# IPN HandS: Efficient Annotation Tool and Dataset for Skeleton-Based Hand Gesture Recognition
## 3 IPN HandS Annotation Tool
The main display shows the annotated video frame along with gesture labels, timeline navigation, and confidence adjustment. The expanded Edit menu illustrates core functionalities such as hand selection, deletion, handedness changes, mirroring, copy–paste, and the interpolation of hand landmarks across frames. the tool includes functionality for interpolating landmark positions between two selected frames, which is especially effective for continuous gestures involving smooth transitions. For static gestures or repeated poses, annotations can also be copied and pasted across frames, eliminating the need to repeat identical adjustments. Together, these tools enable the annotator to efficiently achieve temporally consistent and spatially accurate hand landmark annotations with minimal manual effort. To further streamline the process, each interactive operation is paired with an intuitive and easily accessible keyboard shortcut. For example, dragging a landmark is initiated using simple key combinations (Ctrl + LeftClick), and interpolation is triggered through a pair of dedicated shortcut keys (E and R). Building upon these functionalities, our proposed tool was used to annotate the entire IPN Hand dataset [5], comprising over 800,000 video frames. This large-scale application not only validated the reliability of the tool in practice but also demonstrated its efficiency in producing consistent and precise hand skeleton annotations. The integration of features such as automatic initialization, manual refinement, interpolation, and copy-paste mechanisms enables annotators to efficiently manage long gesture sequences while minimizing repetitive effort. Table 2 summarizes the main capabilities offered by the tool, each contributing to the balance between annotation speed and accuracy. \begin{table}
\begin{tabular}{p{113.8 pt} p{284.5 pt}} \hline \hline
**Feature** & **Description** \\ \hline Automatic Initialization & Applies pose estimation to all frames using MediaPipe Holistic [13] to generate preliminary annotations. \\ Frame-level Re-estimation & Allows landmark re-detection with adjustable detection confidence on individual frames using either MediaPipe Hands or Holistic, depending on accuracy needs. \\ Manual Refinement & Supports interactive adjustment of the entire hand, individual fingers, or single landmarks, with keyboard shortcuts and undo actions, as shown in Figure 3. \\ Copy–Paste Annotations & Enables the duplication of hand annotations across frames for static poses or repeated gestures. \\ Hand Interpolation & Interpolates hand landmarks between two annotated frames, streamlining the annotation of continuous dynamic gestures. \\ Class-Timeline & Includes a gesture-segmented timeline to guide the annotator’s focus and support consistent frame-level annotations. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main features of the IPN HandS annotation tool. Figure 3: Interactive annotation capabilities of the IPN HandS tool. (**a**) Full-hand repositioning, activated by clicking and dragging a landmark without modifiers. (**b**) Finger-level adjustment, enabled by holding Ctrl + Shift and clicking on a fingertip to drag all associated landmarks. (**c**) Individual landmark refinement by holding Ctrl and clicking on any point to reposition it.