Method and apparatus for decoding and encoding video data, storage medium and program product

Abstract

The invention provides a method and apparatus for decoding and encoding video data, a storage medium and a program product. A method of decoding video data from a bitstream is provided, the bitstream comprising video data corresponding to one or more than one slice. The bitstream includes a picture header including syntactic elements to be used in decoding one or more slices and a slice header including syntactic elements to be used in decoding the slices. The decoding includes: in the case of signaling in the picture header information that may be signaled in the picture header or in the slice header, signaling in the picture header in the slice header, allowing parsing in only one of the slice header and the picture header information that may otherwise be signaled in the slice header and the picture header; forcing the picture header not in the slice header, and decoding the bitstream using syntax elements.

Description

[0001] (This application is a divisional application of an application filed on March 5, 2021, with application number 202180020471.7 and title “Advanced Syntax for Video Encoding and Decoding.”) Technical Field

[0002] The present invention relates to video encoding and decoding, and in particular to high-level syntax for use in bitstreams. Background Art

[0003] Recently, the Joint Video Experts Team (JVET) (a collaboration between MPEG and ITU-T Study Group 16, VCEG) began work on a new video coding standard called Versatile Video Coding (VVC). The goal of VVC is to provide significant improvements in compression performance over the existing HEVC standard (i.e., typically twice as fast as before) and to be completed in 2020. Key target applications and services include, but are not limited to, 360-degree and high dynamic range (HDR) video. In total, JVET evaluated feedback from 32 organizations using formal subjective tests conducted by independent test labs. Some proposals showed compression efficiency improvements of 40% or more, typically when compared to using HEVC. Particular improvements were shown on ultra-high-definition (UHD) video test material. Therefore, we can expect compression efficiency improvements far exceeding the targeted 50% for the final standard.

[0004] The JVET Exploration Model (JEM) uses all HEVC tools and has introduced several new tools. These changes require changes to the structure of the bitstream, especially the high-level syntax, which may have an impact on the overall bitrate of the bitstream. Summary of the Invention

[0005] The present invention relates to improvements to high-level syntax structures, which achieve a reduction in complexity without any degradation in coding performance.

[0006] According to a first aspect of the present invention, a method for decoding video data from a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: if information that can be signaled in the picture header or the slice header is signaled in the picture header, forcing the picture header to be not in the slice header (for example, applying a constraint that the picture header is not in the slice header), and decoding the bitstream using the syntax elements.

[0007] Optionally, the decoding further comprises: parsing a first syntax element indicating whether the information is to be signaled in a picture header, and allowing information that can be signaled in both the slice header and the picture header to be parsed in only one of the slice header and the picture header based on the first syntax element.

[0008] Optionally, the first syntax element is information in a picture parameter set flag or information in a picture header flag.

[0009] Optionally, in case the first syntax element indicates that the information is signaled in the picture header, parsing of the information in the slice header is not allowed.

[0010] Optionally, the method further includes: parsing a second syntax element indicating whether the picture header is in the slice header, wherein the second syntax element indicates that the picture header is not in the slice header is a requirement for bitstream conformance when the first syntax element indicates that information is signaled in the picture header.

[0011] Optionally, the information includes one or more of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information and adaptive loop filtering (ALF) information.

[0012] Optionally, this information includes all information that can be signaled in the picture header and slice header.

[0013] Optionally, the reference picture list information includes one or more of slice_collocated_from_l0_flag, slice_collocated_ref_idx, ph_collocated_from_l0_flag and ph_collocated_ref_idx.

[0014] According to a second aspect of the present invention, there is provided a method of encoding video data into a bitstream, the video data corresponding to one or more slices, wherein the bitstream comprises a picture header and a slice header, the picture header comprising syntax elements to be used when decoding the one or more slices, the slice header comprising syntax elements to be used when decoding the slices, and the encoding comprises: in a case where information that may be signaled in the picture header or in the slice header is signaled, signaling that the picture header is not in the slice header, and decoding the video data using the syntax elements.

[0015] Optionally, the encoding further includes: encoding a first syntax element indicating whether the information is to be signaled in a picture header, and allowing information that can be signaled in a slice header and a picture header to be encoded in only one of the slice header and the picture header based on the first syntax element.

[0016] Optionally, the first syntax element is information in a picture parameter set flag or information in a picture header flag.

[0017] Optionally, in case the first syntax element indicates that the information is signaled in the picture header, encoding of the information in the slice header is not allowed.

[0018] Optionally, the method further comprises encoding a second syntax element indicating whether the picture header is in the slice header, wherein the second syntax element indicates that the picture header is not in the slice header is a requirement for bitstream consistency when the first syntax element indicates that the information is signaled in the picture header.

[0019] Optionally, the information includes one or more of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information and adaptive loop filtering (ALF) information.

[0020] Optionally, this information includes all information that can be signaled in the picture header and slice header.

[0021] Optionally, the reference picture list information includes one or more of slice_collocated_from_l0_flag, slice_collocated_ref_idx, ph_collocated_from_l0_flag and ph_collocated_ref_idx.

[0022] In an alternative aspect of the present invention, a method is provided for decoding video data from a bitstream, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: if information that may be signaled in the picture header or the slice header is signaled in the slice header, forcing the picture header to be absent from the slice header; and decoding the bitstream using the syntax elements.

[0023] According to another aspect of the present invention, a method for decoding video data from a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: treating (a) a syntax element indicating that tool information is signaled in a picture header instead of a slice header and (b) a syntax element indicating that the picture header is signaled in a slice header as being non-combinable, and decoding the bitstream using the syntax elements. When the syntax elements (a) and (b) that are considered non-combinable are present, no decoding occurs.

[0024] According to a related aspect of the present invention, a bitstream includes: video data corresponding to one or more slices; a picture header including syntax elements to be used when decoding the one or more slices; and a slice header including syntax elements to be used when decoding the slices. The bitstream has the following constraint: the bitstream must not contain a combination of (a) a syntax element indicating that tool information is signaled in a picture header instead of a slice header and (b) a syntax element indicating that the picture header is signaled in a slice header. The tool information may be any one of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filtering (ALF) information. In a related aspect, a method for decoding the bitstream is provided. In another related aspect, a decoder configured to decode the bitstream is provided. The bitstream may be constrained to conform to a video coding standard. In an embodiment, the video coding standard is a universal video coding standard. The constraint may be systematically applied throughout the bitstream. For example, in an embodiment, constraints are applied to any or all of sequences, pictures, and slices in a bitstream.

[0025] According to another aspect of the present invention, a method for decoding video data from a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: treating (a) a syntax element indicating that tool information is signaled in a slice header instead of a picture header and (b) a syntax element indicating that the picture header is signaled in a slice header as being not applicable in combination; and decoding the bitstream using the syntax elements. When the syntax elements (a) and (b) that are not considered to be applicable in combination are present, no decoding occurs.

[0026] According to another aspect of the present invention, a method for decoding video data from a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, wherein the picture header is to be signaled in the slice header, and wherein information that may otherwise be signaled in the slice header and the picture header is constrained to be parsed in only one of the slice header and the picture header; and decoding includes: if a syntax element (xxx_info_in_ph_flag) indicates that tool information is present in the picture header (e.g., when xxx_info_in_ph_flag=1), not signaling the picture header in the slice header (e.g., forcing picture_header_in_slice_header_flag to 0).

[0027] According to a related aspect of the present invention, a bitstream includes: video data corresponding to one or more slices; a picture header including syntax elements to be used when decoding the one or more slices; and a slice header including syntax elements to be used when decoding the slices. The bitstream has the following constraint: in the bitstream, there must not be a combination of (a) a syntax element indicating that tool information is signaled in a slice header instead of a picture header and (b) a syntax element indicating that a picture header is signaled in a slice header.

[0028] According to another aspect of the present invention, a method for decoding video data from a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, wherein the picture header is to be signaled in the slice header, and wherein information that may otherwise be signaled in the slice header and the picture header is constrained to be parsed in only one of the slice header and the picture header; and decoding includes: if a syntax element (xxx_info_in_ph_flag) indicates that tool information is not present in the picture header (e.g., when xxx_info_in_ph_flag=0), not signaling the picture header in the slice header (e.g., forcing picture_header_in_slice_header_flag to 0).

[0029] In a first further aspect of the present invention, a method is provided for decoding video data from a bitstream, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: if the picture header is to be signaled in the slice header, allowing information that may otherwise be signaled in both the slice header and the picture header to be parsed in only one of the slice header and the picture header; and decoding the bitstream using the syntax elements.

[0030] When the picture header is in the slice header, this means that there is only one slice for the current picture. Therefore, making information sent or transmittable for both the slice and the picture does not increase the flexibility of the encoder or decoder because the parameters will be the same. In other words, if the information is in the picture header, the corresponding information in the slice header will be redundant. Similarly, if the information is in the slice header, the corresponding information in the picture header will be redundant. By only allowing the information to be in the picture header or the slice header, in the case where the picture header is in the slice header, the decoder implementation can be simplified by limiting the redundancy in the signaling. Therefore, parsing can be simplified without any loss in coding efficiency.

[0031] The decoding may further include parsing a first syntax element indicating whether a picture header is to be signaled in a slice header, and allowing information that may be signaled in both the slice header and the picture header to be parsed in only one of the slice header and the picture header based on the first syntax element. The first syntax element may be a picture header in a slice header flag.

[0032] Optionally, when the first syntax element indicates that the picture header is signaled in the slice header, parsing of information in the slice header is not allowed. A second syntax element indicating whether the information is in the picture header may be parsed, wherein when the first syntax element indicates that the picture header is signaled in the slice header, the second syntax element indicates that signaling the information in the picture header is a requirement for bitstream conformance.

[0033] Alternatively, when the first syntax element indicates that the picture header is signaled in the slice header, signaling of the information in the picture header is not permitted. The method may further include parsing a second syntax element indicating whether the information is in the picture header, wherein when the first syntax element indicates that the picture header is signaled in the slice header, the second syntax element indicates that the information is in the picture header as a requirement for bitstream conformance. The second syntax element may be information in a picture parameter set flag, wherein when the flag is set, the information is in the picture header, and when the flag is not set, the information is in the slice header or is not present.

[0034] According to an embodiment, the information may include one or more of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filter (ALF) information. For example, all of the quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filter (ALF) information.

[0035] Optionally, this information includes all information that can be signaled in the picture header and slice header.

[0036] The reference picture list information may include one or more of the following syntax elements: slice_collocated_from_l0_flag, slice_collocated_ref_idx, ph_collocated_from_l0_flag, and ph_collocated_ref_idx.

[0037] In case the picture header is to be signaled in the slice header, the number of resolvable weights for weighted prediction may be limited.

[0038] According to a second further aspect of the present invention, there is provided a method of encoding video data into a bitstream, the video data corresponding to one or more slices, wherein the bitstream comprises a picture header and a slice header, the picture header comprising syntax elements to be used when decoding the one or more slices, the slice header comprising syntax elements to be used when decoding the slices, and the encoding comprises: if the picture header is to be signaled in the slice header, allowing information that may otherwise be signaled in the slice header and the picture header to be encoded in only one of the slice header and the picture header, and encoding the video data using the syntax elements.

[0039] When the picture header is in the slice header, this means that there is only one slice for the current picture. Therefore, making information sent or transmittable for both the slice and the picture does not increase the flexibility of the encoder or decoder because the parameters will be the same. In other words, if the information is in the picture header, the corresponding information in the slice header will be redundant. Similarly, if the information is in the slice header, the corresponding information in the picture header will be redundant. By only allowing information to be in the picture header or the slice header, in the case where the picture header is in the slice header, the decoder implementation can be simplified by limiting the redundancy in the signaling. Therefore, the encoding can be simplified without any loss in coding efficiency and the signaling cost is reduced (because the relevant information is only included once in the bitstream).

[0040] The encoding may further include encoding a first syntax element indicating whether the picture header is to be signaled in the slice header, and allowing information that can be signaled in the slice header and the picture header to be encoded in only one of the slice header and the picture header based on the first syntax element.

[0041] The first syntax element may be a picture header in a slice header flag.

[0042] In case the first syntax element indicates that the picture header is signaled in the slice header, encoding of the information in the slice header may not be allowed.

[0043] A second syntax element indicating whether the information is in a picture header may be encoded, wherein the second syntax element indicating that the information is in the picture header is a requirement for bitstream conformance if the first syntax element indicates that the picture header is signaled in the slice header.

[0044] Alternatively, in case the first syntax element indicates that the picture header is signaled in the slice header, signaling of the information in the picture header is not allowed.

[0045] A second syntax element indicating whether the information is in a picture header may be encoded, wherein the second syntax element indicating that the information is in the picture header is a requirement for bitstream conformance if the first syntax element indicates that the picture header is signaled in the slice header.

[0046] The second syntax element may be information in a picture parameter set flag or information in a picture header flag, where when the flag is set, the information is signaled in the picture header, and when the flag is not set, the information is signaled in the slice header or the information does not exist.

[0047] The information may include one or more of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filter (ALF) information. Optionally, the information includes all information that can be signaled in the picture header and slice header. For example, all quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filter (ALF) information.

[0048] The reference picture list information includes one or more of slice_collocated_from_l0_flag, slice_collocated_ref_idx, ph_collocated_from_l0_flag, and ph_collocated_ref_idx.

[0049] Alternatively, in case the picture header is to be signaled in the slice header, the number of weights used for weighted prediction may be limited.

[0050] In a third further aspect of the present invention, a method for decoding a bitstream containing video data corresponding to one or more slices is provided, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the method includes parsing a syntax element in the slice header indicating whether the picture header is signaled in the slice header, wherein an ALF APS ID-related syntax element is parsed before the syntax element indicating whether the picture header is signaled in the slice header. The ALF APS ID-related information may be parsed at or near the beginning of the slice header.

