Slice types in video codecs

Abstract

Methods and apparatus for video processing are described. The video processing may include video encoding, video decoding, or video transcoding. An example video processing method includes performing conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation conforms to a condition specifying a field in the codec representation that controls, for a video slice, a constraint on a slice type or whether a slice type is included in the codec representation, a format rule, wherein the field includes a general constraint flag, a network abstraction layer unit type, or whether the video slice is in the first video picture of an access unit.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a national phase of International Patent Application No. PCT / US2021 / 024663, filed on March 29, 2021, and claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 002,064, filed on March 30, 2020. The entire disclosures of all of the foregoing patent applications are hereby incorporated by reference. Technical Field

[0003] This patent document relates to image and video processing. Background Art

[0004] Digital video accounts for the largest use of bandwidth on the Internet and other digital communications networks. As the number of connected user devices capable of receiving and displaying video increases, bandwidth demand for digital video usage is expected to continue to grow. Summary of the invention

[0005] This document discloses techniques that can be used by video encoders and decoders to process codec representations of video using control information useful for decoding of the codec representations of video.

[0006] In one example aspect, a video processing method is disclosed. The method includes performing conversion between a video including one or more pictures including one or more slices and a bitstream of the video, wherein the bitstream conforms to a format rule; wherein the format rule specifies whether or how to indicate in the bitstream a slice type of a slice in the one or more slices depends on a condition, wherein the condition is based on a general constraint flag, a network abstraction layer unit type, or whether the slice is in the first picture of an access unit.

[0007] In another example aspect, a video processing method is disclosed. The method includes performing conversion between a video including a picture including a plurality of slices and a bitstream of the video, wherein the bitstream conforms to a format rule that specifies that a flag in a picture header controls applicability of adaptive loop filtering for all slices in the picture.

[0008] In another example aspect, a video processing method is disclosed. The method includes performing conversion between a video including one or more pictures including one or more slices and a bitstream of the video according to a format rule, wherein the format rule specifies a repetition time of a parameter set associated with the video.

[0009] In another example aspect, a video processing method is disclosed. The method includes performing conversion between a video including a picture in a video unit and a bitstream of the video according to a format rule, wherein the format rule specifies that in response to a width of the picture being equal to a maximum allowed picture width in the video unit and a height of the picture being equal to a maximum allowed picture height in the video unit, a consistency window flag in a picture parameter set corresponding to the picture is set to a value of 0.

[0010] In another example aspect, a video processing method is disclosed. The method includes performing conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation conforms to a condition specifying a field in the codec representation that controls, for a video slice, a constraint on a slice type or whether a slice type is included in the codec representation, a format rule, wherein the field includes a general constraint flag, a network abstraction layer unit type, or whether the video slice is in a first video picture of an access unit.

[0011] In another example aspect, another video processing method is disclosed. The method includes performing conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation conforms to a format rule that specifies disabling adaptive loop filtering for all slices in a video picture based on a value of a flag in a picture header of the video picture.

[0012] In another example aspect, another video processing method is disclosed. The method includes performing a conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation conforms to a format rule that specifies setting a consistency window flag to a disabled mode if a height and a width of a current picture are equal to a maximum height and a maximum width in the video.

[0013] In another example aspect, another video processing method is disclosed. The method includes performing conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation complies with a format rule for a repetition time of a specified parameter set.

[0014] In yet another example aspect, a video encoder apparatus is disclosed. The video encoder includes a processor configured to implement the above method.

[0015] In yet another example aspect, a video decoder apparatus is disclosed. The video decoder includes a processor configured to implement the above method.

[0016] In yet another exemplary aspect, a computer readable medium having stored thereon code is disclosed. The code is in the form of processor executable code embodying one of the methods described herein.

[0017] These and other features are described throughout this document. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a block diagram of an example video processing system.

[0019] Figure 2 is a block diagram of a video processing device.

[0020] Figure 3 is a flow chart of an example method of video processing.

[0021] Figure 4 is a block diagram illustrating a video encoding and decoding system according to some embodiments of the present disclosure.

[0022] Figure 5 is a block diagram illustrating an encoder according to some embodiments of the present disclosure.

[0023] Figure 6 is a block diagram illustrating a decoder according to some embodiments of the present disclosure.

[0024] Figure 7 An example of adaptive loop filter (ALF) filter shapes (chroma: 5×5 diamond, luma: 7×7 diamond) is shown.

[0025] Figure 8 Examples of ALF and CC-ALF diagrams are shown.

[0026] Figure 9-11 A flow chart illustrating an example method of video processing is shown. DETAILED DESCRIPTION

[0027] Section headings are used in this document for ease of understanding and do not limit the applicability of the techniques and embodiments disclosed in each section to that section. In addition, H.266 technical terms are used in some descriptions only for ease of understanding and not to limit the scope of the disclosed techniques. Therefore, the techniques described herein are also applicable to other video codec protocols and designs.

[0028] 1. Introduction

[0029] This document relates to video codec technology. Specifically, it is about improvements to the signaling of slice types, ALF and consistency windows, and repetition of some non-VCL NAL units (including VPS, SPS, PPS, APS, and DCI NAL units). These ideas can be applied alone or in various combinations to any video codec standard or non-standard video codec that supports multi-layer video codec, such as the Versatile Video Codec (VVC) under development.

[0030] 2. Abbreviations

[0031] ALF Adaptive Loop Filter

[0032] APS Adaptive Parameter Set

[0033] AU Access Unit

[0034] AUD Access Unit Delimiter

[0035] AVC Advanced Video Codec

[0036] CLVS Codec Layer Video Sequence

[0037] CPB codec picture buffer

[0038] CRA Completely Random Access

[0039] CTU Codec Tree Unit

[0040] CVS codec video sequence

[0041] DCI decoding capability information

[0042] DPB decoded picture buffer

[0043] DU Decoding Unit

[0044] EOB End of bitstream

[0045] EOS sequence end

[0046] GDR Gradual Decode Refresh

[0047] HEVC High Efficiency Video Codec

[0048] HRD Hypothesized Reference Decoder

[0049] IDR Instant Decode Refresh

[0050] JEM Joint Exploration Model

[0051] LMCS Luma Mapping and Chroma Scaling

[0052] MCTS Motion Constraints Episode Set

[0053] NAL Network Abstraction Layer

[0054] OLS output layer set

[0055] PH Image Header

[0056] PPS Picture Parameter Set

[0057] PTL grades, tiers and levels

[0058] PU Picture Unit

[0059] RADL Random Access Decodable Preamble (Image)

[0060] RAP Random Access Point

[0061] RASL Random Access Skip Preamble (picture)

[0062] RBSP Raw Byte Sequence Payload

[0063] RPL Reference Image List

[0064] SAO Sample Adaptive Offset

[0065] SEI auxiliary enhancement information

[0066] SPS Sequence Parameter Set

[0067] STSA Stepwise Temporal Sublayer Access

[0068] SVC Scalable Video Codec

[0069] VCL video codec layer

[0070] VPS Video Parameter Set

[0071] VTM VVC test model

[0072] VUI Video Availability Information

[0073] VVC Multi-functional Video Codec

[0074] 3. Preliminary Discussion

[0075] Video codec standards have evolved primarily through the development of the well-known ITU-T and ISO / IEC standards. ITU-T developed H.261 and H.263, ISO / IEC developed MPEG-1 and MPEG-4 Visual, and the two organizations jointly developed H.262 / MPEG-2 Video, H.264 / MPEG-4 Advanced Video Coding (AVC), and H.265 / HEVC[1] standards. Since H.262, video codec standards have been based on a hybrid video codec structure that uses temporal prediction plus transform codec. To explore future video codec technologies beyond HEVC, VCEG and MPEG jointly established the Joint Video Exploration Team (JVET) in 2015. Since then, JVET has adopted many new approaches and put them into a reference software called the Joint Exploration Model (JEM)[2]. JVET meetings are held simultaneously every quarter, and the goal of the new codec standard is to reduce the bit rate by 50% compared to HEVC. The new video codec standard was officially named Versatile Video Codec (VVC) at the JVET meeting in April 2018, and the first version of the VVC Test Model (VTM) was also released at that time. Due to the continuous efforts on VVC standardization, new codec technologies are adopted into the VVC standard at each JVET meeting. The working draft of VVC and the test model VTM are updated after each meeting. The VVC project now aims to be technically completed (FDIS) at the July 2020 meeting.

