Method and apparatus for generating and encoding projection-based frame with 360-degree content represented by base projection face and lateral projection faces packed in pyramid projection layout

A video processing method comprising:

• receiving an omnidirectional content corresponding to a sphere;
• generating a projection-based frame according to the omnidirectional content and a pyramid projection layout, wherein the projection-based frame has a 360-degree content represented by a base projection face and a plurality of lateral projection faces packed in the pyramid projection layout, the base projection face and the lateral projection faces are obtained according to at least projection relationship between a pyramid and the sphere, a shape of the base projection face is a square, a shape of each of the lateral projection faces is a triangle, and a number of the lateral projection faces is equal to four;
• and
• encoding, by a video encoder, the projection-based frame to generate a part of a bitstream;
• wherein generating the projection-based frame according to the omnidirectional content and the pyramid projection layout comprises:
• mapping the omnidirectional content of the sphere onto a base and a plurality of lateral faces of the pyramid to generate a first projection face and a plurality of second projection faces, respectively;
• deriving the base projection face from the first projection face;
• and
• deriving the lateral projection faces from the second projection faces, respectively, wherein each of the lateral projection faces is derived from re-sampling a corresponding second projection face in its height direction, and re-sampling the corresponding second projection face comprises:
• re-sampling the corresponding second projection face through non-uniform mapping, wherein the corresponding second projection face has a first source region and a second source region, said each of the lateral projection faces has a first re-sampled region and a second re-sampled region, the first re-sampled region is derived from re-sampling the first source region with a first sampling density, and the second re-sampled region is derived from re-sampling the second source region with a second sampling density that is different from the first sampling density.