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  ---
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  license: apache-2.0
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  ---
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
  ---
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  license: apache-2.0
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+ language:
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+ - pa
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+ - hi
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+ library_name: tflite
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+ pipeline_tag: audio-classification
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+ tags:
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+ - keyword-spotting
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+ - wake-word
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+ - streaming
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+ - depthwise-separable-cnn
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+ - tinyml
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+ - microcontroller
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+ - edge-ai
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+ - int8
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+ - stm32
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+ - esp32
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+ - punjabi
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+ - hindi
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+ datasets:
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+ - SherTheCoder/TeamFolklore_UthoKikkar
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  ---
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+
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+ <p align="center">
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+ <img src="assets/banner.png" alt="The kikkar flower, from bud to full bloom" width="100%">
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+ </p>
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+
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+ <h1 align="center">Kikkar KWS</h1>
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+
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+ <p align="center">
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+ <b>A 44 KB int8 streaming model that listens for "Utho Kikkar" on a microcontroller, and for nothing else.</b><br>
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+ We made it for projects and prototypes with less than 256 KB of free RAM
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+ </p>
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+
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+ <p align="center">
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+ <img src="https://img.shields.io/badge/task-keyword%20spotting-2a78d6" alt="Task: keyword spotting">
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+ <img src="https://img.shields.io/badge/format-TFLite%20int8-4a3aa7" alt="Format: TFLite int8">
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+ <img src="https://img.shields.io/badge/size-44%20KB-1baf7a" alt="Size: 44 KB">
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+ <img src="https://img.shields.io/badge/runs%20on-STM32N657%20%7C%20ESP32-e8a33d" alt="Runs on STM32N657 and ESP32">
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+ </p>
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+
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+ <table align="center">
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+ <tr>
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+ <td align="center" width="25%"><h2>44 KB</h2>in flash</td>
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+ <td align="center" width="25%"><h2>32,849</h2>parameters</td>
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+ <td align="center" width="25%"><h2>45,872</h2>multiply-accumulates per step</td>
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+ <td align="center" width="25%"><h2>5</h2>layers</td>
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+ </tr>
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+ <tr>
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+ <td align="center"><h2>30 ms</h2>per step</td>
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+ <td align="center"><h2>≈ 1.5 s</h2>of context</td>
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+ <td align="center"><h2>≈ 38 KB</h2>working memory</td>
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+ <td align="center"><h2>60 ms</h2>phrase end to wake-up</td>
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+ </tr>
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+ </table>
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+
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+ ## Overview & Wake-Word Detection
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+
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+ Our model listens in steps of 30 ms. At every step it takes the three newest
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+ frames of log-mel energy, updates what it remembers of the last one and a half
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+ seconds, and gives back one number: the chance that someone has just finished
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+ saying *Utho Kikkar* (ਉੱਠੋ ਕਿੱਕਰ · उठो किक्कर), which means "wake up, Kikkar". We run it
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+ entirely on the board, and no audio leaves the device until it fires.
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+
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+ We trained it to fire only at the end of the whole phrase. We taught it that
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+ *Utho* on its own, *Kikkar* on its own, the two the wrong way round, and
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+ everyday words that sound close, like *chakkar*, *shakkar* or *kicker*, are all
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+ things that are not the wake word.
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+
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+ It is the listener inside Kikkar, our Smart India Hackathon 2026 project. When
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+ it fires, a flower blooms on the board's screen and we stream whatever you say
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+ next to a speech recogniser in the cloud.
