1. A method for changing lip shape in a voice-driven animation, comprising: obtaining audio signals, and obtaining motion extent proportion of lip shape according to characteristics of the audio signals; obtaining an original lip shape model inputted by a user, and generating a motion extent value of the lip shape according to the original lip shape model and the obtained motion extent proportion of the lip shape; and generating a lip shape grid model set according to the generated motion extent value of the lip shape and a preconfigured lip pronunciation model library; wherein the obtaining motion extent proportion of lip shape according to characteristics of the audio signals comprises: traversing the audio signals, and obtaining a maximum sample data value of the audio signals; dividing the audio signals into windows, dividing each window into groups, obtaining an average of sample data values in each group, obtaining an average group avgGroup of each window, wherein the average group avgGroup comprises averages corresponding to groups in the window; obtaining a maximum value among the average group avgGroup of each window, and obtaining a maximum group windowPeak which comprises maximum values corresponding to all the windows; obtaining a maximum motion extent value of the lip shape corresponding to a current window i according to the obtained maximum group windowPeak and the obtained maximum sample data value; and obtaining the motion extent proportion of the lip shape in a current video frame corresponding to the current window i according to the maximum motion extent value of the lip shape corresponding to the current window i, wherein i>=0.
2. The method of claim 1 , wherein obtaining a maximum motion extent value of the lip shape corresponding to a current window i according to the obtained maximum group windowPeak and the obtained maximum sample data value comprises: obtaining an average of sample data values of each group in the current window i; obtaining a maximum value windowPeak[i] among the averages corresponding to the groups in the current window i; calculating a ratio scale[i] of the maximum value windowPeak[i] and a maximum audio sample data value maxSampleValue; calculating the maximum motion extent value extent[i] of the lip shape corresponding to the current window i, wherein extent[i]=scale[i]*maxLen; wherein maxLen is the maximum motion extent value of the lip shape of all the windows.