[0076] Parameter Set

[0077] AVC, HEVC, and VVC specify parameter sets. Types of parameter sets include SPS, PPS, APS, and VPS. SPS and PPS are supported in all of AVC, HEVC, and VVC. VPS was introduced from HEVC and is included in HEVC and VVC. APS is not included in AVC or HEVC, but is included in the latest VVC draft text.

[0078] SPS is designed to carry sequence-level header information, and PPS is designed to carry picture-level header information that does not change frequently. With SPS and PPS, information that does not change frequently does not need to be repeated for each sequence or picture, so redundant signaling of that information can be avoided. In addition, the use of SPS and PPS enables out-of-band transmission of important header information, thus not only avoiding the need for redundant transmission, but also improving fault tolerance.

[0079] VPS is introduced to carry sequence level header information common to all layers in a multi-layer bitstream.

[0080] APS is introduced to carry such picture-level or slice-level information, which requires quite a lot of bits to encode and decode, can be shared by multiple pictures, and can have quite a lot of different variations in a sequence.

[0081] 3.2.Slice header and picture header in VVC

[0082] Similar to HEVC, the slice header in VVC conveys information about a specific slice. This includes slice address, slice type, slice QP, picture order count (POC) least significant bit (LSB), RPS and RPL information, weighted prediction parameters, loop filter parameters, entry offsets of slices and WPP, etc.

[0083] VVC introduces a picture header (PH), which contains header parameters for a specific picture. Each picture must have one or only one PH. The PH basically carries those parameters that would be in the slice header if the PH was not introduced, but each parameter has the same value for all slices of the picture. These include IRAP / GDR picture indication, inter / intra slice enable flags, POC LSB and optionally POC MSB, information about RPL, deblocking, SAO, ALF, QP increment and weighted prediction, codec block partitioning information, virtual boundaries, collocated picture information, etc. It is often the case that each picture in the entire picture sequence contains only one slice. In order to allow for not having at least two NAL units for each picture in this case, the PH syntax structure is allowed to be included in the PH NAL unit or slice header.

[0084] In VVC, information about collocated pictures used for temporal motion vector prediction is signaled in a picture header or a slice header.

[0085] 3.3. Image resolution changes within a sequence

[0086] In AVC and HEVC, the spatial resolution of a picture cannot be changed unless a new sequence using a new SPS starts with an IRAP picture. VVC enables picture resolution changes within a sequence at locations where IRAP pictures are not encoded, which are always intra-coded. This feature is sometimes called reference picture resampling (RPR) because it requires resampling of reference pictures used for inter prediction when the reference picture has a different resolution than the current picture being decoded.

[0087] The scaling ratio is restricted to be greater than or equal to 1 / 2 (2x downsampling from the reference picture to the current picture) and less than or equal to 8 (8x upsampling). Three resampling filter sets with different frequency cutoffs are specified to handle various scaling ratios between the reference picture and the current picture. The three resampling filter sets are applied to scaling ratios ranging from 1 / 2 to 1 / 1.75, from 1 / 1.75 to 1 / 1.25, and from 1 / 1.25 to 8, respectively. Each resampling filter set has 16 phases for luminance and 32 phases for chrominance, which is the same as the case of motion compensated interpolation filters. In fact, the normal MC interpolation process is a special case of the resampling process, in which the scaling ratio ranges from 1 / 1.25 to 8. The horizontal and vertical scaling ratios are derived based on the picture width and height and the left, right, top, and bottom scaling offsets specified for the reference picture and the current picture.

[0088] Other aspects of the VVC design that support this feature that differ from HEVC include: i) picture resolutions and corresponding consistency windows are signaled in the PPS rather than in the SPS, where the maximum picture resolution is signaled. ii) For a single-layer bitstream, each picture store (a slot in the DPB used to store a decoded picture) occupies the buffer size required to store a decoded picture with the maximum picture resolution.

[0089] 3.4. Adaptive Loop Filter (ALF)

[0090] Two diamond filter shapes (such as Figure 7 ) is used for block-based ALF. 7×7 diamonds are applied to the luma component and 5×5 diamonds are applied to the chroma components. One of up to 25 filters is selected for each 4×4 block based on the direction and activity of the local gradient. Each 4×4 block in the picture is classified according to directionality and activity. Before filtering each 4×4 block, simple geometric transformations such as rotations or diagonal and vertical flips can be applied to the filter coefficients based on the gradient values ​​calculated for the block. This is equivalent to applying these transformations to the samples in the filter support region. The idea is to make different blocks more similar by aligning the directionality of different blocks to which the ALF is applied. Block-based classification is not applied to chroma components.

[0091] ALF filter parameters are signaled in an adaptive parameter set (APS). In one APS, a set of up to 25 luminance filter coefficients and cropping value indices, and a set of up to 8 chrominance filter coefficients and cropping value indices can be signaled. In order to reduce bit overhead, filter coefficients of different classifications of luminance components can be merged. In the picture or slice header, up to 7 APS IDs can be signaled to specify the luminance filter set for the current picture or slice. The filtering process is further controlled at the CTB level. The luminance CTB can select a filter set from 16 fixed filter sets and the filter set signaled in the APS. For chrominance components, the APS ID is signaled in the picture or slice header to indicate the chrominance filter set for the current picture or slice. At the CTB level, if there is more than one chrominance filter set in the APS, the filter index is signaled for each chrominance CTB. When ALF is enabled for a CTB, for each sample within the CTB, a diamond filter with signaled weights is performed, where a clipping operation is applied to clip the difference between neighboring samples and the current sample. The clipping operation introduces nonlinearity to make the ALF more efficient by reducing the impact of neighboring sample values ​​that differ too much from the current sample value.

[0092] A cross-component adaptive loop filter (CC-ALF) can further enhance each chroma component on top of the previously described ALF. The goal of CC-ALF is to refine each chroma component using luma sample values. This is achieved by applying a diamond high-pass linear filter and then using the output of this filtering operation for chroma refinement. Figure 8 A system-level diagram of the CC-ALF process with respect to other loop filters is provided. Figure 8 As shown, CC-ALF uses the same input as the luma ALF to avoid an additional step in the overall loop filtering process.

[0093] 4. Technical problems solved by the disclosed solution

[0094] The existing design in the latest VVC text (JVET-Q2001-vE / v15) has the following problems:

[0095] 1) The value of slice_type is constrained as follows:

[0096] When nal_unit_type is in the range of IDR_W_RADL to CRA_NUT (inclusive) and vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1, slice_type shall be equal to 2.

[0097] However, the value of slice_type must also be equal to 2 under the following two conditions: i) when intra_only_constraint_flag is equal to 1; and ii) when the NAL unit type is an IRAP NAL unit type and the current picture is the first picture in the current AU.

[0098] 2) The semantics of ph_alf_enabled_flag defined below is unclear.

[0099] ph_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled for all slices associated with the PH, and the adaptive loop filter may be applied to the Y, Cb, or Cr color components in the slice. ph_alf_enabled_flag equal to 0 specifies that the adaptive loop filter may be disabled for one or more or all slices associated with the PH. When not present, ph_alf_enabled_flag is inferred to be equal to 0.