[0051] According to a fourth further aspect of the present invention, a method for encoding video data comprising one or more slices into a bitstream is provided, wherein the bitstream comprises a picture header and a slice header, the picture header comprising syntax elements to be used when decoding the one or more slices, the slice header comprising syntax elements to be used when decoding the slices, and the method comprising: parsing a syntax element in the slice header indicating whether a picture header is signaled in the slice header; wherein an ALPAPS ID syntax element is encoded before the syntax element indicating whether a picture header is signaled in the slice header. The ALF APS ID related information may be encoded at or near the beginning of the slice header.

[0052] In a fifth further aspect of the present invention, a method is provided for decoding video data from a bitstream, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the decoding includes: limiting the number of weights signaled for a weighted prediction mode when the picture header is to be signaled in the slice header; and decoding the bitstream using the syntax elements. When the picture header is to be signaled in the slice header, information that may otherwise be signaled in both the slice header and the picture header may be allowed to be parsed in only one of the slice header and the picture header.

[0053] In a sixth further aspect of the present invention, a method for encoding video data in a bitstream is provided, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and the encoding includes: limiting the number of weights to be encoded for a weighted prediction mode when the picture header is to be signaled in the slice header; and encoding the bitstream using the syntax elements. When the picture header is to be signaled in the slice header, information that may otherwise be signaled in both the slice header and the picture header may be allowed to be encoded in only one of the slice header and the picture header.

[0054] According to a seventh further aspect of the present invention, there is provided a decoder for decoding video data from a bitstream, the decoder being configured to perform the method of any one of the first, third and fifth further aspects.

[0055] According to an eighth further aspect of the present invention, there is provided an encoder for encoding video data into a bitstream, the encoder being configured to perform the method of any one of the second, fourth and sixth further aspects.

[0056] According to a ninth further aspect of the present invention, a computer program is provided which, when executed, causes the method of any one of the first to sixth further aspects to be performed. The program may be provided separately, or may be on, carried by, or carried in a carrier medium. The carrier medium may be non-transitory, such as a storage medium, in particular a computer-readable storage medium. The carrier medium may also be temporary, such as a signal or other transmission medium. The signal may be transmitted via any suitable network, including the Internet. Other features of the present invention are characterized by independent and dependent claims.

[0057] According to a first further aspect, a method is provided for decoding video data from a bitstream, the bitstream including video data corresponding to one or more slices, wherein the bitstream includes a picture header and a slice header, the picture header including syntax elements to be used when decoding the one or more slices, the slice header including syntax elements to be used when decoding the slices, and constraining the bitstream such that, when the bitstream includes a first syntax element having a value indicating that information that may be signaled in a picture header or a slice header is signaled in a picture header, the bitstream also includes a second syntax element having a value indicating that the picture header is not in the slice header, the method comprising: decoding the bitstream using the syntax elements. The bitstream may be constrained to conform to a video coding standard. In an embodiment, the video coding standard is a universal video coding standard. The second syntax element may be a picture header in a slice header syntax element. The first syntax element may be a flag indicating that one or more of quantization parameter value information, reference picture list information, deblocking filter information, sample adaptive offset (SAO) information, weighted prediction information, and adaptive loop filtering (ALF) information are signaled in the picture header. Bitstream constraints may be applied systematically. For example, in an embodiment, constraints are applied to any or all of the sequences, pictures, and slices in the bitstream.

[0058] According to a second further aspect, a method of encoding or decoding video data into or from a bitstream is provided, the method comprising: applying a constraint regarding whether a picture header is permitted in a slice header based on whether information that may be signaled in a picture header or in a slice header is signaled in a picture header. According to a third further aspect, an apparatus configured to perform the method of the second further aspect is provided. According to a fourth further aspect, a computer program comprising instructions that, when executed, cause the method of the second further aspect to be performed.

[0059] Any features in one aspect of the invention may be applied to other aspects of the invention in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

[0060] Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any references herein to software and hardware features should be interpreted accordingly.

[0061] Any apparatus features as described herein may also be provided as method features, and vice versa.As used herein, means-plus-function features may alternatively be expressed in terms of their corresponding structure (such as a suitably programmed processor and associated memory, etc.).

[0062] It will also be understood that specific combinations of the various features described and defined in any aspect of the present invention may be independently implemented, provided and / or used. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Reference will now be made by way of example to the accompanying drawings, in which:

[0064] Figure 1 is a diagram for explaining the coding structure used in HEVC and VVC;

[0065] Figure 2 is a block diagram schematically illustrating a data communication system in which one or more embodiments of the present invention may be implemented;

[0066] Figure 3 is a block diagram illustrating components of a processing device that may implement one or more embodiments of the present invention;

[0067] Figure 4 is a flow chart illustrating the steps of an encoding method according to an embodiment of the present invention;

[0068] Figure 5 is a flowchart illustrating the steps of a decoding method according to an embodiment of the present invention;

[0069] Figure 6 shows the structure of a bitstream in an exemplary coding system VVC;

[0070] Figure 7 Another structure of a bit stream in an exemplary coding system VVC is shown;

[0071] Figure 8 Shows Luma Modelling Chroma Scaling (LMCS);

[0072] Figure 9 Shows the sub-tools of LMCS;

[0073] Figure 10 is a diagram illustrating a system including an encoder or a decoder and a communication network according to an embodiment of the present invention;

[0074] Figure 11 is a schematic block diagram of a computing device for implementing one or more embodiments of the present invention;

[0075] Figure 12 is a diagram showing a network camera system; and

[0076] Figure 13 is a diagram showing a smartphone. DETAILED DESCRIPTION

[0077] Figure 1 The present invention relates to a coding structure used in the High Efficiency Video Coding (HEVC) video standard. A video sequence 1 consists of a series of digital images i. Each of these digital images is represented by one or more matrices. The matrix coefficients represent pixels.

[0078] The images 2 of the sequence may be partitioned into slices 3. In some cases, one slice may constitute the entire image. These slices are partitioned into non-overlapping Coding Tree Units (CTUs). The Coding Tree Unit (CTU) is the basic processing unit of the High Efficiency Video Coding (HEVC) video standard and conceptually corresponds in structure to the macroblock unit used in several previous video standards. A CTU is sometimes also called a Largest Coding Unit (LCU). A CTU has luminance and chrominance component parts, each of which is called a Coding Tree Block (CTB). These different color components are not Figure 1 Shown in.

[0079] A CTU is typically 64 pixels by 64 pixels in size. Each CTU can be iteratively partitioned into smaller, variable-sized coding units (CUs) using a quadtree decomposition.

[0080] A coding unit is a basic coding element and is composed of two subunits called prediction units (PUs) and transform units (TUs). The maximum size of a PU or TU is equal to the CU size. A prediction unit corresponds to a partition of a CU used for prediction of pixel values. Various different partitions of a CU into PUs are possible, as shown in 606, including a partition into four square PUs and two different partitions into two rectangular PUs. A transform unit is the basic unit for spatial transformation using DCT. A CU can be partitioned into TUs based on a quadtree representation 607.

[0081] Each slice is embedded in a network abstraction layer (NAL) unit. In addition, the coding parameters of the video sequence are stored in a dedicated NAL unit called a parameter set. In HEVC and H.264 / AVC, two types of parameter set NAL units are used: first, the sequence parameter set (SPS) NAL unit, which collects all parameters that do not change during the entire video sequence. Typically, it handles the coding profile, the size of the video frame, and other parameters. Second, the picture parameter set (PPS) NAL unit, which includes parameters that can change from one image (or frame) of the sequence to other images (or frames). HEVC also includes a video parameter set (VPS) NAL unit, which contains parameters that describe the overall structure of the bitstream. VPS is a new type of parameter set defined in HEVC and applies to all layers of the bitstream. A layer can contain multiple temporal sublayers, and all version 1 bitstreams are limited to a single layer. HEVC has certain layered extensions for scalability and multi-view, and these extensions will allow multiple layers with a backward-compatible version 1 base layer.

[0082] Figure 2 The data communication system in which one or more embodiments of the present invention may be implemented is illustrated. The data communication system includes a transmitting device (in this case, a server 201) operable to transmit data packets of a data stream to a receiving device (in this case, a client terminal 202) via a data communication network 200. The data communication network 200 may be a wide area network (WAN) or a local area network (LAN). Such a network may be, for example, a wireless network (Wifi / 802.11a, b, or g), an Ethernet network, an Internet network, or a hybrid network consisting of several different networks. In a specific embodiment of the present invention, the data communication system may be a digital television broadcast system in which the server 201 transmits the same data content to multiple clients.

[0083] The data stream 204 provided by the server 201 may be composed of multimedia data representing video and audio data. In some embodiments of the present invention, the audio and video data streams may be captured by the server 201 using a microphone and a camera, respectively. In some embodiments, the data streams may be stored on the server 201 or received by the server 201 from other data providers, or generated at the server 201. The server 201 is provided with an encoder for encoding the video and audio streams, in particular for providing a compressed bit stream for transmission, which is a more compact representation of the data presented as input to the encoder.

[0084] In order to obtain a better ratio of quality of transmitted data to the amount of transmitted data, the video data may be compressed, for example, according to the HEVC format or the H.264 / AVC format.

[0085] The client 202 receives the transmitted bitstream and decodes the reconstructed bitstream to reproduce a video image on a display device and reproduce audio data using a speaker.

[0086] Despite Figure 2 A streaming scenario is considered in the examples of FIG, but it will be appreciated that in some embodiments of the invention, data communication between the encoder and decoder may be performed using, for example, a media storage device such as an optical disc.

[0087] In one or more embodiments of the present invention, a video image is transmitted along with data representing a compensating offset to be applied to reconstructed pixels of the image to provide filtered pixels in the final image.

[0088] Figure 3 A processing device 300 configured to implement at least one embodiment of the present invention is schematically illustrated. The processing device 300 may be a device such as a microcomputer, a workstation, or a lightweight portable device. The device 300 includes a communication bus 313 connected to:

[0089] - a central processing unit 311 denoted as CPU, such as a microprocessor;

[0090] - a read-only memory 306 denoted as ROM, for storing the computer program implementing the invention;

[0091] a random access memory 312, represented as a RAM, for storing executable codes of the method according to an embodiment of the present invention, and registers suitable for recording variables and parameters required for implementing the method for encoding a digital image sequence and / or the method for decoding a bit stream according to an embodiment of the present invention; and

[0092] A communication interface 302 connected to a communication network 303, via which digital data to be processed are transmitted or received.

[0093] Optionally, the device 300 may further include the following components:

[0094] - a data storage component 304, such as a hard disk, for storing a computer program for implementing the method of one or more embodiments of the present invention and data used or generated during the implementation of one or more embodiments of the present invention;

[0095] a disk drive 305 for a disk 306, which is suitable for reading data from the disk 306 or writing data to said disk;

[0096] - A screen 309 for displaying data and / or serving as a graphical interface for interaction with the user by means of a keyboard 310 or any other pointing means.

[0097] Device 300 may be connected to various peripheral devices such as digital camera 320 or microphone 308 , each of which is connected to an input / output card (not shown) to provide multimedia data to device 300 .

[0098] The communication bus provides communication and interoperability between the various elements included in or connected to device 300. The representation of a bus is not limiting, and in particular, the central processing unit is operable to communicate instructions to any element of device 300, either directly or via other elements of device 300.

[0099] The disk 306 may be replaced by any information medium, such as a rewritable or non-rewritable compact disk (CD-ROM), a ZIP disk or a memory card, and in general by an information storage element that can be read by a microcomputer or a microprocessor, the disk 306 being integrated into the device or not, possibly removable and suitable for storing one or more programs whose execution enables the implementation of the method for encoding a digital image sequence and / or the method for decoding a bit stream according to the invention.

[0100] The executable code may be stored in a read-only memory 306, on a hard disk 304 or on a removable digital medium such as, for example, the disk 306 as previously described. According to a variant, the executable code of the program may be received via the interface 302 by means of the communication network 303 to be stored in one of the storage means of the device 300 (such as the hard disk 304) before being executed.

[0101] The central processing unit 311 is adapted to control and direct the execution of instructions or portions of software code for executing one or more programs according to the present invention, instructions stored in one of the aforementioned storage means. Upon power-up, one or more programs stored in non-volatile memory (e.g., on the hard disk 304 or in the read-only memory 306) are transferred to the random access memory 312 (which then contains the executable code of the one or more programs) and registers for storing variables and parameters necessary for the implementation of the present invention.

[0102] In this embodiment, the device is a programmable device that implements the invention using software. Alternatively, however, the invention may be implemented in hardware (for example in the form of an application specific integrated circuit or ASIC).

[0103] Figure 4 A block diagram illustrating an encoder according to at least one embodiment of the present invention. The encoder is represented by connected modules, each module being adapted to implement at least one corresponding step of at least one embodiment of a method for encoding an image of a sequence of images according to one or more embodiments of the present invention, e.g., in the form of programming instructions executed by a CPU 311 of an apparatus 300.

[0104] The encoder 400 receives digital images i0 to i n The original sequence 401 of is taken as input. Each digital image is represented by a set of samples (called pixels).

[0105] After implementing the encoding process, the encoder 400 outputs a bitstream 410. The bitstream 410 includes a plurality of coding units or slices, each slice including a slice header for transmitting encoded values ​​of encoding parameters used for slice encoding, and a slice body including encoded video data.

[0106] Module 402 inputs digital images i0 to i n 401 is divided into pixel blocks. A block corresponds to an image portion and can have a variable size (e.g., 4×4, 8×8, 16×16, 32×32, 64×64, 128×128 pixels, and several rectangular block sizes are also considered). A coding mode is selected for each input block. Two families of coding modes are provided: coding modes based on spatial prediction coding (intra-frame prediction) and coding modes based on temporal prediction (inter-frame coding, merge, skip). Possible coding modes are tested.

