Hybrid cubemap projection for 360-degree video coding

A method of decoding a 360-degree video, comprising:

• receiving a picture of the 360-degree video, the picture comprising a face and a projection format corresponding to the face;
• determining whether the face is in a user-defined projection format based on a projection format indication associated with the face;
• determining, based on the face being in the user-defined projection format, a horizontal transform function coefficient for a horizontal direction of the face and a vertical transform function coefficient for a vertical direction of the face;
• determining, based on the horizontal transform function coefficient, a horizontal transform function associated with the face;
• determining, based on the vertical transform function coefficient, a vertical transform function associated with the face;
• and
• performing at least one decoding process on the face using the horizontal transform function and the vertical transform function.

A coding device, comprising:

• a processor configured to:
• receive a plurality of sequences of a 360-degree video, the plurality of sequences being associated with a plurality of projection formats;
• receive a first projection format indication that indicates a first projection format is associated with a first sequence of the plurality of sequences and a second projection format indication that indicates a second projection format is associated with a second sequence of the plurality of sequences;
• determine, based on the first projection format, a first transform function associated with a plurality of pictures in the first sequence;
• determine, based on the second projection format, a second transform function associated with a plurality of pictures in the second sequence;
• and
• perform at least one decoding process on the plurality of pictures in the first sequence using the first transform function and performing the at least one decoding process on the plurality of pictures in the second sequence using the second transform function.