StepAudio 2.5 ASR Stream | EmpirioLabs AI Docs

StepFun · Transcription

WEBSOCKET /v1/realtime

Live transcription over a socket, returning partial results as the speaker talks, with voice activity detection marking each sentence.

At a glance

Field	Value
Model id	`stepaudio-2-5-asr-stream`
Model release date	2026-07-16
Input modalities	Audio
Output modalities	Text
Context window	-
Weight precision	-
Region	International
Features	transcription, speech_to_text, realtime, streaming_asr
Native inference	No
New	Yes
Supported endpoints	`WEBSOCKET /v1/realtime`
Alternate model ids	`stepaudio-2.5-asr-stream`, `stepfun/stepaudio-2-5-asr-stream`

Pricing

Charge	Spec	Rate
Transcription	per hour of audio	$0.18

Example request

curl https://api.empiriolabs.ai/v1/audio/transcriptions \
  -H 'Authorization: Bearer $EMPIRIOLABS_API_KEY' \
  -F model=stepaudio-2-5-asr-stream \
  -F file=@meeting.mp3

Parameters

This model accepts the standard chat completion parameters (see the API reference).

Notes

Live transcription over a WebSocket at wss://api.empiriolabs.ai/v1/realtime?model=stepaudio-2-5-asr-stream, authenticated with the ordinary Authorization Bearer header. Stream 16 kHz pcm16 audio up with input_audio_buffer.append and read partial results back as the speaker is still talking, with server-side voice activity detection marking where each sentence ends. Use this for live captions and voice input; for a finished recording, POST /v1/audio/transcriptions returns the whole transcript in one call. Billing follows the duration of audio you stream, settled when the session closes.

Machine-readable schema: GET https://api.empiriolabs.ai/v1/models/stepaudio-2-5-asr-stream.