Asymmetric Numeral Systems ([1]) is entropy coding family currently replacing Huffman and arithmetic coding in data compressors, among others, of Apple, Facebook and Google, thanks to being up to 30x faster [2]. Its author has made it public to prevent pathology of arithmetic coding, which wide use was blocked by patents for many decades ([3], [4]).

However, currently others are trying to patent basic applications of ANS – including Google for AV1 video compressor (initially suggested by ANS author, who has helped them for the last 3 years: [5]) in very general patent application, to prevent others from using it in image and video compression – claims and sources: [6]

[1] https://en.wikipedia.org/wiki/Asymmetric_Numeral_Systems

[2] benchmarks: https://sites.google.com/site/powturbo/entropy-coder

[3] https://en.wikipedia.org/wiki/Arithmetic_coding#US_patents

[4] Charles Bloom comment: http://cbloomrants.blogspot.com/2015/05/05-21-15-software-patents-are-fucking.html

[5] https://groups.google.com/a/webmproject.org/forum/#!topic/codec-devel/idezdUoV1yY

[6] Google claims and sources: https://encode.ru/threads/2648-Published-rANS-patent-by-Storeleap/page3