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: 12 days ago
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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 (over 6 years ago)
• Default Branch: master
• Last Pushed: 2024-10-26T21:43:43.000Z (12 days ago)
• Last Synced: 2024-10-26T23:24:56.243Z (12 days ago)
• Topics: audio, audio-codec, audio-compression, compression, lossless-audio
• Language: C++
• Homepage:
• Size: 183 KB
• Stars: 47
• Watchers: 5
• Forks: 4
• 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 v0.7.8**

16 files (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|

|:-|:-|:-|:-|:-|

|--normal|26.812.987|00:00:41|00:00:30|8.441|

|--high|26.708.465|00:04:55|00:00:52|8.407|

|--veryhigh|26.621.497|00:32:04|00:01:04|8.379|

|--best|26.554.323|05:17:19|00:01:05|8.358|

 

**Comparison with other lossless audio codecs**

|Program|Parameters|Source|

|:-|:-|:-|

|Sac v0.7.8|--best|open|

|OFR v5.100|--preset max|closed|

|paq8px_v208fix1|-6|open|

|MAC v10.44|--insane|open|

Numbers are bits per sample (bps)

| Name  | Sac | OFR | paq8px | MAC |

|:---|---:|---:|---:|---:|

|ATrain|7.026|7.156|7.353|7,269|

|BeautySlept|7.418|7.790|7.826|8,464|

|chanchan|9.692|9.778|9.723|9,951|

|death2|5.068|5.465|5.215|6,213|

|experiencia|10.866|10.915|10.963|11,005|

|female_speech|4.372|4.498|4.708|5,190|

|FloorEssence|9.081|9.409|9.488|9,537|

|ItCouldBeSweet|8.200|8.310|8.330|8,531|

|Layla|9.490|9.571|9.725|9,783|

|LifeShatters|10.768|10.808|10.868|10,838|

|macabre|8.986|9.026|9.249|9,172|

|male_speech|4.276|4.256|4.509|5,255|

|SinceAlways|10.344|10.409|10.455|10,522|

|thear1|11.379|11.400|11.474|11,451|

|TomsDiner|6.996|7.108|7.057|7,432|

|velvet|9.762|9.990|10.030|10,461|

|*Mean*|**8.358**|8.493|8.561|8,817|