Stream Speech (SSE)

Synthesize speech and stream the audio back over Server-Sent Events. Same body as `/waves/v1/tts` — the only difference is the response is a stream of base64-encoded PCM chunks instead of one binary blob. Pick the model with the `model` body parameter, same as the sync route. <Note> **The same URL serves the WebSocket endpoint.** `wss://api.smallest.ai/waves/v1/tts/live` accepts a WebSocket upgrade for streaming-text scenarios (LLM token streams, live captioning). The HTTP `POST` documented on this page returns SSE; use `wss://` to use the WebSocket protocol instead. See the [WebSocket reference](/waves/api-reference/api-reference/text-to-speech/tts). </Note> ## When to use this - **Use this** when you want playback to start before synthesis is complete — long passages, latency-sensitive UI, live narration. - **Use sync `/waves/v1/tts`** when total latency doesn't matter and you'd rather get one buffer. - **Use `/waves/v1/tts/live`** (WebSocket) when the *text* arrives incrementally (LLM token stream). SSE assumes you have the full text up front. ## How it works 1. POST your text + voice settings — same payload as `/waves/v1/tts`, plus optional `model`. 2. The response is `Content-Type: text/event-stream`. Each chunk frame is `event: audio\n` followed by `data: {"audio": "<base64-pcm>"}\n\n`. 3. Decode each chunk's `audio` field with base64 and feed the PCM bytes to your audio pipeline (browser `MediaSource`, ffmpeg pipe, raw PCM player, etc.). 4. A final `data: {"done": true}\n\n` frame marks end of stream. ## Examples **cURL** ```bash curl -N -X POST "https://api.smallest.ai/waves/v1/tts/live" \ -H "Authorization: Bearer $SMALLEST_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "text": "Streaming this paragraph chunk by chunk so playback can start sooner.", "voice_id": "magnus", "sample_rate": 24000, "output_format": "pcm" }' ``` ## Common gotchas - **Use a streaming-friendly client.** `curl -N`, Python `iter_lines`, or a `fetch` `ReadableStream` reader. Buffering clients will hide the latency win. - **Audio is base64 inside the event payload**, not the raw event bytes. Decode the `data.audio` field per event. - **`output_format=pcm`** gives the lowest overhead for streaming playback. `wav`/`mp3` work but add per-chunk framing bytes.