🗣️ Kokoro TTS - German Voice 'Martin' (ONNX)

Github Repository

This repository provides an ONNX exported version with German text normalization of the German Kokoro TTS model kikiri-german-martin. It is a "German single-speaker TTS model fine-tuned on the Martin Harbecke voice using StyleTTS2 Stage 2. Built on top of kikiri-german-base-51speakers-synthetic."

By using the ONNX format, you can run this german Text-to-Speech model without needing PyTorch. This results in significantly faster inference times (x2), a lower memory footprint, and easier integration into various environments like C++, Rust, mobile apps, or web servers using the ONNX Runtime.

Audio Samples

Main sample: v1.1/v1.2 German normalization

This sample demonstrates the v1.1 normalization layer for dates, times, decimal numbers, units, abbreviations, ordinals and Euro amounts.

Your browser says no to audio (but at least it rhymes)

Spoken text:

Zum 14.05.2026 um 18:20 Uhr ist das Abendessen geplant. Für den Auflauf brauchen wir 1,5 kg Kartoffeln, 500 g Quark, 2 Eier, 1 ltr. Milch und ggf. 3 cm mehr Backpapier. Prof. Klein sagt: "Bitte stelle die Form auf die 2. Schiene, backe alles für 45 Min. und lass es danach 1 Min. oder auch 2 Min. ruhen." Die Kosten liegen bei ca. 12,80 EUR zzgl. Pfand.

Legacy samples: v1.0

These older samples were generated with the initial v1.0 service setup before the v1.1 German normalization layer.

Sample: default (0.25s pause between sentences, speed = 1.125) Your browser says no to audio (but at least it rhymes)

Sample: no additional pauses, speed = 1.0 Your browser says no to audio (but at least it rhymes)

Model Details

Model Description

This is an acoustic Text-to-Speech model based on the Kokoro architecture, specifically tailored for the German language featuring the single male voice "Martin". It has been exported to the ONNX graph format to maximize compatibility and performance.

• Developed by: Original model by dida-80b and kikiri-tts, ONNX conversion by huggingFresse
• Model type: Text-to-Speech (Acoustic Model)
• Language(s) (NLP): German (de)
• License: Apache 2.0
• Finetuned from model: kikiri-tts/kikiri-german-martin

Model Sources

• Original Repository: kikiri-tts/kikiri-german-martin
• Base Model: dida-80b/kokoro-german-hui-multispeaker-base
• Kokoro Architecture: hexgrad/Kokoro-82M

Uses

This model is intended to be used with the ONNX Runtime to synthesize German speech from phonemized text. It is ideal for:

• Local offline text-to-speech generation.
• Integration into low-resource environments (Edge devices, Raspberry Pi).
• Building high-performance TTS microservices.

Bias, Risks, and Limitations

As with any TTS model, the output quality heavily relies on the quality of the input text and the phonemizer used.

• Pronunciation: The model might mispronounce rare words, foreign names, or complex compound nouns if they are not correctly converted to phonemes first.
• Emotion: While the model sounds very natural, precise control over specific emotions (like shouting, crying, or whispering) is limited by the training data of the base model.

How to run it yourself

The repository now contains the same two-service setup I use with Home Assistant Assist:

• onnx-docker/: the Kokoro ONNX FastAPI service. It exposes an OpenAI-compatible /v1/audio/speech endpoint, applies the German text normalization before synthesis and uses process-isolated workers for safe parallel sentence synthesis.
• wyoming_openai_german_separator/: a small overlay image for the Wyoming OpenAI bridge. It patches German sentence segmentation so streaming TTS does not split too early after dotted abbreviations such as Prof., Min., Stck. or ltr..
• german_text_rules.py: the essential shared rule file. It is mounted into both containers, so abbreviation expansion, unit handling and Wyoming sentence-boundary protection use the same source of truth. Keep this file next to docker-compose.yml unless you also adjust the volume mounts.

