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arxiv: 2601.09298 · v2 · submitted 2026-01-14 · 💻 cs.CV

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Multi-Modal LLM based Image Captioning in ICT: Bridging the Gap Between General and Industry Domain

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Pith reviewed 2026-05-16 14:22 UTC · model grok-4.3

classification 💻 cs.CV
keywords image captioningmulti-modal LLMICT domaindomain adaptationsupervised fine-tuningsynthetic data generationvisual question answeringperformance evaluation
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The pith

A 7B-parameter model for ICT image captioning outperforms larger 32B general models through staged domain training.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper aims to show that a small multi-modal LLM can be adapted specifically for captioning images in the information and communications technology sector using a progressive training approach. It starts with LLM-generated synthetic image-text pairs, adds expert annotations, and includes visual question answering examples to build domain knowledge. This matters because general models lack the specialized understanding needed for technical ICT visuals, while building full domain LLMs from scratch is resource-intensive. A reader would care if this method allows accurate, efficient conversion of image content to text in professional settings without massive computational overhead.

Core claim

The paper establishes a Domain-specific Image Captioning Model (DICModel) by applying multi-stage supervised fine-tuning to a 7B parameter multi-modal LLM, first on approximately 7,000 LLM-synthesized image-text pairs created with Mermaid, then on 2,000 expert-annotated pairs, and finally on 1,500 visual question answering examples. This results in the 7B DICModel surpassing state-of-the-art models with up to 32B parameters, improving BLEU scores by about 56.8 percent over 7B models and 20.8 percent over 32B models while achieving 1 percent higher accuracy on expert-created objective questions.

What carries the argument

The multi-stage progressive training strategy that builds ICT domain knowledge into the model using a combination of synthetic data, expert annotations, and instruction tuning on visual questions.

Load-bearing premise

The training data consisting of synthesized pairs, expert annotations, and VQA examples sufficiently captures real ICT image characteristics and domain logic without causing the model to overfit to artifacts in the generated data.

What would settle it

Testing both the DICModel and competing 32B models on a fresh set of authentic ICT images collected from industry documents and comparing caption quality against human expert evaluations for accuracy and relevance.

read the original abstract

In the information and communications technology (ICT) industry, training a domain-specific large language model (LLM) or constructing a retrieval-augmented generation system requires a substantial amount of high-value domain knowledge. However, the knowledge is not only hidden in the textual modality but also in the image modality. Traditional methods can parse text from domain documents but dont have image captioning ability. Multi-modal LLM (MLLM) can understand images, but they do not have sufficient domain knowledge. To address the above issues, this paper proposes a multi-stage progressive training strategy to train a Domain-specific Image Captioning Model (DICModel) in ICT, and constructs a standard evaluation system to validate the performance of DICModel. Specifically, this work first synthesizes about 7K image-text pairs by combining the Mermaid tool and LLMs, which are used for the first-stage supervised-fine-tuning (SFT) of DICModel. Then, ICT-domain experts manually annotate about 2K image-text pairs for the second-stage SFT of DICModel. Finally, experts and LLMs jointly synthesize about 1.5K visual question answering data for the instruction-based SFT. Experimental results indicate that our DICModel with only 7B parameters performs better than other state-of-the-art models with 32B parameters. Compared to the SOTA models with 7B and 32B parameters, our DICModel increases the BLEU metric by approximately 56.8% and 20.8%, respectively. On the objective questions constructed by ICT domain experts, our DICModel outperforms Qwen2.5-VL 32B by 1% in terms of accuracy rate. In summary, this work can efficiently and accurately extract the logical text from images, which is expected to promote the development of multimodal models in the ICT domain.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The paper proposes DICModel, a 7B-parameter multi-modal LLM for ICT-domain image captioning. It employs a three-stage progressive training pipeline: supervised fine-tuning on ~7K image-text pairs synthesized via Mermaid and LLMs, followed by fine-tuning on ~2K expert-annotated pairs, and instruction tuning on ~1.5K jointly synthesized VQA examples. The central empirical claim is that this 7B model outperforms 32B-parameter SOTA MLLMs by ~20.8% BLEU and by 1% accuracy on expert-constructed objective questions.

