feat(main.py): add functionality to reposition segments in multi-segment mode

main.py

@@ -362,6 +362,11 @@ class MediaGrader:
         self.jump_history[current_file].append(self.current_frame)
         
         # Jump to the target frame
+        if self.multi_segment_mode:
+            # In multi-segment mode, reposition all segments relative to the jump target
+            self.reposition_segments_around_frame(target_frame)
+        else:
+            # In single mode, just jump the main capture
             self.current_cap.set(cv2.CAP_PROP_POS_FRAMES, target_frame)
             self.load_current_frame()
         
@@ -514,9 +519,9 @@ class MediaGrader:
         # Calculate segment positions - evenly spaced through video
         self.segment_positions = []
         for i in range(self.segment_count):
-            # Position segments at 0%, 25%, 50%, 75% of video
-            position_ratio = i / max(1, self.segment_count - 1) if self.segment_count > 1 else 0
-            start_frame = int(position_ratio * (self.total_frames - 1))
+            # Position segments at 0%, 25%, 50%, 75% of video (not 0%, 33%, 66%, 100%)
+            position_ratio = i / self.segment_count  # This gives 0, 0.25, 0.5, 0.75
+            start_frame = int(position_ratio * self.total_frames)
             self.segment_positions.append(start_frame)
         
         # Create video captures for each segment
@@ -562,6 +567,37 @@ class MediaGrader:
                     if ret:
                         self.segment_frames[i] = frame
 
+    def reposition_segments_around_frame(self, center_frame: int):
+        """Reposition all segments around a center frame while maintaining spacing"""
+        if not self.multi_segment_mode or not self.segment_caps:
+            return
+            
+        # Calculate new segment positions around the center frame
+        # Keep the same relative spacing but center around the new frame
+        segment_spacing = self.total_frames // (self.segment_count + 1)
+        
+        new_positions = []
+        for i in range(self.segment_count):
+            # Spread segments around center_frame
+            offset = (i - (self.segment_count - 1) / 2) * segment_spacing
+            new_frame = int(center_frame + offset)
+            new_frame = max(0, min(new_frame, self.total_frames - 1))
+            new_positions.append(new_frame)
+        
+        # Update segment positions and seek all captures
+        self.segment_positions = new_positions
+        
+        for i, cap in enumerate(self.segment_caps):
+            if cap and cap.isOpened():
+                cap.set(cv2.CAP_PROP_POS_FRAMES, self.segment_positions[i])
+                
+                # Load new frame
+                ret, frame = cap.read()
+                if ret:
+                    self.segment_frames[i] = frame
+                    # Reset position for next read
+                    cap.set(cv2.CAP_PROP_POS_FRAMES, self.segment_positions[i])
+
     def seek_all_segments(self, frames_delta: int):
         """Seek all segments by the specified number of frames"""
         if not self.multi_segment_mode or not self.segment_caps: