arXiv:2608.12703cs.SDcs.MM2026-08

提出解决ASR自推测解码中的音频位置漂移问题,提升生成速度与准确率。

Alignment Drift in Single-Model Speculative Decoding for ASR: Mechanism, Correction, and Cost

  • 用验证注意力引导草案位置,纠正音频位置漂移
  • 训练阶段引入位置追踪机制,使草案在推理中保持同步
  • 在不同规模模型上均提升端到端生成速度

推测解码通过廉价草案一次性提出多个词元,由目标模型统一验证以加速生成。单模型设计中,草案是附加于目标模型的轻量模块而非独立模型。应用于自动语音识别(ASR)时,草案每步可读取完整音频,但其预测质量随运行逐渐下降,导致位置漂移。尽管接受文本显式保留转录位置,草案需同步跟踪动态音频位置。实验表明,每步访问音频仅轻微影响首词元预测,却使后续词元接受率翻倍;固定窗口分析显示,音频位置解释了部分性能差距:正确位置的窗口恢复连续性,错误位置则降低性能。最坏情况下,晚期草案中位误差达21帧,而目标模型验证时注意力集中于2帧内。本文测试两种纠正方法:一是从验证注意力中读取音频位置以指导下一轮草案,仅当多接受词元抵消读出开销时才节省时间;二是AnchorDraft,在训练中教草案追踪音频位置,不改变推理结构。训练后草案在两种目标规模下均提升端到端速度。结果表明,ASR自推测解码依赖于词元预测、音频位置追踪与草案开销的平衡。

原文摘要 · Abstract (English)

Speculative decoding speeds up generation by letting a cheap draft propose several tokens that a target model checks in one pass. In the single-model form, the draft is a lightweight module attached to the target rather than a separate model. Applying this design to Automatic Speech Recognition (ASR) introduces an extra problem. The draft can read the whole audio at every step, yet its proposals get worse as it runs on its own. Access is not localization. The accepted text keeps the transcript position explicit, but the draft must also track the changing audio position. In the primary matched comparison, per-step audio access changes the first proposal modestly but roughly doubles later-proposal acceptance. Fixed-width windows show that the audio position explains part of this gap. A correctly placed window recovers continuation, while an equally narrow window at the wrong position reduces it. Late-draft median error reaches 21 frames in the hardest reported condition, while target attention during verification stays within a 2-frame median. We test two ways to reduce this drift. The first reads the audio position from verification attention and uses it to guide the next draft round. It saves time only when the extra accepted tokens offset the readout cost. The second is AnchorDraft, which teaches the draft to track the audio position during training without changing the inference graph. The trained draft improves end-to-end speed at both tested target scales. These results show that ASR self-speculation depends on token prediction, audio-position tracking, and draft cost.

语音识别推测解码位置追踪加速生成

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