Quantifying the Subjective Perception of Janks in Transition Animations from the Crowd Pervasive HCI Lab, Tsinghua University | Spring 2017—Present

A scrolling animation with janks. Recorded on an iPhone running iOS 11.

Janks (dropped or delayed frames) are still common in everyday smart phone animations, despite advances in mobile processing power. The goal of this project is to identify and characterize the properties of jank that most affect user experience. To achieve that, we divided this project into of two parts: understanding janks and quantifying the user perception of janks.

PART 1: Understanding Janks with Computer Vision

To understand the properties of janks, we developed a custom computer vision program that analyzed hours of real-world smart phone interactions. We studied the properties of jank during user interaction by examining the videos using a custom analysis program.

Visualization of the displacement in content during animation between two adjacent frames. On the left, the program identifies a movement area. On the right, lines connect matched SURF interest points.

PART 2: User Perception

Through an in-the-wild experiment covering over 3900 participants, we gathered subjective user feedback on four common interaction scenarios where controlled janks were inserted. We analyzed the effect of different factors on jank perception and acquired a holistic model to quantify the subjective perception of janks.

Screenshots of a task in our experiment. The application inserted janks into the tasks, and asked for subjective user feedback.

The results from this study can be useful for analyzing and improving user experience of animations in mobile applications and operating systems.

Publications

  • (In preparation for ACM TOCHI)

Roles

  • Developed the video analysis platform for janks in transition animations using computer vision
  • Designed an Android application that inserted janks during user interaction in four common scenarios and gathered user feedback
  • Conducted the large-scale in-the-wild user experiment
  • Analyzed the experiment data to acquire the perception model of janks
  • Working on a paper for ACM TOCHI (as the first author)