1. Clone the model repository

This is a Hugging Face model repository with Git LFS files, so make sure Git LFS is installed.

git lfs install
git clone https://huggingface.co/huggingFresse/Kokoro-82M-ONNX-German-Martin
cd Kokoro-82M-ONNX-German-Martin

2. Start Kokoro ONNX and the Wyoming bridge

The included docker-compose.yml starts both the TTS service and the Wyoming bridge:

docker compose up -d --build

Full compose file:

services:
  # German Kokoro ONNX FastAPI service with v1.2 process-isolated workers.
  kokoro-onnx:
    build:
      context: .
      dockerfile: onnx-docker/Dockerfile
    container_name: kokoro-onnx
    restart: unless-stopped
    ports:
      - "8881:8881"
    environment:
      - KOKORO_ONNX_THREADS=2
      - KOKORO_ONNX_INTRA_OP_THREADS=2
      - KOKORO_ONNX_INTER_OP_THREADS=1
      - KOKORO_ONNX_EXECUTION_MODE=sequential
      - KOKORO_ONNX_GRAPH_OPT=all
      - KOKORO_ONNX_SPEED=1.125
      - KOKORO_ONNX_TRIM=true
      - KOKORO_ONNX_VOICE=martin
      - KOKORO_ONNX_LANG=de
      - OMP_NUM_THREADS=2
      - OPENBLAS_NUM_THREADS=2
      - MKL_NUM_THREADS=2
      - NUMEXPR_NUM_THREADS=2
      - OMP_WAIT_POLICY=PASSIVE
      - KOKORO_PAUSE_DURATION=0.25
      - KOKORO_WORKERS=2
      - KOKORO_ONNX_ALLOW_SPINNING=0
      - KOKORO_WARMUP_TEXT=Hallo.
    volumes:
      - ./german_text_rules.py:/app/german_text_rules.py:ro

  # Wyoming bridge for Home Assistant Assist.
  wyoming_openai_onnx:
    build: ./wyoming_openai_german_separator
    image: wyoming_openai_german_separator:latest
    container_name: wyoming_openai_onnx
    restart: unless-stopped
    ports:
      - "10203:10203"
    command:
      - python3
      - -m
      - wyoming_openai
      - --uri
      - tcp://0.0.0.0:10203
      - --languages
      - de
      - --tts-openai-url
      - http://kokoro-onnx:8881/v1
      - --tts-models
      - kokoro
      - --tts-streaming-models
      - kokoro
      - --tts-backend
      - KOKORO_FASTAPI
    volumes:
      - ./german_text_rules.py:/app/german_text_rules.py:ro
    depends_on:
      - kokoro-onnx

3. Check that the services are reachable

The Kokoro service should answer on port 8881:

curl http://localhost:8881/v1/audio/voices

For Home Assistant, add the Wyoming integration and point it to the host running Docker:

Host: <your-docker-host>
Port: 10203

Notes on performance

The compose file uses a small-CPU profile that works well on my Intel NUC. KOKORO_WORKERS=2 means that two independent Kokoro/ONNX processes are kept warm and sentence synthesis can run in parallel without sharing the same Kokoro, espeak or tokenizer state across threads.

For very small machines or memory-constrained systems, set KOKORO_WORKERS=1. This is slower for longer texts, but uses less memory. On larger CPUs you can benchmark higher values, but keep an eye on CPU oversubscription: each worker also uses KOKORO_ONNX_INTRA_OP_THREADS ONNX threads.

The recommended NUC profile is:

KOKORO_WORKERS=2
KOKORO_ONNX_INTRA_OP_THREADS=2
KOKORO_ONNX_INTER_OP_THREADS=1
KOKORO_ONNX_ALLOW_SPINNING=0
OMP_NUM_THREADS=2
OPENBLAS_NUM_THREADS=2
MKL_NUM_THREADS=2
NUMEXPR_NUM_THREADS=2

KOKORO_WARMUP_TEXT is synthesized once per worker during startup so the first real request does not have to pay the full model/session initialization cost. The Wyoming bridge keeps its default streaming request concurrency; advanced users can override it with WYOMING_TTS_CONCURRENT_REQUESTS, but the default is usually a good starting point.

