Signaling of reference picture resampling with resampling picture size indication in video bitstream

A device for encoding a 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:
• receiving code configured to cause the at least one processor to receive a current picture,
• first setting code configured to cause the at least one processor to set a conformance window for the current picture, the conformance window corresponding to a subpart of the current picture to be output by a decoder,
• second setting code configured to cause the at least one processor to set a first flag indicating that the conformance window is present in the current picture;
• third setting code configured to cause the at least one processor to set a second flag indicating whether the conformance window is used for determining a resampling ratio between the current picture and a reference picture;
• and
• encoding code configured to cause the at least one processor to encode the video bitstream including the current picture, the conformance window, the first flag, and the second flag,
• wherein the resampling ratio is determined based on a conformance window size based on a determination that the second flag indicates that the conformance window is used for reference picture resampling, and
• wherein the resampling ratio is determined based on a resampling picture size based on a determination that the second flag indicates that the conformance window is not used for reference picture resampling.

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 encoding a video bitstream, cause the one or more processors to:
• receive a current picture;
• set a conformance window for the current picture, the conformance window corresponding to a subpart of the current picture to be output by a decoder;
• set a first flag indicating that the conformance window is present in the current picture;
• set a second flag indicating whether the conformance window is used for determining a resampling ratio between the current picture and a reference picture;
• and
• encode the video bitstream including the current picture, the conformance window, the first flag, and the second flag,
• wherein the resampling ratio is determined based on a conformance window size based on a determination that the second flag indicates that the conformance window is used for reference picture resampling, and
• wherein the resampling ratio is determined based on a resampling picture size based on a determination that the second flag indicates that the conformance window is not used for reference picture resampling.