Signaling for reference picture resampling

A device for decoding an encoded video bitstream, the device comprising:

• at least one memory configured to store program code;
• and
• at least one processor configured to read the program code and operate as instructed by the program code, the program code including:
• first obtaining code configured to cause the at least one processor to obtain a coded picture from the encoded video bitstream;
• decoding code configured to cause the at least one processor to decode the coded picture to generate a decoded picture;
• second obtaining code configured to cause the at least one processor to obtain from the encoded video bitstream a first flag indicating whether reference picture resampling is enabled;
• third obtaining code configured to, based on the first flag indicating that the reference picture resampling is enabled, cause the at least one processor to obtain from the encoded video bitstream a second flag indicating whether reference pictures have a constant reference picture size indicated in the encoded video bitstream;
• fourth obtaining code configured to, based on the first flag indicating that the reference picture resampling is enabled, cause the at least one processor to obtain from the encoded video bitstream a third flag indicating whether output pictures have a constant output picture size indicated in the encoded video bitstream;
• first generating code configured to, based on the second flag indicating that the reference pictures have the constant reference picture size, cause the at least one processor to generate a reference picture by resampling the decoded picture to have the constant reference picture size, and store the reference picture in a decoded picture buffer;
• and
• second generating code configured to, based on the third flag indicating that the output pictures have the constant output picture size, cause the at least one processor to generate an output picture by resampling the decoded picture to have the constant output picture size, and output the output picture.

A non-transitory computer-readable medium storing instructions, the instructions comprising:

• one or more instructions that, when executed by one or more processors of a device for decoding an encoded video bitstream, cause the one or more processors to:
• obtain a coded picture from the encoded video bitstream;
• decode the coded picture to generate a decoded picture;
• obtain from the encoded video bitstream a first flag indicating whether reference picture resampling is enabled;
• based on the first flag indicating that the reference picture resampling is enabled, obtain from the encoded video bitstream a second flag indicating whether reference pictures have a constant reference picture size indicated in the encoded video bitstream;
• based on the first flag indicating that the reference picture resampling is enabled, obtain from the encoded video bitstream a third flag indicating whether output pictures have a constant output picture size indicated in the encoded video bitstream;
• based on the second flag indicating that the reference pictures have the constant reference picture size, generate a reference picture by resampling the decoded picture to have the constant reference picture size, and store the reference picture in a decoded picture buffer;
• and
• based on the third flag indicating that the output pictures have the constant output picture size, generate an output picture by resampling the decoded picture to have the constant output picture size, and output the output picture.