1. A method for processing an audio signal, comprising: receiving, by an audio processing apparatus, spectral data including a current block, and substitution type information indicating whether to apply a shape prediction scheme to the current block; when the substitution type information indicates that the shape prediction scheme is applied to the current block, receiving lag information indicating an interval between spectral coefficients of the current block and the predictive shape vector of a current frame or a previous frame; and, obtaining spectral coefficients by substituting for spectral hole included in the current block using the predictive shape vector.