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+
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+ | At a glance | |
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+ |---|---|
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+ | **Input** | 3 new log-mel frames × 40 bands per 30 ms step, int8 |
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+ | **Output** | one probability per step: has "Utho Kikkar" just ended? |
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+ | **Architecture** | Streaming depthwise-separable CNN, 5 layers |
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+ | **Size** | 32,849 parameters, ≈ 44 KB of flash |
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+ | **Compute** | 45,872 multiply-accumulates per step, 1.53 million a second |
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+ | **Context** | ≈ 1.5 s of audio |
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+ | **Latency** | 60 ms from the end of the phrase to the wake-up |
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+ | **Format** | TensorFlow Lite, int8, streaming state kept inside the model |
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+ | **Runs on** | STM32N657 (Cortex-M55) and ESP32 |
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+ | **Trained on** | About 2,000 real recordings plus synthetic speech, including [SherTheCoder/TeamFolklore_UthoKikkar](https://huggingface.co/datasets/SherTheCoder/TeamFolklore_UthoKikkar) |
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+
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+ ## Quickstart & Verification Pipeline
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+
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+ ```python
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+ # pip install numpy soundfile tensorflow huggingface_hub
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+ import numpy as np
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+ import soundfile as sf
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+ import tensorflow as tf
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+ from huggingface_hub import hf_hub_download
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+
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+ path = hf_hub_download("SherTheCoder/TeamFolklore_Model", "kikkar_kws_int8.tflite")
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+ interp = tf.lite.Interpreter(model_path=path)
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+ interp.allocate_tensors()
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+ inp, out = interp.get_input_details()[0], interp.get_output_details()[0]
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+ ```
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+
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+ We wrote the front end below to follow our model's specification. Features that are even
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+ slightly different will quietly cost accuracy, so if your own pipeline differs
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+ in any detail, trust that instead.
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+
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+ ```python
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+ SR, WIN, HOP, NFFT, MELS, STEP = 16000, 480, 160, 512, 40, 3
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+
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+ def _mel(hz):
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+ return 2595.0 * np.log10(1.0 + hz / 700.0)
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+
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+ def _hz(mel):
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+ return 700.0 * (10.0 ** (mel / 2595.0) - 1.0)
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+
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+ _edges = _hz(np.linspace(_mel(20.0), _mel(7600.0), MELS + 2))
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+ _bins = np.arange(NFFT // 2 + 1) * SR / NFFT
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+ _fbank = np.zeros((MELS, NFFT // 2 + 1))
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+ for b in range(MELS):
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+ lo, mid, hi = _edges[b:b + 3]
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+ rise = (_bins > lo) & (_bins < mid)
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+ fall = (_bins >= mid) & (_bins < hi)
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+ _fbank[b, rise] = (_bins[rise] - lo) / (mid - lo)
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+ _fbank[b, fall] = (hi - _bins[fall]) / (hi - mid)
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+ _hann = np.hanning(WIN)
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+
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+ def features(audio, cms_seconds=3.0):
128
+ """16 kHz mono int16 in, 40 normalised log-mel values per 10 ms frame out."""
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+ x = np.asarray(audio, dtype=np.float64) / 32768.0
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+ frames = np.array([x[s:s + WIN] * _hann for s in range(0, len(x) - WIN + 1, HOP)])
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+ power = np.abs(np.fft.rfft(frames, NFFT)) ** 2
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+ logmel = np.log(np.maximum(power @ _fbank.T, 1e-8)) # floor at -80 dB
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+ a = 1.0 - np.exp(-(HOP / SR) / cms_seconds)
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+ mean = logmel[:50].mean(axis=0) # start from the first 0.5 s
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+ out = np.empty_like(logmel)
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+ for i, frame in enumerate(logmel):
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+ mean += a * (frame - mean)
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+ out[i] = frame - mean
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+ return out
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+
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+ def wake_scores(audio):
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+ """One probability per 30 ms step, fed to the model the way the board feeds it."""
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+ feats = features(audio)
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+ interp.reset_all_variables() # fresh streaming state
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+ scale, zero = inp["quantization"]
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+ scores = []
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+ for s in range(0, len(feats) - STEP + 1, STEP):
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+ x = feats[s:s + STEP]
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+ if inp["dtype"] == np.int8:
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+ x = np.clip(np.round(x / scale) + zero, -128, 127)
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+ interp.set_tensor(inp["index"], x.astype(inp["dtype"]).reshape(inp["shape"]))
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+ interp.invoke()
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+ scores.append(float(interp.get_tensor(out["index"]).reshape(-1)[0]))
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+ return np.array(scores)
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+ ```
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+
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+ Our model ends in a float sigmoid, so each score is already a probability. Then
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+ point it at a clip:
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+
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+ ```python
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+ audio, sr = sf.read("clip.wav", dtype="int16")
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+ assert sr == SR and audio.ndim == 1, "the model expects 16 kHz mono audio"
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+ scores = wake_scores(audio)
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+ smoothed = np.convolve(scores, np.ones(3) / 3)[:len(scores)] # the last 3 steps, 90 ms
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+ print("highest smoothed score:", round(float(smoothed.max()), 3))
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+ ```
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+
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+ To see where the board would wake up (on the board we use a threshold of 0.7,
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+ picked on the int8 model):
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+
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+ ```python
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+ def detect(audio, threshold, refractory_s=1.0):
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+ """Times, in seconds, at which the board would wake up."""
