Patent Description:
This disclosure relates to video encoding and video decoding.

<CIT> relates to a method for encoding and decoding a quantized matrix and an apparatus using same, the method for encoding a quantized matrix according to the present invention comprising the steps of: determining a quantization matrix to be used for quantization and quantizing; determining the prediction method used for the quantization of the quantization matrix; and encoding quantization matrix information on the basis of the determined prediction method, wherein the prediction method can be either a prediction method between coefficients in the quantization matrix or a duplicate of the quantization matrix. <CIT> discloses a method and a device for encoding/decoding an image. The method for decoding an image comprises the steps of: decoding information on a quantization matrix; and restoring the quantization matrix on the basis of the information on the quantization matrix, wherein the information on the quantization matrix includes information indicating a DC value of the quantization matrix and/or information indicating differential values of quantization matrix coefficients. <NPL> relates to quantization signaling and prediction.

The invention is defined in the independent claims, to which the reader is now directed. Preferred or advantageous embodiments are set out in the dependent claims.

Video coding (e.g., video encoding and/or video decoding) typically involves predicting a block of video data from either an already coded block of video data in the same picture (e.g., intra prediction) or an already coded block of video data in a different picture (e.g., inter prediction). In some instances, the video encoder also calculates residual data by comparing the prediction block to the original block. Thus, the residual data represents a difference between the prediction block and the original block. To reduce the number of bits needed to signal the residual data, the video encoder transforms and quantizes the residual data and signals the transformed and quantized residual data in the encoded bitstream. A video encoder may uniformly quantize the transformed residual data based on a value of a quantization parameter (QP). The video encoder may additionally or alternatively, perform a frequency-based quantization of the transformed residual data using a quantization matrix, also referred to as a scaling matrix, which results in different coefficients (associated with different frequencies) being quantized differently. As will be explained in more detail below, the values for a scaling matrix are signaled using a scaling list. The compression achieved by the transform and quantization processes may be lossy, meaning that transform and quantization processes may introduce distortion into the decoded video data.

A video decoder decodes and adds the residual data to the prediction block to produce a reconstructed video block that matches the original video block more closely than the prediction block alone. Due to the loss introduced by the transforming and quantizing of the residual data, the first reconstructed block may have distortion or artifacts. One common type of artifact or distortion is referred to as blocking artifacts, where visible discontinuities across the boundaries of the coding blocks is often observed primarily due to the different coding methods of neighboring coding blocks.

To further improve the quality of decoded video, a video decoder can perform one or more filtering operations on the reconstructed video blocks. Examples of these filtering operations include deblocking filtering, sample adaptive offset (SAO) filtering, and adaptive loop filtering (ALF). Parameters for these filtering operations may either be determined by a video encoder and explicitly signaled in the encoded video bitstream or may be implicitly determined by a video decoder without needing the parameters to be explicitly signaled in the encoded video bitstream.

As will be explained in more detail below, video data can include a luma component and two chroma components. In some video bitstreams, the chroma components may be sub-sampled relative to the luma component, but in other instances, the chroma components may not be sub-sampled. Additionally, in some video bitstreams the decoding of chroma components may be dependent on the luma components. That is, information associated with the luma component may be needed to decode the chroma components. Other types of video bitstreams, however, such as monochrome video bitstreams or video bitstreams encoded using separate color plane coding, only use the decoding processes from luma components and do not use the decoding processes for chroma components.

This disclosure describes techniques for the signaling of scaling lists in video encoding and decoding. Scaling matrices may be signaled using scaling lists. Scaling matrices may be defined for each transform block size and prediction type of the block, and the matrices may be derived from scaling lists. For video bitstreams that do not include chroma components, scaling lists are typically not signaled for the chroma components.

To reduce the bit overhead associated with signaling scaling lists, for some new scaling lists, a video decoder may copy an already decoded scaling list or use an already decoded scaling list as a predictor for the new scaling list. In some coding scenarios, however, a video encoder may include signaling that causes a video decoder to predict a new scaling list from an already decoded scaling list that does not actually exist. For example, the video data may be monochrome video data or separate color plane coded video data that does not include scaling lists for chroma components, but a video encoder may signal to a video decoder that a scaling list associated with a chroma component is to be used as a scaling list predictor. To prevent a decoder from crashing, or otherwise not properly decoding video data in such a scenario, the techniques of this disclosure include determining a new scaling matrix based on a set of default values in response to determining that a new scaling list for a set of scaling lists is to be predicted from a reference scaling list that has not been previously decoded. Such techniques, may prevent a decoder from crashing, or otherwise not properly decoding video, in this scenario.

