ChronoStitch: Training-Free Composition of Visual KV Memories for Long-Horizon Temporal Reasoning
This work addresses the challenge of cross-segment temporal reasoning in long-form video question answering, where existing methods suffer from temporal phase conflicts in visual key-value (KV) caches due to local positional encodings. To overcome this limitation without requiring retraining, the authors propose an efficient approach that reconstructs the KV cache using a global triaxial multimodal RoPE coordinate system, preserving spatiotemporal structural consistency and avoiding spatial-temporal confusion caused by one-dimensional reindexing. Additionally, the method selectively recomputes high-bias visual tokens to compensate for missing contextual information. Notably, this is the first work to employ three-dimensional RoPE for cross-segment temporal alignment, achieving significant performance gains over baselines on Qwen2.5-VL-3B and TempCompass, with improved event ordering accuracy and 3.3× faster inference compared to full re-prefilling.