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Crab: A Unified Audio-Visual Scene Understanding Model with Explicit Cooperation

CVPR 2025 · Vision-language and multimodal › Cross-modal learning · approach: Audio-visual source localization · 1 citations (OpenAlex)

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Crab unifies temporal, spatial, spatio-temporal and pixel-level audio-visual understanding in one LLaMA-2-based model, trained on a refined instruction dataset with explicit reasoning (AV-UIE) and an interaction-aware multi-head LoRA.

Problem

Existing audio-visual models handle one task family at a time, and naive joint multi-task instruction tuning causes interference across heterogeneous audio-visual tasks because labels are simple words with no explicit inter-task relationship.

Approach

Augment existing AV datasets with MLLM-generated explicit reasoning chains (AV-UIE) so tasks share intermediate temporal/spatial information, and replace standard LoRA with an interaction-aware LoRA (shared A matrix, multiple B heads with a router) intended to specialize in temporal, spatial and pixel-level interaction aspects.

Key results

Measured effects reported in the paper

What was changedWhereMeasuredEffect
include explicit reasoning process instead of simple labels (ablation)Crab · AVQAAcc: 76.05 -> 78.94Helped
include explicit reasoning process instead of simple labels (ablation)Crab · AVEAcc: 78.62 -> 80.15Helped
include explicit reasoning process instead of simple labels (ablation)Crab · AVVPSegment-level F1: 52.01 -> 59.00Helped
include explicit reasoning process instead of simple labels (ablation)Crab · AVVPEvent-level F1: 51.36 -> 54.44Helped
replace standard LoRA with interaction-aware LoRA (ablation)Crab · AVQAAcc: 76.92 -> 78.94Helped
replace standard LoRA with interaction-aware LoRA (ablation)Crab · AVEAcc: 79.93 -> 80.15Helped
replace standard LoRA with interaction-aware LoRA (ablation)Crab · AVVPSegment-level F1: 53.54 -> 59.00Helped
replace standard LoRA with interaction-aware LoRA (ablation)Crab · AVVPEvent-level F1: 53.15 -> 54.44Helped
remove LoRA head-1 (ablation)Crab interaction-aware LoRA · AVEAcc: 80.15 -> 75.07Hurt
remove LoRA head-2 (ablation)Crab interaction-aware LoRA · ARIGcIoU: 41.78 -> 29.16Hurt
remove LoRA head-3 (ablation)Crab interaction-aware LoRA · ARIGcIoU: 41.78 -> 38.65Hurt

Surprising findings

Limitations

Experimental setup

Datasets: MUSIC-AVQA AVE LLP AVS-Bench Ref-AVS VALOR Video-LLaVA pre-training data AudioCaps LVIS

Benchmarks: AVE LLP/AVVP AVS-Bench S4 AVS-Bench MS3 AVS-Bench AVSS Ref-AVS MUSIC-AVQA

Metrics: accuracy segment-level F1 event-level F1 cIoU AUC mIoU F-score

Baselines: TimeChat MEERKAT GroundingGPT X-InstructBLIP VALOR AnyRef AVSBench AVSegFormer TSPM MM-Pyramid

Builds on: LoRA HydraLoRA SAM BEATs Video-LLaVA

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