A method for encoding a sound signal using a CELP core module and supplementary codec modules of a sound signal encoder, comprising: allocating to the supplementary codec modules a bit-budget ( b supplementary) fluctuating based on the sound signal; subtracting, from a total codec bit-budget ( b total), the supplementary codec modules bit-budget ( b supplementary) to determine a fluctuating CELP core module bit-budget ( b core); allocating the fluctuating CELP core module bit-budget ( b core) to a plurality of first parts and a second part of the CELP core module, comprising in a frame of the sound signal comprising sub-frames: allocating to the first CELP core module parts respective bit-budgets from the fluctuating CELP core module bit-budget; allocating to the second CELP core module part a bit-budget remaining from the fluctuating CELP core module bit-budget after allocating to the first CELP core module parts the said respective bit-budgets, wherein the second CELP core module part is a CELP fixed codebook, wherein the CELP core module uses, in one sub-frame of the frame of the sound signal, a glottal-impulse-shape codebook, and wherein allocating the second CELP core module part bit-budget comprises, when the second CELP core module part bit-budget cannot be distributed equally between the sub-frames of the frame, distributing the second CELP core module part bit-budget between the sub-frames of the frame by (a) allocating a highest equal number of bits from the second CELP core module part bit-budget to the sub-frames of the frame and (b) allocating to the sub-frame using the glottal-impulse-shape codebook bits remaining from the second CELP core module part bit-budget after allocating the highest equal number of bits to the sub-frames of the frame; encoding the supplementary codec modules using the supplementary codec modules bit-budget ( b supplementary); encoding the first CELP core module parts using the respective, first CELP core module parts bit-budgets; and encoding the second CELP core module part using the second CELP core module part bit-budget distributed between the sub-frames of the frame. allocating to the supplementary codec modules a bit-budget ( b supplementary) fluctuating based on the sound signal; subtracting, from a total codec bit-budget ( b total), the supplementary codec modules bit-budget ( b supplementary) to determine a fluctuating CELP core module bit-budget ( b core); allocating the fluctuating CELP core module bit-budget ( b core) to a plurality of first parts and a second part of the CELP core module, comprising in a frame of the sound signal comprising sub-frames: allocating to the first CELP core module parts respective bit-budgets from the fluctuating CELP core module bit-budget; allocating to the second CELP core module part a bit-budget remaining from the fluctuating CELP core module bit-budget after allocating to the first CELP core module parts the said respective bit-budgets, wherein the second CELP core module part is a CELP fixed codebook, wherein the CELP core module uses, in one sub-frame of the frame of the sound signal, a glottal-impulse-shape codebook, and wherein allocating the second CELP core module part bit-budget comprises, when the second CELP core module part bit-budget cannot be distributed equally between the sub-frames of the frame, distributing the second CELP core module part bit-budget between the sub-frames of the frame by (a) allocating a highest equal number of bits from the second CELP core module part bit-budget to the sub-frames of the frame and (b) allocating to the sub-frame using the glottal-impulse-shape codebook bits remaining from the second CELP core module part bit-budget after allocating the highest equal number of bits to the sub-frames of the frame; allocating to the first CELP core module parts respective bit-budgets from the fluctuating CELP core module bit-budget; allocating to the second CELP core module part a bit-budget remaining from the fluctuating CELP core module bit-budget after allocating to the first CELP core module parts the said respective bit-budgets, wherein the second CELP core module part is a CELP fixed codebook, wherein the CELP core module uses, in one sub-frame of the frame of the sound signal, a glottal-impulse-shape codebook, and wherein allocating the second CELP core module part bit-budget comprises, when the second CELP core module part bit-budget cannot be distributed equally between the sub-frames of the frame, distributing the second CELP core module part bit-budget between the sub-frames of the frame by (a) allocating a highest equal number of bits from the second CELP core module part bit-budget to the sub-frames of the frame and (b) allocating to the sub-frame using the glottal-impulse-shape codebook bits remaining from the second CELP core module part bit-budget after allocating the highest equal number of bits to the sub-frames of the frame; encoding the supplementary codec modules using the supplementary codec modules bit-budget ( b supplementary); encoding the first CELP core module parts using the respective, first CELP core module parts bit-budgets; and encoding the second CELP core module part using the second CELP core module part bit-budget distributed between the sub-frames of the frame.