Methods, devices and systems for configuring different access units in scalable video coding are described. In one example aspect, a method of video processing include performing a conversion between a video comprising one or more pictures in one or more video layers and a bitstream of a video, wherein the bitstream comprises a coded video sequence that includes one or more access units, and wherein the bitstream further comprises a first syntax element indicating whether an access unit includes a picture for each video layer making up the coded video sequence.

Several techniques for video encoding and video decoding are described. One example method includes performing a conversion between a subpicture in a video picture of a video and a bitstream of the video according to a rule. The rule specifies that, in in case a subpicture is treated as a video picture for the conversion, a cross-layer alignment restriction is applied to less than all of the multiple layers including a current layer that includes the subpicture and a subset of layers associated with the current layer.

Several techniques for video encoding and video decoding are described. One example method includes performing a conversion between a subpicture in a video picture of a video and a bitstream of the video according to a rule. The rule specifies that, in in case a subpicture is treated as a video picture for the conversion, a cross-layer alignment restriction is applied to less than all of the multiple layers including a current layer that includes the subpicture and a subset of layers associated with the current layer.

A method for encoding a first stream of video data comprising a plurality of frames of video, the method, for one or more of the plurality of frames of video, comprising the steps of: encoding in a hierarchical arrangement a frame of the video data, the hierarchical arrangement comprising a base layer of video data and a first enhancement layer of video data, said first enhancement layer of video data comprising a plurality of sub-layers of enhancement data, such that when encoded: the base layer of video data comprises data which when decoded renders the frame at a first, base, level of quality; and each sub-layer of enhancement data comprises data which, when decoded with the base layer, render the frame at a higher level of quality than the base level of quality; and wherein the steps of encoding the sub-layers of enhancement data comprises: quantizing the enhancement data at a determined initial level of quantization thereby creating a set of quantized enhancement data; associating to each of the plurality of sub-layers a respective notional quantization level and allocating, for each of the plurality of sub-layers, a sub-set of the set of quantized enhancement data based on the respective notional quantization level.

A method for encoding a first stream of video data comprising a plurality of frames of video, the method, for one or more of the plurality of frames of video, comprising the steps of: encoding in a hierarchical arrangement a frame of the video data, the hierarchical arrangement comprising a base layer of video data and a first enhancement layer of video data, said first enhancement layer of video data comprising a plurality of sub-layers of enhancement data, such that when encoded: the base layer of video data comprises data which when decoded renders the frame at a first, base, level of quality; and each sub-layer of enhancement data comprises data which, when decoded with the base layer, render the frame at a higher level of quality than the base level of quality; and wherein the steps of encoding the sub-layers of enhancement data comprises: quantizing the enhancement data at a determined initial level of quantization thereby creating a set of quantized enhancement data; associating to each of the plurality of sub-layers a respective notional quantization level and allocating, for each of the plurality of sub-layers, a sub-set of the set of quantized enhancement data based on the respective notional quantization level.

A method for encoding a video sequence in a scalable video encoder to generate a scalable bitstream is provided that includes encoding the video sequence in a first layer encoder of the scalable video encoder to generate a first sub-bitstream, encoding the video sequence in a second layer encoder of the scalable video encoder to generate a second sub-bitstream, wherein portions of the video sequence being encoded in the second layer encoder are predicted using reference portions of the video sequence encoded in the first layer encoder, combining the first sub-bitstream and the second sub-bitstream to generate the scalable bitstream, and signaling in the scalable bitstream an indication of a maximum decoded picture buffer (DPB) size needed for decoding the second sub-bitstream and the first sub-bitstream when the second sub-bitstream is a target sub-bitstream for decoding.

A method of decoding may comprise: receiving a bitstream comprising compressed video/image data; parsing or deriving, from the bitstream, an output layer set mode indicator in a video parameter set (VPS); identifying output layer set signaling based on the output layer set mode indicator; identifying one or more picture output layers based on the identified output layer set signaling; and decoding the identified one or more picture output layers.

A method of decoding may comprise: receiving a bitstream comprising compressed video/image data; parsing or deriving, from the bitstream, an output layer set mode indicator in a video parameter set (VPS); identifying output layer set signaling based on the output layer set mode indicator; identifying one or more picture output layers based on the identified output layer set signaling; and decoding the identified one or more picture output layers.

A method for decoding a video according to the present invention may comprise: decoding information indicating whether a non-zero transform coefficient exists in a current block, when the information indicates that the non-zero transform coefficient exists in the current block, determining a scanning order of the current block, and decoding a transform coefficient included in the current block according to the determined scanning order.

A method for decoding a video according to the present invention may comprise: decoding information indicating whether a non-zero transform coefficient exists in a current block, when the information indicates that the non-zero transform coefficient exists in the current block, determining a scanning order of the current block, and decoding a transform coefficient included in the current block according to the determined scanning order.