Server-side Streaming
Backend pushes an audio stream to LansonAI.
Connect your backend to LansonAI to stream audio from server-side sources (files, pipelines, telephony).
Architecture
Your backend LansonAI Upstream STT
│ │ │
├── WS connect (Bearer sk-...) ─→ session.created │
│ │ │
├── read audio file ───────────│ │
├── convert to PCM16LE/16k ─────│ │
├── send binary frames ─────────→ gateway relay ────────────→ VAD + STT
│←── conversation.item.input_audio_transcription.completed ─│←──────────│
│ │ │
├── close ──────────────────────→ meter flush │
Authentication
Server-side connections use the API key directly:
const ws = new WebSocket(
"wss://audio.lansonai.com/v1/audio/transcriptions/stream",
{ headers: { Authorization: "Bearer sk-..." } }
);
No session token needed — the key never leaves your server.
Streaming a file
import { readFileSync } from "fs";
import WebSocket from "ws";
const ws = new WebSocket(
"wss://audio.lansonai.com/v1/audio/transcriptions/stream",
{ headers: { Authorization: "Bearer sk-..." } }
);
ws.on("open", () => {
// Read pre-converted PCM16LE 16kHz mono audio
const audio = readFileSync("audio.pcm");
const FRAME_BYTES = 3200; // 100ms at 16kHz 16-bit mono
let offset = 0;
const sendFrame = () => {
if (offset >= audio.length) {
ws.send(JSON.stringify({ type: "input_audio_buffer.flush" }));
return;
}
const frame = audio.slice(offset, offset + FRAME_BYTES);
ws.send(frame); // binary frame
offset += FRAME_BYTES;
setTimeout(sendFrame, 100); // simulate real-time
};
sendFrame();
});
ws.on("message", (data) => {
const event = JSON.parse(data.toString());
if (event.type === "conversation.item.input_audio_transcription.completed") {
console.log(`[${event.utterance_index}] ${event.text}`);
}
});
Converting audio server-side
ffmpeg -i input.mp3 -ar 16000 -ac 1 -c:a pcm_s16le output.pcm
Connection management
- Keep the connection alive by sending frames at a steady rate
- If audio source pauses, send silent frames to avoid idle timeout
- Close explicitly when done to flush meter data
- For long-running streams, monitor session duration limits
Token management
Server-side connections do not need session tokens. Use Authorization: Bearer sk-... in the WebSocket upgrade headers.
Related
- Realtime Quickstart — basic examples
- Audio Input — format requirements
- Connection Lifecycle — timeouts