A video decoding method includes: decoding a part of a bitstream to generate a decoded frame, and parsing at least one syntax element from the bitstream. The decoded frame is a projection-based frame that includes projection faces packed in a cube-based projection layout. At least a portion of a 360-degree content of a sphere is mapped to the projection faces via cube-based projection. The at least one syntax element is indicative of a guard band configuration of the projection-based frame.