Ambiq/compressionkit-ppg-2x-v1.0

compressionkit-ppg-2x

A PPG signal compression codec using Residual Vector Quantization (RVQ), optimized for edge and wearable devices.

Model Details

• Modality: PPG
• Sample Rate: 64 Hz
• Compression Ratio: 2.0x
• Quantization: INT8
• RVQ Levels: 4
• Codebook Size: 256 entries × 16D
• Encoder Input: [None, 1, 320, 1]
• Encoder Output: [None, 1, 160, 16]

Quality Metrics

Fidelity & Robustness

Both fidelity yardsticks are reported so the codec is judged fairly: faithfulness is PRD vs the recorded (still-noisy) input, while truth fidelity is PRD vs clean ground truth. Lower is better.

Metric	Value
Truth PRD vs clean (%)	0.62
Truth PRD at native noise (%)	34.35
Faithful PRD vs input (%)	2.59
PRD degradation slope (PRD%/dB)	4.40
PRD at 0 dB SNR (%)	75.93
PRD at -6 dB SNR (%)	104.76
Pure-noise imprint autocorr	0.2853

Time Domain

PRD here is faithfulness (vs the recorded input); see Fidelity & Robustness above for the clean-truth and noise-regime view.

Metric	Mean	Median	P90
PRD vs input — faithfulness (%)	2.5884	0.7868	3.3223
RMSE	0.0129	0.0078	0.0251
Cosine Similarity	0.9969	1.0000	1.0000

Spectral

• Band Total Relative Error (median): 0.0091

Bitrate

Usage

Python (compressionkit runtime)

from compressionkit.runtime import RVQCodec

codec = RVQCodec.from_pretrained("Ambiq/compressionkit-ppg-2x")

# Encode: float32 signal → RVQ indices
indices = codec.encode(signal)

# Decode: RVQ indices → reconstructed signal
recon = codec.decode(indices)

Local deployment directory

codec = RVQCodec("path/to/deploy/")

Files

File	Description
encoder_int8.tflite	INT8 quantized encoder (on-device)
encoder.h	C header for encoder
decoder_float32.tflite	Float32 decoder (server-side evaluation)
decoder_int8.tflite	INT8 decoder (optional, on-device)
codebook.npz	RVQ codebook tables
codebook.h	C header for codebook
config.json	Deployment manifest
sample_stimulus.npz	Synthetic test data
quality_scorecard.json	Full evaluation metrics

Dataset & License

Training data: BIDMC + BUT PPG + PPG-DaLiA + WESAD (all open, no restricted-access dependency). Sample data uses synthetic physiokit waveforms only — no patient data is redistributed.

Model weights are released under the Ambiq Model Weights License — deployment is restricted to Ambiq silicon devices. See LICENSE-MODEL-WEIGHTS.md for full terms.

Citation

@software{compressionkit,
  author = {Ambiq AI},
  title = {compressionKIT: Signal Compression for Edge AI},
  url = {https://github.com/AmbiqAI/compressionkit}
}