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A More Word-like Image Tokenization for MLLMs
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Proposes DiVT, a density-based clustering visual tokenizer that replaces the MLP projector in LLaVA-1.5, producing adaptive, semantically disentangled visual tokens with a single similarity threshold controlling granularity.
Problem
Visual tokens from MLLM projectors are semantically entangled, highly redundant, and fixed in number per image, unlike word-like text tokens; this inflates KV-cache and latency.
Approach
Cluster ViT patch features by cosine-similarity density (greedy max-degree centroid selection with a threshold), refine assignments to nearest centroid, and aggregate each cluster via centroid-queried cross-attention with cluster-restricted masks; the token count adapts per image and the threshold can be changed at inference.
Key results
- DiVT at theta=0.75 (136.5 avg tokens) reaches 66.7 MMBench and 78.2 VQAv2 vs. 64.3 and 78.5 for the 576-token MLP baseline on LLaVA-1.5 7B.
- At ~36 tokens (theta=0.5), DiVT gets 65.0 MMB and 77.0 VQAv2 vs. TokenPacker's 62.8 and 75.0 at 36 tokens.
- At theta=0.4 (22.4 tokens), DiVT reduces KV-cache to 11.0 MB vs. 288 MB for the MLP projector and cuts prefill latency to 71.3 ms vs. 138.2 ms.
Surprising findings
- Increasing the similarity threshold beyond 0.75 (to 0.8) yields slight degradation despite more tokens, which the authors attribute to fragmentation.
- DiVT with the DINOv2 encoder underperforms the MLP baseline on MMBench (56.9 vs 59.9) and VQAv2 (74.2 vs 75.5).
Limitations
- Per-encoder thresholds need tuning (e.g., theta 0.6 for SigLIP, 0.66 for DINOv2) and DINOv2 underperforms the MLP baseline on several benchmarks.
- Tokens are formed per image by clustering, so the tokenizer adds clustering overhead, noted as heavier at higher thresholds.
- Evaluation is limited to LLaVA-1.5 style training on 7B/13B Vicuna-based models.
Experimental setup
Datasets: LLaVA-1.5 training data MMBench
Benchmarks: MMBench VQAv2 GQA MME MM-Vet TextVQA SQA-IMG POPE
Metrics: accuracy MME perception score
Baselines: MLP projector ToME FastV PruMerge+ VisionZip VisPruner ATP-LLaVA TokenPacker Resampler C-Abstractor
Builds on: LLaVA-1.5 TokenPacker ViT
Closest papers by meaning
- What Do Visual Tokens Really Encode? Uncovering Sparsity and Redundancy in Multimodal Large Language Models (CVPR 2026 · similarity 0.92)
- From Pixels to Tokens: Byte-Pair Encoding on Quantized Visual Modalities (ICLR 2025 · similarity 0.91)
- Patch-as-Decodable-Token: Towards Unified Multi-Modal Vision Tasks in MLLMs (ICLR 2026 · similarity 0.91)
- Rethinking Visual Token Reduction in LVLMs Under Cross-Modal Misalignment (AAAI 2026 · similarity 0.90)
- Unified Language-Vision Pretraining in LLM with Dynamic Discrete Visual Tokenization (ICLR 2024 · similarity 0.90)
- Vision as a Dialect: Unifying Visual Understanding and Generation via Text-Aligned Representations (NeurIPS 2025 · similarity 0.90)
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