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Junco v0.1: ONNX release, model card, samples

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+ samples/assistant.wav filter=lfs diff=lfs merge=lfs -text
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+ samples/greeting.wav filter=lfs diff=lfs merge=lfs -text
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+ samples/news.wav filter=lfs diff=lfs merge=lfs -text
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+ samples/story.wav filter=lfs diff=lfs merge=lfs -text
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NOTICE ADDED
@@ -0,0 +1,16 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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+ Junco v0.1 (flockspeech/junco)
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+ Copyright 2026 Flock Speech
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+
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+ Licensed under the Apache License, Version 2.0 (see LICENSE). This covers the Junco acoustic model weights
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+ (onnx/encoder.onnx, onnx/decoder-int8.onnx) and the model configuration (onnx/junco.json).
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+
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+ Third-party components:
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+
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+ - Vocos vocoder (onnx/vocoder.onnx): converted from charactr/vocos-mel-24khz,
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+ Copyright (c) 2023 Charactr Inc., MIT License (see onnx/LICENSE-vocos).
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+ - Training data: LJ Speech Dataset (Keith Ito and Linda Johnson), public domain.
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+
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+ Not included, required at run time to turn text into phonemes:
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+
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+ - espeak-ng (GPL-3.0) and phonemizer (GPL-3.0). The flockspeech pip package installs them as separate
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+ dependencies.
README.md ADDED
@@ -0,0 +1,272 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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+ ---
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+ license: apache-2.0
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+ language:
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+ - en
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+ library_name: onnx
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+ pipeline_tag: text-to-speech
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+ tags:
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+ - text-to-speech
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+ - tts
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+ - speech-synthesis
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+ - onnx
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+ - flow-matching
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+ - on-device
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+ - edge
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+ - offline
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+ - cpu
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+ datasets:
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+ - keithito/lj_speech
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+ ---
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+
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+ # Junco v0.1
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+
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+ **A small English text-to-speech model that runs offline on a CPU.**
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+
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+ Junco is an 11.4M-parameter flow-matching TTS model from [Flock Speech](https://huggingface.co/flockspeech). It turns
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+ English text into natural 24 kHz speech on an ordinary CPU, faster than real time. It has no GPU, network or PyTorch
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+ dependency, and the full model is a 44 MB download.
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+
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+ | | |
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+ |---|---|
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+ | **Developed by** | Flock Speech |
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+ | **Model type** | Non-autoregressive TTS: transformer encoder, duration predictor, conditional flow-matching decoder, Vocos vocoder |
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+ | **Language** | English (US) |
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+ | **Voices** | 1 (female, read-aloud style) |
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+ | **Output** | 24 kHz mono audio |
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+ | **Parameters** | 11.4M acoustic model + 13.5M vocoder |
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+ | **Download** | 44 MB (ONNX; int8 decoder, fp16 encoder and vocoder) |
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+ | **Runtime** | ONNX Runtime on CPU (Linux, macOS, Windows; x86-64 and ARM64) |
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+ | **License** | Apache-2.0 (vocoder weights MIT) |
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+ | **Version** | v0.1, November 2026 |
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+
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+ ## Samples
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+
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+ All samples were made with the files in this repository at default settings (8 steps, seed 0), with no editing.
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+
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+ | Use | Text | Audio |
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+ |---|---|---|
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+ | Greeting | *Hello! I'm Junco, a tiny voice that runs entirely on your own device.* | <audio controls src="https://huggingface.co/flockspeech/junco/resolve/main/samples/greeting.wav"></audio> |
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+ | Assistant | *Your next meeting starts in fifteen minutes. Would you like me to read the agenda?* | <audio controls src="https://huggingface.co/flockspeech/junco/resolve/main/samples/assistant.wav"></audio> |
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+ | Narration | *The old lighthouse keeper climbed the spiral stairs one last time, and watched the ships come home through the fog.* | <audio controls src="https://huggingface.co/flockspeech/junco/resolve/main/samples/story.wav"></audio> |
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+ | News | *Researchers announced on Tuesday that the new battery can be charged in under ten minutes, and lasts twice as long.* | <audio controls src="https://huggingface.co/flockspeech/junco/resolve/main/samples/news.wav"></audio> |
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+
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+ ## Quick start
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+
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+ The [`flockspeech`](https://pypi.org/project/flockspeech/) Python package bundles these weights, so nothing is downloaded
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+ at run time.
