Patent ID: 8103514

Claim:
A method of decoding an audio signal, comprising: receiving an audio signal including a downmix signal and spatial information, the spatial information including at least one frame having at least one time slot and at least one parameter set, the parameter set including at least one parameter; extracting time slot information in variable bit length, the time slot information indicating a time slot to which a parameter set is applied; determining whether a dual mode is selected, the dual mode indicating that two modes for a low band range and a high band range; extracting mode information for each a low band range and a high band range, the mode information determining a type of parameter being used for the low band range or the high band range; extracting dual mode parameter band information indicating a number of parameter bands for the low band range; and decoding the audio signal by applying the parameter to the downmix signal based on the time slot information and the dual mode parameter band information, wherein the process of extracting time slot information comprises: extracting a number of time slots and a number of parameter sets from the audio signal to identify time slot information, determining a bit length of the time slot information, the bit length being variable according to the number of time slots, the number of parameter sets and previous time slot information associated with a previous parameter set, and extracting the time slot information based on the bit length, wherein the extracted number of time slot information is equal to the number of parameter sets.