With the advent of social networking, sharing of multimedia has gained tremendous amount of importance and is the widely used form of communication worldwide. In the process of discovering knowledge from videos, challenge is to process huge amount of information which is resource-intensive. One way to minimize the cost of computations is to reduce the amount of information that undergoes processing. The redundant information can be greatly reduced by extracting key frames that represent the entire video. It is an essential task in any video analysis and indexing applications. This paper carries out an extensive survey of different key frame extraction techniques along with their merits and demerits used in current video retrieval applications.