In video compression a Keyframe is a frame in which a complete image is stored in the data stream. In video compression, only changes that occur from one frame to the next are stored in the data stream, in order to greatly reduce the amount of information that must be stored. The more Keyframes, the better the compressed video quality but the larger the video files (the less actual compression). Our suggested default setting is having a Keyframe every 10 frames or an average 3 per second. If you are not happy with the quality of the compressed video we suggest you increase the frequency of Keyframes (I.e. move the slider towards lower numbers).