Method and apparatus for video coding with constraints on reference picture lists of a RADL picture

1. A method for decoding a video sequence, the method comprising:

receiving a video bitstream associated with a current picture, wherein when a current subpicture of the current picture, with nuh_layer_id equal to a particular value layerId and subpicture index equal to a particular value subpicIdx, is a RADL (Random Access Decodable Leading) subpicture, reference picture list 0 or reference picture list 1 associated with the current subpicture is mandatorily required to contain no active entry corresponding to:

a picture for which a value of nuh_layer_id is not equal to layerId containing a RASL (Random Access Skipped Leading) subpicture with the subpicture index equal to subpicIdx; or

a RASL picture for which the value of nuh_layer_id is not equal to the layerId and a value of sps_num_subpics_minus1 is equal to 0;

and

decoding the current subpicture utilizing information comprising the active entries in the reference picture list 0 or the reference picture list 1.

2. An apparatus for decoding a video sequence, the apparatus comprising one or more electronic circuits or processors arranged to:

receive a video bitstream associated with a current picture, wherein when a current subpicture of the current picture, with nuh_layer_id equal to a particular value layerId and subpicture index equal to a particular value subpicIdx, is a RADL (Random Access Decodable Leading) subpicture, reference picture list 0 or reference picture list 1 associated with the current subpicture is mandatorily required to contain no active entry corresponding to:

a picture for which a value of nuh_layer_id is not equal to layerId containing a RASL (Random Access Skipped Leading) subpicture with the subpicture index equal to subpicIdx; or

a RASL picture for which the value of nuh_layer_id is not equal to the layerId and a value of sps_num_subpics_minus1 is equal to 0:

and

decode the current subpicture utilizing information comprising the active entries in the reference picture list 0 or the reference picture list 1.

3. A method for encoding a video sequence, the method comprising:

receiving input data comprising a current picture;

encoding the current picture, wherein when a current subpicture of the current picture, with nuh_layer_id equal to a particular value layerId and subpicture index equal to a particular value subpicIdx, is a RADL (Random Access Decodable Leading) subpicture, reference picture list 0 or reference picture list 1 associated with the current subpicture is mandatorily required to contain no active entry corresponding to;

a picture for which a value of nuh_layer_id is not equal to layerId containing a RASL (Random Access Skipped Leading) subpicture with the subpicture index equal to subpicIdx; or

a RASL picture for which the value of nuh_layer_id is not equal to the layerId and a value of sps_num_subpics_minus1 is equal to 0;

and

generating a video bitstream comprising information of the active entries in the reference picture list 0 or the reference picture list 1.

4. A method for decoding a video sequence, the method comprising:

receiving a video bitstream associated with a current picture, wherein when the current picture is a RADL (Random Access Decodable Leading) picture, reference picture list 0 or reference picture list 1 of the current picture is mandatorily required to contain no active entry corresponding to:

a RASL (Random Access Skipped Leading) picture with pps_mixed_nalu_types_in_pic_flag equal to 0; or

a picture that precedes an associated IRAP (Intra Random Access Point) picture in decoding order, and wherein an active entry in the reference picture list 0 or the reference picture list 1 of the RADL picture refers to a RASL picture with the pps_mixed_nalu_types_in_pic_flag equal to 1 and a referenced RASL picture either belongs to the same layer or a different layer than a layer containing the current picture which is the RADL picture; and

decoding the current picture utilizing information comprising the active entries in the reference picture list 0 or the reference picture list 1.

5. A method for encoding a video sequence, the method comprising:

receiving input data comprising a current picture, wherein when the current picture is a RADL (Random Access Decodable Leading) picture, reference picture list 0 or reference picture list 1 of the current picture is mandatorily required to contain no active entry corresponding to:

a RASL (Random Access Skipped Leading) picture with pps_mixed_nalu_types_inpic_flag equal to 0; or

a picture that precedes an associated IRAP (Intra Random Access Point) picture in decoding order, and wherein an active entry in the reference picture list 0 or the reference picture list 1 of the RADL picture refers to a RASL picture with the pps_mixed_nalu_types_inpic_flag equal to 1 and a referenced RASL picture either belongs to the same layer or a different layer than a layer containing the current picture which is the RADL picture; and

encoding the current picture utilizing information comprising the active entries in the reference picture list 0 or the reference picture list 1.