In an embodiment, when an input picture is divided into one or more (rectangular) sub-region(s), each sub-region may be coded as an independent layer. Each independent layer corresponding to a local region may have a unique layer_id value. For each independent layer, the sub-picture size and location information may be signaled. For example, picture size (width, height), the offset information of the left-top corner (x_offset, y_offset).
In the same embodiment, each sub-picture corresponding to an independent layer may have its unique POC value within an AU. When a reference picture among pictures stored in DPB is indicated by using syntax element(s) in RPS or RPL structure, the POC value(s) of each sub-picture corresponding to a layer may be used.
In the same or another embodiment, in order to indicate the (inter-layer) prediction structure, the layer_id may not be used and the POC (delta) value may be used.
In the same embodiment, a sub-picture with a POC vale equal to N corresponding to a layer (or a local region) may or may not be used as a reference picture of a sub-picture with a POC value equal to N+K, corresponding to the same layer (or the same local region) for motion compensated prediction. In most cases, the value of the number K may be equal to the maximum number of (independent) layers, which may be identical to the number of sub-regions.