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+
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+ ```sh
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+ pip install flockspeech
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+ flockspeech "Hello! I'm Junco." -o hello.wav --play
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+ ```
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+
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+ ```python
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+ from flockspeech import Junco
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+
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+ tts = Junco() # loads in under a second
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+ audio = tts("Hello there.") # float32 numpy array, 24 kHz mono
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+ tts.save("Hello there.", "hello.wav")
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+
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+ # Low latency: audio is produced sentence by sentence
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+ for chunk in tts.stream(long_text):
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+ play(chunk)
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+ ```
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+
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+ To use the files in this repository directly:
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+
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+ ```python
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+ from huggingface_hub import snapshot_download
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+ from flockspeech import Junco
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+
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+ path = snapshot_download("flockspeech/junco", allow_patterns=["onnx/*"])
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+ tts = Junco(model_dir=f"{path}/onnx")
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+ ```
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+
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+ ### Options
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+
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+ | Parameter | Default | Effect |
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+ |---|---|---|
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+ | `speed` | 1.0 | Speaking rate; 1.2 is 20% faster |
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+ | `steps` | 8 | Flow-matching steps; 4 is about 1.5× faster with slightly lower quality |
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+ | `seed` | 0 | Fixes the small random variation in delivery, so output is reproducible |
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+ | `threads` | up to 4 | CPU threads for ONNX Runtime |
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+
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+ ## Evaluation
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+
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+ We benchmarked Junco against open TTS models of similar purpose. Every model was run with the same harness, on the
97
+ same sentences and the same machine, and scored by the same tools.
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+
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+ **Test set.** 150 sentences from LibriTTS-R test-clean (35 speakers, 6 to 40 words each). None of the models trained on
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+ them. F5-TTS was scored on a fixed subset of 75 sentences, because it is slow on a CPU.
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+
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+ **Metrics.**
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+ - **UTMOS22:** predicted naturalness on a 1–5 scale.
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+ - **UTMOSv2:** a second, independent naturalness predictor.
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+ - **WER:** word error rate of Whisper large-v3-turbo transcripts, after Whisper's English text normaliser.
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+
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+ ### Everyday speech
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+
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+ | Model | Size (MB) | UTMOS22 ↑ | UTMOSv2 ↑ | WER ↓ | License |
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+ |---|---:|---:|---:|---:|---|
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+ | Real recordings (reference) | n/a | 4.23 | 3.29 | 2.30% | n/a |
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+ | **Junco v0.1** | **77.2** † | **4.20** | **3.72** | **1.71%** | **Apache-2.0** |
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+ | Matcha-TTS | 274.6 | 4.34 | 3.80 | 1.65% | MIT |
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+ | Piper (lessac, medium) | 63.2 | 4.35 | 3.79 | 2.33% | GPL-3.0 |
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+ | F5-TTS v1 | 1402.9 | 4.24 | 3.52 | 2.58% | CC BY-NC 4.0 weights |
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+ | KittenTTS nano 0.1 | 23.9 | 3.59 | 2.02 | 3.12% | Apache-2.0 |
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+
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+ † Benchmark run with the PyTorch checkpoint. The ONNX release in this repository is **44 MB**; see
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+ [Optimised release](#optimised-release).
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+
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+ Junco's word error rate is lower than that of the real recordings. Its naturalness is close to the real recordings
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+ (4.20 vs 4.23), but about 0.15 below Piper and Matcha-TTS. On the 92-sentence hard-text set (numbers, dates, money,
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+ contact details, names, homographs and assistant-style replies), Junco's WER is 4.9%. Piper scored 4.9%, Matcha-TTS 5.2%,
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+ F5-TTS 7.0% and KittenTTS 9.3%. On one-minute paragraphs, Junco's WER is 0.5%.
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+
126
+ ### Speed
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+
128
+ Speed is measured as seconds of audio produced per second of compute, vocoder included, on 13 typical reply sentences.
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+
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+ | Model | 1 CPU thread ↑ | 4 CPU threads ↑ | NVIDIA T4 GPU ↑ | Peak RAM |
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+ |---|---:|---:|---:|---:|
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+ | Piper | 7.4× | 13.5× | n/a | 382 MB |
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+ | KittenTTS | 3.3× | 5.0× | n/a | 789 MB |
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+ | **Junco v0.1 (PyTorch)** | **3.1×** | **5.1×** | **33×** | **623 MB** |
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+ | Matcha-TTS | 0.7× | 1.3× | 25× | 1,453 MB |
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+ | F5-TTS v1 | 0.006× | 0.011× | 2.1× | 3,698 MB |
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+
138
+ The CPU was an Intel Xeon at 2.2 GHz, a slow cloud CPU. Desktop and laptop CPUs are several times faster.
