1. Audio coding system comprising: a linear prediction (LP) unit for filtering an audio signal based on a LP filter, the LP unit operating on a first frame length of the audio signal; an adaptive length transformation unit for transforming a frame of the audio signal into a transform domain, the transformation being a Modified Discrete Cosine Transform (MDCT) operating on a variable second frame length; a quantization unit for quantizing a MDCT-domain signal; a gain curve generation unit for generating MDCT-domain gain curves based on magnitude responses of the LP filter; and a mapping unit for mapping LP parameters to corresponding frames of the MDCT-domain signal; wherein the mapping unit interpolates LP polynomials generated on a rate corresponding to the first frame length so as to match frames of the MDCT-domain signal generated on a rate corresponding to the second frame length for usage as perceptual weights in the quantization unit.