What is Streaming TTS?
2 min read · Bolcho
Streaming text-to-speech (TTS) synthesises audio incrementally, starting to speak as soon as the first words of a reply are ready — rather than waiting for the complete sentence. It's one of the biggest levers for cutting the pause before a voice agent responds.
Streaming TTS explained
In batch TTS, the system waits for the LLM to finish the whole reply, sends it to the synthesizer, waits for the full audio, then plays it. Every stage waits for the previous one to complete.
In streaming TTS, the first tokens from the LLM are synthesised and played while the rest of the reply is still being generated — so the caller hears speech far sooner.
How it works
Streaming TTS pairs with a streaming LLM and streaming STT so all three overlap. The audio for 'Sure, I can book that…' plays while the model is still deciding the rest of the sentence.
How Bolcho handles it
Streaming TTS is built into Bolcho's unified pipeline, plus phrase caching for repeated audio.
Speaks on the first tokens
Bolcho starts synthesising on the first LLM tokens and serves repeated phrases (greetings, confirmations) from a cache — a core reason time-to-first-word stays under 800ms.
Why it matters for voice AI in India
Streaming TTS matters more when calls are routed far from the caller, as many global stacks do for India. Overlapping synthesis reclaims the time a chained, non-streaming stack wastes.
See it in a real agent
Bolcho handles this for you end-to-end. Start a voice or chat agent free.
Frequently asked questions
What is the difference between streaming and batch TTS?
Batch TTS waits for the full reply text, then synthesises and plays it. Streaming TTS starts speaking on the first words while the rest is still being generated — much lower perceived latency.
Does streaming TTS reduce latency?
Yes, substantially — it removes the wait for the whole sentence to be generated and synthesised before any audio plays.
Does Bolcho use streaming TTS?
Yes — it's part of Bolcho's streaming pipeline, alongside phrase caching, to keep replies under 800ms.