Patent ID: 7848931

Claim:
An audio encoder which compresses and encodes audio signals of N channels, where N>1, said audio encoder comprising: a downmixed signal encoding unit operable to encode a downmixed signal obtained by downmixing the audio signals; and an auxiliary information generation unit operable to generate auxiliary information which is necessary for decoding the downmixed signal encoded by said downmixed signal encoding unit into the audio signals of the N channels, wherein said auxiliary information generation unit includes: a transformation unit operable to transform one of the audio signals into a first frequency domain signal, and to transform another of the audio signals into a second frequency domain signal; a division unit operable to divide a frequency band of each of the first frequency domain signal and the second frequency domain signal into plural sub-bands; a detection unit operable to detect phase difference information and gain ratio information that each indicates a degree of difference between the first frequency domain signal and the second frequency domain signal; and a quantization unit operable to quantize, for each sub-band, the phase difference information and gain ratio information that are detected by said detection unit.