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+ scores = wake_scores(audio)
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+ smoothed = np.convolve(scores, np.ones(3) / 3)[:len(scores)]
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+ wakes, last = [], -np.inf
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+ for i, p in enumerate(smoothed):
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+ t = ((i * STEP + STEP - 1) * HOP + WIN) / SR
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+ if p >= threshold and t - last >= refractory_s:
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+ wakes.append(round(t, 2))
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+ last = t
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+ return wakes
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+ ```
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+
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+ ## Audio Frontend & Feature Extraction
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+
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+ <p align="center">
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+ <img src="assets/features.png" alt="16 kHz audio, 30 ms Hann windows every 10 ms, 512-point power spectrum, 40 mel bands from 20 Hz to 7.6 kHz, log and running-mean normalisation, then 3 frames per 30 ms model step" width="100%">
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+ </p>
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+
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+ | Stage | Setting | Output |
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+ |---|---|---|
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+ | Capture | 16 kHz, mono, 16-bit | 160 samples every 10 ms |
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+ | Window | 30 ms Hann (480 samples), every 10 ms | 480 samples |
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+ | FFT | 512-point, power spectrum | 257 bins |
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+ | Mel | 40 triangular bands, 20 Hz to 7.6 kHz | 40 values |
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+ | Compression | natural log, floored at −80 dB | 40 values |
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+ | Normalisation | per-band running mean subtracted, τ ≈ 3 s | 40 × int8 |
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+ | Model step | the 3 newest frames, every 30 ms | 3 × 40 |
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+
201
+ We rely on the running mean to soak up the differences between microphones,
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+ gain settings and rooms, so we do not need to recalibrate the board for every
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+ house. We start it from the first half second of audio after boot.
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+
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+ ## Model Architecture & Layer Specifications
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+
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+ We built a streaming depthwise-separable CNN in five layers. The first two work across
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+ frequency while that axis still exists, learning spectral shapes cheaply. The
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+ third folds frequency into a single 48-channel vector. Everything after that is
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+ causal depthwise convolution over time plus 1×1 pointwise mixing, which we chose
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+ because it streams as a small ring-buffer update at every step and is the int8
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+ path that microcontroller kernels run fastest.
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+
214
+ <p align="center">
215
+ <img src="assets/architecture.png" alt="Input of 3 new log-mel frames by 40 bands; S1 frequency stem to 3 by 20 by 16; S2 depthwise-separable block to 1 by 10 by 32; S3 collapse from 320 values to 48 channels; six causal temporal blocks at 48 channels; head from 48 to 1 with a sigmoid" width="100%">
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+ </p>
217
+
218
+ ### Layer Breakdown & Compute (MACs)
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+
220
+ Shapes are per 30 ms step. We make every convolution over time causal, padded on
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+ the left only, and every convolution over frequency keeps its size.
