We use different techniques to visualize the world around us at many speeds, like slow motions and time-lapse photography.
A recent paper on arXiv.org proposes Video Temporal Pyramids, an approach for visualizing changes at different timescales and a visualization tool for navigating and exploring the pyramids.
The pyramid consists of a collection of new videos, each of which distills the changes happening at a particular timescale. It allows a smooth viewing experience with no aliasing or flickering effects. The Video Spectrogram plots time vs. timescale, showing clear patterns for strong cyclic changes such as day/night. Users can do an overview scan first and then drill down to lower timescales to view more details.
Researchers validate the approach using multiple long-duration webcam datasets of diverse outdoor scenes such as a construction site.
What can we learn about a scene by watching it for months or years? A video recorded over a long timespan will depict interesting phenomena at multiple timescales, but identifying and viewing them presents a challenge. The video is too long to watch in full, and some occurrences are too slow to experience in real-time, such as glacial retreat. Timelapse videography is a common approach to summarizing long videos and visualizing slow timescales. However, a timelapse is limited to a single chosen temporal frequency, and often appears flickery due to aliasing and temporal discontinuities between frames. In this paper, we propose Video Temporal Pyramids, a technique that addresses these limitations and expands the possibilities for visualizing the passage of time. Inspired by spatial image pyramids from computer vision, we developed an algorithm that builds video pyramids in the temporal domain. Each level of a Video Temporal Pyramid visualizes a different timescale; for instance, videos from the monthly timescale are usually good for visualizing seasonal changes, while videos from the one-minute timescale are best for visualizing sunrise or the movement of clouds across the sky. To help explore the different pyramid levels, we also propose a Video Spectrogram to visualize the amount of activity across the entire pyramid, providing a holistic overview of the scene dynamics and the ability to explore and discover phenomena across time and timescales. To demonstrate our approach, we have built Video Temporal Pyramids from ten outdoor scenes, each containing months or years of data. We compare Video Temporal Pyramid layers to naive timelapse and find that our pyramids enable alias-free viewing of longer-term changes. We also demonstrate that the Video Spectrogram facilitates exploration and discovery of phenomena across pyramid levels, by enabling both overview and detail-focused perspectives.
Research article: Swift, M. E., Ayers, W., Pallanck, S., and Wehrwein, S., “Visualizing the Passage of Time with Video Temporal Pyramids”, 2022. Link: https://arxiv.org/abs/2208.11885