[0100] 3) The consistency window parameters are always signaled in the PPS, including when the picture width and height are the same as the maximum picture width and height signaled in the SPS referenced by the PPS. On the other hand, the consistency window parameters of the pictures with the maximum picture width and height are also signaled in the SPS. The signaling of the consistency window parameters of the pictures with the maximum picture width and height in the PPS is redundant.

[0101] 4) Repetition of most SEI messages is limited to at most 4 times within a PU or DU. Repetition of PH, AUD, EOS, and EOB NAL units is not allowed. It is necessary to allow padding data NAL units to be repeated as many times as required (e.g., to achieve a constant bit rate). However, there is no limit on the number of repetitions of other non-VCL NAL units (i.e., VPS, SPS, PPS, APS, and DCI NAL units).

[0102] 5. List of technical solutions

[0103] In order to solve the above problems and other problems, the following summarized methods are disclosed. The present invention should be considered as an example to explain the general concept and should not be interpreted in a narrow way. In addition, these inventions can be applied alone or combined in any way.

[0104] 1) To solve problem 1, constraints on slice_type and / or signaling of slice_type may depend on conditions related to general constraint flag / NAL unit type / whether the current picture is the first picture in the current AU.

[0105] a. In one example, the conditions may include:

[0106] i. When intra_only_constraint_flag is equal to 1.

[0107] ii. When the NAL unit type is an IRAP NAL unit type and the current picture is the first picture in the current AU.

[0108] iii. When an indication (eg, an SPS flag) tells that only intra slices are allowed in a picture (or a CLVS including the current picture, or any other picture set including the current picture).

[0109] b. The constraint on the slice_type value may be updated so that additionally, if one of the first two conditions or all of the above conditions are true, the value of slice_type is also required to be equal to 2.

[0110] c. Alternatively, when one of the previous two conditions or one of all of the above conditions is true, the signaling of slice_type can be skipped and inferred to be I slice (ie, slice_type is 2).

[0111] d. In addition, when the NAL unit type is an IRAP NAL unit type and the current layer is an independent layer, the signaling of slice_type can also be skipped and inferred to be an I slice.

[0112] 2) To solve problem 2, ph_alf_enabled_flag may be set equal to 0 to disable ALF for all slices of the current picture.

[0113] 3) To solve problem 3, it may be required that when the picture width and height are the maximum picture width and height, the value of pps_conformance_window_flag should be equal to 0.

[0114] a. Additionally, it may be specified that the value of the PPS consistency window syntax element is inferred to be the same as the value signaled in the SPS if the picture width and height are the maximum picture width and height, otherwise it is inferred to be equal to 0.

[0115] 4) To address issue 4, one or more of the following constraints may be specified to provide some restrictions on the repetition times of VPS, SPS, PPS, APS, and DCI NAL units while not

[0116] Affects features such as random access:

[0117] About VPS

[0118] a. When a VPS NAL unit with a specific value of vps_video_parameter_set_id is present in a CVS, the VPS NAL unit shall be present in the first AU of the CVS, may be present in any AU with at least one VCL NAL unit with nal_unit_type in the range of IDR_W_RADL to GDR_NUT (inclusive), and shall not be present in any other AU.

[0119] i. Alternatively, the above "IDR_W_RADL to GDR_NUT" is changed to "IDR_W_RADL to RSV_IRAP_12".

[0120] b. The number of VPS NAL units with a specific value of vps_video_parameter_set_id in a PU shall not be greater than 1.

[0121] About SPS

[0122] c. Let the associated AU set of CLVS be the first AU set in the decoding order containing CLVS. picture A set of AUs starting from the AU of CLVS to the AU containing the last picture of CLVS in decoding order (including the two AUs).

[0123] d. When an SPS NAL unit with a specific value of sps_seq_parameter_set_id is present in the associated AU set associatedAuSet of the CLVS referencing the SPS, the SPS NAL unit shall be present in the first AU of the associatedAuSet, and may be present in any AU of the associatedAuSet that has at least one VCL NAL unit with nal_unit_type in the range of IDR_W_RADL to GDR_NUT (including IDR_W_RADL and GDR_NUT), and shall not be present in any other AU.

[0124] i. Alternatively, when an SPS NAL unit with a specific value of sps_seq_parameter_set_id is present in a CLVS, it shall be present in the first PU of the CLVS, and may be present in any PU with at least one codec slice NAL unit with nal_unit_type in the range of IDR_W_RADL to GDR_NUT, inclusive, and shall not be present in any other PU.

[0125] ii. Alternatively, in item 4.d or 4.di, change "IDR_W_RADL to GDR_NUT" to "IDR_W_RADL to RSV_IRAP_12".

[0126] e. The number of SPS NAL units with a particular value of sps_seq_parameter_set_id in a PU shall not be greater than one.

[0127] About PPS

[0128] f. The number of PPS NAL units with a specific value of pps_pic_parameter_set_id in a PU shall not be greater than 1.

[0129] About APS

[0130] g. The number of APS NAL units in a PU with a specific value of adaptation_parameter_set_id and a specific value of aps_params_type shall not be greater than 1.

[0131] i. Alternatively, the number of APS NAL units in a DU with a specific value of adaptation_parameter_set_id and a specific value of aps_params_type shall not be greater than 1.

[0132] About DCI

[0133] h. When DCI When a NAL unit is present in a bitstream, it shall be present in the first CVS of the bitstream.

[0134] i. When the DCI NAL unit is present in a CVS, it shall be present in the first AU of the CVS, may be present in any AU with at least one VCL NAL unit having a nal_unit_type in the range of IDR_W_RADL to GDR_NUT (inclusive), and shall not be present in any other AU.

[0135] j. The number of DCI NAL units in a PU shall not be greater than 1.

[0136] 6. Example of Embodiment

[0137] The following are some example embodiments of some aspects of the invention summarized above in Section 5, which may be applied to the VVC specification. The changed text is based on the latest VVC text in JVET-Q2001-vE / v15. The most relevant parts that have been added or modified are highlighted in bold italics, and some of the deleted parts are highlighted in bold with double square brackets. There are some other changes that are editorial in nature or are not part of the invention and are therefore not highlighted.

[0138] 6.1. First embodiment

[0139] This embodiment is directed to item 1.

[0140] The following constraints:

[0141] When nal_unit_type is in the range of IDR_W_RADL to CRA_NUT (inclusive) and vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1, slice_type shall be equal to 2.

[0142] is changed as follows:

[0143] when The value of slice_type should be equal to 2 when both of the following conditions are true:

[0144] The value of -nal_unit_type is in the range of IDR_W_RADL to CRA_NUT (including IDR_W_RADL and CRA_NUT).

[0145] - The value of vps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1

[0146] 6.2. Second embodiment

[0147] This embodiment is directed to item 2.

[0148] It is proposed that the semantics of ph_alf_enabled_flag be updated as follows:

[0149] ph_alf_enabled_flag equal to 0 specifies that [[may]] the adaptive loop filter is disabled for [[one, one or more, or]] all slices associated with the PH.

[0150] 6.3. Third embodiment

[0151] This embodiment is directed to item 3.

[0152] 7.4.3.4 Picture parameter set RBSP semantics ...

[0153] pps_conformance_window_flag is equal to 1 The conformance cropping window offset parameter follows in the PPS. pps_conformance_window_flag equal to 0 specifies that the conformance cropping window offset parameter is not present in the PPS.

[0154] pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset specify the samples of the picture output from the decoding process in CLVS, according to the rectangular area specified in the picture coordinates for output.

