            scaled_width = int(width * scale)
+            scaled_height = int(height * scale)
+        
+        # Resize the frame to fit the window while maintaining aspect ratio
+        if scale != 1.0:
+            display_frame = cv2.resize(display_frame, (scaled_width, scaled_height), interpolation=cv2.INTER_LINEAR)
 
         # Create canvas with timeline space
-        canvas = np.zeros((self.window_height, self.window_width, 3), dtype=np.uint8)
+        canvas = np.zeros((actual_height, actual_width, 3), dtype=np.uint8)
 
         # Center the frame on canvas
         frame_height, frame_width = display_frame.shape[:2]
-        available_height = self.window_height - (0 if self.is_image_mode else self.TIMELINE_HEIGHT)
+        available_height = actual_height - (0 if self.is_image_mode else self.TIMELINE_HEIGHT)
         start_y = (available_height - frame_height) // 2
-        start_x = (self.window_width - frame_width) // 2
+        start_x = (actual_width - frame_width) // 2
 
         # Ensure frame fits within canvas bounds
         end_y = min(start_y + frame_height, available_height)
-        end_x = min(start_x + frame_width, self.window_width)
+        end_x = min(start_x + frame_width, actual_width)
         actual_frame_height = end_y - start_y
         actual_frame_width = end_x - start_x