[0107] Module 403 implements an intra-frame prediction process in which a given block to be coded is predicted by a predictor calculated from its neighboring pixels. If intra-frame coding is selected, the selected intra-frame predictor and an indication of the difference between the given block and its predictor are encoded to provide a residual.

[0108] Temporal prediction is implemented by the motion estimation module 404 and the motion compensation module 405. First, a reference image is selected from the reference image set 416, and the motion estimation module 404 selects a portion of the reference image (also called a reference region or image portion) that is closest to the given block to be encoded. The motion compensation module 405 then uses the selected region to predict the block to be encoded. The motion compensation module 405 calculates the difference between the selected reference region and the given block (also called the residual block). The selected reference region is indicated by a motion vector.

[0109] Thus, in both cases (spatial and temporal prediction), the residual is calculated by subtracting the prediction from the original block.

[0110] In the intra-frame prediction implemented by module 403, the prediction direction is encoded. In the temporal prediction, at least one motion vector is encoded. In the inter-frame prediction implemented by modules 404, 405, 416, 418, 417, at least one motion vector or data for identifying such a motion vector is encoded for the temporal prediction.

[0111] If inter prediction is selected, information about the motion vector and the residual block is encoded. To further reduce the bit rate, the motion vector is encoded as a difference relative to the motion vector predictor, assuming that the motion is homogeneous. The motion vector predictor from the set of motion information predictors is obtained by the motion vector prediction and encoding module 417 from the motion vector field 418.

[0112] The encoder 400 further includes a selection module 406 for selecting a coding mode by applying a coding cost criterion, such as a rate-distortion criterion. To further reduce redundancy, a transform (such as DCT) is applied to the residual block by a transform module 407, and the resulting transformed data is then quantized by a quantization module 408 and entropy encoded by an entropy coding module 409. Finally, the encoded residual block of the current block being encoded is inserted into a bitstream 410.

[0113] The encoder 400 also decodes the encoded image to generate a reference image for motion estimation of subsequent images. This allows the encoder and decoder receiving the bitstream to have the same reference frame. The inverse quantization module 411 performs inverse quantization of the quantized data, followed by an inverse transform by the inverse transform module 412. The inverse intra prediction module 413 uses the prediction information to determine which predictor to use for a given block, and the inverse motion compensation module 414 actually adds the residual obtained by module 412 to the reference region obtained from the reference image set 416.

[0114] Post filtering is then applied by module 415 to filter the reconstructed pixel frame. In an embodiment of the present invention, a SAO loop filter is used, wherein a compensating offset is added to the pixel values ​​of the reconstructed pixels of the reconstructed image.

[0115] Figure 5 A block diagram of a decoder 60 according to an embodiment of the present invention is shown, which can be used to receive data from an encoder. The decoder is represented by connected modules, each module being adapted to implement the corresponding steps of the method implemented by the decoder 60, for example in the form of programming instructions to be executed by the CPU 311 of the device 300.

[0116] The decoder 60 receives a bitstream 61 comprising coding units, each consisting of a header containing information about the coded parameters and a body containing the coded video data. Figure 6 The structure of the bitstream in VVC is described in more detail. Figure 4 As illustrated, for a given block, the coded video data is entropy coded on a predetermined number of bits and the index of the motion vector predictor is encoded. The received coded video data is entropy decoded by module 62. The residual data is then dequantized by module 63, after which an inverse transform is applied by module 64 to obtain pixel values.

[0117] Mode data indicating an encoding mode is also entropy-decoded, and based on the mode, an encoding block of image data is subjected to intra-type decoding or inter-type decoding.

[0118] In the case of intra mode, the intra inverse prediction module 65 determines the intra predictor based on the intra prediction mode specified in the bitstream.

[0119] If the mode is inter, motion prediction information is extracted from the bitstream to find the reference region used by the encoder. The motion prediction information consists of a reference frame index and a motion vector residual. The motion vector predictor is added to the motion vector residual to obtain the motion vector by the motion vector decoding module 70.

[0120] A motion vector decoding module 70 applies motion vector decoding to each current block coded by motion prediction. Once the index of the motion vector predictor for the current block has been obtained, the actual value of the motion vector associated with the current block can be decoded and used to apply inverse motion compensation by module 66. The portion of the reference image indicated by the decoded motion vector is extracted from the reference image 68 to apply inverse motion compensation 66. The decoded motion vector is used to update the motion vector field data 71 for use in inverse prediction of subsequently decoded motion vectors.

[0121] Finally, a decoded block is obtained. Post filtering is applied by a post filtering module 67. The decoder 60 finally provides a decoded video signal 69.

[0122] Figure 6 The organization of the bitstream in an exemplary coding system VVC as described in JVET_Q2001-vD is shown.

[0123] The bitstream 61 according to the VVC coding system consists of an ordered sequence of syntax elements and encoded data. The syntax elements and encoded data are placed into network abstraction layer (NAL) units 601-608. There are different NAL unit types. The network abstraction layer provides the ability to encapsulate the bitstream into different protocols (such as RTP / IP (Real Time Protocol / Internet Protocol), ISO base media file format, etc.). The network abstraction layer also provides a framework for packet loss resistance.

[0124] NAL units are divided into video coding layer (VCL) NAL units and non-VCL NAL units. VCL NAL units contain the actual coded video data. Non-VCL NAL units contain additional information. This additional information can be parameters required to decode the coded video data or supplementary data that can enhance the usability of the decoded video data. NAL units 606 correspond to slices and constitute the VCL NAL units of the bitstream.

[0125] Different NAL units 601-605 correspond to different parameter sets, which are non-VCL NAL units. The decoder parameter set (DPS) NAL unit 301 contains parameters that are constant for a given decoding process. The video parameter set (VPS) NAL unit 602 contains parameters defined for the entire video and therefore the entire bitstream. The DPS NAL unit can define parameters that are more static than those in the VPS. In other words, the parameters of the DPS change less frequently than those of the VPS.

[0126] The sequence parameter set (SPS) NAL unit 603 contains parameters defined for a video sequence. Specifically, the SPS NAL unit may define the sub-picture layout and associated parameters of the video sequence. Parameters associated with each sub-picture specify the coding constraints applied to the sub-picture. Specifically, a flag is included to indicate that temporal prediction between sub-pictures is restricted to data from the same sub-picture. Another flag may enable or disable loop filters across sub-picture boundaries.

[0127] Picture parameter set (PPS) NAL unit 604. The PPS contains parameters defined for a picture or group of pictures. Adaptation parameter set (APS) NAL unit 605 contains parameters for the loop filter, which is typically an adaptive loop filter (ALF) or a shaper model (or a luma map with chroma scaling (LMCS) model) or a scaling matrix used at the slice level.

[0128] The syntax of PPS as proposed in the current version of VVC includes syntax elements that specify the size of a picture in units of luma samples and the partitioning of each picture into blocks and slices.

[0129] The PPS contains syntax elements that allow the location of slices within a frame to be determined. Since a sub-picture forms a rectangular area within a frame, the set of slices, tile portions, or tiles belonging to a sub-picture can be determined from the parameter set NAL unit. Like the APS, the PPS has an ID mechanism to limit the number of transmissions of the same PPS.

[0130] The main difference between the PPS and the picture header is its transmission, which is usually sent for a group of pictures, compared to the PH which is systematically sent for each picture. Therefore, in contrast to the PH, the PPS contains parameters that can be constant for several pictures.

[0131] The bitstream may also contain Supplemental Enhancement Information (SEI) NAL units ( Figure 6(Not shown in the image). The periodicity of these parameter sets in the bitstream is variable. A VPS defined for the entire bitstream may appear only once in the bitstream. Conversely, an APS defined for a slice may appear once for each slice in each picture. In practice, different slices may rely on the same APS, and therefore there are typically fewer APSs than slices in each picture. Specifically, the APS is defined in the picture header. However, the ALF APS can be refined in the slice header.

[0132] The Access Unit Delimiter (AUD) NAL unit 607 separates two access units. An access unit is a collection of NAL units that may include one or more coded pictures with the same decoding timestamp. This optional NAL unit contains only one syntax element from the current VVC specification: pic_type, which indicates that the slice_type value is used for all slices of the coded pictures in the AU. If pic_type is set to 0, the AU contains only intra slices. If it is 1, it contains P and I slices. If it is 2, it contains B, P, or intra slices.

[0133] This NAL unit contains only one syntax element, pic-type.

[0134] Table 1 Syntax AUD

[0135]

[0136] In JVET-Q2001-vD, pic-type is defined as follows:

[0137] "pic_type indicates that the slice_type values ​​of all slices of the coded pictures in the AU containing the AU delimiter NAL unit are members of the set listed in Table 2 for the given pic_type value. The value of pic_type shall be equal to 0, 1, or 2 in bitstreams conforming to this version of this specification. Other values ​​of pic_type are reserved for future use by ITUT|ISO / IEC. Decoders conforming to this version of this specification shall ignore the reserved values ​​of pic_type."

[0138] rbsp_trailing_bits() is a function that adds bits to align with the end of a byte. Therefore, after this function, the amount of the bit stream parsed is an integer number of bytes.

[0139] Table 2 Explanation of pic_type

[0140] pic_type Possible slice_type values ​​in AU 0 I 1 P,I 2 B,P,I

[0141] The PH NAL unit 608 is a picture header NAL unit that groups common parameters for a set of slices of one coded picture.A picture may refer to one or more APSs to indicate the AFL parameters, shaper models, and scaling matrices used by the slices of the picture.

[0142] Each VCL NAL unit 606 contains a slice. A slice can correspond to an entire picture or a sub-picture, a single block, or multiple blocks or a fragment of a block. For example, Figure 3 A slice comprises a number of blocks 620 . A slice consists of a slice header 610 and a raw byte sequence payload RBSP 611 , which contains coded pixel data encoded as coded blocks 640 .

[0143] The syntax of the PPS as proposed in the current version of VVC includes syntax elements that specify the size of a picture in units of luma samples and the partitioning of each picture in units of blocks and slices.

[0144] The PPS contains syntax elements that allow the slice positions in a frame to be determined. Since a sub-picture forms a rectangular area in a frame, the set of slices, tile parts or tiles belonging to a sub-picture can be determined from the parameter set NAL units.

[0145] NAL unit slice

[0146] The NAL unit slice layer contains a slice header and slice data, as shown in Table 3.

[0147] Table 3 Stripe layer syntax

[0148]

[0149] APS

[0150] The adaptation parameter set (APS) NAL unit 605 is defined in Table 4 showing the syntax elements.

[0151] As depicted in Table 4, there are 3 possible types of APS given by the aps_params_type syntax element:

[0152] ALF_AP: used for ALF parameters

[0153] LMCS_APS: used for LMCS parameters

[0154] SCALLING_APS: used for scaling list related parameters

[0155] Table 4 Adaptive parameter set syntax

[0156]

[0157] The following discusses these three types of APS parameters in turn.

[0158] ALF APS

[0159] The ALF parameters are described in the adaptive loop filter data syntax element (Table 5). First, four flags are dedicated to specifying whether the ALF filter is sent for luma and / or for chroma and whether CC-ALF (cross-component adaptive loop filtering) is enabled for the Cb component and the Cr component. If the luma filter flag is enabled, another flag is decoded to know whether the clipping value (alf_luma_clip_flag) is signaled. The number of filters signaled is then decoded using the alf_luma_num_filters_signalled_minus1 syntax element. If necessary, the syntax element representing the ALF coefficient increment "alf_luma_coeff_delta_idx" is decoded for each enabled filter. The absolute value and sign of each coefficient of each filter are then decoded.

[0160] If alf_luma_clip_flag is enabled, the clipping index of each coefficient of each enabled filter is decoded.

[0161] In the same way, the ALF chroma coefficients are decoded when needed.

[0162] If CC-ALF is enabled for Cr or Cb, the number of filters is decoded (alf_cc_cbfilters_signalled_minus1 or alf_cc_cr filters_signalled_minus1) and the related coefficients are decoded (alf_cc_cb_mapped_coeff_abs and alf_cc_cb_coeff_sign or alf_cc_cr_mapped_coeff_abs and alf_cc_cr_coeff_sign respectively).

[0163] Table 5 Adaptive loop filter data syntax

[0164]

[0165]

[0166]

[0167] LMCS syntax elements for both luma mapping and chroma scaling

[0168] Table 6 below gives all LMCS syntax elements (LMCS_APS) encoded in the Adaptation Parameter Set (APS) syntax structure when the aps_params_type parameter is set to 1. Up to four LMCS APSs may be used in a coded video sequence, however, for a given picture only a single LMCS APS may be used.

[0169] These parameters are used to construct the forward and inverse mapping functions for luma and the scaling function for chroma.

[0170] Table 6 Luma Mapping with Chroma Scaling Data Syntax

[0171]

[0172]

[0173] Zoom List APS

[0174] The scaling list provides the possibility to update the quantization matrix used for quantization. In VVC, the scaling matrix is ​​signaled in the APS as described in the scaling list data syntax element (Table 7 Scaling list data syntax). The first syntax element specifies whether the scaling matrix is ​​used for the LFNST (Low Frequency Non-separable Transform) tool based on the flag scaling_matrix_for_lfnst_disabled_flag. The second is specified if the scaling list is used for chroma components (scaling_list_chroma_present_flag). Then, the syntax elements required to construct the scaling matrix (scaling_list_copy_mode_flag, scaling_list_pred_mode_flag, scaling_list_pred_id_delta, scaling_list_dc_coef, scaling_list_delta_coef) are decoded.

[0175] Table 7: Scaling List Data Syntax

[0176]

[0177]

[0178] Image header

[0179] A picture header is sent at the beginning of each picture before the other slice data. This is very large compared to previous headers in previous drafts of the standard. A complete description of all these parameters can be found in JVET_Q2001-vD. Table 9 shows these parameters in the current picture header decoding syntax.

