pocket-tts-onnx

Pocket TTS ONNX

ONNX export of Pocket TTS for lightweight multilingual text-to-speech with zero-shot voice cloning.

Model Description

Pocket TTS is a compact text-to-speech model from Kyutai that supports voice cloning from short audio samples. This ONNX export provides:

• Zero-shot voice cloning from any audio reference
• Multilingual bundles for english_2026-04, french_24l, german, german_24l, italian, italian_24l, portuguese, portuguese_24l, spanish, and spanish_24l
• INT8 quantized models for fast CPU inference
• Streaming support with adaptive chunking for real-time playback
• Temperature control for generation diversity
• Dual model architecture for flexible flow matching

Architecture

This export uses a dual model split for the Flow LM:

flow_lm_main   - Transformer/conditioner (produces conditioning vectors)
flow_lm_flow   - Flow network only (Euler integration for latent sampling)

This architecture enables:

• Temperature control: Adjust generation diversity via noise scaling
• Variable LSD steps: Trade off speed vs quality
• External flow loop: Full control over the sampling process

Performance

Performance depends on the selected language bundle, precision, CPU, and lsd_steps.

• 6-layer bundles such as english_2026-04, german, italian, portuguese, and spanish are much smaller and faster than the *_24l bundles.
• INT8 bundles substantially reduce flow_lm_main, flow_lm_flow, and mimi_decoder size for CPU inference.
• mimi_encoder.onnx and text_conditioner.onnx remain FP32.

Optimized Inference

Thread count is automatically tuned to avoid over-subscription on the small sequential matmuls in the autoregressive loop (intra_op_num_threads=min(cpu_count, 4), inter_op_num_threads=1). This alone provides a ~2x speedup over default ORT settings on multi-core machines.

Decoding Strategy

• Offline (generate): Uses threaded parallel decoding — the mimi decoder runs in a background thread, decoding 12-frame chunks while the flow loop generates the next frames. This overlaps generation and decoding for maximum throughput.
• Streaming (stream): Uses adaptive chunking (starts at 2 frames). This ensures instant start (low TTFB) while scaling up chunk sizes for throughput.

Usage

from pocket_tts_onnx import PocketTTSOnnx

# Load the English bundle (INT8 by default)
tts = PocketTTSOnnx(
    models_dir="onnx",
    language="english_2026-04",
)

# Generate speech with built-in voice state
audio = tts.generate(
    text="Hello, this is a test.",
    voice="alba",
)

# Generate speech with voice cloning from audio
audio = tts.generate(
    text="Hello, this is a test of voice cloning.",
    voice="reference_sample.wav"
)

# Save output
tts.save_audio(audio, "output.wav")

Temperature Control

Adjust generation diversity with the temperature parameter:

# More deterministic (lower temperature)
tts = PocketTTSOnnx(temperature=0.3)

# Default balance
tts = PocketTTSOnnx(temperature=0.7)

# More diverse/expressive (higher temperature)
tts = PocketTTSOnnx(temperature=1.0)

LSD Steps

Trade off speed vs quality with lsd_steps:

# Default
tts = PocketTTSOnnx(lsd_steps=1)

# Slower, potentially smoother
tts = PocketTTSOnnx(lsd_steps=4)

Streaming Mode

For real-time applications with low time-to-first-audio:

for chunk in tts.stream("Hello world!", voice="reference_sample.wav"):
    play_audio(chunk)  # Process each chunk as it arrives

Language Bundles

# German bundle with built-in voice
tts = PocketTTSOnnx(language="german", precision="fp32")
audio = tts.generate("Hallo zusammen. Dies ist ein deutscher Test.", voice="alba")

Built-in voice names are loaded from each bundle's metadata. Voice cloning also accepts:

• a reference audio path
• a .safetensors prompt-state file
• a precomputed embedding array

Legacy Layout

Root-level files under onnx/ and the root tokenizer.model are still present for backward compatibility with older integrations that expect the original single-model layout.

New integrations should use the per-language bundle directories under onnx/<language>/.

Command Line

python generate.py "Hello, this is a test." alba output.wav --language english_2026-04
python generate.py "Hallo zusammen." samples/reference.wav output.wav --language german --precision fp32

Files

pocket-tts-onnx/
├── onnx/
│   ├── flow_lm_main.onnx          # Legacy root-level file kept for backward compatibility
│   ├── flow_lm_main_int8.onnx     # Legacy root-level file kept for backward compatibility
│   ├── flow_lm_flow.onnx          # Legacy root-level file kept for backward compatibility
│   ├── flow_lm_flow_int8.onnx     # Legacy root-level file kept for backward compatibility
│   ├── mimi_decoder.onnx          # Legacy root-level file kept for backward compatibility
│   ├── mimi_decoder_int8.onnx     # Legacy root-level file kept for backward compatibility
│   ├── mimi_encoder.onnx          # Legacy root-level file kept for backward compatibility
│   ├── text_conditioner.onnx      # Legacy root-level file kept for backward compatibility
│   ├── english_2026-04/
│   │   ├── bundle.json
│   │   ├── tokenizer.model
│   │   ├── bos_before_voice.npy
│   │   ├── flow_lm_main.onnx
│   │   ├── flow_lm_main_int8.onnx
│   │   ├── flow_lm_flow.onnx
│   │   ├── flow_lm_flow_int8.onnx
│   │   ├── mimi_decoder.onnx
│   │   ├── mimi_decoder_int8.onnx
│   │   ├── mimi_encoder.onnx
│   │   └── text_conditioner.onnx
│   ├── german/
│   ├── german_24l/
│   ├── french_24l/
│   ├── italian/
│   ├── italian_24l/
│   ├── portuguese/
│   ├── portuguese_24l/
│   ├── spanish/
│   └── spanish_24l/
├── reference_sample.wav           # Example voice reference
├── tokenizer.model                # Legacy root tokenizer kept for backward compatibility
├── pocket_tts_onnx.py             # Inference wrapper
├── generate.py                    # CLI script
├── requirements.txt               # Python dependencies
└── README.md

Requirements

onnxruntime>=1.16.0
numpy
soundfile
sentencepiece
scipy  # Only needed if resampling from non-24kHz audio
huggingface_hub
safetensors

Install with:

pip install -r requirements.txt

Notes

• Each bundle is self-contained and includes its own tokenizer and metadata.
• Built-in voice states are fetched from kyutai/pocket-tts via Hugging Face.
• Voice cloning from audio uses the exported mimi_encoder.onnx.

License

• Models: CC BY 4.0 (inherited from kyutai/pocket-tts)
• Code: Apache 2.0

Prohibited Use

Use of our model must comply with all applicable laws and regulations and must not result in, involve, or facilitate any illegal, harmful, deceptive, fraudulent, or unauthorized activity. Prohibited uses include, without limitation, voice impersonation or cloning without explicit and lawful consent; misinformation, disinformation, or deception (including fake news, fraudulent calls, or presenting generated content as genuine recordings of real people or events); and the generation of unlawful, harmful, libelous, abusive, harassing, discriminatory, hateful, or privacy-invasive content. We disclaim all liability for any non-compliant use.

Acknowledgments

• Kyutai for the original Pocket TTS model