---
title: Notesoop STT Ko
emoji: 🎙️
colorFrom: yellow
colorTo: pink
sdk: gradio
sdk_version: 6.31.0
app_file: app.py
python_version: "3.12"
startup_duration_timeout: 1h
short_description: Ultra-fast Korean speech recognition (on-device STT)
license: apache-2.0
---

# Notesoop-STT-Ko-v1 — Korean Speech Recognition

Gradio demo for [Phsoft-ai/Notesoop-STT-Ko-v1](https://huggingface.co/Phsoft-ai/Notesoop-STT-Ko-v1),
an ultra-fast Korean STT model designed for on-device use.

## How it works

1. **Frozen audio encoder** — `google/embeddinggemma-2` (Gemma-4 audio tower,
   bf16) produces frame embeddings, which are Matryoshka-sliced to **256 dims**
   and L2-normalized. The encoder is never fine-tuned.
2. **Conformer CTC reader** — a small 10-layer Conformer (21.5 M params) with a
   cosine-similarity **vector-bank head** over a **25,000-token Korean morpheme
   vocabulary** (blank id 0, unk id 1).
3. **KenLM 3-gram rescoring** — CTC top-k logits are rescored by a Korean
   KenLM language model (`alpha=0.12`, `beta=0.40`, beam 8) and merged back
   across overlapping 16 s windows.

Reported footprint is ~1.5 GB VRAM and ~40× real-time on the author's
hardware; the model card reports **CER 16.21 %** on the Zeroth-Korean test set.

## Usage

Upload a clip (or record from the microphone) and press **Transcribe**.
Korean only. Audio is resampled to 16 kHz mono; up to **180 s** per run.
`ffmpeg`-decodable containers (wav / mp3 / m4a / flac / …) are supported.

## Example clips

The four bundled clips are Korean read-speech utterances from
[Bingsu/zeroth-korean](https://huggingface.co/datasets/Bingsu/zeroth-korean)
(**CC BY 4.0**), the benchmark this model reports on. They are redistributed
here unchanged, with attribution, purely as demo inputs for the model.

## Notes / limitations

- Korean only — no other language is supported by the vocabulary or the LM.
- Very short clips (< ~3 s) are padded to the 16 s window and may transcribe
  poorly; 5 s or longer works best.
- `chunk_sec` / `overlap_sec` / `batch_size` are exposed under **Advanced
  options**; the defaults (16 s / 1 s / 4) are the reference setting.