Squeeze is an experimental novel audio compression codec which uses linear prediction combined with as ANS-based coding of the residuals from the LPC, which theoretically would provide better compression ratio than existing codecs which use Golomb-Rice coding (like FLAC, ALAC, etc.) and theoretically would be faster than existing codecs which use Arithmetic Coding (like OptimFROG). Compatible with OS X.
We use a super-fast Finite State Entropy library (https://github.com/Cyan4973/FiniteStateEntropy) (shoutout to Yann Collett for making this) to do the FSE compression. We also borrow a lot of useful concepts and file-format cues from FLAC.
In practice, it's slower, and offers a worse compression rate than productionized, industry-standard codecs. It's more comparable to the best general-purpose compression algorithms (zstd) in terms of performance. The worse speed is to be expected, as this codec is not yet optimized for speed. It's not quite as good of a compressor as other lossless codecs for a couple of reasons:
- Block size selection is suboptimal
- No use of inter-channel decorrelation (if we were to do stereo encoding too)
- Wasted bits when encoding the residuals
- This is the big one: currently we encode 16-bit residuals no matter what. However, most residuals can be stored with just 6-12 bits, rarely going above that. This is the next obvious step for the algorithm.
Each of these are still open questions, since use of FSE to encode residuals has not been a thoroughly researched topic, but I use some workable placeholders heuristics instead.
Generally, this has been tested for correctness/no-loss, but this project is not significantly fuzzed, so use at your own risk. Currently, this will encode single-channel audio with 16-bit depth. Higher bitrates are currently not supported. I've included some sample .wav files that fit these requirements that you can use to test it out.
make && ./sqz [-e|-d] input_file.wav output_file.sqz
This repository can be built as a library, and you can include 'encode.h' and 'decode.h', to use as an API for encoding/decoding files from your system.
Encoder::Encode(std::string infile, std::string outfile)
Decoder::Decode(std::string infile, std::string outfile)
| Compressor name | Ratio | Compress | Decompress |
|---|---|---|---|
| sqz | 1.266 | 2100 KB/s | 1700 KB/s |
| zstd 1.4.4 -13 | 1.160 | 9900 KB/s | 50400 KB/s |
| flac -8 | 1.526 | 29700 KB/s | 15900 KB/s |
| alac | 1.525 | 20100 KB/s | 14400 KB/s |
| optimFROG -5 | 1.626 | 1200 KB/s | 1300 KB/s |
Recorded on Mac OS X with a very worn-down Macbook Pro 13 with 2Ghz i5 with time on
test_files/CantinaBand.wav (60 seconds duration) for end-to-end file processing with an SSD
To Prof. Stephen Slade for advising this project!