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+
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+ | # | Layer | Operation | Output (T, F, C) | Weights | MACs per step |
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+ |---|---|---|---|---:|---:|
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+ | S1 | Frequency stem | Conv2D 3×3, stride (1, 2), 1 → 16, BN, ReLU | 3, 20, 16 | 144 | 8,640 |
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+ | S2a | Frequency depthwise | Depthwise Conv2D 3×3, stride (3, 2), 16 channels, BN, ReLU | 1, 10, 16 | 144 | 1,440 |
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+ | S2b | Channel mix | Pointwise 16 → 32, BN, ReLU | 1, 10, 32 | 512 | 5,120 |
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+ | S3 | Collapse | Flatten 10 × 32 = 320, 1×1 conv to 48, BN, ReLU | 1, 48 | 15,360 | 15,360 |
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+ | B1 | Temporal block, d = 1 | Depthwise Conv1D k5, pointwise 48 → 48, residual | 1, 48 | 2,544 | 2,544 |
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+ | B2 | Temporal block, d = 1 | same | 1, 48 | 2,544 | 2,544 |
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+ | B3 | Temporal block, d = 2 | same | 1, 48 | 2,544 | 2,544 |
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+ | B4 | Temporal block, d = 2 | same | 1, 48 | 2,544 | 2,544 |
233
+ | B5 | Temporal block, d = 3 | same | 1, 48 | 2,544 | 2,544 |
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+ | B6 | Temporal block, d = 3 | same | 1, 48 | 2,544 | 2,544 |
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+ | H | Head | Pointwise 48 → 1, sigmoid in float | 1, 1 | 48 | 48 |
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+
237
+ <p align="center">
238
+ <img src="assets/temporal-block.png" alt="Inside each temporal block: a causal depthwise 1D convolution with kernel 5 and dilation d, batch norm and ReLU, a pointwise 48 to 48 convolution and batch norm, added back to the input, then ReLU" width="100%">
239
+ </p>
240
+
241
+ We picked dilations of 1, 1, 2, 2, 3, 3, which give the trunk 49 steps of
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+ context, 1.47 s, and the stem and the window overhang add about 40 ms more:
243
+ ≈ 1.51 s in all. We sized that to cover *Utho Kikkar*, which takes about 1.0 to
244
+ 1.2 s to say, with room for slow speakers, and no more. Extra context would cost RAM and let the model latch on
245
+ to background sound.
246
+
247
+ <p align="center">
248
+ <img src="assets/compute.png" alt="Multiply-accumulates per step: S3 collapse 15,360 (33.5 percent), temporal blocks 15,264 (33.3 percent), S1 stem 8,640 (18.8 percent), S2 block 6,560 (14.3 percent), head 48 (0.1 percent)" width="100%">
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+ </p>
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+
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+ | Parameters | Count |
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+ |---|---:|
253
+ | Convolution weights, S1 to S3 | 16,160 |
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+ | Convolution weights, B1 to B6 | 15,264 |
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+ | Head weights | 48 |
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+ | **Convolution subtotal** | **31,472** |
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+ | Batch-norm scale and bias, folded (688 channels × 2) | 1,376 |
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+ | Head bias | 1 |
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+ | **Total** | **32,849** |
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+
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+ At 33.3 steps a second our model does 1.53 million multiply-accumulates a
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+ second.
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+
264
+ ## RAM Allocation & Tensor Arena Budget
265
+
266
+ <p align="center">
267
+ <img src="assets/memory.png" alt="Design budget for the listening path: pre-roll ring 32 KB, TFLM tensor arena about 20 KB, task stacks 8 KB, FFT scratch 4 KB, interpreter about 3 KB, I2S DMA 1.3 KB, frame buffer 1.0 KB, mel and CMS state 0.4 KB, smoothing 0.1 KB" width="100%">
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+ </p>
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+
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+ | Component | RAM |
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+ |---|---:|
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+ | I2S DMA buffers, 4 × 10 ms × int16 | 1.3 KB |
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+ | Frame assembly buffer, 480 samples | 1.0 KB |
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+ | FFT scratch, 512 complex float32 | 4.0 KB |
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+ | Mel output and CMS running state | 0.4 KB |
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+ | TFLM tensor arena: activations, kernel scratch and 2.3 KB of streaming state | ≈ 20 KB |
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+ | Interpreter, op resolver and allocator | ≈ 3 KB |
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+ | Smoothing and refractory state | 0.1 KB |
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+ | Task stacks, audio and inference | 8 KB |
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+ | **Keyword spotting in total** | **≈ 38 KB** |
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+ | Pre-roll ring, 1 s at 16 kHz int16, for the hand-off to the ASR server | 32 KB |
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+ | **Listening path in total** | **≈ 70 KB** |
283
+
284
+ That leaves us about 186 KB of the 256 KB limit for everything else. The peak
285
+ activation is only 960 bytes, at S1's output; the arena is mostly kernel scratch
286
+ and alignment.
287
+
288
+ ### Ring Buffers & Streaming State
289
+
290
+ We keep this state between steps, inside the TFLM arena as resource variables,
291
+ so we allocate nothing separately.
