The Gemma 4 Good Hackathon · Impact Track · Safety & Trust prize
TrueVoice
Built by Shiwon Oh and hyeminss11
A voice-deepfake research prototype with a frozen Gemma audio encoder and a 1.5 MB classification head. Its browser demo requires a notebook session; the claimed 5.2% equal error rate was not independently confirmed.
I also participated in this hackathon with Memory Moment. This coverage was prepared independently after results were announced.
The idea worth stealing
The audio tower is a feature extractor. Freeze it and train 1.5 MB.
TrueVoice never fine-tunes Gemma 4. It runs a mel spectrogram through the model’s frozen audio encoder, mean-pools the 1536-dimensional states, and trains a two-layer head to say real or fake. The decision that mattered was in the data: studio-quality training clips were pushed through an 8 kHz downsample-and-upsample round-trip, so the classifier learns the artifacts of synthetic speech rather than the polish of a studio, the one cue a real phone call would strip away.
What we checked
Date checked: .
Public repository at the submission revision, Kaggle writeup, and linked artifacts; code was read, not executed. Deployment checks and limits are described below.
Labels apply to each finding and the evidence described, not to the project as a whole.
Not independently verified means the available evidence was insufficient to confirm a claim. It does not mean the claim is false.
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The head is 1.5 MB
Verified
classifier_head.pt is 1,578,541 bytes: Linear 1536→256, GELU, Dropout 0.3, Linear 256→2, trained with the audio tower’s requires_grad set to False. The file named metadata.json is a byte-identical copy of it. Source
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The codec is a resample
Verified
codec_simulate takes 16 kHz audio down to 8 kHz and back with torchaudio. No G.711, AMR, or Opus is involved, which the writeup states accurately. Source
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5.2 percent EER
Not independently verified
All four notebooks have their outputs stripped, so the EER, the 96 percent accuracy, and the 148,176-sample test set live only in the README. Reproducing them needs ASVspoof 2021 and an A100. Source
What we need: Executed evaluation notebooks, the ASVspoof test manifest, and per-sample scores for the reported EER and accuracy.
Under the hood
- E4B’s tower, 29-second clips
- Features come from google/gemma-4-e4b-it’s audio_tower with mean pooling over time; inputs are clipped at 29 seconds, and a bfloat16 cast in the collator is what fixed the NaNs.
- The demo lives 72 hours
- Running the last cell of truevoice_demo.ipynb prints a Gradio share link; there is no hosted deployment, so a suspicious call today needs a Colab session first.
Nuance
A sound recipe and a small, checkable artifact, but the repository is four notebooks and a weight file with no tests or requirements, and the training split is 2,580 real clips against 22,800 fake. On-device E2B and non-English coverage are directions the writeup names, not results.
Sources
Last updated: . Editorial updates do not imply a new technical check.
Builder credits reviewed: , using the official announcement, submission, and any linked credit sources.
The official winner announcement credits Shiwon Oh; the writeup uses shiwoni. The second author is credited as hyeminss11; the demo uploader name alone does not confirm a full author name.
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