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Streaming Speech Translation Pipeline

Real-time English → Russian speech translation: Audio In → ASR → NMT → TTS → Audio Out Translates spoken English into spoken Russian with streaming output over WebSocket.

Input can only be English for now (due to ASR NeMo), while output language depending on TranslateGemma (NMT) and XTTSv2 (TTS). You can modify these accordingly.

Architecture

Audio Input → ASR (ONNX) → NMT (GGUF) → TTS (ONNX) → Audio Output
  (PCM16)   Conformer RNN-T  TranslateGemma  XTTSv2     (PCM16)

ASR: NVIDIA NeMo FastConformer RNN-T (cache-aware streaming, ONNX)
NMT: TranslateGemma 4B (GGUF Q8_0, llama-cpp-python) with streaming segmentation and translation merging
TTS: XTTSv2 with GPT-2 AR model + HiFi-GAN vocoder (ONNX), 24kHz output

See ARCHITECTURE.md for detailed design documentation.

Requirements

Python 3.12
CUDA 12.8, CUDNN 9
llama-cpp-python with GPU
onnxruntime with GPU
Model files:
- ASR: NeMo FastConformer RNN-T ONNX model directory
- NMT: TranslateGemma 4B GGUF file
- TTS: XTTSv2 ONNX model directory, BPE vocab, mel normalization stats, reference audio

Installation

For CUDA and CUDNN:

# uninstall, remove, and purge previous CUDA and CUDNN installation if they are not the correct versions
wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2404/x86_64/cuda-keyring_1.1-1_all.deb
sudo dpkg -i cuda-keyring_1.1-1_all.deb
sudo apt-get update
sudo apt-get install -y cuda-toolkit-12-8 cudnn9-cuda-12
echo 'export LD_LIBRARY_PATH=/usr/local/cuda-13.2/lib64:/usr/lib/x86_64-linux-gnu:${LD_LIBRARY_PATH}' >> ~/.bashrc
echo 'export PATH=/usr/local/cuda-12.8/bin:$PATH' >> ~/.bashrc
source ~/.bashrc

For llama-cpp-python (GGUF):

echo 'export CMAKE_ARGS="-DGGML_CUDA=on"' >> ~/.bashrc
echo 'export CUDACXX=/usr/local/cuda/bin/nvcc' >> ~/.bashrc
echo 'export FORCE_CMAKE=1' >> ~/.bashrc
source ~/.bashrc
sudo apt-get install -y build-essential cmake ninja-build python3-dev
pip uninstall -y llama-cpp-python
pip install --no-cache-dir --force-reinstall llama-cpp-python

For this model package:

pip install -r requirements.txt

System Dependencies

# Ubuntu/Debian
apt-get install libsndfile1 libportaudio2

Usage

Start the Server

Recommended to use at least g6.xlarge (L4, 4vCPUs, 16GB RAM). GPU memory usage will be around 8.8 GB for all 3 ASR/NMT/XTTSv2 models.
Total model latencies will be around 300 ms (ASR 18 ms., NMT 150 ms., XTTSv2 150 ms.). g5.xlarge with A10G will have a 1.5x faster processing time.
This, still bounded by the ASR lookahead 560 ms (NeMO Cache-Aware Streaming ASR FastConformer-RNN-T).
Hence, the effective delay is 560 ms, which is near-instantaneous for simultaneous/streaming speech translation.

python app.py \
  --asr-onnx-path models/asr/nemo-cache-aware-streaming-560ms-onnx/ \
  --nmt-gguf-path models/nmt/translategemma-4b-it-q8_0-gguf/translategemma-4b-it-q8_0.gguf \
  --nmt-n-threads 2 \
  --nmt-use-gpu \
  --streaming-tts-config-path configs/tts/xtts/xtts_streaming_tts_config.json \
  --streaming-tts-pipeline-config-path configs/tts/xtts/xtts_streaming_tts_pipeline_config.json \
  --tts-ref-audio-path audio_ref/male_stewie.mp3 \
  --host 0.0.0.0 \
  --port 8765

CLI Options

You can find TTS model specific related configurations in the configs/tts/xtts/ dir., which are used for the streaming-tts-config-path and streaming-tts-pipeline-config-path.
These include TTS's model location, queue sizes, chunk sizes, number of threads, and gpu usage.

