> ## Documentation Index
> Fetch the complete documentation index at: https://gladia-95-feat-diarization-multi-channel.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Speaker Diarization

> Detect speakers and understand who said what.

<Badge color="blue" size="lg" icon="file-audio">
  Pre-recorded
</Badge>

Speaker diarization is the process of detecting multiple speakers in an audio, and understanding which parts of the transcription each speaker said.

<Info>
  On multi-channel audio, diarization runs separately on each channel (see [*with multi-channel audio*](#with-multi-channel-audio)).
</Info>

## Enabling diarization

Diarization is enabled by sending the `diarization` parameter in the transcription request:

```json Pre-recorded theme={"system"}
{
  "audio_url": "<your audio URL>",
  "diarization": true
}
```

## Response

When diarization is enabled, each utterance will contain a `speaker` field, whose value is an index representing the speaker.
Speakers will be assigned indexes by **order of appearance** (i.e. the 1st speaker will be speaker 0, the 2nd speaker 1, etc).

```json Pre-recorded theme={"system"}
{
  "transcription": {
    "utterances": [
      {
        "words": [...],
        "text": "it says you are trained in technology.",
        "language": "en",
        "start": 0.7334100000000001,
        "end": 2.364,
        "confidence": 0.8914285714285715,
        "channel": 0,
        "speaker": 0,
      },
      ...
    ]
  }
}
```

## Improving diarization accuracy

You can improve the accuracy of the diarization by providing the model with hints regarding the expected number or lower/upper bounds ofspeakers using the `diarization_config.num_of_speakers`, `diarization_config.min_speakers` and `diarization_config.max_speakers`  parameters respectively.

**Important:** These parameters are hints, not hard constraints. The actual number of speakers detected by the model may not comply with the provided parameters.

| Key                                     | Type   | Description                                                                                          |
| --------------------------------------- | ------ | ---------------------------------------------------------------------------------------------------- |
| `diarization_config.number_of_speakers` | number | Guiding number of speakers - instructs the model to detect an exact number of speakers in the audio. |
| `diarization_config.min_speakers`       | number | Instructs the model to detect no less than this number of speakers in the audio.                     |
| `diarization_config.max_speakers`       | number | Causes the model to detect no more than this number of speakers in the audio.                        |

## With multi-channel audio

When diarization is enabled on [multi-channel audio](/chapters/limits-and-specifications/multiple-channels), diarization runs separately on each channel. Diarization parameters (`number_of_speakers`, `min_speakers`, `max_speakers`) apply **per channel**.

Speaker indexes are then **normalized across channels** so IDs stay unique in the result. For example, with two channels and two speakers on each, speakers are numbered from `0` to `3` (four speakers total).

Because diarization is run independently per channel, the same physical speaker appearing on two channels will receive two different speaker IDs.