<FIG> is a block diagram illustrating an example video encoding and decoding system <NUM> that may perform the techniques of this disclosure. The techniques of this disclosure are generally directed to coding (encoding and/or decoding) video data. In general, video data includes any data for processing a video. Thus, video data may include raw, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

As shown in <FIG>, system <NUM> includes a source device <NUM> that provides encoded video data to be decoded and displayed by a destination device <NUM>, in this example. In particular, source device <NUM> provides the video data to destination device <NUM> via a computer-readable medium <NUM>. Source device <NUM> and destination device <NUM> may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming device, broadcast receiver devices, or the like. In some cases, source device <NUM> and destination device <NUM> may be equipped for wireless communication, and thus may be referred to as wireless communication devices.

In the example of <FIG>, source device <NUM> includes video source <NUM>, memory <NUM>, video encoder <NUM>, and output interface <NUM>. Destination device <NUM> includes input interface <NUM>, video decoder <NUM>, memory <NUM>, and display device <NUM>. In accordance with this disclosure, video encoder <NUM> of source device <NUM> and video decoder <NUM> of destination device <NUM> may be configured to apply the techniques for scaling list signaling described herein. Thus, source device <NUM> represents an example of a video encoding device, while destination device <NUM> represents an example of a video decoding device. In other examples, a source device and a destination device may include other components or arrangements. For example, source device <NUM> may receive video data from an external video source, such as an external camera. Likewise, destination device <NUM> may interface with an external display device, rather than include an integrated display device.

System <NUM> as shown in <FIG> is merely one example. In general, any digital video encoding and/or decoding device may perform techniques for scaling list signaling described herein. Source device <NUM> and destination device <NUM> are merely examples of such coding devices in which source device <NUM> generates coded video data for transmission to destination device <NUM>. This disclosure refers to a "coding" device as a device that performs coding (encoding and/or decoding) of data. Thus, video encoder <NUM> and video decoder <NUM> represent examples of coding devices, in particular, a video encoder and a video decoder, respectively. In some examples, source device <NUM> and destination device <NUM> may operate in a substantially symmetrical manner such that each of source device <NUM> and destination device <NUM> includes video encoding and decoding components. Hence, system <NUM> may support one-way or two-way video transmission between source device <NUM> and destination device <NUM>, e.g., for video streaming, video playback, video broadcasting, or video telephony.

In general, video source <NUM> represents a source of video data (i.e., raw, unencoded video data) and provides a sequential series of pictures (also referred to as "frames") of the video data to video encoder <NUM>, which encodes data for the pictures. Video source <NUM> of source device <NUM> may include a video capture device, such as a video camera, a video archive containing previously captured raw video, and/or a video feed interface to receive video from a video content provider. As a further alternative, video source <NUM> may generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder <NUM> encodes the captured, pre-captured, or computer-generated video data. Video encoder <NUM> may rearrange the pictures from the received order (sometimes referred to as "display order") into a coding order for coding. Video encoder <NUM> may generate a bitstream including encoded video data. Source device <NUM> may then output the encoded video data via output interface <NUM> onto computer-readable medium <NUM> for reception and/or retrieval by, e.g., input interface <NUM> of destination device <NUM>.

Memory <NUM> of source device <NUM> and memory <NUM> of destination device <NUM> represent general purpose memories. In some examples, memories <NUM>, <NUM> may store raw video data, e.g., raw video from video source <NUM> and raw, decoded video data from video decoder <NUM>. Additionally or alternatively, memories <NUM>, <NUM> may store software instructions executable by, e.g., video encoder <NUM> and video decoder <NUM>, respectively. Although memory <NUM> and memory <NUM> are shown separately from video encoder <NUM> and video decoder <NUM> in this example, it should be understood that video encoder <NUM> and video decoder <NUM> may also include internal memories for functionally similar or equivalent purposes. Furthermore, memories <NUM>, <NUM> may store encoded video data, e.g., output from video encoder <NUM> and input to video decoder <NUM>. In some examples, portions of memories <NUM>, <NUM> may be allocated as one or more video buffers, e.g., to store raw, decoded, and/or encoded video data.