[0155] When pps_conformance_window_flag is equal to 0,

[0156] -

[0157] - The values ​​of pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset are inferred to be equal to 0.

[0158] The consistent cropping window contains luma samples with horizontal picture coordinates from SubWidthC*pps_conf_win_left_offset to pic_width_in_luma_samples-(SubWidthC*pps_conf_win_right_offset+1) (including SubWidthC*pps_conf_win_left_offset and pic_width_in_luma_samples-(SubWidthC*pps_conf_win_right_offset+1)), and vertical picture coordinates from SubHeightC*pps_conf_win_top_offset to pic_height_in_luma_samples-(SubHeightC*pps_conf_win_bottom_offset+1) (including SubHeightC*pps_conf_win_top_offset and pic_height_in_luma_samples-(SubHeightC*pps_conf_win_bottom_offset+1)).

[0159] The value of SubWidthC*(pps_conf_win_left_offset+pps_conf_win_right_offset) shall be less than pic_width_in_luma_samples, and the value of SubHeightC*(pps_conf_win_top_offset+pps_conf_win_bottom_offset) shall be less than pic_height_in_luma_samples.

[0160] When ChromaArrayType is not equal to 0, the corresponding specified samples of the two chroma arrays are samples with picture coordinates (x / SubWidthC, y / SubHeightC), where (x, y) are the picture coordinates of the specified luma sample.

[0161] NOTE 2 – The consistent crop window offset parameters are applied only on output. All internal decoding processes are applied to the uncropped picture size.

[0162] Let ppsA and ppsB be any two PPSs that reference the same SPS. A bitstream conformance requirement is that when ppsA and ppsB have the same values ​​of pic_width_in_luma_samples and pic_height_in_luma_samples, respectively, ppsA and ppsB shall have the same values ​​of pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset, respectively.

[0163] When pic_width_in_luma_samples is equal to pic_width_max_in_luma_samples and pic_height_in_luma_samples is equal to pic_height_max_in_luma_samples, the bitstream conformance requirement is that pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset and pps_conf_win_bottom_offset are equal to sps_conf_win_left_offset, sps_conf_win_right_offset, sps_conf_win_top_offset and sps_conf_win_bottom_offset, respectively.

[0164] Figure 1 1 is a block diagram illustrating an example video processing system 1900 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of system 1900. System 1900 may include an input 1902 for receiving video content. The video content may be received in a raw or uncompressed format, such as 8 or 10 bit multi-component pixel values, or may be in a compressed or encoded format. Input 1902 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interfaces include wired interfaces such as Ethernet, a passive optical network (PON), and wireless interfaces such as Wi-Fi or a cellular interface.

[0165] System 1900 may include a codec component 1904 that can implement various codecs or encoding methods described in this document. Codec component 1904 can reduce the average bit rate of the video from input 1902 to the output of codec component 1904 to generate a codec representation of the video. Codec technology is therefore sometimes referred to as video compression or video transcoding technology. The output of codec component 1904 can be stored or sent via a communication connection as represented by component 1906. The bitstream (or codec) representation of the storage or communication transmission of the video received at input 1902 can be used by component 1908 to generate pixel values ​​or transmit to a displayable video of display interface 1910. The process of generating user-visible video from the bitstream representation is sometimes referred to as video decompression. In addition, although some video processing operations are referred to as "codec" operations or tools, it will be understood that the codec tool or operation is used at the encoder, and the corresponding decoding tool or operation of the inverse codec result will be performed by the decoder.

[0166] Examples of peripheral bus interfaces or display interfaces may include Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), or DisplayPort, etc. Examples of storage interfaces include SATA (Serial Advanced Technology Attachment), PCI, IDE interfaces, etc. The technology described in this document may be embodied in various electronic devices, such as mobile phones, laptops, smart phones, or other devices capable of performing digital data processing and / or video display.

[0167] Figure 2 3600. The apparatus 3600 may be used to implement one or more methods described herein. The apparatus 3600 may be embodied in a smartphone, a tablet computer, a computer, an Internet of Things (IoT) receiver, etc. The apparatus 3600 may include one or more processors 3602, one or more memories 3604, and video processing hardware 3606. The processor(s) 3602 may be configured to implement one or more methods described in this document. The memory(s) 3604 may be used to store data and code for implementing the methods and techniques described herein. The video processing hardware 3606 may be used to implement some of the techniques described in this document in a hardware circuit system.

[0168] Figure 4 is a block diagram illustrating an example video coding system 100 that may utilize the techniques of this disclosure.

[0169] like Figure 4As shown, the video coding system 100 may include a source device 110 and a target device 120. The source device 110 generates encoded video data, wherein the source device 110 may be referred to as a video encoding device. The target device 120 may decode the encoded video data generated by the source device 110, wherein the target device 120 may be referred to as a video decoding device.

[0170] Source device 110 may include a video source 112 , a video encoder 114 , and an input / output (I / O) interface 116 .

[0171] The video source 112 may include a source, such as a video capture device, an interface for receiving video data from a video content provider, and / or a computer graphics system for generating video data, or a combination of these sources. The video data may include one or more pictures. The video encoder 114 encodes the video data from the video source 112 to generate a bit stream. The bit stream may include a bit sequence that forms a codec representation of the video data. The bit stream may include a codec picture and related data. The codec picture is a codec representation of the picture. Related data may include a sequence parameter set, a picture parameter set, and other grammatical structures. The I / O interface 116 may include a modulator / demodulator (modem) and / or a transmitter. The coded video data may be directly sent to the target device 120 via the network 130a via the I / O interface 116. The coded video data may also be stored on a storage medium / server 130b for access by the target device 120.

[0172] Target device 120 may include an I / O interface 126 , a video decoder 124 , and a display device 122 .

[0173] The I / O interface 126 may include a receiver and / or a modem. The I / O interface 126 may obtain coded video data from the source device 110 or the storage medium / server 130b. The video decoder 124 may decode the coded video data. The display device 122 may display the decoded video data to the user. The display device 122 may be integrated with the target device 120, or may be outside the target device 120 configured to interface with an external display device.

[0174] The video encoder 114 and the video decoder 124 may operate in accordance with a video compression standard, such as the High Efficiency Video Codec (HEVC) standard, the Versatile Video Codec (VVC) standard, and other current and / or additional standards.

[0175] Figure 5 is a block diagram showing an example of a video encoder 200, which may be Figure 4 The video encoder 114 in the system 100 is shown.

[0176] Video encoder 200 may be configured to perform any or all of the techniques of this disclosure. Figure 5 In the example of , video encoder 200 includes multiple functional components. The techniques described in this disclosure can be shared between various components of video encoder 200. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0177] The functional components of the video encoder 200 may include a segmentation unit 201, a prediction unit 202 (which may include a mode selection unit 203, a motion estimation unit 204, a motion compensation unit 205 and an intra-frame prediction unit 206), a residual generation unit 207, a transform unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transform unit 211, a reconstruction unit 212, a buffer 213 and an entropy coding unit 214.

[0178] In other examples, the video encoder 200 may include more, fewer, or different functional components. In an example, the prediction unit 202 may include an intra block copy (IBC) unit. The IBC unit may perform prediction in IBC mode, where at least one reference picture is a picture in which the current video block is located.

[0179] Furthermore, some components such as the motion estimation unit 204 and the motion compensation unit 205 may be highly integrated, but for the purpose of explanation, they are not shown in FIG. Figure 5 are represented separately in the examples.

