Pulse (Realtime)

Query Parameters

The WebSocket connection accepts the following query parameters:

Audio Configuration

Parameter	Type	Default	Description
`encoding`	string	`linear16`	Audio encoding format. Options: `linear16`, `linear32`, `alaw`, `mulaw`, `opus`, `ogg_opus`
`sample_rate`	string	`16000`	Audio sample rate in Hz. Options: `8000`, `16000`, `22050`, `24000`, `44100`, `48000`

Language & Detection

Parameter	Type	Default	Description
`language`	string	`en`	Language code for transcription. Use `multi` for automatic language detection. Supported: `it`, `es`, `en`, `pt`, `hi`, `de`, `fr`, `uk`, `ru`, `kn`, `ml`, `pl`, `mr`, `gu`, `cs`, `sk`, `te`, `or`, `nl`, `bn`, `lv`, `et`, `ro`, `pa`, `fi`, `sv`, `bg`, `ta`, `hu`, `da`, `lt`, `mt`, `multi`

Feature Flags

Parameter	Type	Default	Description
`word_timestamps`	string	`true`	Include word-level timestamps in transcription. Options: `true`, `false`
`full_transcript`	string	`false`	Include cumulative transcript received till now in responses where `is_final` is `true`. Options: `true`, `false`
`sentence_timestamps`	string	`false`	Include sentence-level timestamps (utterances) in transcription. Options: `true`, `false`
`redact_pii`	string	`false`	Redact personally identifiable information (name, surname, address). Options: `true`, `false`
`redact_pci`	string	`false`	Redact payment card information (credit card, CVV, zip, account number). Options: `true`, `false`
`numerals`	string	`auto`	”Convert spoken numerals into digit form (e.g., ‘twenty five’ to ‘25’) and `auto` enables automatic detection based on context. Options: `true`, `false`, `auto`
`diarize`	string	`false`	Enable speaker diarization to identify and label different speakers in the audio. When enabled, each word in the transcription includes `speaker` (integer ID) and `speaker_confidence` (float 0-1) fields. Options: `true`, `false`
`keywords`	string	—	Comma-separated list of words/phrases to boost, each optionally followed by `:INTENSIFIER` (e.g. `NVIDIA:5,Jensen`). Intensifier defaults to `1.0` if omitted. Max 100 keywords per session. See Keyword Boosting

Webhook Configuration

Connection Flow

Example Connection URL

const url = new URL("wss://api.smallest.ai/waves/v1/pulse/get_text");
url.searchParams.append("language", "en");
url.searchParams.append("encoding", "linear16");
url.searchParams.append("sample_rate", "16000");
url.searchParams.append("word_timestamps", "true");
url.searchParams.append("full_transcript", "true");
url.searchParams.append("sentence_timestamps", "true");
url.searchParams.append("redact_pii", "true");
url.searchParams.append("redact_pci", "true");
url.searchParams.append("numerals", "true");
url.searchParams.append("diarize", "true");
url.searchParams.append("keywords", "NVIDIA:5,Jensen:4");

const ws = new WebSocket(url.toString(), {
  headers: {
    Authorization: `Bearer ${API_KEY}`,
  },
});

Input Messages

Audio Data (Binary)

Send raw audio bytes as binary WebSocket messages:

const audioChunk = new Uint8Array(4096);
ws.send(audioChunk);

End Signal (JSON)

Signal the end of audio stream. This is used to flush the transcription and receive the final response with is_last=true:

{
  "type": "finalize"
}

Response Format

The server responds with JSON messages containing transcription results:

{
  "session_id": "sess_12345abcde",
  "transcript": "Hello, how are you?",
  "is_final": true,
  "is_last": false,
  "language": "en"
}

Response Fields

Field	Type	Description
`session_id`	string	Unique identifier for the transcription session
`transcript`	string	Partial or complete transcription text for the current segment
`is_final`	boolean	Indicates if this is the final transcription for the current segment
`is_last`	boolean	Indicates if this is the last transcription in the session
`language`	string	Detected primary language code, returns only when `is_final=True`
`languages`	array	List of languages detected in the audio included in Responses where `is_final` is `true`

Optional Response Fields (Based on Query Parameters)

Field	Type	When Included	Description
`full_transcript`	string	`full_transcript=true` AND `is_final=true`	Complete transcription text accumulated till now. Only present in responses when `full_transcript=true` query parameter is set AND `is_final=true`
`words`	array	`word_timestamps=true`	Word-level timestamps with `word`, `start`, `end`, and `confidence` fields. When `diarize=true`, also includes `speaker` and `speaker_confidence` fields
`utterances`	array	`sentence_timestamps=true`	Sentence-level timestamps with `text`, `start`, and `end` fields
`redacted_entities`	array	`redact_pii=true` or `redact_pci=true`	List of redacted entity placeholders (e.g., `[FIRSTNAME_1]`, `[CREDITCARDCVV_1]`)

