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Showing content from https://github.com/slmdev/sac below:

slmdev/sac: state-of-the-art lossless audio compression

Sac is a state-of-the-art lossless audio compression model

Lossless audio compression is a complex problem, because PCM data is highly non-stationary and uses high sample resolution (typically >=16bit). That's why classic context modelling suffers from context dilution problems. Sac employs a simple OLS-NLMS predictor per frame including bias correction. Prediction residuals are encoded using a sophisticated bitplane coder including SSE and various forms of probability estimations. Meta-parameters of the predictor are optimized with DDS on by-frame basis. This results in a highly asymmetric codec design.

This program wouldn't exist without the help from the following people (in no particular order):

Matt Mahoney, Dmitry Shkarin, Eugene D. Shelwien, Florin Ghido, Grzegorz Ulacha

Input: wav file with 1-16 bit sample size, mono/stereo, pcm
Output: sac file including all input metadata
Decoded wav file is bit for bit identical to input wav file
MD5 of raw pcm values

Sac uses fp64 for many internal calculations. The change of compiler options or (cpu-)platform might effect the output. Use at your own risk and for testing purposes only.

Sac v0.7.18

16 files (44.1Khz, stereo) - 51.014.742 bytes - parallel on i7-13700H

Asymmetric encoding profiles - bits per sample (bps) is mean bps over all files

Profile Size Enc-time Dec-time bps FLAC -8 100.0% 29.793.060 00:00:00 00:00:00 9.385 --normal 89.6% 26.691.217 00:00:22 00:00:20 8.401 --high 89.1% 26.546.317 00:03:42 00:00:50 8.352 --veryhigh 88.9% 26.480.793 00:17:38 00:00:53 8.330 --extrahigh 88.8% 26.453.344 00:48:46 00:00:52 8.322 --best 88.6% 26.397.759 04:37:00 00:01:00 8.303

Comparison with other lossless audio codecs

Program Parameters Source Sac v0.7.18 --best open OFR v5.100 --preset max closed paq8px_v208fix1 -6 open MP4ALS RM23 -b -p -z3 open MAC v10.44 -c5000 open FLAC v1.4.3 -8 open

Numbers are bits per sample (bps)

Name Sac OFR paq8px MP4ALS MAC FLAC ATrain 6.991 7.156 7.353 7.232 7.269 7.962 BeautySlept 7.089 7.790 7.826 8.305 8.464 10.134 chanchan 9.658 9.778 9.723 9.886 9.951 10.206 death2 5.036 5.465 5.215 6.660 6.213 6.092 experiencia 10.825 10.915 10.963 10.992 11.005 11.428 female_speech 4.356 4.498 4.708 4.711 5.190 5.364 FloorEssence 9.034 9.409 9.488 9.509 9.537 10.201 ItCouldBeSweet 8.182 8.310 8.330 8.396 8.531 9.064 Layla 9.454 9.571 9.725 9.691 9.783 10.415 LifeShatters 10.748 10.808 10.868 10.836 10.838 11.194 macabre 8.968 9.026 9.249 9.076 9.172 10.043 male_speech 4.229 4.256 4.509 4.813 5.255 5.674 SinceAlways 10.329 10.409 10.455 10.473 10.522 11.254 thear1 11.362 11.400 11.474 11.425 11.451 11.783 TomsDiner 6.991 7.108 7.057 7.268 7.432 8.572 velvet 9.595 9.990 10.030 10.212 10.461 10.770 Mean 8.303 8.493 8.561 8.718 8.817 9.385 Enc-time 04:37:00 00:00:09 00:05:37 00:00:15 00:00:01 00:00:00 Dec-time 00:01:00 00:00:02 00:05:40 00:00:13 00:00:01 00:00:00

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