Computer-readable medium <NUM> may represent any type of medium or device capable of transporting the encoded video data from source device <NUM> to destination device <NUM>. In one example, computer-readable medium <NUM> represents a communication medium to enable source device <NUM> to transmit encoded video data directly to destination device <NUM> in real-time, e.g., via a radio frequency network or computer-based network. Output interface <NUM> may modulate a transmission signal including the encoded video data, and input interface <NUM> may demodulate the received transmission signal, according to a communication standard, such as a wireless communication protocol. The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from source device <NUM> to destination device <NUM>.

In some examples, source device <NUM> may output encoded data from output interface <NUM> to storage device <NUM>. Similarly, destination device <NUM> may access encoded data from storage device <NUM> via input interface <NUM>. Storage device <NUM> may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.

In some examples, source device <NUM> may output encoded video data to file server <NUM> or another intermediate storage device that may store the encoded video data generated by source device <NUM>. Destination device <NUM> may access stored video data from file server <NUM> via streaming or download.

File server <NUM> may be any type of server device capable of storing encoded video data and transmitting that encoded video data to the destination device <NUM>. File server <NUM> may represent a web server (e.g., for a website), a server configured to provide a file transfer protocol service (such as File Transfer Protocol (FTP) or File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and/or a network attached storage (NAS) device. File server <NUM> may, additionally or alternatively, implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, or the like.

Destination device <NUM> may access encoded video data from file server <NUM> through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on file server <NUM>. Input interface <NUM> may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server <NUM>, or other such protocols for retrieving media data.

Output interface <NUM> and input interface <NUM> may represent wireless transmitters/receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of a variety of IEEE <NUM> standards, or other physical components. In examples where output interface <NUM> and input interface <NUM> comprise wireless components, output interface <NUM> and input interface <NUM> may be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as <NUM>, <NUM>-LTE (Long-Term Evolution), LTE Advanced, <NUM>, or the like. In some examples where output interface <NUM> comprises a wireless transmitter, output interface <NUM> and input interface <NUM> may be configured to transfer data, such as encoded video data, according to other wireless standards, such as an IEEE <NUM> specification, an IEEE <NUM> specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. In some examples, source device <NUM> and/or destination device <NUM> may include respective system-on-a-chip (SoC) devices. For example, source device <NUM> may include an SoC device to perform the functionality attributed to video encoder <NUM> and/or output interface <NUM>, and destination device <NUM> may include an SoC device to perform the functionality attributed to video decoder <NUM> and/or input interface <NUM>.

Input interface <NUM> of destination device <NUM> receives an encoded video bitstream from computer-readable medium <NUM> (e.g., a communication medium, storage device <NUM>, file server <NUM>, or the like). The encoded video bitstream may include signaling information defined by video encoder <NUM>, which is also used by video decoder <NUM>, such as syntax elements having values that describe characteristics and/or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, or the like). Display device <NUM> displays decoded pictures of the decoded video data to a user. Display device <NUM> may represent any of a variety of display devices such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

Video encoder <NUM> and video decoder <NUM> may operate according to a video coding standard, such as ITU-T H. <NUM>, also referred to as High Efficiency Video Coding (HEVC) or extensions thereto, such as the multi-view and/or scalable video coding extensions. Alternatively, video encoder <NUM> and video decoder <NUM> may operate according to other proprietary or industry standards, such as ITU-T H. <NUM>, also referred to as Versatile Video Coding (VVC). A recent draft of the VVC standard is described in <NPL> (hereinafter "VVC Draft <NUM>"). The techniques of this disclosure, however, are not limited to any particular coding standard.

As another example, video encoder <NUM> and video decoder <NUM> may be configured to operate according to VVC. According to VVC, a video coder (such as video encoder <NUM>) partitions a picture into a plurality of coding tree units (CTUs). Video encoder <NUM> may partition a CTU according to a tree structure, such as a quadtree-binary tree (QTBT) structure or Multi-Type Tree (MTT) structure. The QTBT structure removes the concepts of multiple partition types, such as the separation between CUs, PUs, and TUs of HEVC. A QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. A root node of the QTBT structure corresponds to a CTU. Leaf nodes of the binary trees correspond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using a quadtree (QT) partition, a binary tree (BT) partition, and one or more types of triple tree (TT) (also called ternary tree (TT)) partitions. A triple or ternary tree partition is a partition where a block is split into three sub-blocks. In some examples, a triple or ternary tree partition divides a block into three sub-blocks without dividing the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT), may be symmetrical or asymmetrical.

