Apparatus, a method and a computer program for video coding and decoding

An apparatus comprising:

• at least one processor and
• at least one storing instructions that, when executed with the at least one processor, causes the apparatus to:
• encode an input picture into a coded picture;
• reconstruct, as a part of said encoding, a decoded picture corresponding to the coded picture;
• encode a spatial region of a second input picture into a coded tile, comprising causing the apparatus to:
• determine a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded picture;
• encode the horizontal offset and the vertical offset;
• determine that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region;
• indicate that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;
• derive the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;
• determine a motion vector for the prediction unit;
• and
• apply the motion vector relative to the prediction-unit anchor position to obtain a prediction block;
• and
• encode, in response to said coded picture and said coded tile comprising different sampling densities, information indicative of a sampling ratio between the coded picture and the coded tile into a bitstream.

A method comprising:

• decoding, from a bitstream, a coded picture;
• decoding a coded tile into a decoded tile, the decoding comprising:
• decoding a horizontal offset and a vertical offset;
• decoding an indication that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;
• deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;
• determining a motion vector for the prediction unit;
• and
• applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block;
• decoding, from the bitstream, information indicative of a sampling ratio between the coded picture and the coded tile, wherein the coded picture is associated with an input picture, wherein the coded tile is associated with a second input picture;
• and
• scaling the first horizontal coordinate and the first vertical coordinate of the prediction unit according ratio for the derivation of the to the sampling prediction-unit anchor position.

An apparatus comprising:

• at least one processor and
• at least one storing instructions that, when executed with the at least one processor, causes the apparatus to perform:
• decode, from a bitstream, a coded picture;
• decode a coded tile into a decoded tile, comprising causing the apparatus to:
• decode a horizontal offset and a vertical offset;
• decode an indication that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;
• derive the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;
• determine a motion vector for the prediction unit;
• and
• apply the motion vector relative to the prediction-unit anchor position to obtain a prediction block;
• decode, from the bitstream, information indicative of a sampling ratio between the coded picture and the coded tile, wherein the coded picture is associated with an input picture, wherein the coded tile is associated with a second input picture;
• and
• scale the first horizontal coordinate and the first vertical coordinate of the prediction unit according to the sampling ratio for the derivation of the prediction-unit anchor position.