arsTechnica:
Inventor says Google is patenting work he put in the public domain
Jarek Duda invented a highly speed optimized kind of Arithmetic Coding named
Asymmetric numeral systems (ANS).
Google now wants to file patents for using this algorithm specifically in video coding. Even though they promise to "license on permissive royalty-free terms", and claim they don't want to patent the generic algorithm, just the specific use in video codecs, Duda questions their motives and their rights (knowing the algorithm in PD as "prior art" and lacking "invention" for just describing a specific use of a generic algorithm).