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+
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+ | Buffer | Shape | Bytes |
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+ |---|---|---:|
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+ | S1 time history | 2 frames × 40 | 80 |
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+ | S2a time history | stride 3 over kernel 3, nothing to keep | 0 |
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+ | B1 ring, d = 1 | 4 × 48 | 192 |
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+ | B2 ring, d = 1 | 4 × 48 | 192 |
299
+ | B3 ring, d = 2 | 8 × 48 | 384 |
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+ | B4 ring, d = 2 | 8 × 48 | 384 |
301
+ | B5 ring, d = 3 | 12 × 48 | 576 |
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+ | B6 ring, d = 3 | 12 × 48 | 576 |
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+ | **Total** | | **2,384** |
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+
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+ A dilated causal depthwise convolution needs (k − 1) × d × C bytes of history
306
+ at int8.
307
+
308
+ ### Flash
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+
310
+ | Item | Bytes |
311
+ |---|---:|
312
+ | int8 weights | 31,472 |
313
+ | int32 biases, 689 channels × 4 | 2,756 |
314
+ | Per-channel scales, 689 × 4 | 2,756 |
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+ | FlatBuffer structure and metadata | ≈ 4,096 |
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+ | Mel filterbank and Hann window tables | ≈ 3,072 |
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+ | **Total** | **≈ 44 KB** |
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+
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+ ## Post-Processing & Trigger Logic
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+
321
+ <p align="center">
322
+ <img src="assets/trigger.png" alt="Illustration: the smoothed score stays low while Utho Kikkar is said, rises once it ends, and crosses the threshold 60 ms later, which wakes the board; a second peak inside the 1 s refractory period is ignored" width="100%">
323
+ </p>
324
+ <p align="center"><sub>An illustration of the rule, not a recording.</sub></p>
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+
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+ | Step | Setting |
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+ |---|---|
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+ | Model output | one probability per 30 ms step |
329
+ | Smoothing | average of the last 3 steps, 90 ms |
330
+ | Threshold τ | 0.7, picked from the DET curve of the int8 model |
331
+ | Refractory | 1 s after a wake-up |
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+ | Phrase end to wake-up | 60 ms: up to 30 ms for the step that holds the end of the phrase, then one more step |
333
+
334
+ The wake-up comes quickly because of how we labelled the model. We turn its
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+ target on one step *before* the phrase ends, so by the time the step holding the
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+ end is done, two of the three steps in the average are already high, and one
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+ more step takes it over τ. Computing a step takes a millisecond or less, so it
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+ barely adds to the 60 ms.
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+
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+ Quantisation moves the operating point, so we always pick the threshold on the
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+ int8 model and never carry it over from the float one. If false activations
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+ will not come down, the cheapest remaining lever we have is two or three frames
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+ of lookahead, paid for directly in latency.
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+
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+ ## Training Methodology & Supervision
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+
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+ <p align="center">
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+ <img src="assets/supervision.png" alt="One label per 30 ms step: for Utho Kikkar only the six steps around the end of the phrase are labelled 1, and mid-phrase steps are 0; wrong order and half a phrase are 0 throughout" width="100%">
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+ </p>
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+
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+ **Phrase-completion supervision.** We built the head as a per-step detector,
352
+ not a clip classifier. We label only the six steps from one before the end of
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+ the phrase to four after it, about 180 ms, as 1. We label every other step 0,
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+ including the middle of the phrase, and partial or reversed phrases 0
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+ throughout. That is what teaches the model word order, and it makes the firing
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+ delay equal to the smoothing window. We get the phrase end from energy-based
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+ silence trimming on recordings, or straight from the synthesiser for TTS clips,
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+ and when we speed a clip up or slow it down, we move its end by the same factor.
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+
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+ | Frames | Label |
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+ |---|---|
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+ | Steps from t_end − 1 to t_end + 4, about 180 ms | 1 |
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+ | Every other step, mid-phrase included | 0 |
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+ | Partial phrase, *utho* or *kikkar* alone | 0 throughout |
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+ | Reversed order, *kikkar utho* | 0 throughout |
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+
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+ **Loss and selection.** We use per-step weighted binary cross-entropy.
