sipgate-ai STT

Speech-to-text API. OpenAI- and ElevenLabs-compatible interfaces on the same key — point whichever SDK you already use at this host.

👉 Interactive playground — try batch & realtime transcription in the browser, no setup.

Endpoints

Authentication

One API key works for both protocols and all endpoints (except /healthz). Send via whichever header your client library already speaks:

Authorization: Bearer <key>       # OpenAI SDKs
xi-api-key: <key>                 # ElevenLabs SDKs

WebSocket clients that can't set custom headers (browsers) also accept the key via the Sec-WebSocket-Protocol subprotocol entry (bearer.<key>) or the ?api_key= / ?token= query parameter.

Models

Pass the model identifier in the model (OpenAI) or model_id (ElevenLabs) field. Authenticated clients can list the available identifiers via /v1/models. Provider-default names from the OpenAI and ElevenLabs SDKs are accepted without modification.

Realtime streaming (WebSocket)

Two bidirectional WebSocket surfaces — the client streams PCM audio up while the server streams transcripts back. These are not in the Swagger/OpenAPI spec: OpenAPI cannot describe WebSocket endpoints. Both pick a backend from the requested model the same way the batch endpoints do, and authenticate with the same key (see above).

WS /v1/realtime — OpenAI Realtime style

Client → server (JSON text frames):

• input_audio_buffer.append — {"audio": "<base64 PCM16LE>"}
• input_audio_buffer.commit (or response.create) — finalise the current utterance
• session.update — optional language hint mid-session

Server → client (JSON):

• session.created
• conversation.item.input_audio_transcription.delta — {"delta": "…"} (incremental)
• input_audio_buffer.committed then conversation.item.input_audio_transcription.completed — {"transcript": "…"}
• error

WS /v1/speech-to-text/realtime — ElevenLabs Realtime style

Connection config is passed as query parameters:

• model_id — backend selector (optional)
• encoding / audio_format — must be pcm_<rate> (default pcm_16000)
• sample_rate — default 16000 (vLLM backends require 16000)
• commit_strategy — manual (default) or vad (server endpoints on silence)
• language_code — optional hint
• include_timestamps — true/false
• VAD tuning (when commit_strategy=vad): vad_threshold, min_speech_duration_ms, vad_silence_threshold_secs

Client → server (JSON): {"audio_base_64": "<base64 PCM>"} to stream audio, {"commit": true} to finalise (when manual).
Server → client (JSON, discriminated by message_type): session_started, partial_transcript {"text": "…"}, committed_transcript (or committed_transcript_with_timestamps) {"text": "…"}, error.

Quick examples

OpenAI-style batch:

curl -X POST https://stt.sipgate.ai/v1/audio/transcriptions \
  -H "Authorization: Bearer $KEY" \
  -F file=@sample.wav \
  -F language=de \
  -F response_format=verbose_json

ElevenLabs-style batch with raw PCM (skips server-side ffmpeg, lower latency):

ffmpeg -i sample.wav -f s16le -ac 1 -ar 16000 sample.pcm
curl -X POST https://stt.sipgate.ai/v1/speech-to-text \
  -H "xi-api-key: $KEY" \
  -F file=@sample.pcm \
  -F file_format=pcm_s16le_16 \
  -F language_code=deu

WebSocket streaming (ElevenLabs flavour, with websocat):

websocat -t "wss://stt.sipgate.ai/v1/speech-to-text/realtime?\
encoding=pcm_16000&sample_rate=16000&\
commit_strategy=MANUAL&language_code=deu&token=$KEY"

API documentation

• Interactive Swagger UI — /docs
• ReDoc — /redoc
• Raw OpenAPI spec — /openapi.json