1. A computer-implemented method for identifying key frames of a presentation video that include stationary informational content, comprising: at a computer system including one or more processors and memory storing one or more programs, the one or more processors executing the one or more programs to perform the operations of: obtaining a sequence of frames from a presentation video; computing differences of pixel values between consecutive frames of the sequence of frames; identifying sets of consecutive frames that are stationary, wherein consecutive frames that are stationary have a proportion of changed pixel values below a first predetermined threshold, and wherein pixel values are deemed to be changed when the difference between the pixel values for corresponding pixels in consecutive frames exceeds a second predetermined threshold; extracting key frames from the sets of consecutive frames; retaining a set of key frames that include stationary informational content; and displaying the set of key frames that include stationary informational content for user interaction.