providing a video wherein the video has a plurality of sentences and a plurality of frames;

applying a key frame extraction step to the frames of the video to acquire a plurality of key frames, wherein the key frame extraction step comprises:

computing the similarity between each frame to obtain a plurality of similarity values; and

choosing the key frames from the frames, wherein the sum of the similarity values between the key frames is the minimum;

applying a key sentence extraction step to the sentences of the video to acquire a plurality of key sentences, wherein the key sentence extraction step comprises:

converting the sentences into a plurality of corresponding sentence vectors;

computing the distance between each sentence vector to obtain a plurality of distance values;

according to the distance values, dividing the sentences into a plurality of clusters, wherein the clusters are members of a set;

computing the importance of each sentence of each cluster to obtain the importance of each cluster;

applying a splitting step to split a most important member with the highest importance in the cluster into a plurality of new clusters, wherein the new clusters replace the original most important member and join the set as members of the set;

repeating the splitting step until the number of the clusters reaches a predetermined value; and

choosing at least one key sentence from each members of the set, wherein the sum of the importance of the key sentences is the maximum; and

outputting the key frames and the key sentences.