A sample adaptive offset (SAO) filtering method for a reconstructed projection-based frame includes: obtaining at least one padding pixel in a padding area that acts as an extension of a face boundary of a first projection face, and applying SAO filtering to a block that has at least one pixel included in the first projection face. In the reconstructed projection-based frame, there is image content discontinuity between the face boundary of the first projection face and a face boundary of a second projection face. The at least one padding pixel is involved in the SAO filtering of the block.