Adaptive hole filling for 3D warping-based virtual view synthesis

In this paper, we discuss a Free viewpoint synthesis with View + Depth format for Multiview applications such as 3DTV and Free View-point Television(FTV)1.When generating a virtual image, 3D warping is used with view and depth of a reference camera. This process includes the problem that holes appear in the virtual image. In conventional method, the holes were dealt with collectively by median filter. There are some different reasons why holes appear through this process. So, it is improper that they are not distinguished particularly and treated all at once like conventional method. We analyze the factors, and recognize that two ones exist, boundary between foreground and background, and reduction of resolution. In this paper, we propose a new hole filling method considering these factors. In the first step, we classify nearby pixels into boundary or same object area according to the gradient of depth value. For boundary case, we hold them and refer to other two real cameras. For another case of same object area, we set up sub-pixels between nearby pixels and warp them if the depth is gradually changing or virtual viewpoint of the warped image is closer to the object than the original view position because they probably cause holes from reduction of resolution. We implement these methods in the simulation. As a result, we prevent boundary in the virtual image from being ambiguous, and confirm the availability of proposed method.