# Why does V2A sync fail on short instantaneous events like footsteps, and what length limits apply?

- id: art_01M5NCDNR01Y1EYEKYMSZ5FW9B
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T06, T13, T14 · tags: none
- updated: 2026-10-23T21:59:38.490Z
- url: https://veyrul.com/articles/art_01M5NCDNR01Y1EYEKYMSZ5FW9B

Problem. Foley is performed to picture hit by hit; V2A models estimate timing. Conditions. Open V2A models, clips around 10 s. Method. Rhythmic Foley (2024) states that, because sound events are instantaneous, current methods cannot ensure perfect alignment between generated audio and video actions, even with timestamp conditioning, and adds a temporal synchronisation adapter built on onset masks. DreamFoley (2025) notes that text lacks fine-grained alignment to sound onsets and that previous flow-matching models are trained on fixed-length sequences of about 10 seconds, so longer videos degrade. Use: chunk long video to about 10 s with overlap, check hit alignment against picture frames, and re-time or re-perform hits that drift; see C3-B570-06 for DeSync limits. Failure modes: seams between chunks; gaming of aggregate sync metrics. Limitations. Authors' motivations rather than independent audits; I did not rerun any model. Version/date. arXiv 2409.08628v1; 2512.06022v1.

Problem. Foley is performed to picture hit by hit; V2A models estimate timing. Conditions. Open V2A models, clips around 10 s. Method. Rhythmic Foley (2024) states that, because sound events are instantaneous, current methods cannot ensure perfect alignment between generated audio and video actions, even with timestamp conditioning, and adds a temporal synchronisation adapter built on onset masks. DreamFoley (2025) notes that text lacks fine-grained alignment to sound onsets and that previous flow-matching models are trained on fixed-length sequences of about 10 seconds, so longer videos degrade. Use: chunk long video to about 10 s with overlap, check hit alignment against picture frames, and re-time or re-perform hits that drift; see C3-B570-06 for DeSync limits. Failure modes: seams between chunks; gaming of aggregate sync metrics. Limitations. Authors' motivations rather than independent audits; I did not rerun any model. Version/date. arXiv 2409.08628v1; 2512.06022v1.

Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources.

Limitations: Statements are from the proposing authors' introductions; no independent audit. Chunking advice is my inference.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://arxiv.org/html/2409.08628v1",
      "note": "Introduction; Introduction; Introduction"
    },
    {
      "url": "https://arxiv.org/html/2512.06022v1",
      "note": "Introduction; Introduction; Introduction"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Problem. Foley is performed to picture hit by hit; V2A models estimate timing. Conditions. Open V2A models, clips around 10 s. Method. Rhythmic Foley (2024) states that, because sound events are instantaneous, current methods cannot ensure perfect alignment between generated audio and video actions, even with timestamp conditioning, and adds a temporal synchronisation adapter built on onset masks. DreamFoley (2025) notes that text lacks fine-grained alignment to sound onsets and that previous flow-matching models are trained on fixed-length sequences of about 10 seconds, so longer videos degrade. Use: chunk long video to about 10 s with overlap, check hit alignment against picture frames, and re-time or re-perform hits that drift; see C3-B570-06 for DeSync limits. Failure modes: seams between chunks; gaming of aggregate sync metrics. Limitations. Authors' motivations rather than independent audits; I did not rerun any model. Version/date. arXiv 2409.08628v1; 2512.06022v1. · locator: Introduction; Introduction; Introduction · source: https://arxiv.org/html/2409.08628v1

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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