Method and system for encoding left and right channels of a stereo sound signal selecting between two and four sub-frames models depending on the bit budget

A stereo sound encoding system for encoding left and right channels of a stereo sound signal, comprising:

• at least one processor;
• and
• a memory coupled to the processor and comprising non-transitory instructions that when executed cause the processor to implement:
• a down mixer of the left and right channels of the stereo sound signal to produce primary and secondary channels;
• an encoder of the primary channel and an encoder of the secondary channel;
• a bit allocation estimator of a first bit budget to encode the primary channel and a second bit budget to encode the secondary channel;
• and
• a decision module to select, if the second bit budget is sufficient, encoding of the secondary channel using a four sub-frames model, and, if the second bit budget is insufficient for using the four sub-frames model, encoding of the secondary channel using a two sub-frames model;
• wherein the primary channel encoder produces primary channel coding parameters, and
• wherein the secondary channel encoder:
• produces secondary channel coding parameters;
• determines a bit budget required to encode, in a current frame, secondary channel coding parameters including (a) LP filter coefficients and/or (b) pitch information, and gains, that are not re-used from the primary channel encoding;
• determines if a remaining bit budget allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks;
• doubles a sub-frame length when the two sub-frames model is used;
• and
• interpolates the LP filter coefficients of the primary channel, when re-used, to adapt said primary channel LP filter coefficients by taking into account the two sub-frames model.

A stereo sound encoding system for encoding left and right channels of a stereo sound signal, comprising:

• a down mixer of the left and right channels of the stereo sound signal to produce primary and secondary channels;
• an encoder of the primary channel and an encoder of the secondary channel;
• a bit allocation estimator of a first bit budget to encode the primary channel and a second bit budget to encode the secondary channel;
• and
• a decision module to select, if the second bit budget is sufficient, encoding of the secondary channel using a four sub-frames model, and, if the second bit budget is insufficient for using the four sub-frames model, encoding of the secondary channel using a two sub-frames model;
• wherein the primary channel encoder produces primary channel coding parameters, and
• wherein the secondary channel encoder:
• produces secondary channel coding parameters;
• determines a bit budget required to encode, in a current frame, secondary channel coding parameters including (a) LP filter coefficients and/or (b) pitch information, and gains, that are not re-used from the primary channel encoding;
• determines if a remaining bit budget allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks;
• doubles a sub-frame length when the two sub-frames model is used;
• and
• interpolates the LP filter coefficients of the primary channel, when re-used, to adapt said primary channel LP filter coefficients by taking into account the two sub-frames model.

A stereo sound encoding system for encoding left and right channels of a stereo sound signal, comprising:

• at least one processor;
• and
• a memory coupled to the processor and comprising non-transitory instructions that when executed cause the processor to:
• down mix the left and right channels of the stereo sound signal to produce primary and secondary channels;
• encode the primary channel and encode the secondary channel;
• estimate a first bit budget to encode the primary channel and a second bit budget to encode the secondary channel;
• and
• select, if the second bit budget is sufficient, encoding of the secondary channel using a four sub-frames model, and, if the second bit budget is insufficient for using the four sub-frames model, encoding of the secondary channel using a two sub-frames model;
• wherein a primary channel encoder produces primary channel coding parameters, and
• wherein a secondary channel encoder:
• produces secondary channel coding parameters;
• determines a bit budget required to encode, in a current frame, secondary channel coding parameters including (a) LP filter coefficients and/or (b) pitch information, and gains, that are not re-used from the primary channel encoding;
• determines if a remaining bit budget allows to quantize, in the current frame, four algebraic codebooks or only two algebraic codebooks;
• doubles a sub-frame length when the two sub-frames model is used;
• and
• interpolates the LP filter coefficients of the primary channel, when re-used, to adapt said primary channel LP filter coefficients by taking into account the two sub-frames model.