1. A method of quantizing frequency envelops of an audio signal, for use by an audio signal encoder, comprising: obtaining N frequency envelopes of a frame of the audio signal, wherein N is a positive integer; organizing the N frequency envelopes into N1 groups, wherein each group comprises M frequency envelopes, and wherein N1 and M are positive integers, M is greater than or equal to 2, and N is greater than N1; quantizing a first group of frequency envelopes to obtain a first vector by using a first codebook wherein the first codebook has 2 B code words and each code word corresponds to a vector, wherein the first codebook is divided into 2 B1 portions, and wherein B is a positive integer greater than or equal to 2, and B1 is a positive integer greater than or equal to 1; determining that a code word corresponding to the first vector is in the i th portion of the first codebook, wherein i is a positive integer greater than or equal to 1 and less than or equal to 2 B1 ; determining a second codebook according to the i th portion of the first codebook; and quantizing a second group of frequency envelopes by using the second codebook.