In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture that has three sample arrays, or a CTB of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples. A CTB may be an NxN block of samples for some value of N such that the division of a component into CTBs is a partitioning. A component is an array or single sample from one of the three arrays (luma and two chroma) that compose a picture in <NUM>:<NUM>:<NUM>, <NUM>:<NUM>:<NUM>, or <NUM>:<NUM>:<NUM> color format or the array or a single sample of the array that compose a picture in monochrome format. In some examples, a coding block is an MxN block of samples for some values of M and N such that a division of a CTB into coding blocks is a partitioning.

The blocks (e.g., CTUs or CUs) may be grouped in various ways in a picture. As one example, a brick may refer to a rectangular region of CTU rows within a particular tile in a picture. A tile may be a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements (e.g., such as in a picture parameter set). A tile row refers to a rectangular region of CTUs having a height specified by syntax elements (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile.

The bricks in a picture may also be arranged in a slice. A slice may be an integer number of bricks of a picture that may be exclusively contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes either a number of complete tiles or only a consecutive sequence of complete bricks of one tile.

Some examples of VVC also provide an affine motion compensation mode, which may be considered an inter-prediction mode. In affine motion compensation mode, video encoder <NUM> may determine two or more motion vectors that represent non-translational motion, such as zoom in or out, rotation, perspective motion, or other irregular motion types.

To perform intra-prediction, video encoder <NUM> may select an intra-prediction mode to generate the prediction block. Some examples of VVC provide sixty-seven intra-prediction modes, including various directional modes, as well as planar mode and DC mode. In general, video encoder <NUM> selects an intra-prediction mode that describes neighboring samples to a current block (e.g., a block of a CU) from which to predict samples of the current block. Such samples may generally be above, above and to the left, or to the left of the current block in the same picture as the current block, assuming video encoder <NUM> codes CTUs and CUs in raster scan order (left to right, top to bottom).

As noted above, following any transforms to produce transform coefficients, video encoder <NUM> may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing the quantization process, video encoder <NUM> may reduce the bit depth associated with some or all of the transform coefficients. For example, video encoder <NUM> may round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, video encoder <NUM> may perform a bitwise right-shift of the value to be quantized.

Following quantization, video encoder <NUM> may scan the transform coefficients, producing a one-dimensional vector from the two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and to place lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In some examples, video encoder <NUM> may utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, video encoder <NUM> may perform an adaptive scan. After scanning the quantized transform coefficients to form the one-dimensional vector, video encoder <NUM> may entropy encode the one-dimensional vector, e.g., according to context-adaptive binary arithmetic coding (CABAC). Video encoder <NUM> may also entropy encode values for syntax elements describing metadata associated with the encoded video data for use by video decoder <NUM> in decoding the video data.

In general, video decoder <NUM> performs a reciprocal process to that performed by video encoder <NUM> to decode the encoded video data of the bitstream. For example, video decoder <NUM> may decode values for syntax elements of the bitstream using CABAC in a manner substantially similar to, albeit reciprocal to, the CABAC encoding process of video encoder <NUM>. The syntax elements may define partitioning information for partitioning of a picture into CTUs, and partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements may further define prediction and residual information for blocks (e.g., CUs) of video data.

This disclosure may generally refer to "signaling" certain information, such as syntax elements. The term "signaling" may generally refer to the communication of values for syntax elements and/or other data used to decode encoded video data. That is, video encoder <NUM> may signal values for syntax elements in the bitstream. In general, signaling refers to generating a value in the bitstream. As noted above, source device <NUM> may transport the bitstream to destination device <NUM> substantially in real time, or not in real time, such as might occur when storing syntax elements to storage device <NUM> for later retrieval by destination device <NUM>.

