PiperTTS as OpenAI-compatible endpoint

[phineas-pta]

A lightweight FastAPI service that wraps Piper in an OpenAI-compatible /v1/audio/speech endpoint.

original code: https://github.com/Kamil-Krawiec/piper-tts-http-server/blob/master/server.py by @Kamil-Krawiec

i simplified the code and add some features:

• allow loading custom onnx file
• auto detect available hardware acceleration: TensorrtExecutionProvider, CUDAExecutionProvider, MIGraphXExecutionProvider, OpenVINOExecutionProvider, CoreMLExecutionProvider, DmlExecutionProvider, CPUExecutionProvider

installation

basic dependencies:

pip install fastapi uvicorn piper-tts

for nvidia cuda:

pip uninstall -y onnxruntime
pip install onnxruntime-gpu # cuda 13, if u want cuda 12, run below command
# pip install onnxruntime-gpu --extra-index-url https://aiinfra.pkgs.visualstudio.com/PublicPackages/_packaging/onnxruntime-cuda-12/pypi/simple/

for amd rocm (linux only): grab onnxruntime-migraphx wheel from https://repo.radeon.com/rocm/manylinux/

for intel openvino:

pip uninstall -y onnxruntime
pip install openvino==2025.4.1 onnxruntime-openvino # at the time of writing onnxruntime only support openvino up to v2025.4.1

for macos: basic dependencies should be good

usage

download file: https://gist.github.com/phineas-pta/7d08a3ac21d64e67ed5fa6b47e93c097#file-pipertts_openai-py

launch the server with:

python pipertts_openai.py --model /path/to/en_US-lessac-medium.onnx

other applications can now connect to http://localhost:5000/v1 to use Piper TTS

example of my use case: read aloud epub file in browser

• run server with additional argument --allow-cors
• install https://github.com/ken107/read-aloud and setup connection to above endpoint
• install https://www.epubread.com/en/add.php and open an epub
• launch ReadAloud and listen to audiobook

limits

streaming wav-format audio only, cannot save to file nor change audio format

if u want, take a look at: https://github.com/remsky/Kokoro-FastAPI/blob/master/api/src/routers/openai_compatible.py

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edit 1 change some links