What Semantics Survive the Connector? Diagnosing VLM-to-DiT Alignment in Video Editing

Fuente: arXiv
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Autores principales: Lin, Hangyu, Wen, Chao, Xu, Chengming, Gao, Jianxiong, Zhang, Jiangning, Hu, Xiaobin, Fu, Yanwei
Formato: Preprint
Publicado: 2026
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author Lin, Hangyu
Wen, Chao
Xu, Chengming
Gao, Jianxiong
Zhang, Jiangning
Hu, Xiaobin
Fu, Yanwei
author_facet Lin, Hangyu
Wen, Chao
Xu, Chengming
Gao, Jianxiong
Zhang, Jiangning
Hu, Xiaobin
Fu, Yanwei
contents Flow matching based video generative models have been increasingly relying on prepended Vision-Language Models (VLMs) to handle complex, instruction-based video editing. The prevailing assumption underlying this paradigm is that a connector module can seamlessly align the VLM's rich multi-modal reasoning with the original text embedding space of DiTs. However, we hypothesize that this alignment acts as a severe semantic bottleneck, degrading fine-grained structural variables. Verifying this is challenging, as end-to-end evaluations conflate alignment failures with generation errors, and natural datasets lack disentangled annotations. To rigorously investigate this, we propose a controlled data processing pipeline based on video composition that results in TRACE-Edit, a diagnostic dataset focusing on relation-based editing. Leveraging this dataset, we propose a comprehensive diagnostic protocol to analyze two important designs of meta-query and connector in the existing video editing models. Systematic evaluation of four representative model cases reveals that fine-grained structural semantics can be severely degraded during alignment. Our findings overturn the assumption of lossless semantic transfer, identifying the VLM-to-DiT alignment as a major bottleneck and providing a new diagnostic foundation for future multi-modal alignment architectures.
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id arxiv_https___arxiv_org_abs_2605_20795
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle What Semantics Survive the Connector? Diagnosing VLM-to-DiT Alignment in Video Editing
Lin, Hangyu
Wen, Chao
Xu, Chengming
Gao, Jianxiong
Zhang, Jiangning
Hu, Xiaobin
Fu, Yanwei
Computer Vision and Pattern Recognition
Flow matching based video generative models have been increasingly relying on prepended Vision-Language Models (VLMs) to handle complex, instruction-based video editing. The prevailing assumption underlying this paradigm is that a connector module can seamlessly align the VLM's rich multi-modal reasoning with the original text embedding space of DiTs. However, we hypothesize that this alignment acts as a severe semantic bottleneck, degrading fine-grained structural variables. Verifying this is challenging, as end-to-end evaluations conflate alignment failures with generation errors, and natural datasets lack disentangled annotations. To rigorously investigate this, we propose a controlled data processing pipeline based on video composition that results in TRACE-Edit, a diagnostic dataset focusing on relation-based editing. Leveraging this dataset, we propose a comprehensive diagnostic protocol to analyze two important designs of meta-query and connector in the existing video editing models. Systematic evaluation of four representative model cases reveals that fine-grained structural semantics can be severely degraded during alignment. Our findings overturn the assumption of lossless semantic transfer, identifying the VLM-to-DiT alignment as a major bottleneck and providing a new diagnostic foundation for future multi-modal alignment architectures.
title What Semantics Survive the Connector? Diagnosing VLM-to-DiT Alignment in Video Editing
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2605.20795