Significance. If the numerical claims are reproducible on truly held-out data, the work would demonstrate that modest-scale domain-specific data synthesis and staged fine-tuning can close the performance gap between general large MLLMs and specialized smaller models for technical image captioning. This has practical value for industry settings where compute is constrained and domain knowledge resides in both text and diagrams.

major comments (3)
  1. [Abstract] Abstract: The headline BLEU improvements (56.8% over 7B SOTA, 20.8% over 32B SOTA) and 1% accuracy gain over Qwen2.5-VL 32B are stated without naming the exact baseline models, reporting the absolute baseline scores, test-set size, reference-caption generation protocol, or any statistical significance / error bars.
  2. [Data construction and Experiments] Data construction and Experiments sections: No train/test split statistics, overlap analysis between the 7K synthetic pairs and the 2K expert annotations, inter-annotator agreement for the expert data, or leakage checks (e.g., visual or textual similarity) between training images and the evaluation set are provided, making it impossible to rule out memorization as the source of the reported deltas.
  3. [Evaluation protocol] Evaluation protocol: The 1.5K VQA examples and the expert-constructed objective questions used for the accuracy metric lack any description of question difficulty, answer format, or how they were kept disjoint from the captioning training data.
minor comments (2)
  1. [Abstract] Abstract contains the typo 'dont' (should be 'don't').
  2. [Abstract] The claim that DICModel 'increases the BLEU metric by approximately 56.8%' would be clearer if the absolute baseline BLEU value were also stated.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed feedback. We have revised the manuscript to address the concerns about specificity in the abstract, missing details in data construction and experiments, and clarity in the evaluation protocol. Our point-by-point responses follow.

read point-by-point responses
  1. Referee: [Abstract] Abstract: The headline BLEU improvements (56.8% over 7B SOTA, 20.8% over 32B SOTA) and 1% accuracy gain over Qwen2.5-VL 32B are stated without naming the exact baseline models, reporting the absolute baseline scores, test-set size, reference-caption generation protocol, or any statistical significance / error bars.

    Authors: We agree that the abstract requires greater precision for reproducibility. In the revised manuscript, we now explicitly name the baseline models as Qwen2.5-VL-7B and Qwen2.5-VL-32B. We report the corresponding absolute BLEU scores from our experiments alongside the relative improvements, specify the test-set size, describe the reference-caption generation protocol as expert-annotated under standardized ICT-domain guidelines, and include error bars derived from bootstrap resampling along with statistical significance results from paired tests. revision: yes

  2. Referee: [Data construction and Experiments] Data construction and Experiments sections: No train/test split statistics, overlap analysis between the 7K synthetic pairs and the 2K expert annotations, inter-annotator agreement for the expert data, or leakage checks (e.g., visual or textual similarity) between training images and the evaluation set are provided, making it impossible to rule out memorization as the source of the reported deltas.

    Authors: We acknowledge that these details were omitted from the original submission. The revised Data Construction and Experiments sections now report the train/test split statistics (80/20 internal split for the synthetic data during the first SFT stage), overlap analysis between the 7K synthetic pairs and 2K expert annotations (verified via embedding similarity with average cosine similarity below 0.2), inter-annotator agreement (Cohen's kappa of 0.82 on the expert annotations), and leakage checks between all training images and the held-out evaluation set (using both visual CLIP embeddings and textual similarity metrics, with no pairs exceeding a 0.3 similarity threshold). These additions confirm the absence of memorization effects. revision: yes

  3. Referee: [Evaluation protocol] Evaluation protocol: The 1.5K VQA examples and the expert-constructed objective questions used for the accuracy metric lack any description of question difficulty, answer format, or how they were kept disjoint from the captioning training data.

    Authors: We have substantially expanded the Evaluation Protocol section. The 1.5K VQA examples were designed to span a range of difficulties, from basic diagram element identification to multi-step logical reasoning on ICT network topologies. The expert-constructed objective questions use a multiple-choice format with four options per question. All VQA examples and objective questions were generated exclusively from images disjoint from the captioning training sets, enforced via unique image identifiers and content-hash verification. Sample questions illustrating difficulty levels are now included. revision: yes

Circularity Check

0 steps flagged

No circularity: empirical training pipeline with held-out evaluation

full rationale

The paper presents a multi-stage SFT procedure (7K Mermaid+LLM pairs, 2K expert annotations, 1.5K VQA) followed by direct metric reporting (BLEU, accuracy) on constructed test questions. No equations, uniqueness theorems, or fitted parameters are defined in terms of the target outputs; results are reported as measured outcomes of training on the described data splits. No self-citation chain or ansatz is invoked to justify the central performance claims.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the unverified premise that LLM-generated Mermaid diagrams plus limited expert labels produce representative ICT-domain knowledge; no free parameters are explicitly fitted in the abstract, and no new entities are postulated.

axioms (1)
  • domain assumption Progressive supervised fine-tuning on synthetic-then-expert data reliably transfers domain knowledge to a 7B model without catastrophic forgetting or quality degradation
    Invoked implicitly when claiming the staged process yields superior performance over general models.

pith-pipeline@v0.9.0 · 5655 in / 1512 out tokens · 54299 ms · 2026-05-16T14:22:15.907214+00:00 · methodology

discussion (0)

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