[0180] The partitioning unit 201 may partition a picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

[0181] The mode selection unit 203 may select one of the coding modes (e.g., intra or inter) based on the error result, and provide the resulting intra-coded block or inter-coded block to the residual generation unit 207 to generate residual block data, and to the reconstruction unit 212 to reconstruct the coded block for use as a reference picture. In some examples, the mode selection unit 203 may select a combination of intra and inter prediction modes (CIIP), where the prediction is based on an inter prediction signal and an intra prediction signal. In the case of inter prediction, the mode selection unit 203 may also select a resolution of the motion vector of the block (e.g., sub-pixel or integer pixel precision).

[0182] To perform inter-frame prediction on the current video block, the motion estimation unit 204 may generate motion information of the current video block by comparing the current video block with one or more reference frames from the buffer 213. The motion compensation unit 205 may determine a predicted video block of the current video block based on the motion information and decoded samples of pictures from the buffer 213 other than the picture associated with the current video block.

[0183] Motion estimation unit 204 and motion compensation unit 205 may perform different operations on the current video block, eg, depending on whether the current video block is in an I slice, a P slice, or a B slice.

[0184] In some examples, the motion estimation unit 204 may perform unidirectional prediction on the current video block, and the motion estimation unit 204 may search the reference picture of list 0 or list 1 for the reference video block of the current video block. The motion estimation unit 204 may then generate a reference index indicating the reference picture in list 0 or list 1, the reference index including the reference video block and a motion vector indicating a spatial displacement between the current video block and the reference video block. The motion estimation unit 204 may output the reference index, the prediction direction indicator, and the motion vector as the motion information of the current video block. The motion compensation unit 205 may generate a predicted video block of the current block based on the reference video block indicated by the motion information of the current video block.

[0185] In other examples, the motion estimation unit 204 may perform bidirectional prediction on the current video block, and the motion estimation unit 204 may search for a reference video block of the current video block in the reference pictures in list 0, and may also search for another reference video block of the current video block in list 1. The motion estimation unit 204 may then generate a reference index indicating the reference pictures in list 0 and list 1 containing the reference video block and a motion vector indicating a spatial displacement between the reference video block and the current video block. The motion estimation unit 204 may output the reference index and the motion vector of the current video block as the motion information of the current video block. The motion compensation unit 205 may generate a predicted video block of the current video block based on the reference video block indicated by the motion information of the current video block.

[0186] In some examples, motion estimation unit 204 may output a complete set of motion information for use in a decoding process of a decoder.

[0187] In some examples, motion estimation unit 204 may not output a complete set of motion information for the current video. Instead, motion estimation unit 204 may signal the motion information of the current video block with reference to the motion information of another video block. For example, motion estimation unit 204 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

[0188] In one example, motion estimation unit 204 may indicate a value in a syntax structure associated with the current video block that indicates to video decoder 300 that the current video block has the same motion information as another video block.

[0189] In another example, the motion estimation unit 204 may identify another video block and a motion vector difference (MVD) in a syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 300 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0190] As discussed above, the video encoder 200 may predictively signal motion vectors. Two examples of predictive signaling techniques that may be implemented by the video encoder 200 include Advanced Motion Vector Prediction (AMVP) and Merge mode signaling.

[0191] The intra prediction unit 206 may perform intra prediction on the current video block. When the intra prediction unit 206 performs intra prediction on the current video block, the intra prediction unit 206 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a prediction video block and various syntax elements.

[0192] The residual generation unit 207 can generate residual data for the current video block by subtracting (e.g., indicated by a minus sign) the predicted video block(s) of the current video block from the current video block. The residual data for the current video block may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0193] In other examples, such as in skip mode, there may be no residual data for the current video block, and the residual generation unit 207 may not perform a subtraction operation.

[0194] Transform processing unit 208 may generate one or more transform coefficient video blocks for a current video block by applying one or more transforms to a residual video block associated with the current video block.

[0195] After transform processing unit 208 generates a transform coefficient video block associated with the current video block, quantization unit 209 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values ​​associated with the current video block.

[0196] The inverse quantization unit 210 and the inverse transform unit 211 may apply inverse quantization and inverse transform to the transform coefficient video block, respectively, to reconstruct the residual video block from the transform coefficient video block. The reconstruction unit 212 may add the reconstructed residual video block to the corresponding samples of one or more predicted video blocks generated by the prediction unit 202 to generate a reconstructed video block associated with the current block for storage in the buffer 213.

[0197] After the reconstruction unit 212 reconstructs the video block, a loop filtering operation may be performed to reduce video blocking artifacts in the video block.

[0198] The entropy coding unit 214 may receive data from other functional components of the video encoder 200. When the entropy coding unit 214 receives the data, the entropy coding unit 214 may perform one or more entropy coding operations to generate entropy coded data and output a bitstream including the entropy coded data.

[0199] Figure 6 is a block diagram showing an example of a video decoder 300, which may be Figure 4 The video decoder 114 in the system 100 is shown.

[0200] Video decoder 300 may be configured to perform any or all of the techniques of this disclosure. Figure 6 In the example of , video decoder 300 includes multiple functional components. The techniques described in this disclosure can be shared between various components of video decoder 300. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0201] exist Figure 6 In the example of FIG. 3 , the video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra-frame prediction unit 303, an inverse quantization unit 304, an inverse transform unit 305, a reconstruction unit 306, and a buffer 307. In some examples, the video decoder 300 can perform the same operations as those generally performed for the video encoder 200 ( Figure 5 ) is the reverse of the encoding process described in .

[0202] The entropy decoding unit 301 may retrieve a coded bitstream. The coded bitstream may include entropy-coded video data (e.g., coded blocks of video data). The entropy decoding unit 301 may decode the entropy-coded video data, and from the entropy-decoded video data, the motion compensation unit 302 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. The motion compensation unit 302 may determine such information, for example, by performing AMVP and Merge modes.

[0203] The motion compensation unit 302 may generate a motion compensated block, and interpolation may be performed based on an interpolation filter. An identifier of an interpolation filter to be used with sub-pixel precision may be included in a syntax element.

[0204] The motion compensation unit 302 may calculate interpolation of sub-integer pixels of the reference block using an interpolation filter as used by the video encoder 200 during encoding of the video block. The motion compensation unit 302 may determine the interpolation filter used by the video encoder 200 based on received syntax information and use the interpolation filter to generate a prediction block.

[0205] The motion compensation unit 302 may use some syntax information to determine the size of blocks used to encode (multiple) frames and / or (multiple) slices of the coded video sequence, partitioning information describing how each macroblock of a picture of the coded video sequence is partitioned, a mode indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-frame coded block, and other information used to decode the coded video sequence.

[0206] The intra prediction unit 303 may form a prediction block from spatially adjacent blocks using, for example, an intra prediction mode received in the bitstream. The inverse quantization unit 303 inversely quantizes, i.e., dequantizes, the quantized video block coefficients provided in the bitstream and decoded by the entropy decoding unit 301. The inverse transform unit 303 applies an inverse transform.

[0207] The reconstruction unit 306 may add the residual block to the corresponding prediction block generated by the motion compensation unit 202 or the intra prediction unit 303 to form a decoded block. If necessary, a deblocking filter may also be applied to filter the decoded block to remove block artifacts. The decoded video block is then stored in a buffer 307 to provide a reference block for subsequent motion compensation / intra prediction and also to generate a decoded video for presentation on a display device.

[0208] A list of some preferred solutions for the embodiments is provided next.

[0209] The following solution illustrates an example embodiment of the technique discussed in the previous section (eg, item 1).

[0210] 1. A video processing method (eg, Figure 3The method 3000 shown in FIG. 3 includes performing a conversion between a video including one or more pictures including one or more slices and a codec representation of the video (3002), wherein the codec representation conforms to a condition that a field in the codec representation controls, for a video slice, a constraint on a slice type or whether a slice type is included in the codec representation, wherein the field includes a general constraint flag, a network abstraction layer unit type, or whether the video slice is in the first video picture of an access unit.