<FIG> are conceptual diagrams illustrating an example quadtree binary tree (QTBT) structure <NUM>, and a corresponding coding tree unit (CTU) <NUM>. The solid lines represent quadtree splitting, and dotted lines indicate binary tree splitting. In each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which splitting type (i.e., horizontal or vertical) is used, where <NUM> indicates horizontal splitting and <NUM> indicates vertical splitting in this example. For the quadtree splitting, there is no need to indicate the splitting type, because quadtree nodes split a block horizontally and vertically into <NUM> sub-blocks with equal size. Accordingly, video encoder <NUM> may encode, and video decoder <NUM> may decode, syntax elements (such as splitting information) for a region tree level of QTBT structure <NUM> (i.e., the solid lines) and syntax elements (such as splitting information) for a prediction tree level of QTBT structure <NUM> (i.e., the dashed lines). Video encoder <NUM> may encode, and video decoder <NUM> may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure <NUM>.

In one example of the QTBT partitioning structure, the CTU size is set as 128x128 (luma samples and two corresponding 64x64 chroma samples), the MinQTSize is set as 16x16, the MaxBTSize is set as 64x64, the MinBTSize (for both width and height) is set as <NUM>, and the MaxBTDepth is set as <NUM>. The quadtree partitioning is applied to the CTU first to generate quad-tree leaf nodes. The quadtree leaf nodes may have a size from 16x16 (i.e., the MinQTSize) to 128x128 (i.e., the CTU size). If the quadtree leaf node is 128x128, the leaf quadtree node will not be further split by the binary tree, because the size exceeds the MaxBTSize (i.e., 64x64, in this example). Otherwise, the quadtree leaf node will be further partitioned by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has the binary tree depth as <NUM>. When the binary tree depth reaches MaxBTDepth (<NUM>, in this example), no further splitting is permitted. A binary tree node having a width equal to MinBTSize (<NUM>, in this example) implies that no further vertical splitting (that is, dividing of the width) is permitted for that binary tree node. Similarly, a binary tree node having a height equal to MinBTSize implies no further horizontal splitting (that is, dividing of the height) is permitted for that binary tree node. As noted above, leaf nodes of the binary tree are referred to as CUs, and are further processed according to prediction and transform without further partitioning.

Video encoder <NUM> and video decoder <NUM> may be configured to process quantization parameters. QP values are used to determine the step size to be used for quantizing/inverse-quantizing the coefficients. QP values are specified in the range of - QpBdOffset to <NUM>, inclusive, where <NUM> is the maximum QP value. QpBdOffset is specified as a fixed value for a particular bit depth, derived as <NUM>*(bitDepth - <NUM>). The QP prime value, calculated by adding QpBdOffset to the specified QP value, is used to derive the actual step size. For ease of description, the QP and QP prime value may be used interchangeably in the rest of the description with the understanding that the QP value may be only used in most QP derivation processes, and the QP prime value may be only used at the final stage just before determining the step size. A change of QP value by <NUM> roughly indicates a change in the step size by <NUM>%, and a change of QP value by <NUM> corresponds to changing the step size by a factor of <NUM>. A higher quantization parameter value means a larger quantization step size and more coarse representation of the coefficients being quantized.

Video encoder <NUM> and video decoder <NUM> may be configured to process quantization and scaling matrices. In video coding, the residual obtained after the prediction operation is transformed using DCT2 or other transform operations. Subsequently, the transform coefficients are quantized, and the quantized coefficients are entropy coded.

The quantization process is controlled by two factors: quantization parameter and scaling matrices. A description of the quantization parameters is described above. At the decoder (e.g., video decoder <NUM>), a scale factor corresponding to the quantization parameter is determined. This scale factor is applied as follows: <MAT> where qP is the quantization parameter, levelScale[ ][ ] is array defined as below
The list levelScale[ ][ ] is specified as levelScale[ j ][ k ] = { { <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> }, { <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> } } with j = <NUM>. <NUM>, k = <NUM>.

A QP difference of six results in a bit-shift of <NUM>, and hence the scale associated with the QP is applied by a shift of (qP / <NUM>) and a scale calculated using qp % <NUM>.

In addition, a scaling parameter is applied for each coefficient. The scaling parameter may be different for different coefficients. The scaling factor associated with the scaling matrices is derived as follows:.

The final scaling factor used in the inverse quantization is obtained by multiplying the two scaling terms (from QP and scaling matrix) as follows:.

The scaled transform coefficient is derived as follows, and the result is then sent to the inverse quantization step.

A description of the signaling and definition of scaling matrices is described next. Video encoder <NUM> and video decoder <NUM> may be configured to process scaling matrices. Scaling matrices are a set of coefficients that are used to scale the transform coefficients. Two uses of scaling matrices are rate control and perceptual quality control. Rate control of video is often performed by adjusting the QP values of blocks. However, the QP difference results in a uniform scale factor applied to the entire block. Scaling matrices may be used for relative control between various coefficients within a transform block. For example, scaling matrices could be defined so that the low frequency coefficients are quantized less than the high frequency coefficients, which may be beneficial for content where there is less high frequency content. For perceptual quality control, scaling matrices may also be used to control the relative accuracy of coefficients within a transform block such that perceptual quality of the video is maintained with lower bitrate. Human Visual System (HVS)-based quantization using scaling matrices can provide better quality video for certain types of content.

The scaling matrices are signaled using scaling lists, which are signaled in the Adaptation parameter set (APS). The scaling list may be enabled or disabled in the SPS. If SPS indicates that scaling lists are enabled, additional signaling in the slice header may be used to switch the scaling matrices on and off.

Scaling matrices are defined for each transform block size and for prediction type of the block. The matrices are derived from scaling lists. The syntax of the scaling lists signaled in the PPS/SPS are as follows:.

The semantics of the scaling matrices are provided in Section <NUM>. <NUM> of JVET-Q2001 (e.g., VVC Draft <NUM>), and are reproduced here for reference.

Scaling list data semantics are described below.

The variables refld and matrixSize are derived as follows: <MAT> <MAT>.

The (matrixSize)x(matrixSize) array ScalingMatrixPred[ x ][ y ] with x = <NUM>. matrixSize - <NUM>, y = <NUM>. matrixSize - <NUM> and the variable ScalingMatrixDCPred may be derived as follows:.

scaling_list_dc_coef[ id - <NUM> ] is used to derive the value of the variable ScalingMatrixDC[ id - <NUM> ] when id is greater than <NUM> as follows: <MAT>.

When not present, the value of scaling_list_dc_coef[ id - <NUM> ] is inferred to be equal to <NUM>. The value of scaling_list_dc_coef[ id - <NUM> ] shall be in the range of -<NUM> to <NUM>, inclusive. The value of ScalingMatrixDCRec[ id - <NUM> ] shall be greater than <NUM>. scaling_list_delta_coef[ id ][ i ] specifies the difference between the current matrix coefficient ScalingList[ id ][ i ] and the previous matrix coefficient ScalingList[ id ][ i - <NUM> ], when scaling_list_copy_mode_flag[ id ] is equal to <NUM>. The value of scaling_list_delta_coef[ id ][ i ] shall be in the range of -<NUM> to <NUM>, inclusive. When scaling_list_copy_mode_flag[ id ] is equal to <NUM>, all elements of ScalingList[ id ] are set equal to <NUM>. The (matrixSize)x(matrixSize) array ScalingMatrixRec[ id ] is derived as follows: <MAT>.

The value of ScalingMatrixRec[ id ][ x ][ y ] shall be greater than <NUM>.

The scaling matrices, represented by the variable ScalingFactor[ wId ][ hId ][ matrixId ][ x ][ y ], are derived from the scaling list data. The wId and hId refer to the sizeID variable representing the size of the transform block. The sizeId and matrixId are given by the following tables:.

Some notable features of the scaling matrices and their derivation are provided below:.

A total of <NUM> scaling lists may be specified in a scaling list APS. Within each of the <NUM> categories, scaling lists may be predicted or copied from other scaling lists that have a smaller ID. For example, a scaling list with ID <NUM> (Category <NUM>) may be predicted from any scaling list with ID <NUM> to <NUM>, inclusive (also Category <NUM>) but cannot be predicted from Category <NUM> and <NUM>, or from scaling lists with IDs <NUM> and <NUM>. The prediction may either be a copy (values of reference scaling list are used without change) or a delta-prediction (delta values are signaled to the values of the reference scaling matrix). When the DC coefficient is also signaled for a particular sizeID, the DC coefficient may also be copied or predicted from the DC coefficient of the reference scaling list or explicitly signaled.

