A stereo sound encoding method for encoding left and right channels of a stereo sound signal, comprising: down mixing the left and right channels of the stereo sound signal to produce primary and secondary channels; encoding the primary channel and encoding the secondary channel, wherein encoding the primary channel and encoding the secondary channel comprise determining a first bit budget to encode the primary channel and a second bit budget to encode the secondary channel; if the second bit budget is sufficient, the secondary channel is encoded using a four subframes encoding model; and if the second bit budget is insufficient for using the four sub-frames encoding model, the secondary channel is encoded using a two sub-frames encoding model; wherein encoding the primary channel comprises producing primary channel coding parameters and encoding the secondary channel comprises producing secondary channel coding parameters; and wherein encoding the secondary channel comprises: - determining from the second bit budget a third budget required to encode, in a current frame, secondary channel coding parameters including - (a) linear prediction, LP, filter coefficients and/or (b) pitch information, and - gains, that are not re-used from the primary channel encoding; - determining if a remaining bit budget, remaining from the second bit budget to encode the secondary channel, allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks. down mixing the left and right channels of the stereo sound signal to produce primary and secondary channels; encoding the primary channel and encoding the secondary channel, wherein encoding the primary channel and encoding the secondary channel comprise determining a first bit budget to encode the primary channel and a second bit budget to encode the secondary channel; if the second bit budget is sufficient, the secondary channel is encoded using a four subframes encoding model; and if the second bit budget is insufficient for using the four sub-frames encoding model, the secondary channel is encoded using a two sub-frames encoding model; wherein encoding the primary channel comprises producing primary channel coding parameters and encoding the secondary channel comprises producing secondary channel coding parameters; and wherein encoding the secondary channel comprises: - determining from the second bit budget a third budget required to encode, in a current frame, secondary channel coding parameters including - (a) linear prediction, LP, filter coefficients and/or (b) pitch information, and - gains, that are not re-used from the primary channel encoding; - determining if a remaining bit budget, remaining from the second bit budget to encode the secondary channel, allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks. - determining from the second bit budget a third budget required to encode, in a current frame, secondary channel coding parameters including - (a) linear prediction, LP, filter coefficients and/or (b) pitch information, and - gains, that are not re-used from the primary channel encoding; - (a) linear prediction, LP, filter coefficients and/or (b) pitch information, and - gains, - determining if a remaining bit budget, remaining from the second bit budget to encode the secondary channel, allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks.