Subpicture Boundary Extension



What is Boundary Extension? Boundary extension refers to the extension of a picture boundary to enable inter prediction from regions outside the picture. In current video coding schemes, only non-adaptive approaches are used with a constant prediction which continues the boundary samples in the extension region. This causes artifacts in the region of the boundary which may be strongly visible. Especially when 360° video is coded using independently decodable subpictures, extension-related artifacts can occur at all subpicture boundaries and are not limited to the picture boundary area. Thereby, the handling of subpicture boundaries becomes more important. Therefore, we are investigating boundary extension approaches to reduce artifacts and improve coding performance.

Scientific Questions

What are we researching? We are currently investigating to adapt intra prediction modes for the boundary task, which are promising candidates. Additionally, other prediction types are considered, e.g. learning-based modes. A novelty of our work is that information about the type of boundary extension is signaled in the bitstream to get a more accurate prediction signal outside the (sub)picture boundary.


New theses are regularly advertised in the area of Subpicture Boundary Extension. In addition to the general overview, there are also numerous topics that have not yet been advertised, which will be gladly presented in a personal conversation.




Nicolas Horst, Priyanka Das and Mathias Wien
Adaptive Boundary Extension for Inter Prediction
In: Picture Coding Symposium (PCS)