Video encoder <NUM> and video decoder <NUM> may be configured to perform chroma format and separate color plane coding. Common formats of video include three components - e.g., a luma component and two chroma components (Cb and Cr). However, some content may be coded as monochrome - i.e., only one component. This is also referred to as <NUM>:<NUM>:<NUM> chroma format indicating no chroma components. In some examples, when there are three components and there is no subsampling of chroma components, the chroma format is referred to as <NUM>:<NUM>:<NUM>. Although <NUM>:<NUM>:<NUM> content is typically coded by considering the luma and chroma components together, some applications code the three components in the <NUM>:<NUM>:<NUM> content independently - i.e., treating each component in <NUM>:<NUM>:<NUM> as monochrome. This separate coding is controlled by the syntax element separate _colour_plane_flag. There is no dependence between the decoding of any of the three components in this case.

The variable ChromaArrayType is referred to as follows:
Depending on the value of separate _colour_plane_flag, the value of the variable ChromaArrayType is assigned as follows:.

NOTE - The variable ChromaArrayType is derived as equal to <NUM> when separate _colour_plane_flag is equal to <NUM> and chroma_format_idc is equal to <NUM>. In the decoding process, the value of this variable is evaluated resulting in operations identical to that of monochrome pictures (when chroma_format_idc is equal to <NUM>).

Existing techniques may suffer from some potential problems. When the ChromaArrayType is zero (i.e., monochrome or <NUM> separate color plane coding), the scaling lists that correspond to the chroma components are not signaled. In this case, scaling_list_chroma_present_flag is set equal to <NUM>. Effectively fewer scaling lists are signaled when ChromaArrayType = <NUM>, as only scaling lists with IDs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are signaled. These scaling lists may be specified to be copied/predicted based on the syntax element scaling_list_copy_mode_flag, scaling _list_pred_mode_flag and scaling _list_pred_id_delta[ ]. However, the allowed values for scaling_list_pred_id_delta[ ] may result in a reference scaling list ID that is not valid/signaled. For example, for a scaling list with ID <NUM>, a pred ID delta value of <NUM> results in the reference scaling list ID to be <NUM> - which corresponds to a chroma scaling list that is absent. Such incorrect references could potentially result in a decoder crash, as there is no behavior defined in the specification for such a situation.

This disclosure describes techniques to improve the signaling of scaling lists in video coding and potentially address some of the problems introduced above. It is to be understood that one or more of these techniques may be used independently, or in combination with other techniques.

The description below provides examples of how one or more techniques described in this disclosure may be implemented.

In one example, the value range of scaling_list_pred_id_delta[ ] and the derivation of reference scaling list ID are modified such that the reference scaling list always points to a valid scaling list. scaling_list_pred_id_delta[ id ] specifies the reference scaling list used to derive the predicted scaling matrix ScalingMatrixPred[ id ]. When not present, the value of scaling_list_pred_id_delta[ id ] is inferred to be equal to <NUM>. The value of scaling_list_pred_id_delta[ id ] shall be in the range of <NUM> to maxIdDelta with maxIdDelta derived depending on id as follows:
<IMG>
The variables refld and matrixSize may be derived as follows:
<IMG>.

In some examples, the value of refld may be derived as follows:
<IMG>.

In some examples, the value of refld may be derived as follows:
<IMG>
<IMG>.

In another example, the derivation of refID and maxIdDelta may be updated as follows:
scaling_list_pred_id_delta[ id ] specifies the reference scaling list used to derive the predicted scaling matrix ScalingMatrixPred[ id ]. When not present, the value of scaling_list_pred_id_delta[ id ] is inferred to be equal to <NUM>. The value of scaling_list_pred_id_delta[ id ] shall be in the range of <NUM> to maxIdDelta with maxIdDelta derived depending on id as follows:
<IMG>
The variables refld and matrixSize are derived as follows:
<IMG>.

