Text to Speech

The Text to Speech (TTS) service converts written text into spoken audio. The unified POST /tasks/audio/speech endpoint is served by the RunPod Orpheus-3B deployment (sunbird-orpheus-tts) — multilingual and multi-speaker, covering 20 African languages with 40+ voices. Voices are catalog tags (e.g. salt_lug_0001); list them with GET /tasks/voice/speakers.

Breaking change (v2.1). This endpoint previously accepted model, platform, and max_new_audio_tokens, and offered a spark-tts model. RunPod Orpheus is now the only TTS backend: those parameters are rejected, and the legacy per-provider routes (/tasks/modal/tts, /tasks/runpod/tts, /tasks/modal/orpheus/*, /tasks/tts, the /stream* and speaker-listing routes, and refresh-url) were removed. Use the endpoints below.

Single Synthesis

Parameters

Parameter	Type	Required	Description
`text`	string	Yes	The text to convert to speech.
`voice`	string	No	Orpheus speaker catalog tag (see `GET /tasks/voice/speakers`). If omitted, a speaker is chosen for `language` (Luganda by default).
`language`	string	No	ISO 639-3 code (e.g. `lug`) or full name.
`response_mode`	string	No	`url` (default), `stream`, or `both` — see Response Modes.
`temperature`, `top_p`, `repetition_penalty`	number	No	Sampling knobs.
`max_tokens`	integer	No	Max tokens per chunk.
`seed`	integer	No	Deterministic seed.

import os
import requests
from dotenv import load_dotenv

load_dotenv()

url = "https://api.sunbird.ai/tasks/audio/speech"
access_token = os.getenv("AUTH_TOKEN")

headers = {
    "accept": "application/json",
    "Authorization": f"Bearer {access_token}",
    "Content-Type": "application/json",
}

payload = {
    "text": "I am a nurse who takes care of many people.",
    "voice": "salt_lug_0001",     # catalog tag; see GET /tasks/voice/speakers
    "language": "eng",            # ISO code or full name; picks a voice if none given
    "response_mode": "url",       # "url" (default), "stream", or "both"
}

response = requests.post(url, headers=headers, json=payload)
print(response.status_code)
print(response.json())

const response = await fetch('https://api.sunbird.ai/tasks/audio/speech', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer <YOUR_TOKEN>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    text: 'I am a nurse who takes care of many people.',
    voice: 'salt_lug_0001',
    language: 'eng',
    response_mode: 'url'
  })
});
console.log(await response.json());

Response

{
  "audio_url": "https://storage.googleapis.com/.../tts_audio/....wav?...",
  "model": "sunbird-orpheus-tts",
  "platform": "runpod",
  "voice": "salt_lug_0001",
  "audio_url_expires_at": "2026-06-03T22:59:36.954061Z",
  "language": "lug",
  "sample_rate": 24000,
  "duration_seconds": 4.0,
  "gcs_object": "orpheus_tts/2026-06-03/....wav",
  "request_id": "0f1e2d3c4b5a...",
  "usage": { "input_characters": 43, "output_audio_bytes": 192044, "duration_seconds": 4.0 },
  "timings_ms": {"inference_ms": 1820.5, "upload_ms": 234.1, "total_ms": 2095.6}
}

The audio_url is a temporary signed URL valid for ~30 minutes. Download or stream the audio promptly, or re-sign it with GET /tasks/audio/speech/url.

Response Modes

response_mode controls how the audio is returned:

url — synthesize, upload to GCP, return a signed URL (valid ~30 minutes) — default
stream — stream the raw audio bytes straight back (constant client memory; no GCS upload)
both — stream the raw audio bytes and return the signed URL in the X-Audio-Url response header

RunPod synthesizes the full waveform before sending the first byte, so stream bounds client memory but does not reduce time-to-first-audio.

Languages and Voices

Speaker IDs encode both the source corpus (salt_*, waxal_*, slr32_*, slr129_*, bateesa_*) and the language. Languages marked with an em dash are present in the model’s training mix but do not currently expose individual voice IDs in this checkpoint.

