I know that the answer to the question "What is an advantage of Opus besides it not costing any money?" is in "There are also open compression formats like Opus and Vorbis that are available free of charge and without any known patent restrictions. Some of the newer audio compression formats, such as AAC, WMA Pro and Vorbis, are free of some limitations inherent to the MP3 format that cannot be overcome by any MP3 encoder.". Can you tell me what it is?
Answer:
without any known patent restrictions