DynaTok: Temporally Adaptive and Positional Bias-Aware Token Compression for Video-LLMs
Pith reviewed 2026-05-20 06:51 UTC · model grok-4.3
The pith
DynaTok reduces visual tokens in Video-LLMs by 90 percent while retaining more than 95 percent of baseline accuracy through adaptive temporal and spatial allocation.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
DynaTok allocates token budgets temporally using a lightweight EMA memory to give more tokens to novel frames and spatially using activation-based attention maps and spatial memory to select important and non-redundant features, enabling seamless integration with models like LLaVA-OneVision and LLaVA-Video to maintain over 95 percent accuracy at 90 percent token reduction on benchmarks including MVBench, LongVideoBench, MLVU, and VideoMME.
What carries the argument
Temporal Budget Allocation module with EMA memory for long-term variation and Spatial Budget Allocation module with activation attention and spatial memory to reduce positional bias.
Load-bearing premise
The lightweight EMA memory and spatial memory mechanisms can effectively capture long-term temporal variations and mitigate positional bias in token selection without requiring any model-specific training or fine-tuning.
What would settle it
Applying DynaTok to videos with sudden scene shifts or to an unseen Video-LLM architecture and measuring whether accuracy falls well below 95 percent of baseline at 90 percent token reduction.
Figures
read the original abstract
Recent advances in Video Large Language Models (Video-LLMs) have greatly expanded multimodal reasoning capabilities. However, the massive number of visual tokens extracted from long video sequences incurs prohibitive computational costs, limiting their deployment in real-world scenarios. Existing training-free token compression methods select tokens based on attention magnitude as a proxy for semantic importance, but often overlook positional bias and rely only on short-term temporal locality, leading to redundant spatio-temporal coverage and inefficient token usage. We present DynaTok, a training-free, temporally adaptive and bias-aware token compression framework that allocates token budgets across both temporal and spatial dimensions. Through a lightweight exponential moving average (EMA) memory, the Temporal Budget Allocation (TBA) module dynamically assigns fewer tokens to redundant frames and more to novel frames, capturing long-term temporal variation. The Spatial Budget Allocation (SBA) module complements this by selecting spatially diverse and semantically important features using activation-based attention maps, while leveraging a spatial memory to reduce redundancy from previously selected regions and mitigate positional bias. DynaTok integrates seamlessly with existing Video-LLMs such as LLaVA-OneVision and LLaVA-Video without retraining, and effectively preserves semantic coverage under aggressive compression. Experiments on four representative VideoQA benchmarks-MVBench, LongVideoBench, MLVU, and VideoMME-show that DynaTok retains over 95% of baseline accuracy even with a 90% token reduction, surpassing recent training-free approaches. These results demonstrate that DynaTok provides a principled foundation for efficient and robust video reasoning, paving the way toward real-time streaming video understanding with future Video-LLMs.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents DynaTok, a training-free token compression framework for Video-LLMs. It introduces a Temporal Budget Allocation (TBA) module that uses a lightweight exponential moving average (EMA) memory to dynamically allocate fewer tokens to redundant frames and more to novel ones, capturing long-term temporal variation. This is complemented by a Spatial Budget Allocation (SBA) module that selects spatially diverse and semantically important features via activation-based attention maps while using spatial memory to reduce redundancy and mitigate positional bias. The method integrates with existing models such as LLaVA-OneVision and LLaVA-Video without retraining. Experiments on MVBench, LongVideoBench, MLVU, and VideoMME report that DynaTok retains over 95% of baseline accuracy at 90% token reduction, outperforming recent training-free approaches.
Significance. If the reported empirical results hold under detailed scrutiny, DynaTok offers a practical advance for efficient long-video reasoning in Video-LLMs by providing a training-free, modular approach to spatio-temporal token allocation. The emphasis on long-term temporal dynamics via EMA and positional-bias mitigation via spatial memory addresses documented limitations in prior attention-magnitude-based methods. Seamless plug-in compatibility with existing models and strong retention of accuracy at aggressive compression rates would make this relevant for real-time and resource-constrained video understanding applications.
major comments (2)
- §4 (Experiments): The central performance claim of >95% baseline accuracy retention at 90% token reduction is load-bearing for the paper's contribution, yet the manuscript provides no error bars, standard deviations across multiple runs, or statistical significance tests against the listed baselines; this weakens the ability to assess whether the reported gains over recent training-free methods are robust.
- §3.2 (TBA module): The description of the EMA memory update and budget allocation formula lacks explicit pseudocode or parameter values (e.g., decay rate), making it difficult to verify that the mechanism indeed captures long-term variations independently of short-term locality assumptions in prior work.
minor comments (2)
- Abstract and §1: The list of benchmarks is given as 'MVBench, LongVideoBench, MLVU, and VideoMME' but referred to collectively as 'four representative VideoQA benchmarks'; ensure consistent terminology and add a brief note on dataset characteristics (e.g., average video length) for context.
- Figure 2 or equivalent architecture diagram: The interaction between TBA and SBA modules and the final token selection step would benefit from an explicit flowchart or equation showing how the allocated budgets are combined.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback on our manuscript. We address each of the major comments in detail below, proposing specific revisions to improve clarity and robustness.
read point-by-point responses
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Referee: §4 (Experiments): The central performance claim of >95% baseline accuracy retention at 90% token reduction is load-bearing for the paper's contribution, yet the manuscript provides no error bars, standard deviations across multiple runs, or statistical significance tests against the listed baselines; this weakens the ability to assess whether the reported gains over recent training-free methods are robust.
Authors: We agree that statistical analysis would strengthen the presentation of our results. Although DynaTok is training-free, minor variations can occur due to data loading or inference settings. In the revised manuscript, we will add standard deviations from multiple runs (using different random seeds for frame sampling where applicable) and report statistical significance tests comparing against the baselines. revision: yes
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Referee: §3.2 (TBA module): The description of the EMA memory update and budget allocation formula lacks explicit pseudocode or parameter values (e.g., decay rate), making it difficult to verify that the mechanism indeed captures long-term variations independently of short-term locality assumptions in prior work.
Authors: We appreciate the suggestion to improve reproducibility. Section 3.2 currently provides the mathematical formulation of the EMA update and budget allocation, but we agree that pseudocode and explicit parameter values would be helpful. In the revision, we will add an algorithm box with pseudocode for the TBA module and state the specific decay rate and other hyperparameters used in our experiments. revision: yes
Circularity Check
No significant circularity detected
full rationale
The paper introduces DynaTok as a training-free algorithmic framework consisting of independent TBA and SBA modules that rely on lightweight EMA memory and spatial memory heuristics for token allocation. These components are defined procedurally and evaluated through direct empirical measurements on external benchmarks (MVBench, LongVideoBench, MLVU, VideoMME), with performance quantified as retention of baseline accuracy under token reduction. No derivation chain, equations, or self-citations are presented that reduce the central claims to quantities fitted from the paper's own inputs or prior results by construction; the reported outcomes are end-to-end experimental results rather than tautological restatements of fitted parameters or renamed heuristics.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Attention magnitude and activation maps serve as reliable proxies for semantic importance and spatial diversity.
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