[0180] The relevant syntactic elements that can be decoded are:

[0181] Whether to use the image or reference frame

[0182] Type of image

[0183] Output frame

[0184] Number of images

[0185] Use sub-images (if needed)

[0186] List of reference images (if required)

[0187] Color plane (if needed)

[0188] Partition update (if overwrite flag is enabled)

[0189] Incremental QP parameters (if needed)

[0190] Motion information parameters (if necessary)

[0191] ALF parameters (if required)

[0192] SAO parameters (if needed)

[0193] Quantization parameters (if needed)

[0194] LMCS parameters (if required)

[0195] Scale list parameters (if needed)

[0196] Image header expansion (if necessary)

[0197] ·etc

[0198] Image "Type"

[0199] The first flag is grd_or_irap_pic_flag, which indicates whether the current picture is a resynchronization picture (IRAP or GDR). If this flag is true, gdr_pic_flag is decoded to know whether the current picture is an IRAP picture or a GDR picture.

[0200] The ph_inter_slice_allowed_flag is then decoded to identify that inter slices are allowed.

[0201] When they are allowed, the flag ph_infra_slice_allowed_flag is decoded to know whether intra slices are allowed for the current picture.

[0202] Then decode non_reference_picture_flag, ph_pic_parameter_set_id indicating PPS ID, and picture order count ph_pic_order_cnt_lsb. The picture order count gives the number of the current picture.

[0203] If the picture is a GDR or IRAP picture, the flag no_output_of_prior_pics_flag is decoded.

[0204] And if the picture is GDR, then decode recovery_poc_cnt. Then, if necessary, decode ph_poc_msb_present_flag and poc_msb_val.

[0205] ALF

[0206] After these parameters that describe important information about the current picture, a set of ALF APS ID syntax elements are decoded if ALF is enabled at the SPS level and if ALF is enabled at the picture header level. ALF is enabled at the SPS level due to the sps_alf_enabled_flag flag. ALF is signaled at the picture header level due to alf_info_in_ph_flag being 1, otherwise (alf_info_in_ph_flag being 0), ALF is signaled at the slice level.

[0207] alf_info_in_ph_flag is defined as follows:

[0208] "alf_info_in_ph_flag equal to 1 specifies that ALF information is present in the PH syntax structure and is not present in slice headers referencing PPSs that do not contain a PH syntax structure. alf_info_in_ph_flag equal to 0 specifies that ALF information is not present in the PH syntax structure and may be present in slice headers referencing PPSs that do not contain a PH syntax structure."

[0209] First, ph_alf_enabled_present_flag is decoded to determine whether ph_alf_enabled_flag should be decoded. If ph_alf_enabled_present_flag is enabled, ALF is enabled for all slices of the current picture.

[0210] If ALF is enabled, the pic_num_alf_aps_ids_luma syntax element is used to decode the amount of ALF APS ID for luma. For each APS ID, the APS ID value "ph_alf_aps_id_luma" for luma is decoded.

[0211] For chroma, the syntax element ph_alf_chroma_idc is decoded to determine whether ALF is enabled for chroma, only for Cr, or only for Cb. If enabled, the value of the APS ID for chroma is decoded using the ph_alf_aps_id_chroma syntax element.

[0212] In this way, if required by the Cb and / or Cr components, the APSID for the CC-ALF method is decoded.

[0213] LMCS

[0214] If LMCS is enabled at the SPS level, the set of LMCS APS ID syntax elements is decoded. First, ph_lmcs_enabled_flag is decoded to determine whether LMCS is enabled for the current picture. If LMCS is enabled, the ID value ph_lmcs_aps_id is decoded. For chroma, only ph_chroma_residual_scale_flag is decoded to enable or disable the method for chroma.

[0215] Zoom List

[0216] If scaling lists are enabled at the SPS level, the set of scaling list APS IDs is decoded. The ph_scaling_list_present_flag is decoded to determine whether the scaling matrix is ​​enabled for the current picture. And then the value of the APS ID (ph_scaling_list_aps_id) is decoded.

[0217] Sub-image

[0218] When sub-picture parameters are enabled at the SPS and if the sub-picture ID is signaled to be disabled, the sub-picture parameters are enabled. Also contains some information about the virtual boundaries. For sub-picture parameters, eight syntax elements are defined:

[0219] ·ph_virtual_boundaries_present_flag

[0220] ·ph_num_ver_virtual_boundaries

[0221] ·ph_virtual_boundaries_pos_x[i]

[0222] ·ph_num_hor_virtual_boundaries

[0223] ·ph_virtual_boundaries_pos_y[i]

[0224] Output Flag

[0225] These sub-picture parameters are followed by pic_output_flag (if present).

[0226] Reference Image List

[0227] If the reference picture list is signaled in the picture header (due to rpl_info_in_ph_flag being equal to 1), the parameter ref_pic_lists() of the reference picture list is decoded, which contains the following syntax elements:

[0228] rpl_sps_flag[]

[0229] rpl_idx[]

[0230] ·poc_lsb_lt[][]

[0231] ·delta_poc_msb_present_flag[][]

[0232] delta_poc_msb_cycle_lt[][]

[0233] Partition

[0234] If required, a partition parameter set is decoded and contains the following syntax elements:

[0235] ·partition_constraints_override_flag

[0236] ·ph_log2_diff_min_qt_min_cb_intra_slice_luma

[0237] ·ph_max_mtt_hierarchy_depth_intra_slice_luma

[0238] ·ph_log2_diff_max_bt_min_qt_intra_slice_luma

[0239] ·ph_log2_diff_max_tt_min_qt_intra_slice_luma

[0240] ·ph_log2_diff_min_qt_min_cb_intra_slice_chroma

[0241] ·ph_max_mtt_hierarchy_depth_intra_slice_chroma

[0242] ·ph_log2_diff_max_bt_min_qt_intra_slice_chroma

[0243] ·ph_log2_diff_max_tt_min_qt_intra_slice_chroma

[0244] ·ph_log2_diff_min_qt_min_cb_inter_slice

[0245] ·ph_max_mtt_hierarchy_depth_inter_slice

[0246] ·ph_log2_diff_max_bt_min_qt_inter_slice

[0247] ·ph_log2_diff_max_tt_min_qt_inter_slice

[0248] Weighted prediction

[0249] If the weighted prediction method is enabled at the PPS level and if the weighted prediction parameters are signaled in the picture header (wp_info_in_ph_flag is equal to 1), the weighted prediction parameters pred_weight_table() are decoded.

[0250] When bi-predictive weighted prediction is enabled, pred_weight_table() contains weighted prediction parameters for list L0 and list L1. As depicted in the pred_weight_table() syntax table (Table 8), when weighted prediction parameters are sent in the picture header, the number of weights for each list is explicitly sent.

[0251] Table 8 Weighted prediction parameter syntax

[0252]

[0253]

[0254]

[0255] Incremental QP

[0256] When the picture is intra, ph_cu_qp_delta_subdiv_intra_slice and ph_cu_chroma_qp_offset_subdiv_intra_slice are decoded if needed. And if inter slices are allowed, ph_cu_qp_delta_subdiv_inter_slice and ph_cu_chroma_qp_offset_subdiv_inter_slice are decoded if needed. Finally, the picture header extension syntax element is decoded if needed.

[0257] All parameters alf_info_in_ph_flag, rpl_info_in_ph_flag, qp_delta_info_in_ph_flag, sao_info_in_ph_flag, dbf_info_in_ph_flag, wp_info_in_ph_flag are signaled in the PPS.

[0258] Table 9 Picture header structure

[0259]

[0260]

[0261]

[0262]

[0263]

[0264]

[0265]

[0266] Strip header

[0267] A slice header is sent at the beginning of each slice. The slice header contains approximately 65 syntax elements. This is very large compared to previous slice headers in earlier video coding standards. A complete description of all slice header parameters can be found in JVET-Q2001-vD. Table 10 shows these parameters in the current slice header decoding syntax.

[0268] Table 10 Partial strip header

[0269]

[0270]

[0271]

[0272]

[0273]

[0274] First, picture_header_in_slice_header_flag is decoded to know whether picture_header_structure() exists in the slice header.

[0275] Then, if necessary, decode slice_subpic_id to determine the sub-picture ID of the current slice. Then decode slice_address to determine the address of the current slice. If the number of tiles in the current picture is greater than 1, decode num_tiles_in_slice_minus1.

[0276] Then decode the slice_type.

[0277] If ALF is enabled at the SPS level (sps_alf_enabled_flag) and if ALF is signaled in the slice header (alf_info_in_ph_flag is equal to 0), the ALF information is decoded. This includes a flag indicating that ALF is enabled for the current slice (slice_alf_enabled_flag). If enabled, the number of APS ALF IDs for luma (slice_num_alf_aps_ids_luma) is decoded, followed by the APS ID (slice_alf_aps_id_luma[i]). Then, slice_alf_chroma_idc is decoded to know if ALF is enabled for the chroma components and which chroma component is enabled. Then, if necessary, the APS ID for chroma (slice_alf_aps_id_chroma) is decoded. In the same way, if necessary, slice_cc_alf_cb_enabled_flag is decoded to know if the CC ALF method is enabled. If CC ALF is enabled, if CC ALF is enabled for Cr and / or Cb, decode the relevant APS ID for Cr and / or Cb.

[0278] If the colour planes are sent independently (separate_colour_plane_flag equal to 1), colour_plane_id is decoded.

[0279] When the reference picture list is not sent in the picture header (rpl_info_in_ph_flag equal to 0) and when the NAL unit is not IDR or if the reference picture list is sent for an IDR picture (sps_idr_rpl_present_flag equal to 1), the reference picture list parameters are decoded; these are similar to those in the picture header.

[0280] If a reference picture list is sent in the picture header (rpl_info_in_ph_flag is equal to 1) or the NAL unit is not IDR, or if a reference picture list is sent for an IDR picture (sps_idr_rpl_present_flag is equal to 1), and if the number of references of at least one list is greater than 1, the override flag num_ref_idx_active_override_flag is decoded.

[0281] If this flag is enabled, the reference indices of the individual lists are decoded.

[0282] When the slice type is not intra, and if necessary, decode cabac_init_flag. If the reference picture list is sent in the slice header and other conditions occur, decode slice_collocated_from_l0_flag and slice_collocated_ref_idx. These data are related to CABAC coding and collocated motion vectors.

[0283] In the same manner, when the slice type is not intra, parameters pred_weight_table() of weighted prediction are decoded.

[0284] If delta QP information is sent in the slice header (qp_delta_info_in_ph_flag is equal to 0), decode slice_qp_delta. If needed, decode the syntax elements slice_cb_qp_offset, slice_cr_qp_offset, slice_joint_cbcr_qp_offset, and cu_chroma_qp_offset_enabled_flag.

[0285] If SAO information is sent in the slice header (sao_info_in_ph_flag equal to 0) and if it is enabled at the SPS level (sps_sao_enabled_flag), then the SAO enablement flags are decoded for both luma and chroma: slice_sao_luma_flag, slice_sao_chroma_flag.

[0286] Then, if the deblocking filter parameters are signaled in the slice header (dbf_info_in_ph_flag equal to 0), the deblocking filter parameters are decoded.

[0287] The flag slice_ts_residual_coding_disabled_flag is system-decoded to know whether the transform skip residual coding method is enabled for the current slice.

[0288] If LMCS is enabled in the picture header (ph_lmcs_enabled_flag is equal to 1), the flag slice_lmcs_enabled_flag is decoded.

[0289] In the same way, if the scaling list is enabled in the picture header (phpic_scaling_list_presentenabled_flag is equal to 1), the flag slice_scaling_list_present_flag is decoded.

[0290] Then, if necessary, other parameters are decoded.

[0291] Picture header in the strip header

[0292] In a specific signaling manner, such as Figure 7 As depicted in FIG, the picture header 708 may be signaled within the slice header 710. In this case, there is no NAL unit containing only the picture header 608. Units 701, 702, 703, 704, 705, 706, 707, 720, and 740 correspond to Figure 6601, 602, 603, 604, 605, 606, 606, 620, and 640 of FIGURE 1 and can therefore be understood from the foregoing description. This can be enabled in the slice header due to the flag picture_header_in_slice_header_flag. Furthermore, when a picture header is signaled within the slice header, a picture should contain only one slice. Therefore, each picture always has only one picture header. Furthermore, the flag picture_header_in_slice_header_flag should have the same value for all pictures of a CLVS (Coding Layer Video Sequence). This means that all pictures between two IRAPs, including the first IRAP, have only one slice per picture.

[0293] The flag picture_header_in_slice_header_flag is defined as follows:

[0294] "picture_header_in_slice_header_flag equal to 1 specifies that the PH syntax structure is present in the slice header. picture_header_in_slice_header_flag equal to 0 specifies that the PH syntax structure is not present in the slice header.

[0295] It is a requirement for bitstream conformance that the value of picture_header_in_slice_header_flag should be the same in all coded slices in CLVS.

[0296] When picture_header_in_slice_header_flag is equal to 1 for a coded slice, it is a requirement for bitstream conformance that no VCL NAL units with nal_unit_type equal to PH_NUT shall be present in the CLVS.

[0297] When picture_header_in_slice_header_flag is equal to 0, all coded slices in the current picture shall have picture_header_in_slice_header_flag equal to 0, and the current PU shall have a PH NAL unit.

[0298] picture_header_structure() contains the syntax elements of picture_rbsp() except for the padding bits rbsp_trailing_bits(). "

[0299] Interaction between picture header in slice header and signaling of tools in picture header and slice header

[0300] QP increment information, reference picture list parameters, deblocking filter parameters, sample adaptive offset parameters, weighted prediction parameters and ALF parameters can be sent in the picture header or slice header thanks to the following corresponding flags:

[0301] qp_delta_info_in_ph_flag

[0302] rpl_info_in_ph_flag

[0303] dbf_info_in_ph_flag

[0304] sao_info_in_ph_flag

[0305] wp_info_in_ph_flag

[0306] alf_info_in_ph_flag

[0307] These flags are sent in the PPS.

