Coding scheme for depth data

A method of decoding depth data comprising:

• receiving a bitstream, wherein the bitstream comprises a depth map and metadata,
• wherein the depth map comprises an array of map values,
• wherein each map value is one of a plurality of levels,
• wherein the metadata defines a first subset of the plurality of levels and a second subset of the plurality of levels,
• wherein the first subset represents an occupied part of the depth map,
• wherein the second subset represents an unoccupied part of the depth map;
• decoding the depth map,
• wherein the decoding comprises converting each map value in the first subset to a corresponding depth value,
• wherein at least one map value is not equal to the corresponding depth value;
• and
• outputting the depth values.

An encoder comprising:

• an input circuit,
• wherein the input circuit is arranged to receive source data,
• wherein the source data comprises depth values;
• an analyzer circuit,
• wherein the analyzer circuit is arranged to analyze the depth values,
• wherein the analyzer circuit is arranged to define a depth map based on a result of the analysis,
• wherein the depth map comprises an array of map values,
• wherein each map value has one of a plurality of levels,
• wherein the analyzer circuit is arranged to determine an encoding of the depth values into the map values,
• wherein a range of the map values is not equal to a range of the depth values,
• wherein the analyzer circuit is arranged to define a first subset comprising an occupied part of the depth map based on a result of the analysis,
• wherein the analyzer circuit is arranged to define a second subset comprising an unoccupied part of the depth map based on the result of the analysis;
• and
• a depth value encoder circuit,
• wherein the analyzer circuit is arranged to assign one or more map values to the second subset of the depth map;
• wherein the analyzer circuit is arranged to convert the depth values to map values in the first subset of the depth map;
• and
• wherein the analyzer circuit is arranged generate a bitstream,
• wherein the bitstream comprises the depth map and metadata,
• wherein the metadata comprises a definition of the first subset and the second subset.

A decoder comprising:

• an input circuit,
• wherein the input circuit is arranged to receive a bitstream,
• wherein the bitstream comprises a depth map and metadata,
• wherein the depth map comprises an array of map values,
• wherein each map value is one of a plurality of levels,
• wherein the metadata defines a first subset of an occupied part of the depth map,
• wherein the metadata defines a second subset of an unoccupied part of the depth map;
• a depth value decoder circuit,
• wherein the depth value decoder circuit is arranged to decode the depth map,
• wherein the decoding comprises converting each map value in the first subset to a corresponding depth value,
• wherein at least one map value is not equal to the corresponding depth value;
• and
• an output circuit,
• wherein the output circuit is arranged to output the depth values.