Encoder and decoder, encoding method and decoding method for reference picture resampling extensions

A method for decoding an encoded video signal comprising encoded picture data to decode a plurality of pictures of a video sequence of a video, the method comprising:

• receiving the encoded video signal comprising the encoded picture data and a sequence parameter set (SPS) that includes an indication that a sample aspect ratio (SAR) is changeable within a coded video sequence (CVS);
• receiving a first supplemental enhancement information (SEI) message within the encoded video signal, the first SEI message comprising a first SAR value for a first group of one or more of the plurality of pictures within the CVS;
• receiving a second SEI message within the encoded video signal, the second SEI message comprising a second SAR value for a second group of one or more of the plurality of pictures within the CVS, wherein the second SAR value is different than the first SAR value, and wherein the second group is different than the first group;
• decoding the encoded picture data corresponding to the first group and the second group of one or more of the plurality of pictures to obtain a plurality of decoded pictures;
• and
• outputting the plurality of decoded pictures, wherein one or more of the plurality of decoded pictures have a different SAR than one or more other pictures of the plurality of decoded pictures;
• wherein the first group of the one or more of the plurality of pictures of the CVS comprises the one or more of the plurality of pictures of the CVS that are encoded in the encoded picture data that is received after the first SEI message comprising the first SAR value is received and before the second SEI message comprising the second SAR value is received, and
• wherein the second group of the one or more of the plurality of pictures of the CVS comprises the one or more of the plurality of pictures of the CVS that are encoded in the encoded picture data that is received after the second SEI message comprising the second SAR value is received.

A video encoder for encoding a plurality of pictures of a video sequence of a video, the video encoder comprising:

• at least one memory;
• at least one processor comprising processor circuitry communicatively coupled to the at least one memory, the at least one processor configured individually and/or collectively to read instructions from the at least one memory to perform operations comprising:
• encoding the plurality of pictures of a coded video sequence (CVS) into encoded picture data;
• generating a sequence parameter set (SPS) comprising an indication that a sample aspect ratio (SAR) is changeable within the CVS;
• generating a first supplemental enhancement information (SEI) message comprising a first SAR value for a first group of one or more of the plurality of pictures within the CVS;
• generating a second SEI message comprising a second SAR value for a second group of one or more of the plurality of pictures within the CVS, wherein the second SAR value is different than the first SAR value, and wherein the second group is different than the first group;
• generating an encoded video signal such that the encoded video signal comprises the encoded picture data, the SPS, the first SEI message, and the second SEI message;
• and
• transmitting the encoded video signal;
• wherein the encoded video signal is arranged such that:
• the sequence parameter set is before the first SEI message;
• the first SEI message is before an encoding of the first group of the one or more of the plurality of pictures of the CVS;
• the encoding of the first group of the one or more of the plurality of pictures of the CVS is before the second SEI message;
• and
• the second SEI message is before an encoding of the second group of the one or more of the plurality of pictures of the CVS.

A method for encoding a plurality of pictures of a video sequence of a video, the method comprising:

• encoding the plurality of pictures of a coded video sequence (CVS) into encoded picture data;
• generating a sequence parameter set (SPS) comprising an indication that a sample aspect ratio (SAR) is changeable within the CVS;
• generating a first supplemental enhancement information (SEI) message comprising a first SAR value for a first group of one or more of the plurality of pictures within the CVS;
• generating a second SEI message comprising a second SAR value for a second group of one or more of the plurality of pictures within the CVS, wherein the second SAR value is different than the first SAR value, and wherein the second group is different than the first group;
• generating an encoded video signal such that the encoded video signal comprises the encoded picture data, the SPS, the first SEI message, and the second SEI message;
• and
• transmitting the encoded video signal;
• wherein the encoded video signal is arranged such that:
• the sequence parameter set is before the first SEI message;
• the first SEI message is before an encoding of the first group of the one or more of the plurality of pictures of the CVS;
• the encoding of the first group of the one or more of the plurality of pictures of the CVS is before the second SEI message;
• and
• the second SEI message is before an encoding of the second group of the one or more of the plurality of pictures of the CVS.