368
+ Positives are about 6 steps in 300, but a positive weight of 50 over-fires, so
369
+ we start it at 8; we weight confusable negatives 8 and easy ones 1. We choose
370
+ checkpoints on the fewest false activations per hour of held-out continuous
371
+ speech first, and on recall only among those that meet the false-activation
372
+ target, never on accuracy.
373
+
374
+ **Positives.** We use about 2,000 real recordings, split by speaker so that
375
+ the model never hears validation and test speakers in training. On top of that,
376
+ we add several thousand synthetic renditions from AI4Bharat Indic-TTS, IndicF5,
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+ Indic Parler-TTS, MMS-TTS in Punjabi and Hindi, and Piper, with varied prosody
378
+ and gaps between the two words. We oversample the real recordings so they carry
379
+ 25 to 40% of the positive signal, otherwise the model learns vocoder artefacts.
380
+
381
+ **Confusable negatives.**
382
+
383
+ | Kind | Examples |
384
+ |---|---|
385
+ | Partial phrase | *utho*, *kikkar* |
386
+ | Wrong order | *kikkar utho* |
387
+ | Sounds like *kikkar* | kukkad, kukkar, chakkar, takkar, shakkar, nikkar, fikar, Makkar, Thakkar, kirkiri |
388
+ | Sounds like *utho* | utha, uthao, uthe, utha lo, uncha |
389
+ | Natural continuations | utho ji, utho beta, utho jaldi |
390
+ | Across word boundaries | "…jhoota kikar…", "…peeche kikar…" |
391
+ | English in the middle | kicker, quicker, sticker, liquor, auto, photo |
392
+
393
+ **Background negatives.** We use continuous Hindi and Punjabi speech from
394
+ Common Voice, IndicVoices and Shrutilipi, plus sounds from around the house, and
395
+ stream them as long segments so that training sees what the board hears.
396
+
397
+ **Augmentation.** We apply room impulse responses (OpenSLR-28, BUT ReverbDB) at
398
+ different distances; noise from MUSAN, DEMAND and ESC-50 at 0 to 20 dB SNR; gain from −20
399
+ to 0 dBFS; speed 0.9 to 1.1; pitch ±2 semitones; microphone response tilt; mild
400
+ clipping; frequency masking. We keep time masking light, because the labels
401
+ depend on timing.
402
+
403
+ **Hard negatives.** We train, stream the model over more than 10 hours of
404
+ Hindi, Punjabi and English speech, collect every false trigger as a new
405
+ negative, and train again, two or three times over.
406
+
407
+ **Streaming.** We train with causal convolutions over long 8 to 10 s chunks,
408
+ which is fast and parallel, then deploy the same weights running step by step
409
+ on ring buffers. We check that the streaming and full-chunk outputs agree
410
+ within 1e-3 before quantising.
411
+
412
+ **Quantisation.** We quantise after training, with a representative set of
413
+ real streaming features rather than synthetic clips, and fold batch norm into
414
+ the convolutions before export.
415
+
416
+ | Tensor | Scheme |
417
+ |---|---|
418
+ | Activations | int8, asymmetric, per tensor |
419
+ | Weights | int8, symmetric, per channel |
420
+ | Bias | int32 |
421
+ | Final sigmoid | float32, on a single number |
422
+
423
+ ## Hardware Profiling & Benchmarks
424
+
425
+ <table>
426
+ <tr>
427
+ <td align="center" width="50%"><img src="assets/board-stm32n657.jpg" alt="STM32N6570-DK with the kikkar flower in full bloom on its display" width="100%"></td>
428
+ <td align="center" width="50%"><img src="assets/board-esp32.jpg" alt="ESP32 board with an I2S microphone on perfboard" width="100%"></td>
429
+ </tr>
430
+ <tr>
431
+ <td align="center"><b>Premium:</b> STM32N657, Ethernet and an 800 × 480 display</td>
432
+ <td align="center"><b>Budget:</b> ESP32 and an I2S microphone, on Wi-Fi</td>
433
+ </tr>
434
+ </table>
435
+
436
+ <p align="center">
437
+ <img src="assets/on-device.png" alt="Idle CPU: STM32N657 0.5%, ESP32 4%, limit 10%. RAM used: STM32N657 150 KB, ESP32 190 KB, limit 256 KB. Handoff latency: STM32N657 80 ms, ESP32 90 ms." width="100%">
438
+ </p>
439
+
440
+ | | STM32N657, premium | ESP32, budget | SIH limit |
441
+ |---|---|---|---|
442
+ | CPU while idling in continuous listening | **0.5%** | **4%** | under 10% |
443
+ | RAM used | **150 KB** | **190 KB** | under 256 KB |
444
+ | Latency, keyword end to audio at the ASR server | **80 ms** | **90 ms** | as low as possible |
445
+
446
+ These are our numbers for the whole application, networking and display
447
+ included, not the model alone. Of the 80 ms, 60 ms is our model making sure; the other
448
+ 20 ms is the board getting the first audio to the server over Ethernet. Wi-Fi
449
+ takes 30 ms for the same step on the ESP32.
