Licensing and Patents
No licenses or payments are required to be able to stream or distribute content in AAC format. This reason alone makes AAC a much more attractive format to distribute content than MP3, particularly for streaming content (such as Internet radio).
However, a patent license is required for all manufacturers or developers of AAC codecs. For this reason free and open source software implementations such as FFmpeg and FAAC may be distributed in source form only, in order to avoid patent infringement. (See below under Products that support AAC, Software.)
Read more about this topic: Advanced Audio Coding