Encoding and decoding methods and apparatus as described. In one example, a method of embedding auxiliary information into an audio signal includes sampling the audio signal to create an audio block; receiving a code; determining frequency components that will be used to represent the code, wherein different sets of frequency components represent respectively different information and wherein one frequency component from each set of frequency components is located in a code band and there are multiple code bands and spacing between adjacent code bands is equal to or less than the spacing between adjacent frequency components of each code band; determining amplitudes of the frequency components that will be used to represent the information, wherein the amplitudes of the frequency components are determined by a masking ability of the audio block; synthesizing the frequency components that will be used to represent the information, wherein the frequency components are synthesized with the determined amplitudes; and combining the synthesized code frequency components with the audio block.