Embodiments of the disclosure provide methods and devices for decoding video signals using inter prediction. According to an embodiment of the disclosure, a method for processing a video signal comprises constructing a reference picture list of a current picture in the video signal and performing a prediction for a current picture by using the reference picture list, wherein constructing the reference picture list comprising, if a first entry of the reference picture list corresponds to a short-term reference picture (STRP), obtaining a picture order count (POC) difference between a picture related to the first entry and another picture, and if a second entry of the reference picture list corresponds to a long-term reference picture (LTRP), obtaining a POC modulo value of a picture related to the second entry. A reference picture list for identifying a picture may be generated in a simplified and effective manner. Thus, the compression performance may be increased, and the computation time may be decreased.

Methods, systems, apparatus for video processing are described. The processing may include encoding, decoding or transcoding. One example video processing method includes performing a conversion between a video and a bitstream of the video according to a rule, and wherein the rule specifies that a syntax field is included to specify whether a reference picture list information is present or not in a video unit level of an instantaneous decoding refresh picture.

An apparatus (200) for receiving an input video data stream according to an embodiment is provided. The input video data stream has a video encoded thereinto. The apparatus (200) is configured to generate an output video data stream from the input video data stream.

Methods and apparatus for video processing are described. The processing may include video encoding, video decoding, or video transcoding. An example video processing method includes performing a conversion between a video including one or more pictures including one or more subpictures and a bitstream of the video. The one or more pictures and/or the one or more subpictures are included into the bitstream according to an order rule. The order rule specifies a relationship between a position of a current instantaneous decoder refresh (IDR) picture or a current IDR subpicture in the bitstream with respect to another picture referred to by an entry in a reference picture list for a current slice of the current IDR picture or the current IDR subpicture.

A method of video processing includes performing a conversion between a video and a bitstream of the video. The bitstream includes one or more output layer sets each including one or more video layers. The bitstream conforms to a format rule, wherein the format rule specifies that a number of decoded picture buffer parameter syntax structures included in a video parameter set for the bitstream is equal to: zero, in a case that each output layer set includes a single video layer; or one plus a value of a syntax element, in a case that each output layer set includes a single layer is not true.

Innovations in syntax and semantics of coded picture buffer removal delay (“CPBRD”) values potentially simplify splicing operations. For example, a video encoder sets a CPBRD value for a current picture that indicates an increment value relative to a nominal coded picture buffer removal time of a preceding picture in decoding order, regardless of whether the preceding picture has a buffering period SEI message. The encoder can signal the CPBRD value according to a single-value approach in which a flag indicates how to interpret the CPBRD value, according to a two-value approach in which another CPBRD value (having a different interpretation) is also signaled, or according to a two-value approach that uses a flag and a delta value. A corresponding video decoder receives and parses the CPBRD value for the current picture. A splicing tool can perform simple concatenation operations to splice bitstreams using the CPBRD value for the current picture.

An image decoding method according to the present invention includes: receiving information on a set of reference pictures for configuring a set of reference pictures of a current picture, wherein the information on the set of reference pictures includes the most significant bit (MSB) information that may calculate the MSB of the picture order count (POC) of a long-term reference picture relative to the current picture, and flag information that represents whether there is MSB information; and eliciting the set of reference pictures by using received MSB information when the flag information is 1, and performing marking on the reference picture, wherein the flag information may be 1 when a temporal sub-layer identifier is 0, and there is at least one POC value for which a remainder obtained by dividing by a maximum value MaxPicOrderCntLsb capable of being represented by the LSB is the same as the least significant bit (LSB) of the POC of the long-term reference picture, in a set of POCs of a previous picture including POC values related to the previous picture that may not be discarded without affecting whether other pictures of the same temporal layer may be decoded.

An image decoding method according to the present invention includes: receiving information on a set of reference pictures for configuring a set of reference pictures of a current picture, wherein the information on the set of reference pictures includes the most significant bit (MSB) information that may calculate the MSB of the picture order count (POC) of a long-term reference picture relative to the current picture, and flag information that represents whether there is MSB information; and eliciting the set of reference pictures by using received MSB information when the flag information is 1, and performing marking on the reference picture, wherein the flag information may be 1 when a temporal sub-layer identifier is 0, and there is at least one POC value for which a remainder obtained by dividing by a maximum value MaxPicOrderCntLsb capable of being represented by the LSB is the same as the least significant bit (LSB) of the POC of the long-term reference picture, in a set of POCs of a previous picture including POC values related to the previous picture that may not be discarded without affecting whether other pictures of the same temporal layer may be decoded.

Examples of video encoding methods and apparatus and video decoding methods and apparatus are described. An example method of video processing includes performing a conversion between a current picture of a video and a bitstream of the video according to a rule. The rule specifies that responsive to a picture being referred to by an inter-layer reference picture (ILRP) entry in a reference picture list of a slice of the current picture, the picture is allowed to have a gradual decoding refresh (GDR) type and a syntax element specifying a recovery point of the picture in an output order is 0.

An image coding method includes: writing, into a sequence parameter set, buffer description defining information for defining a plurality of buffer descriptions; writing, into the sequence parameter set, reference list description defining information for defining a plurality of reference list descriptions corresponding to the buffer descriptions; and writing, into a first header of each processing unit which is included in a coded bitstream, buffer description selecting information for specifying a selected buffer description.