compressionkit-ppg-4x-v1.0

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: 4x
• Quantization: INT8
• RVQ Levels: 4
• Codebook Size: 256 entries × 16D
• Encoder Input: [None, 1, 320, 1]
• Encoder Output: [None, 1, 80, 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 (%)	1.14
Truth PRD at native noise (%)	34.36
Faithful PRD vs input (%)	3.44
PRD degradation slope (PRD%/dB)	4.40
PRD at 0 dB SNR (%)	75.92
PRD at -6 dB SNR (%)	104.75
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 (%)	3.4358	1.3207	4.2732
RMSE	0.0183	0.0131	0.0318
Cosine Similarity	0.9959	0.9999	0.9999

Spectral

• Band Total Relative Error (median): 0.0065

Bitrate

Encoder Precision Parity

Difference from FP32 reconstruction on a disjoint real-data holdout; lower is better.

Encoder	P90 PRD	Worst PRD	Status
FP16	0.21%	1.01%	recommended
INT16X8	0.63%	1.80%	recommended
INT8	2.70%	3.31%	recommended

Usage

Python (compressionkit runtime)

from compressionkit.runtime import RVQCodec

codec = RVQCodec.from_pretrained("Ambiq/compressionkit-ppg-4x-v1.0")

# 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_float32.tflite	Float32 encoder for browser/server runtimes
encoder_fp16.tflite	FP16 encoder variant for supported edge runtimes
encoder_int16x8.tflite	INT16x8 encoder variant for supported edge runtimes
encoder.h	C header for encoder
encoder.keras	Float32 Python reference encoder (training/inspection use)
decoder_float32.tflite	Float32 decoder (server-side evaluation)
decoder_int8.tflite	INT8 decoder (optional, on-device)
decoder.keras	Float32 Python reference decoder (training/inspection use)
codebook.npz	RVQ codebook tables
codebook.h	C header for codebook
config.json	Deployment manifest
sample_stimulus.npz	Synthetic test data
demo_recordings.npz	10 real, quality-gated browser-demo recordings
demo_recordings_manifest.json	Recording provenance, license, and quality metadata
quality_scorecard.json	Full evaluation metrics

Dataset & License

Training data provenance is not recorded in this package; sample data uses synthetic physiokit waveforms only — no patient data is redistributed. Demo recordings: BIDMC PPG and Respiration Dataset v1.0.0 (source); real, quality-gated excerpts are released under ODC-By-1.0. https://opendatacommons.org/licenses/by/1-0/

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}
}