Adaptive picture resolution rescaling for inter-prediction and display

1. A method of decoding a coded picture of a coded video sequence, the method being performed by at least one processor and the method comprising:

decoding, from a first high level syntax structure for a plurality of pictures, a syntax element related to a reference picture resolution and a reference tile resolution;

decoding, from a second high level syntax structure that changes from a first coded picture to a second coded picture, a plurality of syntax elements related to a plurality of decoded tile resolutions, the first coded picture comprising a plurality of tiles at different resolutions that correspond to the plurality of decoded tile resolutions;

obtaining a sample from a reference picture buffer for use for prediction by a decoder, the sample from the reference picture buffer being in the reference picture resolution;

decoding the plurality of tiles in the different resolutions into a plurality of decoded tiles in the plurality of decoded tile resolutions;

resampling the plurality of decoded tiles so a resolution of each resampled segment matches the reference tile resolution and a resolution of a source tile from which a corresponding decoded segment was encoded, wherein a resolution of a combination of the resampled tiles matches the reference picture resolution; and

storing the plurality of decoded tiles into the reference picture buffer.

2. The method of claim 1 , wherein a resampling filter is used for at least one of resampling the sample from the reference picture buffer for use for prediction by a decoder and the resampling the plurality of decoded tiles into the reference tile resolution, wherein the resampling filter is a non-adaptive interpolation filter.

3. The method of claim 2 , wherein the resampling filter is chosen from a plurality of resampling filters based on a relationship between decoding resolution and reference picture resolution.

4. The method of claim 1 , further comprising:

decoding, from a third high level syntax structure, a syntax element related to an output resolution; and

resampling a sample of the plurality of decoded tiles to the output resolution.

5. The method of claim 1 , wherein the resampling uses different resampling factors for width and height.

6. An apparatus for decoding a coded picture of a coded video sequence, the apparatus comprising:

at least one memory configured to store computer program code; and

at least one processor configured to access the at least one memory and operate according to the computer program code, the computer program code comprising:

first decoding code configured to decode, from a first high level syntax structure for a plurality of pictures, a syntax element related to a reference picture resolution and a reference tile resolution;

second decoding code configured to decode, from a second high level syntax structure that changes from a first coded picture to a second coded picture, a plurality of syntax elements related to a plurality of decoded tile resolutions, the first coded picture comprising a plurality of tiles at different resolutions that correspond to the plurality of decoded tile resolutions;

first obtaining code configured to obtain, a sample from a reference picture buffer for use for prediction by a decoder, the sample from the reference picture buffer being in the reference picture resolution;

third decoding code configured to decode the plurality of tiles in the different resolutions into a plurality of decoded tiles in the plurality of decoded tile resolutions;

first resampling code configured to resample the plurality of decoded tiles so a resolution of each resampled tile matches the reference tile resolution and a resolution of a source tile from which a corresponding decoded tile was encoded, wherein a resolution of a combination of the resampled tiles matches the reference picture resolution; and

storing code configured to store the plurality of decoded tiles into the reference picture buffer.

7. The apparatus of claim 6 , wherein a resampling filter is used for at least one of resampling the sample from the reference picture buffer for use for prediction by a decoder and the resampling the plurality of decoded tiles into the reference tile resolution, wherein the resampling filter is a non-adaptive interpolation filter.

8. The apparatus of claim 7 , wherein the resampling filter is chosen from a plurality of resampling filters based on a relationship between decoding resolution and reference picture resolution.

9. The apparatus of claim 6 , wherein the resampling uses different resampling factors for width and height.

10. A non-transitory computer-readable storage medium storing a program for decoding a coded picture of a coded video sequence, the program comprising instructions that cause a processor to:

decode, from a first high level syntax structure for a plurality of pictures, a syntax element related to a reference picture resolution and a reference tile resolution;

decode, from a second high level syntax structure that changes from a first coded picture to a second coded picture, a plurality of syntax elements related to a plurality of decoded tile resolutions, the first coded picture comprising a plurality of tiles at different resolutions that correspond to the plurality of decoded tile resolutions;

obtain, a sample from a reference picture buffer for use for prediction by a decoder, the sample from the reference picture buffer being in the reference picture resolution;

decode the plurality of tiles in the different resolutions into a plurality of decoded tiles in the plurality of decoded tile resolutions;

resample the plurality of decoded tiles so a resolution of each resampled tile matches the reference tile resolution and a resolution of a source tile from which a corresponding decoded tile was encoded, wherein a resolution of a combination of the resampled tiles matches the reference picture resolution; and

store the plurality of decoded tiles into the reference picture buffer.

11. The non-transitory computer-readable storage medium of claim 10 , wherein a resampling filter is used for at least one of resampling the sample from the reference picture buffer for use for prediction by a decoder and the resampling the plurality of decoded tiles into the reference tile resolution, wherein the resampling filter is a non-adaptive interpolation filter.

12. The non-transitory computer-readable storage medium of claim 11 , wherein the resampling filter is chosen from a plurality of resampling filters based on a relationship between decoding resolution and reference picture resolution.