Use mp4v codec for VideoWriter

app.py

@@ -221,7 +221,7 @@ def process_video_movenet(video_path, model_variant='lightning', pose_type='fron
         output_path = os.path.join(app.config['UPLOAD_FOLDER'], output_filename)
         print(f"Output path: {output_path}")
         
-        fourcc = cv2.VideoWriter_fourcc(*'avc1')
+        fourcc = cv2.VideoWriter_fourcc(*'mp4v')
         out = cv2.VideoWriter(output_path, fourcc, fps, (total_width, height))
         if not out.isOpened():
             raise ValueError(f"Failed to create output video writer at {output_path}")
@@ -383,7 +383,7 @@ def process_video_mediapipe(video_path):
         print(f"Processing video with MediaPipe: {width}x{height} @ {fps}fps")
         output_filename = f'output_mediapipe.mp4'
         output_path = os.path.join(app.config['UPLOAD_FOLDER'], output_filename)
-        fourcc = cv2.VideoWriter_fourcc(*'avc1')
+        fourcc = cv2.VideoWriter_fourcc(*'mp4v')
         out = cv2.VideoWriter(output_path, fourcc, fps, (total_width, height))
         if not out.isOpened():
             raise ValueError(f"Failed to create output video writer at {output_path}")