Example Response with All Features

{
  "session_id": "sess_12345abcde",
  "transcript": "[CREDITCARDCVV_1] and expiry [TIME_2].",
  "is_final": true,
  "is_last": true,
  "full_transcript": "Hi, my name is [FIRSTNAME_1] [FIRSTNAME_2] You can reach me at [PHONENUMBER_1] and I paid using my Visa card [ZIPCODE_1] [ACCOUNTNUMBER_1] with [CREDITCARDCVV_1] and expiry [TIME_1].",
  "language": "en",
  "languages": ["en"],
  "words": [
    {
      "word": "[creditcardcvv_1]",
      "start": 15.44,
      "end": 17.36,
      "confidence": 0.97,
      "speaker": 0,
      "speaker_confidence": 0.67
    },
    {
      "word": "and",
      "start": 18.0,
      "end": 18.32,
      "confidence": 0.94,
      "speaker": 0,
      "speaker_confidence": 0.76
    },
    {
      "word": "expiry",
      "start": 18.32,
      "end": 19.2,
      "confidence": 1.0,
      "speaker": 0,
      "speaker_confidence": 0.91
    },
    {
      "word": "[time_2]",
      "start": 19.2,
      "end": 19.92,
      "confidence": 0.91,
      "speaker": 0,
      "speaker_confidence": 0.82
    },
  ],
  "utterances": [
    {
      "text": "Hi, my name is Hans Miller.",
      "start": 0.0,
      "end": 2.64,
      "speaker": 0
    },
    {
      "text": "You can reach me at [PHONENUMBER_1], and I paid using my Visa card 4242 42424242 with CVV123 and expiry [TIME_1].",
      "start": 2.64,
      "end": 21.04,
      "speaker": 0
    }
  ],
  "redacted_entities": [
    "[CREDITCARDCVV_1]",
    "[TIME_2]"
  ]
}

Code Examples

import asyncio
import json
import argparse
import numpy as np
import websockets
import librosa
from urllib.parse import urlencode

BASE_WS_URL = "wss://api.smallest.ai/waves/v1/pulse/get_text"

async def stream_audio(audio_file, api_key, language="en", encoding="linear16", sample_rate=16000, word_timestamps="true", full_transcript="false", sentence_timestamps="false", redact_pii="false", redact_pci="false", numerals="auto", diarize="false"):
    params = {
        "language": language,
        "encoding": encoding,
        "sample_rate": sample_rate,
        "word_timestamps": word_timestamps,
        "full_transcript": full_transcript,
        "sentence_timestamps": sentence_timestamps,
        "redact_pii": redact_pii,
        "redact_pci": redact_pci,
        "numerals": numerals,
        "diarize": diarize
    }
    ws_url = f"{BASE_WS_URL}?{urlencode(params)}"
    
    async with websockets.connect(ws_url, additional_headers={"Authorization": f"Bearer {api_key}"}) as ws:
        print(f"Connected: {ws_url}")
        
        async def send():
            audio, _ = librosa.load(audio_file, sr=sample_rate, mono=True)
            chunk_size = int(0.160 * sample_rate)
            
            for i in range(0, len(audio), chunk_size):
                chunk = audio[i:i + chunk_size]
                await ws.send((chunk * 32768.0).astype(np.int16).tobytes())
                await asyncio.sleep(len(chunk) / sample_rate)
            
            await ws.send(json.dumps({"type": "finalize"}))
        
        sender = asyncio.create_task(send())
        
        async for message in ws:
            data = json.loads(message)
            print("Received:", json.dumps(data, indent=2))
            if data.get("is_last"):
                break
        
        await sender

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("audio_file", nargs="?", default="path/to/audio.wav")
    parser.add_argument("--api-key", "-k", default="your_api_key_here")
    parser.add_argument("--language", "-l", default="en")
    parser.add_argument("--encoding", "-e", default="linear16")
    parser.add_argument("--sample-rate", "-sr", type=int, default=16000)
    parser.add_argument("--word-timestamps", "-wt", default="true")
    parser.add_argument("--full-transcript", "-ft", default="false")
    parser.add_argument("--sentence-timestamps", "-st", default="false")
    parser.add_argument("--redact-pii", default="false")
    parser.add_argument("--redact-pci", default="false")
    parser.add_argument("--numerals", default="auto")
    parser.add_argument("--diarize", default="false")
    
    args = parser.parse_args()
    asyncio.run(stream_audio(
        args.audio_file,
        args.api_key,
        args.language,
        args.encoding,
        args.sample_rate,
        args.word_timestamps,
        args.full_transcript,
        args.sentence_timestamps,
        args.redact_pii,
        args.redact_pci,
        args.numerals,
        args.diarize
    ))

API References

Text to Speech

Speech to Text

Voices

Voice Cloning

Pronunciation Dictionaries

Pulse (Realtime)

Query Parameters

Audio Configuration

Language & Detection

Feature Flags

Webhook Configuration

Connection Flow

Example Connection URL

Input Messages

Audio Data (Binary)

End Signal (JSON)

Response Format

Response Fields

Optional Response Fields (Based on Query Parameters)

Example Response with All Features

Code Examples

​Query Parameters

​Audio Configuration

​Language & Detection

​Feature Flags

​Webhook Configuration

​Connection Flow

​Example Connection URL

​Input Messages

​Audio Data (Binary)

​End Signal (JSON)

​Response Format

​Response Fields

​Optional Response Fields (Based on Query Parameters)

​Example Response with All Features

​Code Examples

Query Parameters

Audio Configuration

Language & Detection

Feature Flags

Webhook Configuration

Connection Flow

Example Connection URL

Input Messages

Audio Data (Binary)

End Signal (JSON)

Response Format

Response Fields

Optional Response Fields (Based on Query Parameters)

Example Response with All Features

Code Examples