# Fish Audio S2 Pro - Core.Today AI API

> Fish Audio S2-generation TTS: 80+ languages, bracketed natural-language emotion and tone tags, Voice Library voices. Same price as S2.1 Pro; kept for pipelines tuned on S2. Billed per UTF-8 byte.

- **Provider**: Fish Audio
- **Model ID**: fishaudio/s2-pro
- **Category**: Audio & TTS
- **Credits**: 105 per 1,000 Korean characters (0.034875 credits per UTF-8 byte; ~35 credits per 1,000 English characters)
- **Speed**: Fast
- **Quality**: High

## Features
- 80+ languages from a single model
- Bracketed natural-language emotion and tone tags ([sad], [shouting], [sighing])
- Voice Library voices via reference_id, plus cloned voices
- Same price as S2.1 Pro — keep it for pipelines tuned on S2
- mp3 / wav / opus output, speed and volume prosody control

## Use Cases
- Korean narration for shorts, ads and explainer videos
- Multilingual product voice-overs from one model
- Audiobooks and long-form storytelling with emotion tags
- Announcements and IVR prompts
- Podcast intros and character voices

## API Endpoint

Base URL: https://api.core.today/v1
Create Prediction: POST /predictions
Get Status: GET /predictions/{job_id}

## Authentication
Header: X-API-Key: YOUR_API_KEY

## Input Parameters

### Required
- **text**: string - Text to synthesize (UTF-8). Billed by UTF-8 bytes — one Korean character is 3 bytes. Emotion, tone and effect cues go in brackets before the text they steer, e.g. [sad] I missed you, [shouting], [sighing], [long-break].

### Optional
- **reference_id**: string (default: 2f06c7a428e9431fadd60af4dfe91763) - Voice ID (32-hex id from the Fish Audio Voice Library). 37 curated voices (15 Fish Official Korean, 18 Korean community, 4 robot/character) can be previewed and copied from the Voice Gallery on this model's Core.Today Docs page (docs/models/fishaudio/…); any other public or cloned voice id works too — you are responsible for the rights to the voice you pass.
- **format**: string (default: mp3) - Output audio format.
  Options: mp3, wav, opus
- **mp3_bitrate**: integer (default: 128) - MP3 bitrate in kbps (mp3 only).
  Options: 64, 128, 192
- **speed**: number (default: 1.0) - Speaking rate multiplier, 0.5–2.0 (1.0 = default).
- **volume**: number (default: 0) - Volume adjustment in dB, -20 to 20 (0 = default).
- **latency**: string (default: balanced) - balanced favors low latency (default); normal favors stability — a good choice for batch generation.
  Options: balanced, normal
- **normalize**: boolean (default: true) - Expand numbers, dates and units into spoken form.
- **temperature**: number (default: 0.7) - Sampling temperature, 0.1–1.0. Lower is more consistent, higher more expressive.
- **top_p**: number (default: 0.7) - Nucleus sampling probability mass, 0.1–1.0.
- **chunk_length**: integer (default: 200) - Internal chunk length, 100–300. Affects phrasing of long passages.

## Examples

### Core.Today intro
Same script as the voice gallery, rendered by S2 Pro.
```json
{
  "model": "fishaudio/s2-pro",
  "input": {
    "text": "안녕하세요, 코어닷투데이입니다. 하나의 API 키로 이미지, 영상, 음성 생성 모델을 모두 연결해 보세요.",
    "reference_id": "29da56534ac84ccd81092be4359a1639",
    "format": "mp3"
  }
}
```

### Emotion tags
Bracketed natural-language cues, same syntax as S2.1 Pro.
```json
{
  "model": "fishaudio/s2-pro",
  "input": {
    "text": "[calm] 오늘의 사용량 리포트를 읽어 드릴게요. [emphasis] 크레딧이 20% 남았습니다.",
    "reference_id": "d74f023d1525420797aed41b5d421c05"
  }
}
```

## Response Format
```json
{
  "job_id": "abc123",
  "status": "pending | processing | completed | failed",
  "result": "URL or data (when completed)"
}
```

## Usage Flow
1. POST /predictions with model and input -> receive job_id
2. GET /predictions/{job_id} -> poll until status is completed or failed
3. Result contains output URL(s)

## Tips
- The 15 Fish Official Korean voices (지우, 민준, …) are designed by Fish rather than cloned from a person, which makes their rights position the simplest — a good baseline to compare against
- The 4 robot voices are registered as English but were measured on Korean: our gateway synthesized a Korean line and our own ASR transcribed it back at 0.85–0.97 similarity. Voices that failed that test are not in the gallery
- Voices cloned from named characters or identifiable voice actors are deliberately absent. You can still pass any reference_id to the API — the rights to that voice are yours to clear
- Prefer S2.1 Pro for new work — same price, better quality and latency; S2 Pro is here for pipelines already tuned on it
- Bracket tags work the same as S2.1 Pro: [happy], [whispering], [break]
- Korean is 3 UTF-8 bytes per character — 1,000 Korean characters cost about 105 credits
- The docs Voice Gallery samples were rendered with S2.1 Pro; the voice ids are identical, only the model differs

## Documentation
https://docs.fish.audio/features/text-to-speech