An envelope encoding method comprising: transforming an audio signal from a time domain to a frequency domain to generate an audio spectrum; obtaining, in a sub-band basis, an envelope value of a sub-band including a plurality of transform coefficients corresponding to the sub-band included in the audio spectrum; quantizing, in the sub-band basis, the envelope value of the sub-band to obtain a quantization index of the sub-band, based on an optimized logarithmic scale; obtaining a quantization delta value of a current sub-band from a difference between a quantization index of a current sub-band and a quantization index of a previous sub-band; and lossless encoding the quantization delta value of the current sub-band, wherein the lossless encoding comprises: obtaining a context for the quantization delta value of the current sub-band based on a quantization delta value of the previous sub-band; and lossless coding the quantization delta value of the current sub-band based on the context, characterized in that the lossless coding comprises determining whether the quantization delta value of the previous sub-band belongs to a first group, a second group or a third group, performing Huffman coding on the quantization delta value of the current sub-band by using a first Huffman table if the quantization delta value of the previous sub-band belongs to the second group, performing Huffman coding on the quantization delta value of the current sub-band by using a second Huffman table if the quantization delta value of the previous sub-band belongs to the third group, and performing Huffman coding on the quantization delta value of the current sub-band by using the second Huffman table by reversing the quantization delta value of the current sub-band if the quantization delta value of the previous sub-band belongs to the first group, wherein the first Huffman table and the second Huffman table are determined according to probability distributions of the first group, the second group and the third group. transforming an audio signal from a time domain to a frequency domain to generate an audio spectrum; obtaining, in a sub-band basis, an envelope value of a sub-band including a plurality of transform coefficients corresponding to the sub-band included in the audio spectrum; quantizing, in the sub-band basis, the envelope value of the sub-band to obtain a quantization index of the sub-band, based on an optimized logarithmic scale; obtaining a quantization delta value of a current sub-band from a difference between a quantization index of a current sub-band and a quantization index of a previous sub-band; and lossless encoding the quantization delta value of the current sub-band, wherein the lossless encoding comprises: obtaining a context for the quantization delta value of the current sub-band based on a quantization delta value of the previous sub-band; and lossless coding the quantization delta value of the current sub-band based on the context, characterized in that the lossless coding comprises determining whether the quantization delta value of the previous sub-band belongs to a first group, a second group or a third group, performing Huffman coding on the quantization delta value of the current sub-band by using a first Huffman table if the quantization delta value of the previous sub-band belongs to the second group, performing Huffman coding on the quantization delta value of the current sub-band by using a second Huffman table if the quantization delta value of the previous sub-band belongs to the third group, and performing Huffman coding on the quantization delta value of the current sub-band by using the second Huffman table by reversing the quantization delta value of the current sub-band if the quantization delta value of the previous sub-band belongs to the first group, wherein the first Huffman table and the second Huffman table are determined according to probability distributions of the first group, the second group and the third group. obtaining a context for the quantization delta value of the current sub-band based on a quantization delta value of the previous sub-band; and lossless coding the quantization delta value of the current sub-band based on the context, characterized in that the lossless coding comprises determining whether the quantization delta value of the previous sub-band belongs to a first group, a second group or a third group, performing Huffman coding on the quantization delta value of the current sub-band by using a first Huffman table if the quantization delta value of the previous sub-band belongs to the second group, performing Huffman coding on the quantization delta value of the current sub-band by using a second Huffman table if the quantization delta value of the previous sub-band belongs to the third group, and performing Huffman coding on the quantization delta value of the current sub-band by using the second Huffman table by reversing the quantization delta value of the current sub-band if the quantization delta value of the previous sub-band belongs to the first group, wherein the first Huffman table and the second Huffman table are determined according to probability distributions of the first group, the second group and the third group.