[0211] 2. The method according to solution 1, wherein the format rule specifies that the condition is that intra-only constraint has been enabled for the video slice.

[0212] The following solution illustrates an example embodiment of the technique discussed in the previous section (eg, item 2).

[0213] 3. A video processing method, comprising: performing conversion between a video including one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation conforms to a format rule that specifies disabling adaptive loop filtering for all slices in a video picture based on a value of a flag in a picture header of the video picture.

[0214] The following solution illustrates an example embodiment of the technique discussed in the previous section (eg, item 3).

[0215] 4. A video processing method, comprising: performing a conversion between a video including one or more pictures including one or more strips and a codec representation of the video, wherein the codec representation conforms to a format rule that specifies setting a consistency window flag to a disabled mode when a height and a width of a current picture are equal to a maximum height and a maximum width in the video.

[0216] The following solution illustrates an example implementation of the technique discussed in the previous section (eg, item 4).

[0217] 5. A video processing method, comprising: performing conversion between a video comprising one or more pictures including one or more slices and a codec representation of the video, wherein the codec representation complies with format rules for a repetition time of a specified parameter set.

[0218] 6. The method according to solution 5, wherein the parameter set is a video parameter set or a sequence parameter set or a picture parameter set of an adaptive parameter set.

[0219] 7. The method of solution 5, wherein the parameter set is a decoding capability information network abstraction layer unit (DCINAL).

[0220] 8. A method according to solution 6, wherein the parameter set is a video parameter set, and wherein the format rule specifies that the video parameter set is included in the first access unit of the codec video representation if the video parameter set includes a specific value of the identifier field.

[0221] 9. A method according to solution 8, wherein the format rule further specifies that a video parameter set with a specific value of the identifier field is included if and only if the other access unit has a network abstraction layer type in a range between two pre-specified values.

[0222] 10. A method according to solution 6, wherein the parameter set is a sequence parameter set, and wherein the format rule specifies that the codec representation is organized as one or more access units of one or more codec layers of a video sequence, and wherein the format rule specifies that a network abstraction layer including a sequence parameter set having a specific identifier value is to be included in the first access unit in a set of access units that references the sequence parameter set.

[0223] 11. The method of solution 7, wherein the format rule specifies that, in case the DCI NAL is included in a codec representation of a video, the DCI NAL is included in a first codec video sequence of the video.

[0224] 12. The method according to solution 7 or 11, wherein the format rule further specifies that the number of DCINAL units in a prediction unit is limited to one.

[0225] 13. A method according to any one of solutions 1 to 12, wherein the conversion includes encoding the video into a codec representation.

[0226] 14. A method according to any one of solutions 1 to 12, wherein the conversion includes decoding the codec representation to generate pixel values ​​of the video.

[0227] 15. A video decoding device, comprising a processor configured to implement the method according to one or more of solutions 1 to 14.

[0228] 16. A video encoding device comprising a processor configured to implement the method according to one or more of solutions 1 to 14.

[0229] 17. A computer program product storing a computer code, which, when executed by a processor, causes the processor to implement the method according to any one of solutions 1 to 14.

[0230] 18. A method, apparatus or system as described in this document.

[0231] The following list provides a second set of preferred solutions implemented by some embodiments.

[0232] The following solution illustrates an example embodiment of the technique discussed in the previous section (eg, item 1).

[0233] 1. A video processing method (eg, Figure 3 The method 3000 described in the claims includes: performing conversion between a video including one or more pictures including one or more slices and a bitstream of the video (3002), wherein the bitstream conforms to a format rule; wherein the format rule specifies whether or how to indicate in the bitstream a slice type of a slice in the one or more slices depends on a condition, wherein the condition is based on at least one of the following: a general constraint flag, a network abstraction layer unit type, or whether the slice is in the first picture of an access unit.

[0234] 2. The method according to solution 1, wherein the condition includes or corresponds to a general constraint flag indicating intra-only constraints on the slice.

[0235] 3. The method according to solution 1, wherein the condition includes or corresponds to that the slice is in the first picture of the access unit and the network abstraction layer unit type has a specific type, wherein the specific type indicates an intra random access point type.

[0236] 4. The method of solution 1, wherein the condition comprises or corresponds to a bitstream indication that only intra slices are permitted in a picture set comprising the picture.

[0237] 5. The method according to solution 4, wherein a picture set corresponds to the picture.

[0238] 6. The method according to solution 4, wherein the picture set corresponds to a codec layer video sequence (CLVS) including the pictures.

[0239] 7. A method according to any one of solutions 1-6, wherein the format rule specifies that in response to (a) a general constraint flag or a network abstraction layer unit type satisfies the condition, or (b) the slice is in the first picture of the access unit, a slice type value of 2 is indicated in the bitstream.

[0240] 8. The method of solution 1, wherein the format rule specifies that the slice type has a value of 2, and in response to (a) the general constraint flag or the network abstraction layer unit type satisfying the condition, or (b) the slice is in the first picture of the access unit, the indication of the slice type is omitted from the bitstream.

[0241] 9. The method of solution 1, wherein the format rule specifies that the slice type has a value of 2, and in response to (a) the network abstraction layer unit type is an intra random access point type, and (b) the layer to which the picture containing the slice belongs is an independently decodable layer, the indication of the slice type is omitted from the bitstream.

[0242] The following solutions illustrate additional examples of example embodiments of the techniques discussed in the previous section (eg, items 2 and 4).

[0243] 1. A video processing method (eg, Fig. 9 ), comprising: performing conversion between a video comprising a picture including a plurality of slices and a bitstream of the video (902), wherein the bitstream conforms to a format rule that specifies that a flag in a picture header controls the applicability of adaptive loop filtering for all slices in the picture.

[0244] 2. The method according to solution 1, wherein a value of 0 for the flag indicates that adaptive loop filtering is disabled for all slices in the picture.

[0245] 3. The method according to solution 1, wherein a value of 1 of the flag indicates that adaptive loop filtering is enabled for all slices in the picture.

[0246] 4. A video processing method (eg, Fig.10 The method 1000 depicted in , comprises: performing conversion (1002) between a video comprising one or more pictures including one or more slices and a bitstream of the video according to a format rule, wherein the format rule specifies a repetition time of a parameter set associated with the video.

[0247] 5. The method of solution 4, wherein the parameter set is a video parameter set (VPS).

[0248] 6. A method according to solution 5, wherein the format rule specifies that, in response to a VPS network abstraction layer (NAL) unit of a codec video sequence (CVS) containing a VPS having a specific identifier value, the VPS NAL unit is included in a first access unit (AU) of the CVS, and based on the value of another VPS NAL unit in another AU of the CVS, is selectively included in another AU and excluded from the remaining AUs of the CVS.

[0249] 7. The method of solution 6, wherein the value of another VPS NAL unit in another AU is in the range of IDR_W_RADL to GDR_NUT.

[0250] 8. The method of solution 6, wherein the value of another VPS NAL unit in another AU is in the range of IDR_W_RADL to RSV_IRAP_12.

[0251] 9. A method according to any of solutions 5-8, wherein the format rules further specify that no more than one VPS NAL unit of a given identifier value is included in a picture unit (PU) in the bitstream.

[0252] 10. The method of solution 4, wherein the parameter set is a sequence parameter set (SPS).

[0253] 11. A method according to solution 10, wherein a codec layer video sequence (CLVS) in a bitstream includes an associated access unit (AU) set, the associated AU set including AUs starting from a first AU containing a first picture of the CLVS in a decoding order and a last AU containing a last picture of the CLVS in a decoding order.

