Abstract: Accounting for ITU-T G.719 codec standard for full-band audio without stereo compression, an extension module of parametric stereo audio codec based on the discrete Fourier transform(DFT) was proposed and designed. Several spatial parameters were extracted from the subband after DFT of the input audio, and then the left and right channels were down-mixed to the sum channel when encoding. To conserve the energy of the original audio, energy compensation for the sum channel is essential before utilizing approaches of equations and singular value decomposition (SVD) based on the rotation of Givens respectively when decoding. Test results demonstrate that the method of equation can get higher quality for modest music in low complexity and SVD sacrifices the high complexity for slightly better quality for fast-changing music.