A de-blocking method is applied to a reconstructed projection-based frame having a first projection face and a second projection face, and includes obtaining a first spherical neighboring block for a first block with a block edge to be de-blocking filtered, and selectively applying de-blocking to the block edge of the first block for at least updating a portion of pixels of the first block. There is image content discontinuity between a face boundary of the first projection face and a face boundary of the second projection face. The first block is a part of the first projection face, and the block edge of the first block is a part of the face boundary of the first projection face. A region on a sphere to which the first spherical neighboring block corresponds is adjacent to a region on the sphere from which the first projection face is obtained.