[0308] As shown in Table 11 (Summary of Signaling XXX According to Flags picture_header_in_slice_header_flag and xxx_info_in_ph_flag), by considering "xxx" of one of the mentioned tools, xxx can be signaled in the slice header when xxx_info_in_ph_flag is set to 0 using the current syntax. In other words, we use the abbreviation XXX or xxx in the subsequent description to refer to the type of information that can be signaled in both the picture header and the slice header (an example of which is given above).

[0309] Table 11 Summary of signaling XXX according to flags picture_header_in_slice_header_flag and xxx_info_in_ph_flag

[0310]

[0311] When the picture header is in the slice header, this means that there is only one slice for the current picture. Therefore, making information sent or transmittable for both the slice and the picture does not increase the flexibility of the encoder or decoder because the parameters will be the same. In other words, if the information is in the picture header, the corresponding information in the slice header will be redundant. Similarly, if the information is in the slice header, the corresponding information in the picture header will be redundant. The embodiments described herein simplify decoder implementation by limiting redundancy in signaling of identical encodings. In particular, embodiments allow information to be in the picture header instead of the slice header when the picture header is signaled in the slice header.

[0312] Streaming applications

[0313] Some streaming applications extract only certain portions of the bitstream. These extractions can be spatial (as sub-pictures) or temporal (sub-portions of a video sequence). These extracted portions can then be merged with the rest of the bitstream. Others reduce the frame rate by extracting only some frames. Typically, the primary goal of these streaming applications is to use the maximum allowed bandwidth to produce the highest quality for the end user.

[0314] In VVC, for frame rate reduction, APS ID numbering is already restricted so that new APS ID numbers for a frame cannot be used for frames in upper layers in the temporal hierarchy. However, for streaming applications that extract portions of a bitstream, it is necessary to track APS IDs to determine which APSs should be retained for a sub-portion of the bitstream, since frames (due to IRAP) do not reset the APS ID numbering.

[0315] LMCS (Luminance Mapping with Chroma Scaling)

[0316] The Luma Mapping with Chroma Scaling (LMCS) technique is a sample value conversion method applied to a block before applying a loop filter in a video decoder such as VVC.

[0317] LMCS can be divided into two sub-tools. The first sub-tool is applied to luma blocks, while the second sub-tool is applied to chroma blocks, as described below:

[0318] 1) The first sub-tool is an in-loop mapping of the luma component based on an adaptive piecewise linear model. Luma component in-loop mapping adjusts the dynamic range of the input signal to improve compression efficiency by redistributing codewords across the dynamic range. Luma mapping utilizes a forward mapping function into the "mapping domain" and a corresponding inverse mapping function back into the "input domain."

[0319] 2) The second sub-tool is related to the chroma components, which apply luma-dependent chroma residual scaling. Chroma residual scaling is designed to compensate for the interaction between the luma signal and its corresponding chroma signal. Chroma residual scaling depends on the average of the neighboring luma samples reconstructed above and / or to the left of the current block.

[0320] Like most other tools in video encoders such as VVC, LMCS can be enabled / disabled at the sequence level using an SPS flag. Whether chroma residual scaling is enabled is also signaled at the slice level. If luma mapping is enabled, an additional flag is signaled to indicate whether luma-dependent chroma residual scaling is enabled. When luma mapping is not used, luma-dependent chroma residual scaling is completely disabled. Additionally, luma-dependent chroma residual scaling is always disabled for chroma blocks of size less than or equal to 4.

[0321] Figure 8 The principle of LMCS as described above for the Luma Mapping Sub-Tool is shown. Figure 8 The shaded blocks in the figure are the new LMCS functional blocks, which include the forward and inverse mapping of the luminance signal. It is important to note that when LMCS is used, some decoding operations are applied in the "mapping domain". These operations are performed by the Figure 8 They generally correspond to the inverse quantization, inverse transform, luma intra prediction and reconstruction steps (which consists in adding the luma prediction to the luma residual). Figure 8 The solid blocks in indicate where the decoding processes are applied in the original (ie non-mapped) domain, and this includes loop filtering such as deblocking, ALF and SAO, motion compensated prediction, and storage of decoded pictures as reference pictures (DPB).

[0322] Figure 9 Shown with Figure 8 Similar diagram, but this time for the Chroma Scaling sub-tool of the LMCS tool. Figure 9 The shaded blocks in the figure are new LMCS functional blocks, which include the luma-dependent chroma scaling process. However, in terms of chroma, there are some important differences compared to the luma case. Here, for the chroma samples, only the inverse quantization and inverse transform, represented by the blocks in the dashed line, are performed in the "mapped domain". All other steps of intra chroma prediction, motion compensation, and loop filtering are performed in the original domain. Figure 9 As shown, for brightness mapping, there is only a scaling process, and no forward and inverse processes.

[0323] Brightness mapping using a piecewise linear model

[0324] The Luma Mapping sub-tool uses a piecewise linear model, which means that the piecewise linear model divides the input signal dynamic range into 16 equal sub-ranges and, for each sub-range, uses the number of codewords assigned to that range to represent its linear mapping parameters.

[0325] Semantics of brightness mapping

[0326] The syntax element lmcs_min_bin_idx specifies the minimum bin (interval) index used in the construction process of the Luma Map with Chroma Scale (LMCS). The value of lmcs_min_bin_idx shall be in the range of 0 to 15 (inclusive).

[0327] The syntax element lmcs_delta_max_bin_idx specifies the delta value between 15 and the maximum bin index LmcsMaxBinIdx used in the construction of the luma map with chroma scaling. The value of lmcs_delta_max_bin_idx shall be in the range of 0 to 15, inclusive. The value of LmcsMaxBinIdx shall be set equal to 15 - lmcs_delta_max_bin_idx. The value of LmcsMaxBinIdx shall be greater than or equal to lmcs_min_bin_idx.

[0328] The syntax element lmcs_delta_cw_prec_minus1 plus 1 specifies the number of bits used to represent the syntax lmcs_delta_abs_cw[i].

[0329] The syntax element lmcs_delta_abs_cw[i] specifies the absolute delta codeword value for the i-th bin.

[0330] The syntax element lmcs_delta_sign_cw_flag[i] specifies the sign of the variable lmcsDeltaCW[i]. When lmcs_delta_sign_cw_flag[i] is not present, it is inferred to be equal to 0.

[0331] LMCS intermediate variable calculation for brightness mapping

[0332] In order to apply the forward and inverse brightness mapping processes, some intermediate variables and data arrays are required.

[0333] First, export the variable OrgCW as follows:

[0334] OrgCW=(1< <BitDepth) / 16

[0335] Then, the variable lmcsDeltaCW[i] (where i=lmcs_min_bin_idx . . . LmcsMaxBinIdx) is calculated as follows:

[0336] lmcsDeltaCW[i]=(1-2*lmcs_delta_sign_cw_flag[i])*lmcs_delta_abs_cw[i]

[0337] The new variable lmcsCW[i] is derived as follows:

[0338] - For i=0...lmcs_min_bin_idx-1, lmcsCW[i] is set equal to 0.

[0339] - For i = lmcs_min_bin_idx ... LmcsMaxBinIdx, the following applies:

[0340] lmcsCW[i]=OrgCW+lmcsDeltaCW[i]

[0341] The value of lmcsCW[i] should be in the range of (OrgCW>>3) to (OrgCW<<3-1) (inclusive).

[0342] - For i=LmcsMaxBinIdx+1...15, lmcsCW[i] is set equal to 0.

[0343] The variable InputPivot[i] (where i=0...16) is derived as follows:

[0344] InputPivot[i]=i*OrgCW

[0345] The variables LmcsPivot[i] (where i=0...16), ScaleCoeff[i] and InvScaleCoeff[i] (where i=0...15) are calculated as follows:

[0346] LmcsPivot[0]=0;

[0347] for(i=0;i<=15;i++){

[0348] LmcsPivot[i+1]=LmcsPivot[i]+lmcsCW[i]

[0349] ScaleCoeff[i]=(lmcsCW[i]*(1<<11)+(1<<(Log2(OrgCW)-1)))>>(Log2(OrgCW))

[0350] if(lmcsCW[i] == 0)

[0351] InvScaleCoeff[i]=0

[0352] else

[0353] InvScaleCoeff[i]=OrgCW*(1<<11) / lmcsCW[i]

[0354] Forward Luminance Map

[0355] like Figure 8 As shown, when LMCS is applied to luma, luma remap samples called predMapSamples[i][j] are obtained from the prediction samples predSamples[i][j].

[0356] predMapSamples[i][j] is calculated as follows:

[0357] First, the index idxY is calculated from the predicted sample predSamples[i][j] at position (i, j).

[0358] idxY=predSamples[i][j]>>Log2(OrgCW)

[0359] Then, predMapSamples[i][j] is derived as follows by using the intermediate variables idxY, LmcsPivot[idxY], and InputPivot[idxY] of part 0:

[0360] predMapSamples[i][j]=LmcsPivot[idxY]

[0361] +(ScaleCoeff[idxY]*(predSamples[i][j]-InputPivot[idxY])+(1<<10))>>11

[0362] Luminance reconstruction samples

[0363] The reconstruction process is obtained from the predicted luma samples predMapSample[i][j] and the residual luma samples resiSamples[i][j].

[0364] The reconstructed luma picture samples recSamples[i][j] are simply obtained by adding predMapSample[i][j] to resiSamplei[i][j] as follows:

[0365] recSamples[i][j] = Clip1(predMapSamples[i][j] + resiSamples[i][j]])

[0366] In the above relationship, the Clip1 function is a clipping function to ensure that the reconstructed samples are between 0 and 1 << BitDepth - 1.

[0367] Inverse luminance mapping

[0368] When applying the inverse luminance mapping according to Figure 8 the following operations are applied to each sample recSample[i][j] of the current block being processed:

[0369] First, the index idxY is calculated from the reconstructed sample recSamples[i][j] at position (i, j).

[0370] idxY = recSamples[i][j] >> Log2(OrgCW)

[0371] The inverse-mapped luminance sample invLumaSample[i][j] is derived based on the following:

[0372] invLumaSample[i][j] =

[0373] InputPivot[idxYInv] + (InvScaleCoeff[idxYInv] *

[0374] (recSample[i][j] - LmcsPivot[idxYInv]) + (1 << 10)) >> 11

[0375] Then a clipping operation is performed to obtain the final sample:

[0376] finalSample[i][j] = Clip1(invLumaSample[i][j])

[0377] Chroma scaling

[0378] LMCS semantics for chroma scaling

[0379] The syntax element lmcs_delta_abs_crs in Table 6 specifies the absolute codeword value of the variable lmcsDeltaCrs. The value of lmcs_delta_abs_crs should be in the range of 0 to 7 (including the end values). When it does not exist, it is inferred that lmcs_delta_abs_crs is equal to 0.

[0380] The syntax element lmcs_delta_sign_crs_flag specifies the sign of the variable lmcsDeltaCrs. When not present, lmcs_delta_sign_crs_flag is inferred to be equal to 0.

[0381] LMCS intermediate variable calculation for chroma scaling

[0382] In order to apply the chroma scaling process, some intermediate variables are needed.

[0383] The variable lmcsDeltaCrs is derived as follows:

[0384] lmcsDeltaCrs=(1-2*lmcs_delta_sign_crs_flag)*lmcs_delta_abs_crs

[0385] The variable ChromaScaleCoeff[i] (where i=0...15) is derived as follows:

[0386] if(lmcsCW[i] == 0)

[0387] ChromaScaleCoeff[i]=(1<<11)

[0388] else

[0389] ChromaScaleCoeff[i]=OrgCW*(1<<11) / (lmcsCW[i]+lmcsDeltaCrs)

[0390] Chroma scaling

[0391] In the first step, the variable invAvgLuma is derived to calculate the average luma value of the reconstructed luma samples around the current corresponding chroma block. The average luma is calculated from the left and top luma blocks surrounding the corresponding chroma block.

[0392] If no samples are available, the variable invAvgLuma is set as follows:

[0393] invAvgLuma=1<<(BitDepth-1)

[0394] Based on the intermediate array LmcsPivot[] of part 0, the variable idxYInv is then derived as follows:

[0395] For(idxYInv=lmcs_min_bin_idx; idxYInv<=LmcsMaxBinIdx; idxYInv++){

[0396] if(invAvgLuma <LmcsPivot[idxYInv+1])break

[0397] }

[0398] IdxYInv=Min(idxYInv,15)

[0399] The variable varScale is exported as follows:

[0400] varScale=ChromaScaleCoeff[idxYInv]

[0401] When the transform is applied to the current chroma block, the reconstructed chroma picture sample array recSamples is derived as follows:

[0402] recSamples[i][j]=Clip1(predSamples[i][j]+

[0403] Sign(resiSamples[i][j])*((Abs(resiSamples[i][j])*varScale+(1<<10))>>11))

[0404] If no transform has been applied to the current block, the following is applied:

[0405] recSamples[i][j]=Clip1(predSamples[i][j])

[0406] Encoder Considerations

[0407] The basic principle of the LMCS encoder is to first allocate more codewords to those dynamic range segments with codewords with lower variance than the average. In an alternative concept, the main goal of LMCS is to allocate fewer codewords to those dynamic range segments with codewords with higher variance than the average. In this way, smooth areas of the picture will be encoded with more codewords than the average, and vice versa.

[0408] All parameters of the LMCS tool stored in the APS are determined on the encoder side (see Table 6). The LMCS encoder algorithm is based on the evaluation of local luminance variance and optimizes the determination of LMCS parameters according to the basic principles described above. The optimization is then performed to obtain the best PSNR metric for the final reconstructed samples of a given block.

