> ## Documentation Index
> Fetch the complete documentation index at: https://slng.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Parameters coverage

> Compatibility matrix for the SLNG Unified API. Which TTS and STT request parameters are supported by Deepgram, ElevenLabs, Cartesia, Sarvam, and Rime.

The SLNG Unified API accepts a common set of parameters across all providers. Some parameters are universal, others depend on the model. Provider-specific values (like voice identifiers or language codes) are passed through the same fields. The platform forwards them to the underlying provider.

## TTS parameters

| Parameter | Type | Required | Description |
| - | - | - | - |
| `text` | string | Yes | Text to synthesize |
| `voice` | string | No | Voice identifier. Accepted values depend on the provider and model |
| `config.sample_rate` | integer | No | Output sample rate in Hz |
| `config.encoding` | string | No | Output encoding format |
| `config.language` | string | No | Language code. Accepted values depend on the provider |
| `config.speed` | number | No | Speech speed multiplier |

### TTS provider support

The matrix below covers the most commonly used SLNG-hosted models. Providers not listed here (Cartesia Sonic 3, Murf Falcon, Kugel, Soniox TTS v1) accept the same `text` and `voice` fields. Check each model's [API reference](https://slng.mintlify.site/api-reference) for the exact list of supported `config.*` fields.

| Parameter | Rime Arcana | Deepgram Aura 2 | Sarvam Bulbul |
| - | - | - | - |
| `voice` | Yes | Yes | Yes |
| `config.sample_rate` | Yes | Yes | Yes |
| `config.encoding` | Yes | Yes | Yes |
| `config.language` | Yes | Yes | Yes |
| `config.speed` | — | Yes | — |

### Provider-specific values

The `voice` and `config.language` fields accept provider-specific values. For example:

* **Rime Arcana** voices: `luna`, `orion`, `astra`, `nova`
* **Deepgram Aura 2** voices: `aura-2-thalia-en`, `aura-2-asteria-en`, `aura-2-celeste-es` (set the `voice` field explicitly)
* **Rime Arcana** language codes: `en`, `fr`, `es`, `hi`, `ar`, `de`
* **Cartesia Sonic 3**, **Murf Falcon**, **Kugel**, **Soniox TTS v1**: see the [voice catalog](https://slng.mintlify.site/voices) for each provider's `voice_id` values

The platform passes these values directly to the provider. If you send a voice identifier that the selected model does not support, the provider returns an error through the standard error response format.

### Supported sample rates and encodings

Sample-rate and encoding support varies by model and protocol. The Unified API uses a common request shape, but the selected model still controls which audio formats are valid.

| Model or endpoint family | Common sample rates | Encoding support | Notes |
| - | - | - | - |
| Unified TTS bridge | `8000`-`48000` Hz, model-dependent | `linear16`, `mp3`, `opus`, `mulaw`, `alaw` | Accepted by the bridge schema; the selected model may still reject unsupported values |
| Deepgram Aura 2, proxied | See endpoint reference | `linear16`, `mp3`, `opus` | Use the direct Aura 2 reference for provider-specific behavior |
| Deepgram Aura 2, SLNG-hosted | See endpoint reference | `linear16`, `mulaw`, `alaw` | Optimized for real-time and telephony-style output |
| Sarvam Bulbul | See endpoint reference | `mp3`, `linear16`, `mulaw`, `alaw`, `opus` | Indian-language TTS provider |
| Cartesia Sonic 3 | See endpoint reference | `linear16`, `mulaw`, `alaw` | Streaming TTS over WebSocket |

For exact allowed values, use the model-specific API reference page as the source of truth.

## STT parameters

| Parameter | Type | Required | Description |
| - | - | - | - |
| `audio` | file | Yes | Audio file to transcribe |
| `language` | string | No | Language code. Accepted values depend on the provider |
| `sample_rate` | integer | No | Audio sample rate in Hz |
| `encoding` | string | No | Audio encoding format |
| `enable_vad` | boolean | No | Enable voice activity detection |
| `enable_partials` | boolean | No | Enable partial transcription results |

### STT provider support

| Parameter | Deepgram Nova 3 | Deepgram Nova 2 | Soniox Speech AI v5 |
| - | - | - | - |
| `language` | Yes | Yes | Auto-detect |
| `sample_rate` | Yes | Yes | Yes |
| `encoding` | Yes | Yes | Yes |
| `enable_vad` | Yes | Yes | Yes |
| `enable_partials` | Yes | Yes | Yes |

### Supported STT encodings

`linear16`, `mp3`, `opus`.

## How provider-specific parameters work

The Unified API uses a schema-driven approach. All parameters are defined in the request schema. There is no generic passthrough or arbitrary key-value mechanism. The `voice`, `language`, and `config` fields accept provider-specific values as strings, and the platform forwards them to the underlying provider without transformation.

This means:

* You use the same field names regardless of provider
* Provider-specific values (voice names, language codes) go into the same fields
* Validation happens at the provider level. If a value is not supported, you get a standard error response with the provider's error message

## Model identifiers

Models follow the pattern `provider/model:variant` for third-party and `slng/provider/model:variant` for SLNG-hosted. For example:

* `deepgram/aura:2`: third-party, proxied to Deepgram
* `slng/deepgram/aura:2-en`: SLNG-hosted Deepgram Aura 2 (English)
* `slng/rime/arcana:3-en`: SLNG-hosted Rime Arcana v3 (English)

For the full list of model identifiers, see [Supported models](https://slng.mintlify.site/execution-layer/unified-api-models.md).


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