iPlayer: an open-source tool for time-windowed video annotation of human physical activity and behaviour

We present iPlayer, a video annotation tool for direct observation of human activity. In contrast to other tools generally designed for continuous or intermittent annotation, iPlayer is optimized for annotations of specific time windows. The tool is cross-platform (MacOS, Windows, and Linux), open-source, locally-run, and configurable to support different labels and time window sizes. Users can annotate multiple activities per window and the video can be optionally looped over the window, reducing annotation error particularly for small window sizes. We developed and used the tool to annotate toddler activity and position in 1-second windows to be synchronized with raw accelerometer data. We also provide examples of how iPlayer could be used with other annotation frameworks. While the tool was optimized for annotations of human activity, we believe it may be of use to any researchers looking to precisely annotate segments of video recordings.