Config	Language	Region	Speaker IDs
`ach`	Acholi	Uganda, South Sudan	`salt_ach_0001`, `waxal_ach_0001`, `waxal_ach_0005`, `waxal_ach_0006`, `waxal_ach_0008`
`afr`	Afrikaans	South Africa, Namibia	`slr32_afr_0009`
`eng`	English	(control language)	`salt_eng_0001`, `salt_eng_0002`, `salt_eng_0003`
`ewe`	Ewe	Ghana, Togo	`slr129_ewe_0001`
`ful`	Fulah	West Africa (Sahel)	`waxal_ful_0003`, `waxal_ful_0004`, `waxal_ful_0006`
`hau`	Hausa	Nigeria, Niger, Chad	`waxal_hau_0004`, `waxal_hau_0006`, `waxal_hau_0007`, `waxal_hau_0008`
`ibo`	Igbo	Nigeria	`waxal_ibo_0003`, `waxal_ibo_0005`, `waxal_ibo_0008`
`kik`	Kikuyu	Kenya	`waxal_kik_0003`, `waxal_kik_0004`
`kin`	Kinyarwanda	Rwanda	`bateesa_kin_0001`
`lgg`	Lugbara	Uganda, DRC	—
`lin`	Lingala	DRC, Republic of Congo	`slr129_lin_0001`
`lug`	Luganda	Uganda	`salt_lug_0001`, `waxal_lug_0002`–`waxal_lug_0008`
`luo`	Luo (Dholuo)	Kenya, Tanzania	`waxal_luo_0001`–`waxal_luo_0004`
`nyn`	Runyankole	Uganda	`salt_nyn_0001`, `waxal_nyn_0003`, `waxal_nyn_0004`, `waxal_nyn_0007`, `waxal_nyn_0008`
`sot`	Sesotho	Lesotho, South Africa	—
`swa`	Swahili	East Africa	`waxal_swa_0006`, `waxal_swa_0007`
`teo`	Ateso	Uganda, Kenya	`salt_teo_0001`
`tsn`	Setswana	Botswana, South Africa	—
`xho`	Xhosa	South Africa	`slr32_xho_0012`
`yor`	Yoruba	Nigeria, Benin	`waxal_yor_0002`, `waxal_yor_0006`, `waxal_yor_0008`

Per-language quality scales with the amount of training data collected for that language. Audition the voices before relying on a particular speaker — use the discovery snippet under Listing Voices.

Listing Voices

auth = {"Authorization": f"Bearer {access_token}"}

# Orpheus voices grouped by language (default)
print(requests.get("https://api.sunbird.ai/tasks/voice/speakers", headers=auth).json())

# Voices for one language
print(requests.get(
    "https://api.sunbird.ai/tasks/voice/speakers",
    headers=auth,
    params={"language": "lug"},
).json())

Batch Synthesis

Synthesize up to 16 items in a single request (RunPod cap). Per-item failures are reported with status="error"; the request returns 200 if at least one item succeeds and 502 if every item fails.

url = "https://api.sunbird.ai/tasks/audio/speech/batch"
payload = {
    "items": [
        {"text": "Good morning.", "voice": "salt_lug_0001"},
        {"text": "How are you?", "voice": "salt_eng_0001"},
    ]
}
response = requests.post(url, headers=headers, json=payload)
print(response.json())

Refreshing an Expired URL

Signed URLs expire after ~30 minutes. Re-sign a stored object with GET /tasks/audio/speech/url:

print(requests.get(
    "https://api.sunbird.ai/tasks/audio/speech/url",
    headers={"Authorization": f"Bearer {access_token}"},
    params={"gcs_object": "orpheus_tts/2026-06-03/abc.wav"},
).json())

Getting Started

Guides

Support

Single Synthesis

Parameters

Response

Response Modes

Languages and Voices

Listing Voices

Batch Synthesis

Refreshing an Expired URL

​Single Synthesis

​Parameters

​Response

​Response Modes

​Languages and Voices

​Listing Voices

​Batch Synthesis

​Refreshing an Expired URL

Single Synthesis

Parameters

Response

Response Modes

Languages and Voices

Listing Voices

Batch Synthesis

Refreshing an Expired URL