139
+
140
+ ### Optimised release
141
+
142
+ The ONNX graphs in this repository were checked against the PyTorch model:
143
+ - **Before quantisation:** they match PyTorch to over 78 dB SNR.
144
+ - **After quantisation:** we compared quality and speed on 40 sentences from the same test set, measured on an Apple M1.
145
+
146
+ | Build | Size | UTMOS22 | 1 thread | 4 threads | Peak RAM |
147
+ |---|---:|---:|---:|---:|---:|
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+ | fp32 reference | 100 MB | 4.21 | 5.1× | n/a | n/a |
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+ | **This release** (int8 decoder, fp16 storage) | **44 MB** | **4.18** | **8.7×** | **19×** | **265 MB** |
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+ | This release, `steps=4` | 44 MB | 4.12 | 13.6× | 27× | 265 MB |
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+
152
+ The UTMOS difference between the fp32 reference and this release is −0.03 ± 0.05 (95% confidence interval), which is
153
+ not significant. We quantised only the decoder, which does most of the computation. An int8 vocoder cost 0.15 UTMOS,
154
+ so the vocoder stays at full precision; its weights are stored as fp16 and computed in fp32.
155
+
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+ **Latency.** Start-up takes about 0.7 s. When streaming on 4 M1 threads, the first audio arrives about 0.25 s after
157
+ the request.
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+
159
+ ## Intended use
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+
161
+ **Suitable for:**
162
+ - Voice output on devices and in apps that must work offline or keep text private: assistants, accessibility and
163
+ screen-reading tools, kiosks, robotics, games and embedded products.
164
+ - CPU-only servers where cost or latency matters.
165
+ - Prototyping and research on small TTS models.
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+
167
+ **Out of scope:**
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+ - Languages other than English, or speaker voices other than the one provided. Junco has no voice cloning.
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+ - Expressive, emotional or conversational styles. The voice reads in a neutral, read-aloud style.
170
+ - Impersonating a real person, or producing audio meant to deceive listeners about who is speaking or whether the
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+ speech is synthetic.
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+
173
+ ## Limitations
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+
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+ - **No text normalisation.** Write numbers, currency, dates and abbreviations in words: "five dollars", not "$5";
176
+ "Doctor", not "Dr.". Raw digits and symbols are read by espeak-ng's rules, which may not be what you want. Most of
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+ Junco's errors on the hard-text set are of this kind:
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+ - assistant-style replies: 20% WER;
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+ - contact details: 13%;
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+ - money: 12%;
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+ - names: 11%.
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+ - **Pronunciation comes from espeak-ng.** Rare names, brands and some homographs, such as *read* and *lead*, can be
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+ mispronounced.
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+ - **One voice, one accent.** The model learned from a single US English speaker.
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+ - **Long-form audio.** Text is synthesised sentence by sentence. Prosody does not carry across sentences, and
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+ naturalness on long paragraphs is lower (UTMOS22 3.88).
187
+ - **Bright high frequencies.** About 14% of Junco's energy lies above 4 kHz, against 2% for real recordings. On some
188
+ playback systems this may sound slightly bright or hissy.
189
+ - **Automatic metrics only.** The quality figures come from automatic predictors (UTMOS22, UTMOSv2) and Whisper, not
190
+ from a formal human listening test.
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+
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+ ## Risks and responsible use
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+
194
+ Synthetic speech can be misused for deception. Junco produces a single fixed voice and cannot clone speakers, which
195
+ limits impersonation risk. We still ask that you:
196
+ - tell listeners when speech is synthetic, where that matters;
197
+ - not use the model for fraud, harassment or deceptive impersonation;
198
+ - review output before you use it in safety-critical or high-stakes settings.
199
+
200
+ ## Model details
201
+
202
+ ### Architecture
203
+
204
+ The model runs in four stages:
205
+ 1. **Text front end:** espeak-ng converts text to IPA phonemes (en-us, with stress marks). A blank token is inserted
206
+ between phonemes.
207
+ 2. **Text encoder (3.2M parameters):** 3 ConvNeXt pre-net blocks, then 6 transformer layers (width 192, RoPE, SwiGLU,
208
+ RMSNorm). It predicts a per-phoneme mel prior.
209
+ 3. **Duration predictor (0.3M parameters):** a convolutional regressor of log-durations. It was trained on alignments from Monotonic
210
+ Alignment Search, so no external aligner is needed.
211
+ 4. **Decoder (7.9M parameters):** a flow-matching U-Net hybrid.
212
+ - ConvNeXt blocks run at the full frame rate, and four adaLN transformer blocks run at half the frame rate.