[0409] An embodiment of signaling information in a picture header instead of a slice header

[0410] In an embodiment, when a picture header is signaled in a slice header, information that can be signaled in a picture header or a slice header is signaled in a picture header instead of a slice header. In an equivalent manner, when information that can be signaled in a picture header or a slice header is signaled in a slice header, the picture header is not signaled in a slice header. In another equivalent manner, when information that can be signaled in a picture header or a slice is signaled in a picture header, the picture header is signaled in a slice header. Table 12 shows an implementation of an embodiment in which the tool name is replaced by xxx. In this table, when a picture header is signaled in a slice header, parameter signaling is not authorized in a slice header.

[0411] Table 12 Summary of signaling

[0412]

[0413] In one embodiment, the following condition is added to the semantics of xxx_info_in_ph_flag:

[0414] "When the slice header of the referenced PPS contains the PH syntax structure, it is a requirement for bitstream conformance that XXX_info_in_ph_flag shall be equal to 1."

[0415] and / or

[0416] “When XXX_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0.”

[0417] When the picture header is in the slice header, this means that there is only one slice for the current picture. Therefore, making information sent or transmittable for both the slice and the picture does not increase the flexibility of the encoder or decoder because the parameters will be the same. In other words, if the information is in the picture header, the corresponding information in the slice header will be redundant. Similarly, if the information is in the slice header, the corresponding information in the picture header will be redundant. By enforcing the condition that such information can be in the picture header but not in the slice header when the picture header is in the slice header, the decoder implementation can be simplified by limiting the redundancy in the signaling.

[0418] QP (quantization parameter) increment

[0419] In an embodiment, when a picture header is signaled in a slice header, a QP increment is avoided from being signaled in a slice header. In an equivalent manner, when a QP increment is signaled in a slice header, a picture header is not signaled in a slice header. In another equivalent manner, when a QP increment is signaled in a picture header, a picture header is signaled in a slice header. In other words, the tool XXX is a QP increment.

[0420] Table 13 shows an approach that may be implemented such that when a picture header is signaled in a slice header, signaling of QP increment information is not authorized (ie, not allowed).

[0421] Table 13 Signaling of QP increment

[0422]

[0423] When the picture header is in the slice header (meaning there is only one slice for the current picture), the information can be sent in both the slice and picture headers without increasing the flexibility of the encoder or decoder, since the parameters will be the same. Therefore, to reduce decoder implementation complexity, it is better to have only one possible signaling of the QP delta information in one of the slice and picture headers to encode the same coding possibility (in this case the QP delta parameter (qp_delta_info)).

[0424] In the implementation of the first embodiment, the following conditions may be added to the semantics of qp_delta_info_in_ph_flag:

[0425] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that qp_delta_info_in_ph_flag shall be equal to 1."

[0426] and / or

[0427] “When qp_delta_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0.”

[0428] In another embodiment, as depicted in Table 14, decoding of QP delta parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set to 0. The modifications to the syntax are shown underlined. In the table, if QP delta information is signaled at the slice level (qp_delta_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0), the slice_qp_delta information of the slice header can be decoded.

[0429] Table 14 shows the modified partial slice header for QP increment

[0430]

[0431] In an embodiment, as depicted in Table 15, decoding of QP delta parameters in the picture header is systematically authorized when the value of the flag picture_header_in_slice_header_flag is set equal to 1. According to the table, the QP delta information of the slice header can be decoded only if the QP delta information is signaled in the picture header (qp_delta_info_in_ph_flag is equal to 1) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1).

[0432] Table 15 shows the modified partial picture header for QP increment

[0433]

[0434] Reference Picture List (RPL)

[0435] In one embodiment, when a picture header is signaled in a slice header, the reference picture list is avoided from being signaled in the slice header. In an equivalent manner, when a reference picture list is signaled in a slice header, the picture header is not signaled in the slice header. In another equivalent manner, when a reference picture list is signaled in a picture header, the picture header is signaled in the slice header. In other words, the tool XXX is an RPL. In other words, the tool XXX is an RPL.

[0436] Table 16 shows an implementation of this embodiment, where signaling of RPL is not authorized when the picture header is signaled in the slice header.

[0437] Table 16 Summary of RPL signaling

[0438]

[0439] When the picture header is in the slice header (meaning that there is only one slice for the current picture), the information can be sent in both the slice and picture headers without increasing the flexibility of the encoder or decoder because the parameters will be the same. According to this embodiment, the decoder implementation complexity is reduced because it is better to have only one possible signaling of information in one of the slice and picture headers to encode the same coding possibility (in this case, the reference picture list (RPL) information (rpl_info)).

[0440] In an embodiment, the following condition is added to the semantics of rpl_info_in_ph_flag:

[0441] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that rpl_info_in_ph_flag shall be equal to 1."

[0442] and / or

[0443] "When rpl_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0."

[0444] In an embodiment, as depicted in Table 17, decoding of reference picture list parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set to be equal to 0. In this table, if reference picture list information is signaled at the slice level (rpl_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0), the ref_pic_lists() information of the slice header can be decoded.

[0445] In an embodiment, as depicted in Table 17, when the picture header is in the slice header, the temporal parameters slice_collocated_from_l0_flag and slice_collocated_ref_idx cannot be decoded.

[0446] Table 17 shows the modified partial stripe header of RPL

[0447]

[0448]

[0449] In an embodiment, as depicted in Table 18, decoding of RPL parameters in the picture header is systematically authorized when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In this table, the RPL information of the picture header can be decoded only if the RPL information is signaled at the picture level (rpl_info_in_ph_flag is equal to 1) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1).

[0450] In an embodiment, as depicted in Table 18, when the picture header is in the slice header, the temporal parameters ph_collocated_from_flag and ph_collocated_ref_idx may be decoded.

[0451] Table 18 shows the modified partial picture header of RPL

[0452]

[0453]

[0454] Deblocking Filter (DBF)

[0455] In an embodiment, when the picture header is signaled in the slice header, the deblocking filter parameters are avoided from being signaled in the slice header. In an equivalent manner, when the deblocking filter parameters are signaled in the slice header, the picture header is not signaled in the slice header. In another equivalent manner, when the deblocking filter parameters are signaled in the picture header, the picture header is signaled in the slice header. In other words, the above-mentioned tool XXX is DBF. In other words, the above-mentioned tool XXX is DBF.

[0456] Table 19 shows an implementation according to this embodiment, where signaling of DBF is not authorized when the picture header is signaled in the slice header.

[0457] Table 19 Summary of DBF signaling

[0458]

[0459] When the picture header is in the slice header, since there is only one slice for the current picture, sending the information in the slice or picture does not increase the flexibility of the encoder or decoder because the parameters are the same. Therefore, to reduce decoder implementation complexity, it is better to have only one possible signaling of the DBF information to encode the same coding possibility.

[0460] In an embodiment, the following condition is added to the semantics of dbf_info_in_ph_flag:

[0461] "When the slice header of the referenced PPS contains the PH syntax structure, it is a requirement for bitstream conformance that dbf_info_in_ph_flag shall be equal to 1."

[0462] and / or

[0463] "When dbf_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0."

[0464] In an embodiment, as depicted in Table 20, DBF parameters in the slice header are authorized only when the value of the flag picture_header_in_slice_header_flag is set equal to 0. In this table, if DBF information is signaled at the slice level (dbf_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0), the slice_deblocking_filter_override_flag flag of the slice header can be decoded.

[0465] Table 20 shows the modified partial slice header of DBF

[0466]

[0467] In an embodiment, as depicted in Table 21, DBF parameters in the picture header are systematically authorized when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In this table, the DBF information of the slice header can be decoded only if the DBF information is signaled in the picture header (dbf_info_in_ph_flag is equal to 1) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1).

[0468] Table 21 shows the modified partial picture header of DBF

[0469]

[0470] SAO (Sample Adaptive Offset)

[0471] In one embodiment, when a picture header is signaled in a slice header, SAO is avoided from being signaled in the slice header. In an equivalent manner, when SAO signaling is signaled in a slice header, the picture header is not signaled in the slice header. In another equivalent manner, when SAO signaling is signaled in a picture header, the picture header is signaled in the slice header. In other words, the above tool XXX is SAO.

[0472] Table 22 shows the embodiment in which the signaling of SAO is not authorized when the picture header is signaled in the slice header.

[0473] Table 22 Summary of SAO signaling

[0474]

[0475] When the picture header is in the slice header, since there is only one slice for the current picture, sending the information in the slice or picture does not increase the flexibility of the encoder or decoder because the parameters are the same. Therefore, in order to reduce the decoder implementation complexity, it is better to have only one possible signaling of the SAO information to encode the same coding possibility.

[0476] In an embodiment, the following condition is added to the semantics of sao_info_in_ph_flag:

[0477] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that sao_info_in_ph_flag shall be equal to 1."

[0478] and / or

[0479] “When sao_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0.”

[0480] In an embodiment, as depicted in Table 23, decoding of SAO parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set equal to 0. In this table, the slice_sao_luma_flag flag of the slice header can be decoded if SAO information is signaled at the slice level (sao_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0).

[0481] Table 23 shows the modified partial slice header of SAO

[0482]

[0483]

[0484] In an embodiment, as depicted in Table 24, decoding of SAO parameters in the picture header is systematically authorized when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In this table, the SAO information of the slice header can be decoded only if the SAO information is signaled in the picture header (sao_info_in_ph_flag is equal to 1) or the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1).

[0485] Table 24 shows the modified partial picture header of SAO

[0486]

[0487] Weighted Prediction (WP)

[0488] In one embodiment, when a picture header is signaled in a slice header, weighted prediction is avoided from being signaled in the slice header. In an equivalent manner, when weighted prediction is signaled in a slice header, the picture header is not signaled in the slice header. In another equivalent manner, when weighted prediction is signaled in a picture header, the picture header is signaled in the slice header. In other words, the tool XXX is WP.

[0489] As depicted in Table 25, when wp_info_in_ph_flag is set equal to 0 with the current syntax, WP parameters may be signaled in the slice header.

[0490] Table 25 shows an implementation of this embodiment, where signaling of WP is not authorized when the picture header is signaled in the slice header.

[0491] Table 25 Summary of WP signaling

[0492]

[0493] When the picture header is in the slice header, since there is only one slice for the current picture, sending the information in the slice or picture does not increase the flexibility of the encoder or decoder because the parameters are the same. Therefore, in order to reduce the decoder implementation complexity, it is better to have only one possible signaling of the WP information to encode the same coding possibility.

[0494] In an embodiment, the following condition is added to the semantics of wp_info_in_ph_flag:

[0495] "When the slice header of the referenced PPS contains the PH syntax structure, it is a requirement for bitstream conformance that wp_info_in_ph_flag shall be equal to 1."

[0496] and / or

[0497] "When wp_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0".

[0498] In an embodiment, as depicted in Table 26, decoding of WP parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set equal to 0. In this table, if WP information is signaled at the slice level (wp_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0), the pred_weight_table() function containing weighted prediction parameters can be decoded.

[0499] Table 26 shows the modified partial slice header of WP

[0500]

[0501] In an embodiment, as depicted in Table 27, decoding of WP parameters in the picture header is systematically authorized when the value of picture_header_in_slice_header_flag is set equal to 1. In this table, WP information can be decoded only if WP information is signaled in the picture header (wp_info_in_ph_flag equal to 1) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag equal to 1).

[0502] Table 27 shows the modified part of the picture header of WP

[0503]

[0504] ALF

[0505] In one embodiment, when the picture header is signaled in the slice header, the ALF is avoided from being signaled in the slice header. In an equivalent manner, when the ALF is signaled in the slice header, the picture header is not signaled in the slice header. In another equivalent manner, when the ALF is signaled in the picture header, the picture header is signaled in the slice header. In other words, the tool XXX is the ALF.

[0506] In fact, currently, when the picture header is signaled in the slice header (picture_header_in_slice_header_flag = 1) and when the ALF is signaled in the slice header (alf_info_in_ph_flag = 0), all parameters of the picture header should be parsed before obtaining the ALF APS ID. Therefore, the parsing complexity of some streaming applications is increased because all variables such as PPS, SPS, picture header, etc. should be kept in memory to parse the ALF APS ID.

[0507] Furthermore, when the picture header is in the slice header, since there is only one slice for the current picture, sending the information in the slice or picture does not increase the flexibility of the encoder or decoder since the parameters are the same. Therefore, to reduce decoder implementation complexity, it is better to have only one possible signaling to encode the same coding possibility.

[0508] Table 28 shows this embodiment, where signaling of ALF is not authorized when the picture header is signaled in the slice header.

[0509] Table 28 Summary of ALF signaling

[0510]

[0511] In an embodiment, the following condition is added to the semantics of alf_info_in_ph_flag:

[0512] "When the slice header of the referenced PPS contains the PH syntax structure, it is a requirement for bitstream conformance that alf_info_in_ph_flag shall be equal to 1."

[0513] and / or

[0514] “When alf_info_in_ph_flag is equal to 0, picture_header_in_slice_header_flag shall be equal to 0.”

[0515] In an embodiment, as depicted in Table 29, decoding of ALF parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set equal to 0. In this table, the ALF information of the slice header can be decoded only if ALF is enabled at the SPS level (sps_alf_enabled_flag is equal to 1) and if ALF information is signaled at the slice level (alf_info_in_ph_flag is equal to 0) and if the picture header is not sent in the slice header (picture_header_in_slice_header_flag is equal to 0).

[0516] Table 29 shows the modified partial slice header of ALF

[0517]

[0518]

[0519] In an embodiment, as depicted in Table 30, decoding of ALF parameters in the picture header is systematically authorized when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In this table, the ALF information of the slice header can be decoded only if ALF is enabled at the SPS level (sps_alf_enabled_flag equal to 1) and ALF information is signaled at the picture level (alf_info_in_ph_flag equal to 1) or the picture header is sent in the slice header (picture_header_in_slice_header_flag equal to 1).

