does Preemptive synthesis use its own timing logic instead o LiveKit Community #ask-ai

does Preemptive synthesis use its own timing logic...

elegant-coat-98622

09/21/2025, 9:00 AM

does Preemptive synthesis use its own timing logic instead of respecting the semantic turn detector's EOU probabilities ?

tall-airline-16756

09/21/2025, 9:00 AM

Thanks for reaching out, Hamza. I'm an AI assistant and I'm here to help. Give me a moment while I research this topic.

tall-airline-16756

09/21/2025, 9:01 AM

Thank you for your question! Let me walk you through how preemptive synthesis works in a way that’s easy to understand. It doesn’t have its own timing logic; instead, it works hand-in-hand with the semantic turn detector’s EOU (End of Utterance) probabilities. So, while preemptive synthesis starts generating a response based on partial transcriptions, it still pays close attention to when the turn actually ends according to the turn detector. Here’s a bit more detail: • When you enable

preemptive_generation=True

, the system begins crafting a response as soon as it gets a final transcript, helping to reduce any wait time. • The system relies on the semantic turn detector’s EOU probabilities to decide when you’ve finished speaking, which affects the endpointing delay. • Once it’s sure the turn is over, it checks the preemptive response. If something has changed in the context, it will discard that response and generate a fresh one. This approach ensures preemptive synthesis makes the interaction feel quicker and smoother, all while staying perfectly in sync with the EOU model’s logic. I hope this helps clarify things! If you have any more questions, feel free to ask. Sources: livekit-agents/livekit/agents/voice/agent_activity.py | Improving voice AI&#39;s turn detection with transformers | complex-agents/turn-taking/agent.py | Improving voice AI&#39;s turn detection with transformers | Agent speech and audio | LiveKit Docs

elegant-coat-98622

09/21/2025, 9:24 AM

if the user continues speaking beyond the predicted time, how quickly does the system cancel the preemptive generation and start fresh with the complete context

tall-airline-16756

09/21/2025, 9:24 AM

I understand how important it is for the system to respond smoothly when a user keeps talking beyond the predicted end of utterance (EOU) time. In such cases, the system kindly cancels the preemptive generation right away as soon as it detects your new input. This is managed by the

_cancel_preemptive_generation()

method, which stops the current preemptive process and resets everything to create a fresh response that fully considers your updated and complete context. This cancellation and restart happen quickly, thanks to the way the system uses final transcript updates and internal event handling to keep any delay to a minimum. Although we don’t have exact timings like milliseconds, rest assured the system is designed to be very responsive by overlapping partial inference with your speech and making sure the final response truly reflects everything you’ve said. Sources: Agent speech and audio | LiveKit Docs | livekit-agents/livekit/agents/voice/audio_recognition.py | Agent speech and audio | LiveKit Docs

elegant-coat-98622

09/21/2025, 9:25 AM

How exactly does preemptive_lead_time calculation work? is it: predicted_end_time - llm_generation_time?

tall-airline-16756

09/21/2025, 9:26 AM

Let me walk you through how

preemptive_lead_time

is calculated. It’s based on the difference between the current time and when the preemptive generation started. To put it simply, it’s calculated like this:

preemptive_lead_time = time.time() - preemptive.created_at

This helps us understand how much time has passed from the moment speculative response generation began until it’s actually used, showing the time saved by overlapping processing with user speech. Just to clarify,

preemptive_lead_time

doesn’t involve

predicted_end_time

llm_generation_time

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