Over the last years surgeons adopted to record and archive videos of endoscopic surgeries. There are several reasons to use endoscopic videos after the procedure: to train young surgeons, for documentation, to show patients what has been done, for comparative analysis of procedures, etc. In most of these use cases not the entire video, which can be several hours long, is relevant but rather a summary of the video or certain interesting segments from it. Since manual processing of these videos is tedious, automatic techniques of abstracting and indexing these long-duration videos are needed. One important task in this context is the extraction of a set of representative frames, so called keyframes, from the long-duration video.