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Ambiq/
compressionkit-ecg-hybrid-4x-v1.0

Name: compressionkit-ecg-hybrid-4x-v1.0
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compressionkit-ecg-hybrid-4x

A ECG signal compression codec: a learned wavelet-gain denoiser (trained weights) followed by wavelet + SPIHT + arithmetic coding. The deployable artifact is the denoiser weights, the bitstream contract, and a portable C99 reference implementation for the SPIHT stage.

Operating point

Field	Value
Modality	ECG
Sample rate	256 Hz
Frame size	512 samples
Target CR	4x
Wavelet	`bior4.4`
DWT levels	6
Bit budget	2048 bits/frame
Entropy coder	arithmetic coding

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 (%)	7.69
Truth PRD at native noise (%)	34.61
Faithful PRD vs input (%)	8.99
PRD degradation slope (PRD%/dB)	2.43
PRD at 0 dB SNR (%)	37.89
PRD at -6 dB SNR (%)	54.39
Pure-noise imprint autocorr	0.1243

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 (%)	8.9916	7.3665	14.5831
RMSE	0.0899	0.0737	0.1458
Cosine Similarity	0.9948	0.9978	0.9995

Spectral

Band Total Relative Error (median): 0.1385

Bitrate

Python quickstart

python

from compressionkit.runtime import load_codec

codec = load_codec("Ambiq/compressionkit-ecg-hybrid-4x")
enc = codec.compress(frame)   # frame: (frame_size,) float32
recon = codec.decompress(enc)

C quickstart

The SPIHT stage ships a portable C99 reference; the denoiser (denoiser_gain_model.keras) currently only has a Python/TFLite runtime path. Run the denoiser stage first (Python, or a converted TFLite Micro model) and feed its output into the C SPIHT encoder below.

#include "spiht_app_config.h"

float frame[APP_SPIHT_FRAME_SIZE];
uint8_t bitstream[APP_SPIHT_MAX_BYTES];
/* ... fill frame from sensor (post-denoise, if hybrid) ... */
size_t nbits = spiht_encode_frame(&enc, bitstream, APP_SPIHT_MAX_BITS);

Files

File	Description
`config.json`	Deploy manifest (`family: "hybrid"`)
`spiht_config.json`	Codec parameters (language-neutral)
`sample_stimulus.npz`	Synthetic test frames
`reference_vectors.npz`	Reference encode/decode vectors
`c_sources/spiht.[ch]`	Portable C99 reference
`c_sources/spiht_app_config.h`	Codec-specific defines
`model_card.json`	Provenance metadata
`scorecard.json`	Frozen evaluation summary
`denoiser_gain_model.keras`	Learned wavelet-gain denoiser (trained weights)
`hybrid_manifest.json`	Pipeline stage order (denoise → SPIHT)

Dataset & license

Evaluation data: PTB-XL (CC BY 4.0). Sample data may include excerpts under the original license terms.

Codec source released under the OTHER license.

Citation

bibtex

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

Ambiq/compressionkit-ecg-hybrid-4x-v1.0