213
+ - It uses classifier-free guidance (weight 1.0) and 8 Euler steps with a sway-sampling schedule.
214
+ - It outputs a 100-band log-mel spectrogram (hop 256, 24 kHz).
215
+
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+ The vocoder is [Vocos](https://huggingface.co/charactr/vocos-mel-24khz) (charactr/vocos-mel-24khz, MIT). In ONNX it
217
+ predicts the STFT magnitude and phase, and the inverse STFT runs in numpy.
218
+
219
+ ### Files
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+
221
+ | File | Contents | Size |
222
+ |---|---|---:|
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+ | `onnx/encoder.onnx` | Text encoder and duration predictor (fp16 weights, fp32 compute) | 7.2 MB |
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+ | `onnx/decoder-int8.onnx` | One guided flow-matching step (int8 dynamic quantisation) | 9.9 MB |
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+ | `onnx/vocoder.onnx` | Vocos backbone and spectral head (fp16 weights, fp32 compute) | 27.1 MB |
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+ | `onnx/junco.json` | Mel normalisation statistics and default inference settings | <1 kB |
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+ | `samples/` | The audio samples above | |
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+
229
+ ### Training
230
+
231
+ | | |
232
+ |---|---|
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+ | **Data** | [LJ Speech](https://keithito.com/LJ-Speech-Dataset/): 13,100 clips, about 24 hours, one speaker, public domain |
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+ | **Objective** | Conditional flow matching (logit-normal time sampling, σ_min 1e-4), MAS prior loss, duration MSE |
235
+ | **Guidance** | Condition dropped for 10% of training examples, for classifier-free guidance |
236
+ | **Optimiser** | AdamW (lr 2e-4, β 0.9/0.98, weight decay 0.01), 1,000 warm-up steps, EMA 0.999 |
237
+ | **Batching** | Dynamic batches of up to 20,000 mel frames |
238
+ | **Compute** | 44,485 steps in 3 hours on one NVIDIA T4 GPU |
239
+ | **Released weights** | EMA weights |
240
+
241
+ **Environmental impact.** The final training run used about 3 GPU-hours on one NVIDIA T4 (70 W TDP), or about
242
+ 0.2 kWh. Architecture experiments before it used more.
243
+
244
+ ## License
245
+
246
+ - **Junco weights and configuration:** [Apache License 2.0](LICENSE). Commercial use, modification and redistribution
247
+ are allowed.
248
+ - **Vocos vocoder weights** (`onnx/vocoder.onnx`): MIT, © 2023 Charactr Inc. See `onnx/LICENSE-vocos`.
249
+ - **Training data:** LJ Speech, public domain.
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+
251
+ **Run-time dependency.** Text-to-phoneme conversion uses espeak-ng and phonemizer. Both are GPL-3.0 and are **not**
252
+ included in this repository. The `flockspeech` package installs them as separate dependencies. If you plan to ship
253
+ Junco inside a closed-source product, review their licence terms, or replace the phonemiser with one under a licence
254
+ that suits you. See [NOTICE](NOTICE).
255
+
256
+ ## Citation
257
+
258
+ ```bibtex
259
+ @misc{flockspeech2026junco,
260
+ title = {Junco: a small flow-matching text-to-speech model for on-device use},
261
+ author = {{Flock Speech}},
262
+ year = {2026},
263
+ howpublished = {\url{https://huggingface.co/flockspeech/junco}},
264
+ note = {Version 0.1}
265
+ }
266
+ ```
267
+
268
+ ## Acknowledgements
269
+
270
+ Junco builds on ideas from Matcha-TTS (conditional flow matching for TTS), Glow-TTS (Monotonic Alignment Search),
271
+ F5-TTS (sway sampling), ZipVoice and SupertonicTTS (efficient decoder design), and Vocos (vocoder). We thank the authors
272
+ of these works and of LJ Speech, LibriTTS-R, UTMOS and Whisper.
onnx/LICENSE-vocos ADDED
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+ MIT License
2
+
3
+ Copyright (c) 2023 Charactr Inc.
4
+
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+ Permission is hereby granted, free of charge, to any person obtaining a copy
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+ of this software and associated documentation files (the "Software"), to deal
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+ in the Software without restriction, including without limitation the rights
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+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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+ copies of the Software, and to permit persons to whom the Software is
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+ furnished to do so, subject to the following conditions:
11
+
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+ The above copyright notice and this permission notice shall be included in all
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+ copies or substantial portions of the Software.
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+
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+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21
+ SOFTWARE.
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