450
+
451
+ ### Core Utilization & RTOS Tasks
452
+
453
+ On an ESP32-S3 at 240 MHz with ESP-NN int8 kernels:
454
+
455
+ | Task | Rate | Share of one core |
456
+ |---|---|---|
457
+ | FFT, mel and CMS | 100 a second | ≈ 0.6% |
458
+ | Inference | 33.3 a second | 0.7 to 2.6% |
459
+ | I2S, DMA and housekeeping | | ≈ 0.5% |
460
+ | **Idle listening in total** | | **≈ 2 to 4%** |
461
+
462
+ We run capture and inference as separate FreeRTOS tasks pinned to different cores.
463
+ A classic ESP32 has no vector unit and runs the inference about three times
464
+ slower, which still fits well inside 10% of a core.
465
+
466
+ ## Target Firmware Integration (STM32 & ESP32)
467
+
468
+ On the ESP32 we run the model under TensorFlow Lite for Microcontrollers, with
469
+ int8 kernels from ESP-NN. Its 2.4 KB of streaming state lives inside the TFLM
470
+ arena as resource variables, so we have nothing extra to allocate. Size the
471
+ arena from `arena_used_bytes()` measured on the device, not from the estimate
472
+ above.
473
+
474
+ On the STM32N657 we do not use TFLM at all. We wrote a small exporter that turns
475
+ this `.tflite` into a flat list of 23 operations, and our firmware runs them with
476
+ its own int8 kernels, using Helium vector instructions for the dot products. It keeps the
477
+ same 2,384 bytes of history in rings, one per layer that looks back in time,
478
+ and the whole model works inside a 5.3 KB arena. Our firmware, the exporter,
479
+ the flower and the streaming pipeline are on [GitHub](https://github.com/SherTheCoder/Folklore).
480
+
481
+ ## Field Testing & Edge Constraints
482
+
483
+ - **Test it on real people in real rooms,** and pick the threshold there, on
484
+ the int8 model.
485
+ - **It knows one phrase.** Ours is not a general speech model, and our model cannot
486
+ currently tell who is speaking.
487
+ - **The front end has to match.** The running-mean normalisation is part of
488
+ the input, and it needs its first half second after boot to settle.
489
+ - **Privacy is the point of our design.** We keep all audio on the board
490
+ until the wake word is confirmed.
491
+
492
+ ## Licence
493
+
494
+ We release it under the [Apache 2.0](https://www.apache.org/licenses/LICENSE-2.0)
495
+ licence.
496
+
497
+ ## Citation
498
+
499
+ ```bibtex
500
+ @misc{teamfolklore2026kikkarkws,
501
+ title = {Kikkar KWS: a 44 KB streaming wake-word model for Utho Kikkar},
502
+ author = {{Team Folklore}},
503
+ year = {2026},
504
+ howpublished = {\url{https://huggingface.co/SherTheCoder/TeamFolklore_Model}}
505
+ }
506
+ ```
507
+
508
+ ## Made by
509
+
510
+ We are Team Folklore, and we made this for Smart India Hackathon 2026. Our
511
+ firmware, flower and streaming pipeline are on [GitHub](https://github.com/SherTheCoder/Folklore);
512
+ our training data is [SherTheCoder/TeamFolklore_UthoKikkar](https://huggingface.co/datasets/SherTheCoder/TeamFolklore_UthoKikkar).
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