Changelog

v1.2 (May 22, 2026)

• Replaced thread-based parallel sentence synthesis with process-isolated Kokoro workers.
• Avoids sharing Kokoro, espeak and tokenizer state across worker threads, addressing possible word-order corruption under parallel synthesis.
• Added real ONNX Runtime session tuning via KOKORO_ONNX_INTRA_OP_THREADS, KOKORO_ONNX_INTER_OP_THREADS, KOKORO_ONNX_EXECUTION_MODE, KOKORO_ONNX_GRAPH_OPT and KOKORO_ONNX_ALLOW_SPINNING.
• Added background warm-up for process workers to reduce the first-request latency after startup.
• Added KOKORO_WORKERS as the single public knob for parallel synthesis workers, while keeping KOKORO_MAX_WORKERS as a backwards-compatible alias.
• Added optional Wyoming bridge tuning via WYOMING_TTS_CONCURRENT_REQUESTS.
• Updated the included compose file with the recommended Intel NUC profile: 2 workers, 2 ONNX intra-op threads per worker, 1 inter-op thread and spinning disabled.

v1.1 (May 14, 2026)

• Added German text normalization before synthesis in the included FastAPI service.
• Decimal numbers with units are spoken correctly, for example "2,5 kWh" as "zwei komma fünf Kilowattstunden".
• Added singular/plural handling for units, for example "1 Kilowattstunde" vs. "2 Kilowattstunden".
• Added and improved abbreviations and units such as zzgl., mAh, mA, g, Stck., Min. and ltr..
• Added better handling for Euro amounts such as "49,99 EUR" as "neunundvierzig Euro neunundneunzig".
• Improved German ordinal/cardinal handling in contexts such as dates, quarters, tracks, chapters and numbered labels.
• Fixed sentence pauses around common German abbreviations and dotted unit abbreviations.
• Added a v1.1 audio sample and the exact spoken text used for it.

v1.0 (initial release)

• Initial ONNX conversion of the German Martin voice.
• Included the basic Docker/FastAPI service files.
• Fixed pauses after common abbreviations in the initial service setup.

Training Details

This repository only contains a format conversion. No additional training or fine-tuning was performed. For details regarding the training data, hyperparameters, and procedures, please refer to the base model: kikiri-tts/kikiri-german-martin.

Citation

If you use this model, please credit the original authors:

@misc{kikiri-german-martin,
  author = {kikiri-tts},
  title = {Kokoro German Voice - Martin},
  year = {2026},
  publisher = {Hugging Face},
  howpublished = {\url{https://huggingface.co/kikiri-tts/kikiri-german-martin}}
}

@misc{kokoro-german-hui-multispeaker-base,
  author = {dida-80b},
  title = {Kokoro German — HUI Multispeaker Base (Stage 1)},
  year = {2026},
  publisher = {Hugging Face},
  howpublished = {\url{https://huggingface.co/dida-80b/kokoro-german-hui-multispeaker-base/tree/main}}
}

@misc{kokoro-82m,
  author = {hexgrad},
  title = {Kokoro-82M},
  year = {2024},
  publisher = {Hugging Face},
  howpublished = {\url{https://huggingface.co/hexgrad/Kokoro-82M}}
}

@misc{kokoro-82m-onnx-german-martin,
  author = {Godelaune},
  title = {Kokoro-82M ONNX German Martin},
  year = {2026},
  publisher = {Hugging Face},
  howpublished = {\url{https://huggingface.co/Godelaune/Kokoro-82M-ONNX-German-Martin}}
}