A multi-reference quantization device for quantizing an input LPC filter in a speech or audio codec which uses both a super-frame and a multi-mode structure, the multi-reference quantization device comprising: a plurality of differential quantizers (103 1, 103 2,... 103 n) using respective, different reference filters (1, 2,..., n), characterized in that: the different reference filters are based on respective already quantized past or future LPC filters, the device further comprising: means for selecting a reference filter amongst the different reference filters of the differential quantizers using a reference filter selection criterion selected to minimize a bit rate to achieve a target level of distortion or to minimize the level of distortion produced at a given bit rate, wherein the input LPC filter is differentially quantized by the differential quantizer (103 1, 103 2,... 103 n) using the selected reference filter; and means (105 2) for transmitting to a decoder indices representative of the selected reference filter and the differential quantizer using the selected reference filter. a plurality of differential quantizers (103 1, 103 2,... 103 n) using respective, different reference filters (1, 2,..., n), characterized in that: the different reference filters are based on respective already quantized past or future LPC filters, the device further comprising: means for selecting a reference filter amongst the different reference filters of the differential quantizers using a reference filter selection criterion selected to minimize a bit rate to achieve a target level of distortion or to minimize the level of distortion produced at a given bit rate, wherein the input LPC filter is differentially quantized by the differential quantizer (103 1, 103 2,... 103 n) using the selected reference filter; and means (105 2) for transmitting to a decoder indices representative of the selected reference filter and the differential quantizer using the selected reference filter. the different reference filters are based on respective already quantized past or future LPC filters, the device further comprising: means for selecting a reference filter amongst the different reference filters of the differential quantizers using a reference filter selection criterion selected to minimize a bit rate to achieve a target level of distortion or to minimize the level of distortion produced at a given bit rate, wherein the input LPC filter is differentially quantized by the differential quantizer (103 1, 103 2,... 103 n) using the selected reference filter; and means (105 2) for transmitting to a decoder indices representative of the selected reference filter and the differential quantizer using the selected reference filter. means for selecting a reference filter amongst the different reference filters of the differential quantizers using a reference filter selection criterion selected to minimize a bit rate to achieve a target level of distortion or to minimize the level of distortion produced at a given bit rate, wherein the input LPC filter is differentially quantized by the differential quantizer (103 1, 103 2,... 103 n) using the selected reference filter; and means (105 2) for transmitting to a decoder indices representative of the selected reference filter and the differential quantizer using the selected reference filter.