Ambiq/compressionkit-e2a2-audio-v0.3

E2A2 audio codec for compressionkit

E2A2 (Encoding Efficient Asymmetric Autoencoders) audio is an audio codec for 44.1 kHz stereo music, the two channels coded together. This repository holds its weights in the layout that compressionkit v0.3 reads, with an encoder half and a decoder half that load separately.

Source and permission

The weights are redistributed from their original public release, danjacobellis/E2A2, subfolder audio/, revision aafe5975, with the permission of the author, Dan Jacobellis. Ambiq did not train this codec. Its description, development and evaluation are documented at the original source and on the codec's page, https://danjacobellis.net/compressors/E2A2_audio. The entropy coder is GGDLPC (https://danjacobellis.net/GGDLPC/).

Every tensor here equals the tensor of the same name at that revision; this repository divides them into the encoder and decoder halves listed below and adds the files compressionkit uses.

Files

• encoder/config.json, encoder/weights.safetensors (the merged.{op}.encoders.* tensors) and encoder/entropy.json (the GGDLPC tables): everything needed to encode.
• decoder/config.json, decoder/weights.safetensors (the merged.{op}.decoder.* tensors): everything needed to decode. Each config.json is the full source configuration, so each half constructs alone.
• rd.json: the rate–distortion curve of the original release, byte-identical to it. Each validation item was zero-meaned and peak-normalized over its whole length before coding, a scaling a real-time encoder cannot compute within its block latency, so the curve is not a measurement of a configuration deployable in real time.
• calibrations/<dataset>.json (musdb): fixed input maps, published by Ambiq for compressionkit.calibrate.load, that turn int16 codes of a dataset into the codec's input with two constants (an offset and a scale).
• web/: the decoder of each operating point that the compressionkit browser demo offers, as LiteRT files (section below). The compressionkit loaders do not download web/.

file	bytes	SHA-256
calibrations/musdb.json	6,541	6da7d18d21657312254bfa572a7486f8b306494f340d0ef8ae56ecb3130ec901
decoder/config.json	2,280	296eecf80011ff77a0efda76d208586ed70a197eb98b2cabbc566127555373f8
decoder/weights.safetensors	4,855,248,808	3ecdc061c498bb2fe6159f20a50c134a790d2f793ceb8572ad6254f11c857a73
encoder/config.json	2,280	296eecf80011ff77a0efda76d208586ed70a197eb98b2cabbc566127555373f8
encoder/entropy.json	13,601	d0a03b4886c89f37e53984b5efdd3717343525ab3577de25e45a99d0695f0f0f
encoder/weights.safetensors	183,932	a0196b471984981c5734f84924672ca1cf507487fc7b46d945d2afd5cca8c4a2
rd.json	1,151	1b8ca06684a13c573c1e6e34f2e1b4c05a87c8093fe4ad4d2656be9ab59843d6

Input, output and operating points

Input: float32 (2, L) samples in [−1, 1] at 44.1 kHz. Output: a reconstruction in the same form. Operating points (cumulative latent channels): [4, 9, 15, 21, 33, 42, 51]. The stream of a lower operating point is a literal bit-prefix of the stream of the highest, and the rates are entropy-coded bits. compressionkit converts nothing: each codec states its input type and range.

Using it with compressionkit

compressionkit v0.3 is in pre-release; these loaders are part of it.

from compressionkit.e2a2 import hub

# both halves
config, weights, coder, ops = hub.load_split_from_hub('audio')
model = hub.load_codec(config=config, weights=weights, n_ch=ops[-1])

# one half (encode-only shown; half='decoder' for decode-only)
cfg, w, coder, ops = hub.load_split_from_hub('audio', half='encoder')
encoder = hub.build_partial(cfg, w, ops[-1])

from compressionkit import calibrate
cal = calibrate.load('audio', 'musdb')   # the published map for that dataset

Status and limitations

• A reference codec for evaluation and development with compressionkit, redistributed as released; not a production model, and not qualified for any product or regulated use.
• Its quality on data unlike the data of its original release is not characterized here; measure it on your own data (compressionkit.calibrate fits an input map on your training split).
• Maintainer for compressionkit: Dan Jacobellis (Ambiq). Questions about the codec itself: the original source.

Browser decoders (web/)

For each operating point the compressionkit browser demo offers, its decoder as a LiteRT .tflite window decoder, which runs in a web browser on LiteRT.js (CPU), with a .json beside it that gives its shapes and windowing. A window decodes chunk output samples (pixels along each side for the image codec) with margin of context on each side; the latent grid is cut into overlapping windows and the outputs joined. The PSNR column is the largest difference between the PSNR of the joined output, decoded in LiteRT.js in Chromium, and that of the full-size PyTorch decode, over the example recordings of the demo. The compressionkit loaders do not download web/.

file	operating point	chunk	margin	bytes	PSNR difference (dB, rows)	decoder weights (SHA-256)
web/audio_op4_chunk16384_m4096.tflite	4	16384 samples	4096	404,739,432	7.0e-09 (1)	3ecdc061c498
web/audio_op9_chunk16384_m4096.tflite	9	16384 samples	4096	404,800,872	1.4e-07 (1)	3ecdc061c498
web/audio_op15_chunk16384_m4096.tflite	15	16384 samples	4096	808,238,040	4.1e-07 (1)	3ecdc061c498
web/audio_op21_chunk16384_m4096.tflite	21	16384 samples	4096	808,385,496	3.6e-07 (1)	3ecdc061c498
web/audio_op33_chunk16384_m4096.tflite	33	16384 samples	4096	808,975,320	2.9e-07 (1)	3ecdc061c498
web/audio_op42_chunk16384_m4096.tflite	42	16384 samples	4096	809,860,056	2.2e-07 (1)	3ecdc061c498
web/audio_op51_chunk16384_m4096.tflite	51	16384 samples	4096	811,629,528	1.1e-06 (1)	3ecdc061c498

Weights fp32, converted from decoder/weights.safetensors with litert-torch 0.10.0. The last column gives the start of the SHA-256 of the decoder/weights.safetensors it was converted from, which is this repository's.