HY-Himmel Technical Report: Hierarchical Interleaved Multi-stream Motion Encoding for Long Video Understanding

Fuente: arXiv
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Autores principales: Jin, Haopeng, Yi, Hongzhu, Zhao, Wenlong, Luo, Jinwen, Ye, Shani, Guan, Zhenyu, Dong, Shiquan, Yang, Tiankun, Yu, Tao
Formato: Preprint
Publicado: 2026
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author Jin, Haopeng
Yi, Hongzhu
Zhao, Wenlong
Luo, Jinwen
Ye, Shani
Guan, Zhenyu
Dong, Shiquan
Yang, Tiankun
Yu, Tao
author_facet Jin, Haopeng
Yi, Hongzhu
Zhao, Wenlong
Luo, Jinwen
Ye, Shani
Guan, Zhenyu
Dong, Shiquan
Yang, Tiankun
Yu, Tao
contents Long-video understanding with multimodal language models suffers from three compounding bottlenecks: heavy decode cost to obtain dense RGB frames, quadratic token growth with frame count, and weak motion perception under sparse keyframe sampling. We present HY-Himmel, a hierarchical video-language framework that allocates semantic and motion capacity separately. A small set of sparse anchor I-frames is routed to the expensive host ViT to ground object identity and scene layout, while the far denser inter-frame intervals are encoded by a lightweight compressed-domain tri-stream adapter that distils motion evidence from motion-vector maps, residual maps, and I-frame context into aligned motion tokens. These tokens are injected into the LLM via a differentiable placeholder mechanism after a dedicated Stage-1 contrastive alignment that places the motion representation in a geometry compatible with the frozen visual backbone. On Video-MME, HY-Himmel surpasses the dense 32-frame baseline by +2.3 pp (61.2 to 63.5%) while using 3.6x fewer context tokens. Extensive ablations over stream composition, motion encoder family, fusion mode, alignment objective, anchor count, LoRA rank, and video duration confirm that the full tri-stream is necessary and sufficient for the observed gains.
format Preprint
id arxiv_https___arxiv_org_abs_2605_08158
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle HY-Himmel Technical Report: Hierarchical Interleaved Multi-stream Motion Encoding for Long Video Understanding
Jin, Haopeng
Yi, Hongzhu
Zhao, Wenlong
Luo, Jinwen
Ye, Shani
Guan, Zhenyu
Dong, Shiquan
Yang, Tiankun
Yu, Tao
Computer Vision and Pattern Recognition
Artificial Intelligence
I.2.10; I.4.8; I.5.4
Long-video understanding with multimodal language models suffers from three compounding bottlenecks: heavy decode cost to obtain dense RGB frames, quadratic token growth with frame count, and weak motion perception under sparse keyframe sampling. We present HY-Himmel, a hierarchical video-language framework that allocates semantic and motion capacity separately. A small set of sparse anchor I-frames is routed to the expensive host ViT to ground object identity and scene layout, while the far denser inter-frame intervals are encoded by a lightweight compressed-domain tri-stream adapter that distils motion evidence from motion-vector maps, residual maps, and I-frame context into aligned motion tokens. These tokens are injected into the LLM via a differentiable placeholder mechanism after a dedicated Stage-1 contrastive alignment that places the motion representation in a geometry compatible with the frozen visual backbone. On Video-MME, HY-Himmel surpasses the dense 32-frame baseline by +2.3 pp (61.2 to 63.5%) while using 3.6x fewer context tokens. Extensive ablations over stream composition, motion encoder family, fusion mode, alignment objective, anchor count, LoRA rank, and video duration confirm that the full tri-stream is necessary and sufficient for the observed gains.
title HY-Himmel Technical Report: Hierarchical Interleaved Multi-stream Motion Encoding for Long Video Understanding
topic Computer Vision and Pattern Recognition
Artificial Intelligence
I.2.10; I.4.8; I.5.4
url https://arxiv.org/abs/2605.08158