In the past, many organizations have claimed ownership of patents related to MP3 decoding or encoding. These claims led to a number of legal threats and actions from a variety of sources. As a result, uncertainty about which patents must be licensed in order to create MP3 products without committing patent infringement in countries that allow software patents was a common feature of the early stages of adoption of the technology.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Legal threats and confusion made it difficult to ensure what about patents regarding MP3 products?
which patents must be licensed