Fish Audio S2-Pro

Fish Audio S2-Pro is a text-to-speech model served through /v1/audio/speech. It supports plain TTS, voice cloning with a reference clip, and streaming audio chunks.

Prerequisites

Install sglang-omni by following Installation.

Fish Audio uses the Descript DAC codec, which is not included in the base sglang-omni package. From the SGLang-Omni repository root, install its model-specific dependencies:

uv pip install \
  "descript-audiotools==0.7.2" \
  "descript-audio-codec==1.0.0"

Then download the model:

hf download fishaudio/s2-pro

Server Configuration

sgl-omni serve \
  --model-path fishaudio/s2-pro \
  --config examples/configs/s2pro_tts.yaml \
  --port 8000

Reference audio encoding runs on GPU 0 in the preprocessing process by default, using the checkpoint’s FP32 codec. Tokenization and audio loading remain on CPU. The preprocessing process has a 6 GiB PyTorch allocator limit; this is a memory budget, not a reference-duration limit or a reservation of all GPU allocations. Long references can exceed it and fail encoding.

Set --preprocessing.total_reserve_bytes 8GiB to increase the budget, while leaving enough GPU memory for the autoregressive engine and vocoder. To encode references on CPU instead, clear both the GPU placement and its budget:

sgl-omni serve \
  --model-path fishaudio/s2-pro \
  --config examples/configs/s2pro_tts.yaml \
  --preprocessing.gpu null \
  --preprocessing.total_reserve_bytes null \
  --port 8000

Synthesize Speech

Plain TTS:

curl -X POST http://localhost:8000/v1/audio/speech \
  -H "Content-Type: application/json" \
  -d '{
    "model": "fishaudio/s2-pro",
    "voice": "default",
    "input": "Hello, how are you?"
  }' \
  --output output.wav

Voice cloning:

curl -X POST http://localhost:8000/v1/audio/speech \
  -H "Content-Type: application/json" \
  -d '{
    "model": "fishaudio/s2-pro",
    "voice": "default",
    "input": "Get the trust fund to the bank early.",
    "references": [{
      "audio_path": "https://huggingface.co/datasets/zhaochenyang20/seed-tts-eval-mini/resolve/main/en/prompt-wavs/common_voice_en_10119832.wav",
      "text": "We asked over twenty different people, and they all said it was his."
    }]
  }' \
  --output output.wav

Streaming:

curl -N -X POST http://localhost:8000/v1/audio/speech \
  -H "Content-Type: application/json" \
  -d '{
    "model": "fishaudio/s2-pro",
    "voice": "default",
    "input": "Get the trust fund to the bank early.",
    "references": [{
      "audio_path": "https://huggingface.co/datasets/zhaochenyang20/seed-tts-eval-mini/resolve/main/en/prompt-wavs/common_voice_en_10119832.wav",
      "text": "We asked over twenty different people, and they all said it was his."
    }],
    "stream": true,
    "response_format": "pcm"
  }' \
  --output output.pcm

Request Parameters

Parameter	Type	Default	Description
model	string	served model	Served model identifier
input	string	required	Text to synthesize
voice	string	default	Voice identifier for non-reference requests
response_format	string	wav	Output audio format
speed	float	1.0	Playback speed multiplier
stream	bool	false	Stream raw PCM audio chunks
references	list	null	Reference clip for voice cloning. Each item has audio_path and text
ref_audio / ref_text	string	null	Shorthand for references[0].audio_path and references[0].text
max_new_tokens	int	2048	Maximum generated semantic tokens
temperature	float	0.8	Sampling temperature
top_p	float	0.8	Top-p sampling
top_k	int	30	Top-k sampling. It must be -1 or between 1 and 30
repetition_penalty	float	1.1	Repetition penalty

Known Limitations

• top_k is constrained to -1 or 1..30; keep requests inside this range because invalid values currently fail the S2-Pro pipeline instead of returning a clean parameter error.

• Reference quality strongly affects cloned voice quality.

• Use streaming for interactive playback; CLI inspection of raw audio responses is awkward.