https://github.com/slmdev/sac
state-of-the-art lossless audio compression
https://github.com/slmdev/sac
audio audio-codec audio-compression compression lossless-audio
Last synced: about 1 year ago
JSON representation
state-of-the-art lossless audio compression
- Host: GitHub
- URL: https://github.com/slmdev/sac
- Owner: slmdev
- License: mit
- Created: 2018-06-11T17:58:47.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2025-03-10T07:35:06.000Z (about 1 year ago)
- Last Synced: 2025-03-10T08:29:25.162Z (about 1 year ago)
- Topics: audio, audio-codec, audio-compression, compression, lossless-audio
- Language: C++
- Homepage:
- Size: 321 KB
- Stars: 49
- Watchers: 4
- Forks: 5
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-compopt - SAC - State of the Art Lossless Codec, best alternative to OptimFROG. (Audio / Lossless compressors)
README
# Sac
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](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2005WR004723) 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
## Technical features
* 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
## Technical limitations
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.
## Benchmarks
**Sac v0.7.13**
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%|26.692.524|00:00:32|00:00:27|8.401|
|--high|89.2%|26.561.562|00:05:24|00:00:50|8.359|
|--veryhigh|88.9%|26.499.219|00:31:06|00:00:57|8.337|
|--best|88.7%|26.424.040|07:35:00|00:01:19|8.313|
**Comparison with other lossless audio codecs**
|Program|Parameters|Source|
|:-|:-|:-|
|Sac v0.7.13|--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|6.994|7.156|7.353|7.232|7.269|7.962|
|BeautySlept|7.109|7.790|7.826|8.305|8.464|10.134|
|chanchan|9.658|9.778|9.723|9.886|9.951|10.206|
|death2|5.040|5.465|5.215|6.660|6.213|6.092|
|experiencia|10.824|10.915|10.963|10.992|11.005|11.428|
|female_speech|4.363|4.498|4.708|4.711|5.190|5.364|
|FloorEssence|9.051|9.409|9.488|9.509|9.537|10.201|
|ItCouldBeSweet|8.183|8.310|8.330|8.396|8.531|9.064|
|Layla|9.467|9.571|9.725|9.691|9.783|10.415|
|LifeShatters|10.751|10.808|10.868|10.836|10.838|11.194|
|macabre|8.971|9.026|9.249|9.076|9.172|10.043|
|male_speech|4.230|4.256|4.509|4.813|5.255|5.674|
|SinceAlways|10.327|10.409|10.455|10.473|10.522|11.254|
|thear1|11.364|11.400|11.474|11.425|11.451|11.783|
|TomsDiner|6.990|7.108|7.057|7.268|7.432|8.572|
|velvet|9.687|9.990|10.030|10.212|10.461|10.770|
|*Mean*|**8.313**|8.493|8.561|8.718|8.817|9.385|
|||||||
|Enc-time|07:35:00|00:00:09|00:05:37|00:00:15|00:00:01|00:00:00|
|Dec-time|00:01:19|00:00:02|00:05:40|00:00:13|00:00:01|00:00:00|