Inter prediction candidate selection in point cloud compression

1 . A method of processing point cloud data, the method comprising:

processing a syntax element indicative that a previous previous frame can be used for inter prediction for one or more points of a current frame of the point cloud data, wherein the previous previous frame comprises a reference frame of a previous reference frame;

determining that resampling is not applied to the current frame of the point cloud data;

applying, to the previous previous frame, a first set of one or more global motion parameters signaled with the current frame to generate a global motion compensated previous previous frame, wherein applying the first set of one or more global motion parameters signaled with the current frame to generate the global motion compensated previous previous frame is based the determination that resampling is not applied to the current frame; and

coding the one or more points of the current frame based on the global motion compensated previous previous frame.

2 . The method of claim 1 , wherein the current frame is a first current frame, the syntax element is a first syntax element, the previous previous frame is a first previous previous frame, the reference frame is a first reference frame, the previous reference frame is a first previous reference frame, and the global motion compensated previous previous frame is a global motion compensated first previous previous frame the method further comprising:

processing a second syntax element indicative that a second previous previous frame can be used for inter prediction for one or more points of a second current frame of the point cloud data, wherein the second previous previous frame comprises a second reference frame of a second previous reference frame;

determining that resampling is applied to the second current frame of the point cloud data;

processing a second set of one or more global motion parameters;

applying the second set of one or more global motion parameters to the second previous previous frame to generate a global motion compensated second previous previous frame; and

coding the one or more points of the second current frame based on the global motion compensated second previous previous frame.

3 . The method of claim 1 , wherein the current frame is a first current frame, the method further comprising:

determining that global motion is not enabled for a second current frame of the point cloud data; and

based on global motion not being enabled, disabling resampling for the second current frame of the point cloud data.

4 . The method of claim 3 , further comprising using an uncompensated reference frame rather than a resampled reference frame for the second current frame of the point cloud data.

5 . The method of claim 1 , further comprising using a next candidate from a reference frame in place of a next next candidate, the next next candidate being a candidate after a first candidate and a second candidate in a inter predictor candidate list.

6 . The method of claim 1 , further comprising:

determining that global motion compensation is enabled; and

processing a flag at a frame level or a slice level indicative of whether global motion compensation is to be applied to the current frame of the point cloud data.

7 . The method of claim 6 , wherein the current frame is a first current frame, wherein global motion compensation is not to be applied to a second current frame and wherein the method further comprises disallowing a last two entries of an inter predictor candidate list for the second current frame.

8 . The method of claim 7 , wherein the previous previous frame is a first previous previous frame, the method further comprising determining that a second previous previous frame is not used for inter prediction for the second current frame and wherein disallowing the last two entries of the inter predictor candidate list for the second current frame is based on the previous previous frame not being used for inter prediction for the second current frame.

9 . The method of claim 1 , wherein the current frame is a first current frame, the method further comprising:

determining that global motion compensation is disabled for a second current frame;

determining that resampling is enabled for the second current frame; and

based on global motion compensation being disabled for the second current frame and resampling being enabled for the second current frame, selecting a previous resampled reference frame as the reference frame for inter prediction for the second current frame.

10 . The method of claim 1 , wherein the current frame is a first current frame, the method further comprising:

determining that global motion compensation is disabled for a second current frame;

determining that resampling is disabled for the second current frame; and

based on global motion compensation being disabled for the second current frame and resampling being disabled for the second current frame, selecting a previous unresampled reference frame as the reference frame for inter prediction for the second current frame.

11 . The method of claim 1 , wherein the current frame is a first current frame, the method further comprising:

determining that global motion compensation is enabled for a second current frame;

determining that resampling is enabled for the second current frame; and

based on global motion compensation being enabled for the second current frame and resampling being enabled for the second current frame, selecting a previous resampled reference frame as the reference frame for inter prediction for the second current frame.

12 . The method of claim 1 , wherein code comprises decode and process the syntax element comprises parse the syntax element to determine a value of the syntax element indicative that the previous previous frame can be used for inter prediction.

13 . The method of claim 1 , wherein code comprises encode and process the syntax element comprises encode the syntax element to include a value indicative that the previous previous frame can be used for inter prediction.

14 . A device for processing a point cloud, the device comprising:

one or more memories configured to store point cloud data; and

one or more processors implemented in circuitry and communicatively coupled to the one or more memories, the one or more processors configured to:

process a syntax element indicative that a previous previous frame can be used for inter prediction for one or more points of a current frame of the point cloud data, wherein the previous previous frame comprises a reference frame of a previous reference frame;

determine that resampling is not applied to the current frame of the point cloud data;

apply, to the previous previous frame, a first set of one or more global motion parameters signaled with the current frame to generate a global motion compensated previous previous frame, wherein applying the first set of one or more global motion parameters signaled with the current frame to generate the global motion compensated previous previous frame is based the determination that resampling is not applied to the current frame; and

code the one or more points of the current frame based on the global motion compensated previous previous frame.

15 . The device of claim 14 , wherein the current frame is a first current frame, the syntax element is a first syntax element, the previous previous frame is a first previous previous frame, the reference frame is a first reference frame, the previous reference frame is a first previous reference frame, and the global motion compensated previous previous frame is a global motion compensated first previous previous frame, and wherein the one or more processors are further configured to:

process a second syntax element indicative that a second previous previous frame can be used for inter prediction for one or more points of a second current frame of the point cloud data, wherein the second previous previous frame comprises a second reference frame of a second previous reference frame;

determine that resampling is applied to the second current frame of the point cloud data;

process a second set of one or more global motion parameters;

apply the second set of one or more global motion parameters to the second previous previous frame to generate a global motion compensated second previous previous frame; and

code the one or more points of the second current frame based on the global motion compensated second previous previous frame.

16 . The device of claim 14 , wherein the device comprises a decoder configured to parse the syntax element, and wherein as part of parsing the syntax element, the one or more processors are configured determine a value of the syntax element indicative that the previous previous frame can be used for inter prediction.

17 . The device of claim 14 , wherein the device comprises an encoder configured to signal the syntax element, and wherein the syntax element has a value indicative that the previous previous frame can be used for inter prediction.

18 . Non-transitory computer-readable storage media comprising instructions, which when executed, cause one or more processors to:

process a syntax element indicative that a previous previous frame can be used for inter prediction for one or more points of a current frame of point cloud data, wherein the previous previous frame comprises a reference frame of a previous reference frame;

determine that resampling is not applied to the current frame of the point cloud data;

apply, to the previous previous frame, a first set of one or more global motion parameters signaled with the current frame to generate a global motion compensated previous previous frame, wherein applying the first set of one or more global motion parameters signaled with the current frame to generate the global motion compensated previous previous frame is based the determination that resampling is not applied to the current frame; and

code the one or more points of the current frame based on the global motion compensated previous previous frame.