Method and apparatus for predicting high band excitation signal

A decoder, comprising:

• at least one processor, and at least one memory;
• wherein the at least one memory store instructions which, when executed by the at least one processor, cause the at least one processor to perform the following operations:
• decoding a low band bitstream to obtain a set of spectral frequency (LSF) parameters;
• wherein the set of LSF parameters have an ordering relationship according to frequencies;
• calculate LSF difference values associated with at least two pairs of the set of LSF parameters, wherein each pair of the spectral frequency parameters comprises two adjacent LSF parameters according to the ordering relationship;
• determine a minimum LSF difference value from the LSF difference values;
• calculate, according to the minimum LSF difference value, a start frequency bin for predicting a high band excitation signal from a low band excitation signal synthesized via the decoding;
• and
• generate the high band excitation signal by selecting a frequency band with a preset bandwidth from the low band excitation signal according to the start frequency bin.