Flag	Default	Description
`--asr-onnx-path`	(required)	ASR ONNX model directory
`--asr-chunk-ms`	10	ASR audio chunk duration (ms)
`--asr-sample-rate`	16000	ASR expected sample rate
`--nmt-gguf-path`	(required)	NMT GGUF model file
`--nmt-n-threads`	2	NMT CPU threads
`--nmt-use-gpu`	False	Toggle to use GPU for NMT
`--streaming-tts-config-path`	(required)	Config file for StreamingTTS instantiation
`--streaming-tts-pipeline-config-path`	(required)	Config file for StreamingTTSPipeline instantiation
`--tts-ref-audio-path`	(required)	TTS reference speaker audio
`--tts-language`	ru	TTS target language code
`--audio-queue-max`	256	Audio input queue max size
`--audio-out-queue-max`	32	Audio output queue max size
`--host`	0.0.0.0	Server bind host
`--port`	8765	Server port

Python Client

Captures microphone audio and plays back translated speech:

pip install -r requirements_client.txt
python clients/python_client.py --uri ws://<server_ip_address/localhost>:8765

Web Client

TBD

WebSocket Protocol

Direction	Type	Format	Description
Client→	Binary	PCM16	Raw audio at declared sample rate
Client→	Text	JSON	`{"action": "start", "sample_rate": 16000}`
Client→	Text	JSON	`{"action": "stop"}`
→Client	Binary	PCM16	Synthesized audio at 24kHz
→Client	Text	JSON	`{"type": "transcript", "text": "..."}`
→Client	Text	JSON	`{"type": "translation", "text": "..."}`
→Client	Text	JSON	`{"type": "status", "status": "started"}`

Docker

TBD

Project Structure

streaming_speech_translation/
├── app.py                              # Main entry point
├── requirements.txt
├── README.md
├── ARCHITECTURE.md
├── Dockerfile
├── models/
│   ├── asr/
│   │   └── nemo-cache-aware-streaming-560ms-onnx/
│   ├── nmt/
│   │   ├── translategemma-4b-it-q8_0-gguf/
│   │   └── translategemma-4b-it-q4_k_m-gguf/
│   └── tts/
│       └── xttsv2-onnx/
├── src/
│   ├── asr/
│   │   ├── streaming_asr.py            # StreamingASR wrapper
│   │   ├── cache_aware_modules.py      # Audio buffer + streaming ASR
│   │   ├── cache_aware_modules_config.py
│   │   ├── modules.py                  # ONNX model loading
│   │   ├── modules_config.py
│   │   ├── onnx_utils.py
│   │   └── utils.py                    # Audio utilities
│   ├── nmt/
│   │   ├── streaming_nmt.py            # StreamingNMT wrapper
│   │   ├── streaming_segmenter.py      # Word-group segmentation
│   │   ├── streaming_translation_merger.py
│   │   └── translator_module.py        # TranslateGemma via llama-cpp
│   ├── tts/
│   │   ├── base
│   │   │   ├── streaming_tts_base.py               # Base class for StreamingTTS wrapper
│   │   │   └── streaming_tts_pipeline_base.py      # Base class for StreamingTTSPipeline wrapper
│   │   ├── base
│   │   │   ├── streaming_tts_factory.py            # Factory class for StreamingTTS wrapper
│   │   │   └── streaming_tts_pipeline_factory.py   # Factory class for StreamingTTSPipeline wrapper
│   │   ├── pipeline
│   │   │   └── xtts/
│   │   │        └── xtts_streaming_pipeline.py     # XTTSv2-specific StreamingTTSPipeline class
│   │   ├── streaming
│   │   │   └── xtts/
│   │   │        └── xtts_streaming_tts.py          # XTTSv2-specific StreamingTTS class
│   │   └── utils/
│   │       ├── tts_segmenter.py                    # Handler for TTS text input segmenter
│   │       └── xtts/
│   │            ├── xtts_onnx_orchestrator.py      # ONNX sessions handler for XTTSv2 modules
│   │            ├── xtts_tokenizer.py              # XTTSv2 BPE tokenizer
│   │            ├── xtts_tts_warmup.py             # Warmup handler for XTTSv2 ONNX sessions
│   │            └── zh_num2words.py                # XTTSv2 Chinese text normalization
│   ├── pipeline/
│   │   ├── orchestrator.py             # PipelineOrchestrator
│   │   └── config.py                   # PipelineConfig
│   └── server/
│       └── websocket_server.py         # WebSocket server
└── clients/
    ├── python_client.py                # Python CLI client
    └── web_client.html                 # Browser client

See ARCHITECTURE.md for the full concurrency diagram and queue map.

LICENSE and COPYRIGHT

This repository is released under Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). This means:

✅ Research and academic use
✅ Personal experimentation
✅ Open-source contributions
❌ Commercial applications
❌ Production deployment
❌ Monetized services

By: Patrick Lumbantobing

Copyright@VertoX-AI

Citation

If you use this system in your research, please cite:

@misc{vertoxai2026streamingspeechtranslation,
  title={Streaming Speech Translation — VertoX-AI},
  author={Tobing, P. L., VertoX-AI},
  year={2026},
  publisher={HuggingFace},
}

Acknowledgments

NVIDIA for Cache-Aware ASR NeMo
istupakov for the ONNX reference
Google for the TranslateGemma NMT model
Coqui for the XTTSv2

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GGUF

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4B params

Architecture

gemma3

Hardware compatibility

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