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Speculative decoding cuts speech latency below 250 ms

Full‑duplex speech assistants still incur a noticeable pause while waiting for the next audio chunk. Speculative Listening slashes that pause by up to 2.8×, keeping total response lag under 250 ms.

Prior systems decode each chunk only after the audio arrives, forcing a serial bottleneck where listening time sits idle and speaking or tool‑call chunks block the pipeline. This asymmetric workload has made real‑time turn‑taking difficult for voice agents.

Speculative Listening speeds up speak‑chunk generation by 2.6–2.8× on the eight‑task TickTock‑Bench benchmark. The method drafts the next chunk during idle compute under a silence assumption, then verifies it when the audio arrives, all without any additional training [1].

It also cuts the decoding delay before a response starts by 73%, shrinking it to a 74–241 ms window that sits comfortably below the ≈200 ms human turn‑taking gap. By keeping post‑audio latency in this narrow band, the framework delivers end‑to‑end lag well under the sub‑250 ms threshold [1].

The approach hinges on the empirical finding that silent drafts match real audio output in more than 95% of chunks, a property that may degrade with noisy inputs or highly dynamic speech patterns. Moreover, verification still incurs a small overhead, and the reported gains are limited to the eight tasks evaluated, leaving open whether the same speedups hold for larger vocabularies or multilingual scenarios [1].

Voice services can now achieve sub‑250 ms round‑trip latency by enabling Speculative Listening as a drop‑in, training‑free wrapper around existing full‑duplex models. This eliminates the need to redesign architectures or fine‑tune new decoders, offering an immediate latency boost for low‑latency assistants and streaming speech applications.

References

  1. Decode Before You Hear: Speculative Listening for Chunk-Interleaved Full-Duplex Speech Language Models

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