Patents
MPEG-1 video and Layer I/II audio may be able to be implemented without payment of license fees. The ISO patent database lists one patent for ISO 11172, US 4,472,747, which expired in 2003. The near-complete draft of the MPEG-1 standard was publicly available as ISO CD 11172 by December 6, 1991. Due to its age, many of the patents on the technology have expired. Neither the Kuro5hin article "Patent Status of MPEG-1, H.261 and MPEG-2" nor a thread on the gstreamer-devel mailing list were able to list a single unexpired MPEG-1 video and Layer I/II audio patent. A discussion on whatwg mentioned the now expired US 5,214,678 patent as a possible patent on audio layer II. A full MPEG-1 decoder and encoder can not be implemented royalty free since there are companies that require patent fees for implementations of MPEG-1 Layer 3 Audio as discussed in the MP3 article.
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