[0520] Table 30 shows the modified partial picture header of ALF

[0521]

[0522]

[0523] All tools / parameters

[0524] In one embodiment, when the picture header is signaled in the slice header, all tools (and / or parameters) that can be signaled in the picture header or in the slice header are restricted to being signaled in the picture header. As mentioned in the above description, in an embodiment, the relevant tools are: QP increment information, reference picture list, deblocking filter, SAO weighted prediction, and ALF. However, other tools are also possible if they can be signaled in both the slice and picture headers.

[0525] This can be expressed by adding the following constraints:

[0526] “When at least one of the flags rpl_info_in_ph_flag, dbf_info_in_ph_flag, sao_info_in_ph_flag, alf_info_in_ph_flag, wp_info_in_ph_flag, qp_delta_info_in_ph_flag is set equal to 0, the value of picture_header_in_slice_header_flag shall be equal to 0.”

[0527] And / or by adding:

[0528] “When picture_header_flag_in_slice_header_flag is equal to 1, the flags rpl_info_in_ph_flag, dbf_info_in_ph_flag, sao_info_in_ph_flag, wp_info_in_ph_flag, qp_delta_info_in_ph_flag shall be equal to 1.”

[0529] And / or by adding the following constraints to each XXX_info_in_ph_flag:

[0530] "When the slice header of the referenced PPS contains the PH syntax structure, it is a requirement for bitstream conformance that XXX_info_in_ph_flag shall be equal to 1."

[0531] When all these parameters are signaled in the same header, the decoder implementation complexity is reduced, since it is best to have only one possible signaling to encode the same encoding possibility.

[0532] Example of a signaling sequence

[0533] In an alternative embodiment to the previous embodiment related to ALF, information related to the ALF APS ID in the slice header is set before the picture header structure as depicted in Table 31. With this embodiment, when the ALF is signaled in the slice header and when the picture header is signaled in the slice header, the APS ID can be quickly obtained without parsing all parameters of the picture header.

[0534] Table 31 shows the modified partial slice header

[0535]

[0536]

[0537] Example of the number of weights

[0538] In an embodiment, as depicted in the partial table of syntax element table 32, when the picture header is in the slice header, the number of weights for weighted prediction of the respective lists L0, L1 is decoded. Therefore, the signaling of the number of weights may be limited to the picture header.

[0539] Table 32: Partial weighted prediction parameter syntax

[0540]

[0541] Summary of embodiments where information is signaled in a slice header instead of a picture header

[0542] In one embodiment, when a picture header is signaled in a slice header, information that can be signaled in a picture header or in a slice header is signaled in a slice header instead of in a picture header. In an equivalent manner, when information that can be signaled in a picture header or in a slice header is signaled in a picture header, the picture header is not signaled in a slice header. In another equivalent manner, when information that can be signaled in a picture header or in a slice header is signaled in a slice header, the picture header is signaled in a slice header. Table 33 shows this embodiment, where the tool (or parameter) name is replaced by XXX. In this table, when a picture header is signaled in a slice header, parameter signaling in the picture header is not authorized.

[0543] Table 33 Summary of tool signal notifications

[0544]

[0545] In one embodiment, the following condition is added to the semantics of XXX_info_in_ph_flag:

[0546] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that XXX_info_in_ph_flag shall be equal to 0"

[0547] and / or

[0548] "When XXX_info_in_ph_flag is equal to 1, picture_header_in_slice_header_flag shall be equal to 0"

[0549] When the picture header is in the slice header, this means that there is only one slice for the current picture. Therefore, making information sent or transmittable for both the slice and the picture does not increase the flexibility of the encoder or decoder because the parameters will be the same. In other words, if the information is in the picture header, the corresponding information in the slice header will be redundant. Similarly, if the information is in the slice header, the corresponding information in the picture header will be redundant. The embodiments described herein simplify decoder implementation by limiting redundancy in signaling of identical encodings. In particular, embodiments allow information to be in the slice header instead of the picture header when the picture header is signaled in the slice header.

[0550] QP increment

[0551] In one embodiment, tool XXX is QP delta. In an embodiment, as depicted in Table 33, when the value of the flag picture_header_in_slice_header_flag is set to 1, decoding of the QP delta parameter in the slice header is authorized. In an equivalent manner, as depicted in Table 33, when the QP delta parameter is signaled in the picture header, picture_header_in_slice_header_flag is set to 0. In another equivalent manner, as depicted in Table 33, when the QP delta parameter is signaled in the slice header, picture_header_in_slice_header_flag is set to 1. In this table, if QP delta information is signaled at the slice level (qp_delta_info_in_ph_flag is equal to 0) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1), the slice header slice_qp_delta information can be decoded.

[0552] This can be obtained by adding to the semantics:

[0553] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that qp_delta_info_in_ph_flag shall be equal to 0."

[0554] and / or

[0555] “When qp_delta_info_in_ph_flag is equal to 1, picture_header_in_slice_header_flag shall be equal to 0.”

[0556] In an embodiment, as depicted in Table 35, decoding of QP delta parameters in the picture header is systematically avoided when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In this table, the QP delta information of the picture header can be decoded only if QP delta information is signaled in the picture header (qp_delta_info_in_ph_flag is equal to 1) and if picture_header_in_slice_header_flag is set equal to 0.

[0557] RPL (Reference Picture List)

[0558] In one embodiment, tool XXX is a reference picture list. In an embodiment, as depicted in Table 33, decoding of reference picture list parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set to 1. In an equivalent manner, as depicted in Table 33, when the reference picture list parameters are signaled in the picture header, picture_header_in_slice_header_flag is set to 0. In another equivalent manner, as depicted in Table 33, when the reference picture list parameters are signaled in the slice header, picture_header_in_slice_header_flag is set to 1. In this table, if the reference picture list information is signaled at the slice level (rpl_info_in_ph_flag is equal to 0) and if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1), then the ref_pic_list() information of the slice header can be decoded.

[0559] In an embodiment, as depicted in Table 34, when the picture header is in the slice header, the temporal parameters slice_collocated_from_l0_flag and slice_collocated_ref_idx may be decoded.

[0560] In an embodiment, decoding of RPL parameters in the picture header is systematically avoided when the value of the flag picture_header_in_slice_header_flag is set equal to 1, as depicted in Table 35. In this table, the RPL information of the picture header can be decoded only if RPL information is signaled at the picture level (rpl_info_in_ph_flag is equal to 1) and if picture_header_in_slice_header_flag is set equal to 0.

[0561] In an embodiment, as depicted in Table 35, when the picture header is in the slice header, the temporal parameters ph_collocated_from_l0_flag and ph_collocated_ref_idx cannot be decoded.

[0562] Deblocking filter (DBF)

[0563] In one embodiment, tool XXX is a deblocking filter (DBF). In an alternative or additional embodiment, as depicted in Table 33, when the value of the flag picture_header_in_slice_header_flag is set to 1, DBF parameters in the slice header are authorized. In an equivalent manner, as depicted in Table 33, when DBF parameters are signaled in the picture header, picture_header_in_slice_header_flag is set to 0. In another equivalent manner, as depicted in Table 33, when DBF parameters are signaled in the slice header, picture_header_in_slice_header_flag is set to 1. In this table, the slice_deblocking_filter_override_flag flag of the slice header can be decoded if DBF information is signaled at the slice level (dbf_info_in_ph_flag is equal to 0) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1).

[0564] In an embodiment, DBF parameters in the picture header are systematically avoided when the value of the flag picture_header_in_slice_header_flag is set equal to 1, as depicted in Table 35. In this table, the DBF information of the picture header can be decoded only if DBF information is signaled in the picture header (dbf_info_in_ph_flag is equal to 1) and if picture_header_in_slice_header_flag is equal to 0.

[0565] Sample Adaptive Offset (SAO)

[0566] In one embodiment, tool XXX is SAO (Sample Adaptive Offset). In an alternative or additional embodiment, as depicted in Table 33, SAO parameters in the slice header are authorized only when the value of the flag picture_header_in_slice_header_flag is set to 1. In an equivalent manner, as depicted in Table 33, when SAO parameters are signaled in the picture header, the value of picture_header_in_slice_header_flag is set to 0. In another equivalent manner, as depicted in Table 33, when SAO parameters are signaled in the slice header, picture_header_in_slice_header_flag is set to 1. In this table, if SAO information is signaled at the slice level (sao_info_in_ph_flag is equal to 0) and if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1), the slice header's slice_sao_luma_flag flag can be decoded.

[0567] In an embodiment, the SAO parameters in the picture header are systematically avoided when the value of the flag picture_header_in_slice_header_flag is set equal to 1, as depicted in Table 35. In this table, the SAO information of the picture header can be decoded only if SAO information is signaled in the picture header (sao_info_ph_flag is equal to 1) and if picture_header_in_slice_header_flag is set equal to 0.

[0568] WP (Weighted Prediction)

[0569] In one embodiment, tool XXX is WP (weighted prediction). In an embodiment, as depicted in Table 33, WP parameters in the slice header are authorized only when the value of the flag picture_header_in_slice_header_flag is set to 1. In an equivalent manner, as depicted in Table 33, when WP parameters are signaled in the picture header, picture_header_in_slice_header_flag is set to 0. In another equivalent manner, as depicted in Table 33, when WP parameters are signaled in the slice header, picture_header_in_slice_header_flag is set to 1. In this table, if WP information is signaled at the slice level (wp_info_in_ph_flag is equal to 0) or if the picture header is sent in the slice header (picture_header_in_slice_header_flag is equal to 1), the pred_weight_table() function containing weighted prediction parameters can be decoded.

[0570] In an additional embodiment, the decoding of WP parameters in the picture header is systematically avoided when the value of the flag picture_header_in_slice_header_flag is set equal to 1, as described in Table 35. In this table, the WP information can be decoded only if WP information is signaled in the picture header (wp_info_in_ph_flag is equal to 1) and if picture_header_in_slice_header_flag is set equal to 0.

[0571] ALF (Adaptive Loop Filter)

[0572] In one embodiment, tool XXX is an ALF (Adaptive Loop Filter). In an embodiment, as depicted in Table 33, decoding of ALF parameters in the slice header is authorized only when the value of the flag picture_header_in_slice_header_flag is set equal to 1. In an equivalent manner, as depicted in Table 33, when ALF parameters are signaled in the picture header, picture_header_in_slice_header_flag is set equal to 0. In another equivalent manner, as depicted in Table 33, when ALF parameters are signaled in the slice header, picture_header_in_slice_header_flag is set equal to 1. In this table, the ALF information of the slice header can be decoded only if ALF is enabled at the SPS level (sps_alf_enabled_flag is equal to 1) and if ALF information is signaled at the slice level (alf_info_in_ph_flag is equal to 1) and if the picture header is sent in the slice header (picture_hearder_in_slice_flag is equal to 1).

[0573] In an embodiment, decoding of ALF parameters in the picture header is systematically avoided when the value of picture_header_slice_header_flag is set equal to 1, as depicted in Table 35. In this table, the ALF information of the slice header can be decoded only if ALF is enabled at the SPS level (sps_alf_enabled_flag is equal to 1) and if ALF information is signaled at the picture level (alf_info_in_ph_flag is equal to 1) and if picture_hearder_in_slice_flag is set equal to 0.

[0574] Table 34 shows the modified portion of the slice header

[0575]

[0576]

[0577]

[0578] Table 35 shows the modified part of the picture header

[0579]

[0580]

[0581] All tools / parameters

[0582] In an embodiment, when a picture header is signaled in a slice header, all tools (and / or parameters) that can be signaled in a picture header or a slice header are signaled in the slice header. As mentioned in the above description of the embodiment, the relevant tools are: QP increment information, reference picture list, deblocking filter, SAO weighted prediction, and ALF. However, other tools are also possible if they can be signaled in both the slice and picture headers.

[0583] This can be expressed by adding the following constraints:

[0584] “When at least one of the flags rpl_info_in_ph_flag, dbf_info_in_ph_flag, sao_info_in_ph_flag, alf_info_in_ph_flag, wp_info_in_ph_flag, qp_delta_info_in_ph_flag is set equal to 1, the value of picture_header_in_slice_header_flag shall be equal to 0.”

[0585] And / or by adding the following constraints:

[0586] “When picture_header_in_slice_header_flag is equal to 1, the flags rpl_info_in_ph_flag, dbf_info_in_ph_flag, sao_info_in_ph_flag, wp_info_in_ph_flag, qp_delta_info_in_ph_flag shall be equal to 0.”

[0587] and / or by adding the following constraints to each XXX_info_in_ph_flag:

[0588] "When the slice header of the referenced PPS contains the PH syntax structure, it is a bitstream conformance requirement that XXX_info_in_ph_flag shall be equal to 0."

[0589] When all these parameters are signaled in the same header, the complexity of the decoder implementation is reduced, since it is better to have only one possible signaling for tools or parameters that will necessarily have the same value or property.

