| Time-compressed video is video that is played back in less time than that in which it was originally recorded. For example, a 50-minute video of a lecture that is played in 40 minutes is time-compressed by 20%. The purpose of this study was to analyze two issues important to the design of computer interfaces that allow users to access time-compressed video.;The first issue was to determine the Just Noticeable Difference (JND) of a change in speed in video. The subjects were 90 university students. The design was a 3 x 3 between subjects design. One factor was media type with the three levels: (a) audio track and video track together, (b) video track only, and (c) audio track only. The second factor was the speed of the standard stimuli which had three levels of time-compression: 0%, 30%, and 60%. The analysis revealed a significant interaction between media type and the value of the standard stimuli. Posthoc analysis indicated that the video-only condition yielded a higher JND than the audio-only and the audio and video together when the standard stimulus was at 0%, but media condition had no effect on the JND when the standard stimuli were 30% or 60% time-compression.;The second issue was concerned with giving the learner dynamic control of the speed of the video and asking the learner to search for information in the video. The learners were 26 university students. A 2 x 2 split-plot design was used. The dependent variable was the amount of time required to find the information. The repeated factor was the information type that the learner was searching for with the two levels (a) primarily audio and (b) primarily video. The non-repeating factor was content type with the two levels (a) "talking head" and (b) several short vignettes. Neither of these two factors had a significant effect on searching time.;The results from these two studies have very practical implications for the design of user interfaces to time-compressed video. |
