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MA-LMM: Memory-Augmented Large Multimodal Model for Long-Term Video Understanding
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Proposes MA-LMM, which processes video frames online and stores past features in a visual and query memory bank with similarity-based compression, letting a BLIP-2-style multimodal LLM model long videos efficiently.
Problem
LLM-based large multimodal models can only process a limited number of video frames due to LLM context length and GPU memory limits, hindering long-term video understanding.
Approach
Process frames sequentially and store past visual features and learned queries in memory banks that serve as keys/values in the Q-Former's attention, with a memory bank compression that merges the most similar adjacent frame features so the bank length stays constant while keeping temporal order.
Key results
- Achieves 63.0 average top-1 on LVU, improving over the prior best S5 (59.2) by 3.8%.
- Reaches 93.0% on Breakfast and 93.2% on COIN, outperforming S5 by 2.3% and 2.4%.
- Gets 48.5 on MSRVTT-QA, 60.6 on MSVD-QA, and 49.8 on ActivityNet-QA, beating Video-LLaMA on all three.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add visual and query memory banks instead of using neither (ablation) | MA-LMM · LVU | top-1 accuracy: 48.3 -> 63.0 | Helped |
| Add the visual memory bank while retaining the query memory bank (ablation) | MA-LMM · LVU | top-1 accuracy: 58.0 -> 63.0 | Helped |
| Add the query memory bank while retaining the visual memory bank (ablation) | MA-LMM · LVU | top-1 accuracy: 61.5 -> 63.0 | Helped |
| Add both memory banks rather than neither (ablation) | MA-LMM · Breakfast | top-1 accuracy: 74.6 -> 93.0 | Helped |
| Add both memory banks rather than neither (ablation) | MA-LMM · COIN | top-1 accuracy: 72.3 -> 93.2 | Helped |
| Add a long-term memory bank in the off-the-shelf setting (ablation) | baseline large multimodal model · ActivityNet-QA | score: 29.9 -> 37.2 | Helped |
| Add a long-term memory bank in the off-the-shelf setting (ablation) | baseline large multimodal model · LVU | score: 23.6 -> 32.8 | Helped |
| Use memory bank compression (MBC) instead of FIFO memory eviction (ablation) | MA-LMM · LVU | top-1 accuracy: 61.3 -> 63.0 | Helped |
| Use memory bank compression (MBC) instead of FIFO memory eviction (ablation) | MA-LMM · Breakfast | top-1 accuracy: 88.5 -> 93.0 | Helped |
| Use memory bank compression (MBC) instead of FIFO memory eviction (ablation) | MA-LMM · COIN | top-1 accuracy: 90.4 -> 93.2 | Helped |
| Use Vicuna-7B rather than FlanT5-XL (ablation) | MA-LMM · MSRVTT-QA | top-1 accuracy: 46.5 -> 48.5 | Helped |
| Use Vicuna-7B rather than FlanT5-XL (ablation) | MA-LMM · MSVD-QA | top-1 accuracy: 57.6 -> 60.6 | Helped |
Surprising findings
- Adding the memory bank to the off-the-shelf InstructBLIP baseline without retraining improves results, e.g., +9.2 on LVU.
- Performance saturates when memory bank length is around 10 to 20 frames, suggesting high temporal redundancy in long videos.
Limitations
- Video QA on ActivityNet trails VideoCoCa, which uses large-scale video-text pretraining while MA-LMM uses only image-text pretraining.
- LVU evaluation limited to seven classification tasks since the LLM generates text and lacks regression capability.
Experimental setup
Datasets: LVU Breakfast COIN MSRVTT-QA MSVD-QA ActivityNet-QA MSRVTT MSVD YouCook2 EpicKitchens-100
Benchmarks: LVU Breakfast COIN MSRVTT-QA MSVD-QA ActivityNet-QA MSRVTT MSVD YouCook2 EpicKitchens-100
Metrics: top-1 accuracy METEOR CIDEr top-5 accuracy recall
Baselines: Video-LLaMA S5 ViS4mer VideoCoCa mPLUG-2 GIT Video-ChatGPT FIFO ToMe
Builds on: BLIP-2 InstructBLIP Video-LLaMA Vicuna
Closest papers by meaning
- Understanding Long Videos with Multimodal Language Models (ICLR 2025 · similarity 0.92)
- AdaCM^2: On Understanding Extremely Long-Term Video with Adaptive Cross-Modality Memory Reduction (CVPR 2025 · similarity 0.92)
- LongVideoBench: A Benchmark for Long-context Interleaved Video-Language Understanding (NeurIPS 2024 · similarity 0.92)
- Leveraging Textual Memory and Key Frame Reasoning for Full Video Understanding Using Off-the-Shelf LLMs and VLMs (Student Abstract) (AAAI 2025 · similarity 0.91)
- Enhancing Temporal Understanding in Video-LLMs through Stacked Temporal Attention in Vision Encoders (NeurIPS 2025 · similarity 0.91)
- TimeChat: A Time-sensitive Multimodal Large Language Model for Long Video Understanding (CVPR 2024 · similarity 0.90)
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