[0590] accomplish

[0591] Figure 10Systems 191 and 195 according to embodiments of the present invention are shown, comprising at least one of encoder 150 or decoder 100 and a communication network 199. According to embodiments, system 195 is configured to process and provide content (e.g., video and audio content for display / output or streaming) to a user, who accesses decoder 100, for example, via a user terminal including decoder 100 or a user interface of a user terminal capable of communicating with decoder 100. Such a user terminal may be a computer, mobile phone, tablet computer, or any other type of device capable of providing / displaying (provided / streamed) content to a user. System 195 obtains / receives bitstream 101 (in the form of a continuous stream or signal (e.g., when displaying / outputting earlier video / audio)) via communication network 199. According to embodiments, system 191 is configured to process content and store processed content, such as video and audio content processed for display / output / streaming at a later time. System 191 obtains / receives content comprising a raw image sequence 151, which is received and processed by encoder 150 (including filtering using a deblocking filter according to the present invention), and encoder 150 generates a bitstream 101 to be transmitted to decoder 100 via communication network 191. Bitstream 101 is then transmitted to decoder 100 in a variety of ways. For example, it can be pre-generated by encoder 150 and stored as data in a storage device in communication network 199 (e.g., on a server or cloud storage device) until a user requests content (i.e., bitstream data) from the storage device, at which time the data is transmitted / streamed from the storage device to decoder 100. System 191 may also include a content providing device for providing / streaming content information (e.g., the title of the content and other metadata / storage location data used to identify, select, and request the content) of the content stored in the storage device to the user (e.g., by transmitting data for a user interface to be displayed on a user terminal), and for receiving and processing user requests for content so that the requested content can be transmitted / streamed from the storage device to the user terminal. Alternatively, the encoder 150 generates the bitstream 101 and transmits / streams it directly to the decoder 100 when the user requests content. The decoder 100 then receives the bitstream 101 (or signal) and filters it using the deblocking filter according to the present invention to obtain / generate a video signal 109 and / or an audio signal, which the user terminal then uses to provide the requested content to the user.

[0592] Any step of the method / process according to the present invention or the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the step / function may be stored as one or more instructions or codes or programs or computer-readable media on one or more hardware-based processing units or sent via one or more hardware-based processing units and executed by one or more hardware-based processing units, such as a programmable computing machine, which may be a PC ("personal computer"), a DSP ("digital signal processor"), a circuit, a circuit system, a processor and memory, a general-purpose microprocessor or central processing unit, a microcontroller, an ASIC ("application-specific integrated circuit"), a field programmable logic array (FPGA), or other equivalent integrated or discrete logic circuit system. Thus, the term "processor" as used herein may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein.

[0593] Embodiments of the present invention may also be implemented by various devices or apparatuses, including wireless handsets, integrated circuits (ICs), or JC collections (e.g., chipsets). Various components, modules, or units are described herein to illustrate functional aspects of apparatuses / devices configured to perform these embodiments, but they do not necessarily need to be implemented by different hardware units. Instead, the various modules / units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors in conjunction with appropriate software / firmware.

[0594] The embodiments of the present invention can be implemented by a computer of a system or device that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium to perform one or more modules / units / functions in the above-described embodiments and / or includes one or more processing units or circuits for performing one or more functions in the above-described embodiments, and can be implemented by a method performed by a computer of the system or device, for example, reading and executing computer-executable instructions from a storage medium to perform one or more functions in the above-described embodiments and / or controlling one or more processing units or circuits to perform one or more functions in the above-described embodiments. The computer may include a network of separate computers or separate processing units to read and execute computer-executable instructions. The computer-executable instructions may be provided to the computer from a computer-readable medium such as a communication medium, for example, via a network or a tangible storage medium. The communication medium may be a signal / bit stream / carrier. Tangible storage media are “non-transitory computer-readable storage media” and may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), a storage device of a distributed computing system, an optical disk (such as a compact disk (CD), a digital versatile disk (DVD), or a Blu-ray disk (BD)). TM ), one or more of a flash memory device, a memory card, etc. At least some steps / functions may also be implemented in hardware by a machine or dedicated components such as an FPGA (“field programmable gate array”) or an ASIC (“application-specific integrated circuit”).

[0595] Figure 112 is a schematic block diagram of a computing device 2000 for implementing one or more embodiments of the present invention. The computing device 2000 may be a device such as a microcomputer, a workstation, or a lightweight portable device. The computing device 2000 includes a communication bus connected to the following: - a central processing unit (CPU) 2001, such as a microprocessor; - a random access memory (RAM) 2002 for storing executable code of the method of the embodiment of the present invention and registers suitable for recording variables and parameters required to implement the method for encoding or decoding at least a portion of an image according to the embodiment of the present invention, the storage capacity of which may be expanded, for example, by an optional RAM connected to an expansion port; - a read-only memory (ROM) 2003 for storing computer programs for implementing the embodiment of the present invention; - a network interface (NET) 2004, which is typically connected to a communication network through which digital data to be processed is transmitted or received. The network interface (NET) 2004 may be a single network interface, or may be composed of a group of different network interfaces (e.g., wired and wireless interfaces, or different kinds of wired or wireless interfaces). Under the control of a software application in 2001, data packets are written to a network interface for transmission or read from the network interface for reception; a user interface (UI) 2005, which can be used to receive input from a user or display information to a user; a hard disk (HD) 2006, which can be configured as a mass storage device; and an input / output module (IO) 2007, which can be used to receive and send data from and to external devices (such as a video source or display). Executable code can be stored in ROM 2003, on HD 2006, or on a removable digital medium such as a disk. According to a variation, the executable code of a program can be received via NET 2004 via a communications network for storage in one of the storage components of computing device 2000 (such as HD 2006) prior to execution. CPU 2001 is adapted to control and direct the execution of instructions or portions of software code of one or more programs according to embodiments of the present invention, the instructions being stored in one of the aforementioned storage components. For example, after power-up, CPU 2001 is capable of executing those instructions relating to a software application from main RAM memory 2002 after loading instructions from program ROM 2003 or HD 2006. Such a software application, when executed by CPU 2001, causes the steps of the method according to the invention to be performed.

[0596] It will also be appreciated that, according to other embodiments of the present invention, a decoder according to the above-described embodiments is provided in a user terminal such as a computer, a mobile phone (cellular phone), a tablet, or any other type of apparatus capable of providing / displaying content to a user (e.g., a display device). According to yet another embodiment, an encoder according to the above-described embodiments is provided in an image capture device that also includes a camera, a video camera, or a webcam (e.g., a closed-circuit television or video surveillance camera) for capturing and providing content for encoding by the encoder. See below. Figure 11 and 12 Two such examples are provided.

[0597] Web camera

[0598] Figure 11 21 is a diagram illustrating a network camera system 2100 including a network camera 2102 and a client device 2104 .

[0599] The network camera 2102 includes an imaging unit 2106 , an encoding section 2108 , a communication unit 2110 , and a control unit 2112 .

[0600] The network camera 2102 and the client device 2104 are connected to each other via the network 200 so as to be able to communicate with each other.

[0601] The camera unit 2106 includes a lens and an image sensor (eg, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS)), and captures an image of a subject and generates image data based on the image. The image may be a still image or a video image.

[0602] The encoding section 2108 encodes the image data by using the encoding method described above.

[0603] The communication unit 2110 of the network camera 2102 transmits the encoded image data encoded by the encoding section 2108 to the client device 2104 .

[0604] Furthermore, the communication unit 2110 receives commands from the client device 2104. The commands include commands for setting parameters for encoding by the encoding section 2108.

[0605] The control unit 2112 controls other units in the network camera 2102 according to the commands received by the communication unit 2110 .

[0606] The client device 2104 includes a communication unit 2114 , a decoding section 2116 , and a control unit 2118 .

[0607] The communication unit 2114 of the client device 2104 transmits a command to the network camera 2102 .

[0608] Furthermore, the communication unit 2114 of the client device 2104 receives the encoded image data from the network camera 2102 .

[0609] The decoding section 2116 decodes the encoded image data by using the decoding method described above.

[0610] The control unit 2118 of the client device 2104 controls other units in the client device 2104 according to user operations or commands received by the communication unit 2114 .

[0611] The control unit 2118 of the client device 2104 controls the display device 2120 to display the image decoded by the decoding section 2116 .

[0612] The control unit 2118 of the client device 2104 also controls the display device 2120 to display a GUI (Graphical User Interface) for specifying values ​​of parameters of the network camera 2102 (including parameters used for encoding by the encoding section 2108 ).

[0613] The control unit 2118 of the client device 2104 also controls other units in the client device 2104 according to user operation input to the GUI displayed by the display device 2120 .

[0614] The control unit 2118 of the client device 2104 controls the communication unit 2114 of the client device 2104 according to user operation input to the GUI displayed by the display device 2120 to transmit a command for specifying the value of the parameter of the network camera 2102 to the network camera 2102 .

[0615] smartphone

[0616] Figure 12 2 is a diagram illustrating a smartphone 2200 .

[0617] The smartphone 2200 includes a communication unit 2202 , a decoding section 2204 , a control unit 2206 , a display unit 2208 , an image recording device 2210 , and a sensor 2212 .

[0618] The communication unit 2202 receives the encoded image data via the network 200 .

[0619] The decoding section 2204 decodes the encoded image data received by the communication unit 2202 .

[0620] The decoding section 2204 decodes the encoded image data by using the decoding method described above.

[0621] The control unit 2206 controls other units in the smartphone 2200 according to user operations or commands received by the communication unit 2202 .

[0622] For example, the control unit 2206 controls the display unit 2208 to display the image decoded by the decoding section 2204 .

[0623] Although the present invention has been described with reference to the embodiments, it will be understood that the present invention is not limited to the disclosed embodiments. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the appended claims. All features disclosed in this specification (including any appended claims, abstracts and drawings), and / or all steps of any method or process disclosed, may be combined in any combination, except for at least some mutually exclusive combinations of such features and / or steps. Unless expressly stated otherwise, each feature disclosed in this specification (including any appended claims, abstracts and drawings) may be replaced by alternative features for the same, equivalent or similar purposes. Therefore, unless expressly stated otherwise, each feature disclosed is merely an example of a general series of equivalent or similar features.

[0624] It should also be understood that any results of the above-described comparisons, determinations, evaluations, selections, performance, performance, or considerations (e.g., selections made during an encoding or filtering process) may be indicated in data in the bitstream (e.g., a flag or data indicating the results) or may be determined / inferred from data in the bitstream, such that the indicated or determined / inferred results may be used in processing rather than actually being compared, determined, evaluated, selected, performed, performed, or considered, for example, during a decoding process.

[0625] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

[0626] Reference signs appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

1. A method for decoding video data from a bitstream, the bitstream comprising a picture header syntax structure, a slice header, and a first flag, wherein: The picture header syntax structure includes syntax elements to be used when decoding one or more slices, the slice header includes syntax elements to be used when decoding the slice, and the first flag indicates whether the picture header syntax structure is present in the slice header, wherein the method comprises: decoding the video data from the bitstream, Wherein, in a case where information that can be signaled in the picture header syntax structure or in the slice header is signaled in the picture header syntax structure, the first flag should have a value indicating that the picture header syntax structure does not exist in the slice header, The information that can be signaled in the picture header syntax structure or the slice header is an adaptive parameter set ID for adaptive loop filtering (ALF), and the adaptive parameter set (APS) indicated by the adaptive parameter set ID includes a second flag indicating whether a cropping index related to ALF is to be decoded for luma, and In the case where reference picture list information, i.e., RPL information, exists in the picture header syntax structure, the first flag should have a value indicating that the picture header syntax structure does not exist in the slice header.

2. The method according to claim 1, further comprising: A first syntax element indicating whether the information is signaled in the picture header syntax structure is parsed, and the information is allowed to be parsed from only one of the slice header and the picture header syntax structure based on the first syntax element.

3. The method according to claim 2, wherein: The first syntax element is a flag in a picture parameter set.

4. The method according to claim 2, wherein: In case the first syntax element indicates that the information is signaled in the picture header syntax structure, parsing the information from the slice header is not allowed.

5. The method according to claim 1, wherein The picture header syntax structure is picture_header_structure().

6. The method according to claim 1, wherein The second flag is alf_luma_clip_flag, and each of the clipping indexes corresponds to alf_luma_clip_idx.

7. The method according to claim 1, wherein The adaptive parameter set indicated by the adaptive parameter set ID, ie, the APS, includes information corresponding to the number of filters for luma.

8. The method according to claim 1, wherein The first flag is decoded from the slice header.

9. A method of encoding video data into a bitstream, the bitstream comprising a picture header syntax structure, a slice header, and a first flag, wherein: The picture header syntax structure includes syntax elements to be used when decoding one or more slices, the slice header includes syntax elements to be used when decoding the slice, and the first flag indicates whether the picture header syntax structure is present in the slice header, wherein the method comprises: encoding the video data into the bitstream, Wherein, in a case where information that can be signaled in the picture header syntax structure or in the slice header is signaled in the picture header syntax structure, the first flag should have a value indicating that the picture header syntax structure does not exist in the slice header, The information that can be signaled in the picture header syntax structure or the slice header is an adaptive parameter set ID for adaptive loop filtering (ALF), and the adaptive parameter set (APS) indicated by the adaptive parameter set ID includes a second flag indicating whether a cropping index related to ALF is to be decoded for luma, and In the case where reference picture list information, i.e., RPL information, exists in the picture header syntax structure, the first flag should have a value indicating that the picture header syntax structure does not exist in the slice header.

10. The method according to claim 9, further comprising: A first syntax element indicating whether the information is signaled in the picture header syntax structure is encoded, and encoding of the information into only one of the slice header and the picture header syntax structure is allowed based on the first syntax element.

11. The method according to claim 10, wherein: The first syntax element is a flag in a picture parameter set.

12. The method according to claim 10, wherein: In case the first syntax element indicates that the information is signaled in the picture header syntax structure, encoding of the information in the slice header is not allowed.

13. The method according to claim 9, wherein The picture header syntax structure is picture_header_structure().

14. The method according to claim 9, wherein The second flag is alf_luma_clip_flag, and each of the clipping indexes corresponds to alf_luma_clip_idx.

15. The method according to claim 9, wherein The first flag is signaled in the slice header.

16. An apparatus for decoding video data from a bitstream, configured to perform the method according to any one of claims 1 to 8.

17. An apparatus for encoding video data into a bitstream, configured to perform the method according to any one of claims 9 to 15.

18. A computer-readable storage medium storing a computer program which, when run on a computer or a processor, causes the computer or the processor to perform the method according to any one of claims 1 to 15.

19. A computer program product comprising a computer program which, when run on a computer or a processor, causes the computer or the processor to perform the method according to any one of claims 1 to 15.

Images