[0254] 12. A method according to solution 11, wherein the format rule specifies that, in response to an SPS network abstraction layer (NAL) unit containing an SPS with a specific identifier value, the SPS NAL unit is included in a first AU in an associated AU set, and is selectively included in another AU based on the value of another SPS NAL unit in another AU in the associated set, and is excluded from the remaining AUs of the CVS.

[0255] 13. A method according to solution 11, wherein the format rule specifies that, in response to a codec layer video sequence (CVLS) containing an SPS with a specific identifier value in a first picture unit (PU) of the CVLS, the SPS NAL unit is selectively included in another PU based on the value of a slice NAL unit in another PU of the CVLS and excluded from the remaining PUs of the CVLS.

[0256] 14. The method of solution 12, wherein the value of another SPS NAL unit in another AU is in the range of IDR_W_RADL to GDR_NUT.

[0257] 15. The method of solution 13, wherein the value of the slice NAL unit in another PU is in the range of IDR_W_RADL to GDR_NUT.

[0258] 16. The method of solution 12, wherein the value of another SPS NAL unit in another AU is in the range of IDR_W_RADL to RSV_IRAP_12.

[0259] 17. The method of solution 13, wherein the value of the slice NAL unit in another PU is in the range of IDR_W_RADL to RSV_IRAP_12.

[0260] 18. A method according to any of solutions 11-17, wherein the format rules further specify that no more than one SPS NAL unit of a given identifier value is included in a picture unit (PU) in the bitstream.

[0261] 19. The method of solution 4, wherein the parameter set is a picture parameter set (PPS), and wherein the format rule further specifies that no more than one PPS network abstraction layer (NAL) unit for a given identifier value is included in a picture unit (PU) in the bitstream.

[0262] 20. The method of solution 4, wherein the parameter set is an adaptive parameter set (APS).

[0263] 21. The method of solution 20, wherein the format rule further specifies that no more than one APS network abstraction layer (NAL) unit for a given identifier value and a specific value of a parameter type is included in a picture unit (PU) in the bitstream.

[0264] 22. The method of solution 20, wherein the format rule further specifies that no more than one APS network abstraction layer (NAL) unit for a given identifier value and a specific value of a parameter type is included in a decoding unit (DU) in the bitstream.

[0265] 23. The method of solution 4, wherein the parameter set is a Decoding Capability Information Network Abstraction Layer unit (DCI NAL).

[0266] 24. The method of solution 23, wherein the format rule specifies that, when present, DCI NAL units are not allowed to be included in a codec video sequence (CVS) that is not the first CVS in the bitstream.

[0267] 25. A method according to solution 23, wherein the format rule specifies that, in response to a codec video sequence (CVS) including a DCI NAL unit, the DCI NAL unit is in a first access unit (AU) of the CVS and is selectively present in another AU based on whether the other AU includes a video codec layer (VCL) NAL unit with a specific NAL unit identifier value and is excluded from the remaining AUs of the CVS.

[0268] 26. The method of solution 21, wherein the specific identifier value is in the range of IDR_W_RADL to GDR_NUT.

[0269] 27. A method according to any of solutions 23-26, wherein the format rules specify that a picture unit (PU) includes at most one DCI NAL unit.

[0270] The following solutions illustrate additional examples of preferred embodiments of the techniques discussed in the previous section (eg, item 3).

[0271] 1. A video processing method (eg, Fig.11 The method 1100 described in the claims includes: performing conversion between a video including a picture in a video unit and a bitstream of the video according to a format rule (1102), wherein the format rule specifies that in response to a width of the picture being equal to a maximum allowed picture width in the video unit and a height of the picture being equal to a maximum allowed picture height in the video unit, a consistency window flag in a picture parameter set corresponding to the picture is set to a value of 0.

[0272] 2. The method of solution 1, wherein the maximum allowed picture width and the maximum allowed picture height are indicated in a sequence parameter set referenced by the video unit.

[0273] 3. A method according to solution 2, wherein the format rule specifies that, in response to the width of the picture being equal to the maximum allowed picture width in the video unit and the height of the picture being equal to the maximum allowed picture height in the video unit, the consistency window syntax element is excluded from the picture parameter set and is inferred to have the same value as indicated in the sequence parameter set.

[0274] 4. A method according to solution 2, wherein the format rule specifies that, in response to the width of the picture not being equal to the maximum allowed picture width in the video unit or the height of the picture not being equal to the maximum allowed picture height in the video unit, the consistency window syntax element is inferred to have a value of 0.

[0275] In the solutions listed above, the conversion involves encoding the video into a bitstream.

[0276] In the solutions listed above, the conversion consists of generating a video from a bitstream.

[0277] In some embodiments, a video decoding device may include a processor configured to implement the method according to one or more of the above solutions.

[0278] In some embodiments, a video encoding device comprising a processor may be configured to implement the method according to one or more of the above solutions.

[0279] In some embodiments, a computer-readable medium may have codes stored thereon, which, when executed by a processor, cause the processor to implement a method according to any one of the above solutions.

[0280] In some embodiments, a method of video processing includes generating a bitstream according to any one or more of the methods described in the above solutions, and storing the bitstream on a computer-readable medium.

[0281] In some embodiments, a computer-readable medium may have stored thereon a bitstream generated from a video according to any one or more of the methods described in the above solutions.

[0282] In this document, the term "video processing" may refer to video encoding, video decoding, video compression, or video decompression. For example, during the conversion from a pixel representation of a video to a corresponding bitstream representation, a video compression algorithm may be applied, and vice versa. As defined by the syntax, the bitstream representation of the current video block may correspond, for example, to bits that are juxtaposed or interspersed in different places within the bitstream. For example, macroblocks may be encoded according to error residual values ​​of transforms and codecs and also using bits in headers and other fields in the bitstream. In addition, during conversion, the decoder may parse the bitstream based on this determination, knowing that some fields may or may not be present, as described in the above solution. Similarly, the encoder may determine whether to include or not include specific syntax fields, and generate the codec representation accordingly by including the syntax fields or excluding the syntax fields from the codec representation.

[0283] The disclosed and other solutions, examples, embodiments, modules and functional operations described in this document can be implemented in digital electronic circuits, or in computer software, firmware or hardware (including the structures disclosed in this document and their structural equivalents), or in a combination of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium, which are used to be executed by a data processing device or control the operation of the data processing device. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a combination of substances that affect machine-readable propagation signals, or a combination of one or more of them. The term "data processing device" includes all devices, equipment and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the device may also include code that creates an execution environment for the computer program in question, for example, code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagation signal is an artificially generated signal generated to encode information for transmission to a suitable receiver device, such as a machine-generated electrical signal, an optical signal, or an electromagnetic signal.

[0284] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language (including compiled or interpreted languages), and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or code portions). A computer program may be deployed to execute on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0285] The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuits, and the apparatus can also be implemented as special purpose logic circuits, such as FPGAs (field programmable gate arrays) or ASICs (application specific integrated circuits).

[0286] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, or operably coupled to receive data from or transfer data to or from the one or more mass storage devices. However, a computer does not require such a device. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory can be supplemented by or incorporated into a dedicated logic circuit.

[0287] Although this patent document contains many details, these details should not be interpreted as limitations on any subject matter or the scope of possible protection, but rather as descriptions of features of specific embodiments specified for specific technologies. Certain features described in the context of separate embodiments in this patent document may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although features may be described above as working in certain combinations and even initially claimed as such, one or more features from the claimed combination may be excluded from the combination in some cases, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination.

[0288] Similarly, although operations are depicted in a particular order in the drawings, this should not be understood as requiring that such operations be performed in the particular order shown or in a sequential order, or that all of the operations shown be performed, to achieve the desired results. In addition, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

[0289] Only a few implementations and examples are described, and other implementations, enhancements, and variations may be made based on what is described and shown in this patent document.

