1. In a Noise Feedback Coding (NFC) system having a corresponding ZERO-STATE filter structure, the ZERO-STATE filter structure including multiple filters, a method of producing a ZERO-STATE response error vector, comprising: (a) transforming the ZERO-STATE filter structure including multiple filters to a ZERO-STATE filter structure including only an all-zero filter, the all-zero filter having a filter response substantially equivalent to a filter response of the ZERO-STATE filter structure including multiple filters; and (b) filtering a VQ codevector with the all-zero filter to produce the ZERO-STATE response error vector corresponding to the VQ codevector.