Adaptive resolution change in video processing

1. A computer-implemented video processing method, comprising:

comparing resolutions of a target picture and a first reference picture, the first reference picture having at least a first version and a second version, the first version having an original resolution, and the second version having a maximum resolution allowed for resampling the first reference picture;

in response to the target picture and the first reference picture having different resolutions, resampling the second version of the first reference picture to generate a second reference picture; and

encoding or decoding the target picture using the second reference picture.

2. The method according to claim 1 , further comprising:

storing the second reference picture in a first buffer, the first buffer being different from a second buffer storing decoded pictures that are used for prediction of future pictures; and

removing the second reference picture from the first buffer after the encoding or decoding of the target picture is completed.

3. The method according to claim 1 , wherein encoding or decoding the target picture comprises:

encoding or decoding the target picture by using no more than a predetermined number of resampled reference pictures.

4. The method according to claim 3 , wherein encoding or decoding the target picture comprises:

signaling the predetermined number as part of a sequence parameter set or a picture parameter set.

5. The method according to claim 1 , further comprising:

storing the first version and the second version of the first reference picture in a decoded picture buffer; and

outputting the first version for coding future pictures.

6. The method according to claim 1 , wherein resampling the first reference picture to generate the second reference picture comprises:

generating the second reference picture in a supported resolution.

7. The method according to claim 6 , wherein further comprising:

signaling, as part of a sequence parameter set or a picture parameter set, information indicating:

a number of supported resolutions, and

pixel dimensions corresponding to the supported resolutions.

8. The method according to claim 7 , wherein the information comprises:

an index corresponding to at least one of the supported resolutions.

9. The method according to claim 7 , further comprising:

setting the number of supported resolutions based on a configuration of a video application or a video device.

10. The method according to claim 1 , wherein resampling the first reference picture to generate the second reference picture comprises:

performing progressive down-sampling of the first reference picture to generate the second reference picture.

11. A device, comprising:

one or more memories storing computer instructions; and

one or more processors configured to execute the computer instructions to cause the device to:

compare a resolution of a target picture to a resolution of a first reference picture, the first reference picture having at least a first version and a second version, the first version having an original resolution, and the second version having a maximum resolution allowed for resampling the first reference picture;

in response to the target picture and the first reference picture having different resolutions, resample the second version of the first reference picture to generate a second reference picture; and

encode or decode the target picture using the second reference picture.

12. The device according to claim 11 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

store the second reference picture in a first buffer, the first buffer being different from a second buffer storing decoded pictures that are used for prediction of future pictures; and

remove the second reference picture from the first buffer after the encoding or decoding of the target picture is completed.

13. The device according to claim 11 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

encode or decode the target picture by using no more than a predetermined number of resampled reference pictures.

14. The device according to claim 13 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

signal the predetermined number as part of a sequence parameter set or a picture parameter set.

15. The device according to claim 11 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

store the first version and the second version of the first reference picture in a decoded picture buffer; and

output the first version for coding future pictures.

16. The device according to claim 11 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

generate the second reference picture in a supported resolution.

17. The device according to claim 16 , wherein the one or more processors is further configured to execute the computer instructions to cause the device to:

signal, as part of a sequence parameter set or a picture parameter set, information indicating:

a number of supported resolutions, and

pixel dimensions corresponding to the supported resolutions.

18. A non-transitory computer readable medium storing a set of instructions that is executable by at least one processor of a computer system to cause the computer system to perform a method for processing video content, the method comprising:

comparing resolutions of a target picture and a first reference picture, the first reference picture having at least a first version and a second version, the first version having an original resolution, and the second version having a maximum resolution allowed for resampling the first reference picture;

in response to the target picture and the first reference picture having different resolutions, resampling the second version of the first reference picture to generate a second reference picture; and

encoding or decoding the target picture using the second reference picture.