Methods and apparatus for deriving composite tracks

A decoding method for decoding video data, the method comprising:

• receiving:
• (a) video data including a plurality of two-dimensional sub-picture tracks associated with a viewport, wherein the plurality of two-dimensional sub-picture tracks are at a first level of a hierarchical track structure;
• and
• (b) a composition operation to compose the plurality of two-dimensional sub-picture tracks for the viewport, wherein the composition operation is associated with a composite track at a second level in the hierarchical track structure that is above the first level of the plurality of two-dimensional sub-picture tracks, and comprises data indicative of:
• a composition to perform on the plurality of two-dimensional sub-picture tracks to compose the plurality of two-dimensional sub-picture tracks into a canvas associated with the viewport, wherein the canvas comprises a plurality of portions and each of the plurality of two-dimensional sub-picture tracks comprises video data for at least an associated portion of the plurality of portions;
• and
• a composition layout operation to adjust the composition if the canvas comprises a composition layout created by two or more of the plurality of two- dimensional sub-picture tracks composed on the canvas;
• and
• composing the plurality of two-dimensional sub-picture tracks into the canvas according to the composition, comprising:
• determining two or more of the composed two-dimensional sub-picture tracks comprise the composition layout;
• and
• adjusting the composition based on the composition layout operation to compensate for the composition layout.

An apparatus configured to decode video data, the apparatus comprising a processor in communication with memory, the processor being configured to execute instructions stored in the memory that cause the processor to:

• receive:
• (a) video data including a plurality of two-dimensional sub-picture tracks associated with a viewport, wherein the plurality of two-dimensional sub-picture tracks are at a first level of a hierarchical track structure;
• and
• (b) a composition operation to compose the plurality of two-dimensional sub-picture tracks for the viewport, wherein the composition operation is associated with a composite track at a second level in the hierarchical track structure that is above the first level of the plurality of two-dimensional sub-picture tracks, and comprises data indicative of:
• a composition to perform on the plurality of two-dimensional sub-picture tracks to compose the plurality of two-dimensional sub-picture tracks into a canvas associated with the viewport, wherein the canvas comprises a plurality of portions and each of the plurality of two-dimensional sub-picture tracks comprises video data for at least an associated portion of the plurality of portions;
• and
• a composition layout operation to adjust the composition if the canvas comprises a composition layout created by two or more of the plurality of two- dimensional sub-picture tracks composed on the canvas;
• and
• compose the plurality of two-dimensional sub-picture tracks into the canvas according to the composition, comprising:
• determining two or more of the composed two-dimensional sub-picture tracks comprise the composition layout;
• and
• adjusting the composition based on the composition layout operation to compensate for the composition layout.

An apparatus for encoding video data, the apparatus comprising a processor in communication with memory, the processor being configured to execute instructions stored in the memory that cause the processor to:

• encode video data in a hierarchical track structure, comprising:
• receiving the video data including a plurality of two-dimensional sub-picture tracks associated with a viewport, wherein the plurality of two-dimensional sub-picture tracks are at a first level of the hierarchical track structure;
• and
• encoding a composition operation for composing the plurality of two-dimensional sub-picture tracks for the viewport, wherein the composition operation is associated with a composite track at a second level in the hierarchical track structure that is above the first level of the plurality of two-dimensional sub-picture tracks, and comprises data indicative of:
• a composition to perform on the plurality of two-dimensional sub-picture tracks to compose the plurality of two-dimensional sub-picture tracks into a canvas associated with the viewport, wherein the canvas comprises a plurality of portions and each of the plurality of two-dimensional sub-picture tracks comprises video data for at least an associated portion of the plurality of portions;
• and
• a composition layout operation to adjust the composition if the canvas comprises a composition layout created by two or more of the plurality of two-dimensional sub-picture tracks composed on the canvas;
• and
• provide the received video data and the encoded composition operation.