Sentence-level timestamps

Sentence-level timestamps (utterances) are supported in both Pre-Recorded and Real-Time transcription APIs. The utterances array aggregates contiguous words into sentence-level segments, providing structured timing information for longer audio chunks.

Enabling sentence-level timestamps

Pre-Recorded API

For the Pre-Recorded API, set word_timestamps=true in your query parameters. When word timestamps are enabled, the response includes both words and utterances arrays.

$
curl --request POST \
>
  --url "https://waves-api.smallest.ai/api/v1/pulse/get_text?model=pulse&language=en&word_timestamps=true&diarize=true" \
>
  --header "Authorization: Bearer $SMALLEST_API_KEY" \
>
  --header "Content-Type: audio/wav" \
>
  --data-binary "@/path/to/audio.wav"

Real-Time API (WebSocket)

For the Real-Time WebSocket API, set sentence_timestamps=true as a query parameter when establishing the WebSocket connection.

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const url = new URL("wss://waves-api.smallest.ai/api/v1/pulse/get_text");
2
url.searchParams.append("language", "en");
3
url.searchParams.append("sentence_timestamps", "true");
4
5
const ws = new WebSocket(url.toString(), {
6
  headers: {
7
    Authorization: `Bearer ${API_KEY}`,
8
  },
9
});

Output format

Each utterances entry contains text, start, end, and optional speaker fields (when diarization is enabled). Use these sentence-level timestamps when you need to display readable captions, synchronize larger chunks of audio, or store structured call summaries.

Sample response

Pre-Recorded API

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{
2
  "status": "success",
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  "transcription": "Hello world. How are you?",
4
  "words": {...}
5
  "utterances": [
6
    { "text": "Hello world.", "start": 0.0, "end": 0.9, "speaker": "speaker_0" },
7
    { "text": "How are you?", "start": 1.0, "end": 2.1, "speaker": "speaker_1" }
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  ]
9
}

Real-Time API (WebSocket)

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{
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  "session_id": "sess_12345abcde",
3
  "transcript": "Hello world. How are you?",
4
  "is_final": true,
5
  "is_last": false,
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  "language": "en",
7
  "utterances": [
8
    { "text": "Hello world.", "start": 0.0, "end": 0.9 },
9
    { "text": "How are you?", "start": 1.0, "end": 2.1 }
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  ]
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}