Are all audio codecs patented?
Most older, higher-bitrate codecs are not subject to patent protection. However, G.723, G.729.1 and GSM are covered by various patents. For example, U.S. patent 4,752,956, Digital speech coder with baseband residual coding modifies coding using short term fine structure speech data produced by analysers within encoder-multiplexers applies to GSM and is assigned to Philips.