Claims

1. A video processing method, comprising: performing conversion between a video comprising one or more pictures comprising one or more slices and a bitstream of said video, wherein the bit stream complies with format rules; wherein the format rule specifies that a constraint on a syntax element included in the bitstream depends on at least one condition, wherein the syntax element indicates a slice type of a slice of the one or more slices, wherein the at least one condition is based on at least one of a general constraint flag, a network abstraction layer unit type, or whether the slice is in a first picture of an access unit; Wherein, the format rule further specifies that a flag in the picture header controls the applicability of adaptive loop filtering for all slices in the picture; The flag has a value of 0 indicating that the adaptive loop filter is disabled for all slices in the picture; the flag has a value of 1 indicating that the adaptive loop filter is enabled for all slices in the picture; The at least one condition includes that the value of the general constraint flag is equal to 1 and indicates intra-only constraint on the slice, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

2. The method according to claim 1, wherein: The at least one condition includes: (a) the slice is in the first picture of the access unit, and (b) the network abstraction layer unit type has a specific type, wherein the specific type indicates an intra-frame random access point type and its constraint on the syntax element is that the value of the syntax element is equal to 2.

3. The method according to claim 1, wherein: The at least one condition includes: (a) the network abstraction layer unit type is an intra random access point type, and (b) the layer to which the picture containing the slice belongs is an independently decodable layer, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

4. The method according to claim 1, wherein: The converting includes decoding the video from the bitstream.

5. The method according to claim 1, wherein: The converting includes encoding the video into the bitstream.

6. The method according to claim 1, wherein: The at least one condition comprises that the bitstream indicates that only intra slices are permitted in a picture set that includes the picture.

7. The method according to claim 6, wherein: The picture set corresponds to the picture.

8. The method according to claim 6, wherein: The picture set corresponds to a codec layer video sequence (CLVS) including the pictures.

9. The method according to claim 1, wherein: The format rule specifies that a syntax element indicating the slice type has a value of 2, and in response to (a) the general constraint flag or the network abstraction layer unit type satisfying a condition, or (b) the slice is in the first picture of the access unit, the syntax element is omitted from the bitstream.

10. The method according to claim 1, wherein: The format rule specifies that a syntax element indicating the slice type has a value of 2, and in response to (a) the network abstraction layer unit type is an intra random access point type, and (b) a layer to which the picture containing the slice belongs is an independently decodable layer, the syntax element is omitted from the bitstream.

11. An apparatus for processing video data, comprising a processor and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to: performing conversion between a video comprising one or more pictures comprising one or more slices and a bitstream of said video, in, The bit stream complies with format rules; wherein the format rule specifies that a constraint on a syntax element included in the bitstream depends on at least one condition, wherein the syntax element indicates a slice type of a slice of the one or more slices, wherein the at least one condition is based on at least one of a general constraint flag, a network abstraction layer unit type, or whether the slice is in a first picture of an access unit; Wherein, the format rule further specifies that a flag in the picture header controls the applicability of adaptive loop filtering for all slices in the picture; The flag has a value of 0 indicating that the adaptive loop filter is disabled for all slices in the picture; the flag has a value of 1 indicating that the adaptive loop filter is enabled for all slices in the picture; The at least one condition includes that the value of the general constraint flag is equal to 1 and indicates intra-only constraint on the slice, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

12. The device according to claim 11, wherein The at least one condition includes: (a) the slice is in the first picture of the access unit, and (b) the network abstraction layer unit type has a specific type, wherein the specific type indicates an intra-frame random access point type and its constraint on the syntax element is that the value of the syntax element is equal to 2.

13. The device according to claim 11, wherein: The at least one condition includes: (a) the network abstraction layer unit type is an intra random access point type, and (b) the layer to which the picture containing the slice belongs is an independently decodable layer, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

14. A non-transitory computer-readable storage medium storing instructions that cause a processor to: performing conversion between a video comprising one or more pictures comprising one or more slices and a bitstream of said video, in, The bit stream complies with format rules; wherein the format rule specifies that a constraint on a syntax element included in the bitstream depends on at least one condition, wherein the syntax element indicates a slice type of a slice of the one or more slices, wherein the at least one condition is based on at least one of a general constraint flag, a network abstraction layer unit type, or whether the slice is in a first picture of an access unit; Wherein, the format rule further specifies that a flag in the picture header controls the applicability of adaptive loop filtering for all slices in the picture; The flag has a value of 0 indicating that the adaptive loop filter is disabled for all slices in the picture; the flag has a value of 1 indicating that the adaptive loop filter is enabled for all slices in the picture; The at least one condition includes that the value of the general constraint flag is equal to 1 and indicates intra-only constraint on the slice, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

15. The non-transitory computer-readable storage medium of claim 14, wherein: in, The at least one condition comprises: (a) the slice is in the first picture of the access unit, and (b) the network abstraction layer unit type has a specific type, wherein the specific type indicates an intra random access point type and its constraint on the syntax element is that the value of the syntax element is equal to 2; or The at least one condition includes: (a) the network abstraction layer unit type is an intra random access point type, and (b) the layer to which the picture containing the slice belongs is an independently decodable layer, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

16. A non-transitory computer-readable recording medium storing a bit stream of a video, wherein the bit stream of the video is generated by a method performed by a video processing device, wherein the method comprises: generating a bitstream of video comprising one or more pictures including one or more slices, wherein the bit stream complies with format rules; wherein the format rule specifies that a constraint on a syntax element included in the bitstream depends on at least one condition, wherein the syntax element indicates a slice type of a slice of the one or more slices, wherein the at least one condition is based on at least one of a general constraint flag, a network abstraction layer unit type, or whether the slice is in a first picture of an access unit; Wherein, the format rule further specifies that a flag in the picture header controls the applicability of adaptive loop filtering for all slices in the picture; The flag has a value of 0 indicating that the adaptive loop filter is disabled for all slices in the picture; the flag has a value of 1 indicating that the adaptive loop filter is enabled for all slices in the picture; The at least one condition includes that the value of the general constraint flag is equal to 1 and indicates intra-only constraint on the slice, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

17. The non-transitory computer-readable recording medium according to claim 16, wherein: in, The at least one condition comprises: (a) the slice is in the first picture of the access unit, and (b) the network abstraction layer unit type has a specific type, wherein the specific type indicates an intra random access point type and its constraint on the syntax element is that the value of the syntax element is equal to 2; or The at least one condition includes: (a) the network abstraction layer unit type is an intra random access point type, and (b) the layer to which the picture containing the slice belongs is an independently decodable layer, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

18. A method for storing a bitstream of a video, comprising: generating a bitstream of video comprising one or more pictures including one or more slices, storing the bitstream on a computer readable medium, wherein the bit stream complies with format rules; wherein the format rule specifies that a constraint on a syntax element included in the bitstream depends on at least one condition, wherein the syntax element indicates a slice type of a slice of the one or more slices, wherein the at least one condition is based on at least one of a general constraint flag, a network abstraction layer unit type, or whether the slice is in a first picture of an access unit; Wherein, the format rule further specifies that a flag in the picture header controls the applicability of adaptive loop filtering for all slices in the picture; The flag has a value of 0 indicating that the adaptive loop filter is disabled for all slices in the picture; the flag has a value of 1 indicating that the adaptive loop filter is enabled for all slices in the picture; The at least one condition includes that the value of the general constraint flag is equal to 1 and indicates intra-only constraint on the slice, and its constraint on the syntax element is that the value of the syntax element is equal to 2.

19. A video decoding apparatus comprising a processor configured to implement the method according to any one of claims 1 to 10 and 18.

20. A video encoding apparatus comprising a processor configured to implement the method according to any one of claims 1 to 10 and 18.

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