In some examples, the two or more chroma matrices may be added corresponding to max( nTbW, nTbH ) = <NUM> in Table <NUM>. In such cases, the matrices with indices <NUM>, <NUM>, <NUM> and <NUM> may be assigned to chroma and list ID <NUM> may be assigned to luma. In such a case, the derivation of refld and maxIdDelta may be further simplified as follows:
scaling_list_pred_id_delta[ id ] specifies the reference scaling list used to derive the predicted scaling matrix ScalingMatrixPred[ id ]. When not present, the value of scaling_list_pred_id_delta[ id ] is inferred to be equal to <NUM>. The value of scaling_list_pred_id_delta[ id ] shall be in the range of <NUM> to maxIdDelta with maxIdDelta derived depending on id as follows:
<IMG>.

The variables refld and matrixSize are derived as follows:
<IMG>.

In another example, the array lumaIndices may be set as {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. The value of refld may be derived as follows:
<IMG>.

The above definition of lumaIndices is only an example, and other definitions of lumaIndices may also be specified.

In another example, the inference of predicted scaling list is made such that when scaling list points to an invalid scaling list, a default behavior is specified for the scaling list derivation.

The following step may be added in the derivation of ScalingMatrixPred and ScalingMatrixDCPred:.

The value of N may be fixed, or set as a function of refld and id, or as a function of scaling_list_pred_id_delta, or a function of scaling_list_copy_flag and scaling _list_pred_flag or a combination of the above. For example, N may be fixed to be equal to <NUM>. In another example, N may be set equal to
<NUM>*(scaling_list_pred_id_delta+<NUM>) when scaling_list_copy_mode_flag is equal to <NUM>, and when scaling_list_pred_mode _flag is equal to <NUM>, the value of N may be set equal to <NUM>*(scaling_list_pred_id_delta + <NUM>).

In another example, the range of scaling_list_pred_id_delta[ ] is not modified. Instead, when the refld points to an unavailable/chroma matrix, video encoder <NUM> and video decoder <NUM> may be configured to remap the refld to a corresponding luma scaling matrix.

For example, video encoder <NUM> and video decoder <NUM> may be configured to derive or update the value of refld as follows:
<IMG>.

In another example, video encoder <NUM> and video decoder <NUM> may be configured to equivalently derive or update the value of refld as follows:
<IMG>.

In another example, video encoder <NUM> and video decoder <NUM> may be configured to derive or update the value of refld as follows:
<IMG>.

In another example of this disclosure , the chroma scaling lists corresponding to IDs <NUM> and <NUM> are not signalled when the chroma format is <NUM> and the content is not coded with separate colour plane coding. The syntax table may be modified as follows:.

scaling_list_chroma_2x2_absent_flag equal to <NUM> specifies that the scaling lists corresponding to IDs <NUM> and <NUM> are not signalled in the scaling list APS. scaling_list_chroma_2x2_absent_flag equal to <NUM> specifies that the scaling lists corresponding to IDs <NUM> and <NUM> may be signalled in the scaling list APS.

When scaling_list_chroma_2x2_absent_flag is equal to <NUM>, the semantics of the syntax elements may be modified so that default lists may be derived for the scaling list IDs <NUM> and <NUM>.

In one example, the chroma_format_idc may be signalled in place of scaling_list_chroma_2x2 absent flag and the condition to not signal scaling lists with IDs <NUM> and <NUM> is when chroma_format_idc corresponds to <NUM> coding.

In one example, a constraint may be added that the syntax element scaling_list_chroma_2x2_absent_flag is equal to <NUM> when chroma_format_idc corresponds to <NUM> coding and <NUM> otherwise.

In accordance with the techniques above, video decoder <NUM> may be configured to determine a set of scaling lists for the video data, with each scaling list of the set of scaling lists being used to determine an associated scaling matrix in a set of scaling matrices. Each scaling list and each associated scaling matrix determined may have an identification (ID) number, such as <NUM>-<NUM> as shown above in Table <NUM>-<NUM>. Video decoder <NUM> may be configured to determine based on, for example, a value of scaling_list_pred_mode_flag, that a new scaling list for the set of scaling lists is to be predicted from a reference scaling list and determine a new scaling matrix based on the new scaling list. Video decoder <NUM> may be configured to receive a syntax element, such as scaling_list_pred_id_delta[ id ], that identifies an ID number corresponding to a scaling list of the set of scaling lists that is to be used as the reference scaling list. Video decoder <NUM> may determine that the set of scaling lists does not include a scaling list with the ID number, and in response to determining that the set of scaling lists does not include the scaling list with the ID number, determine the new scaling matrix based on a set of default values, such as <NUM>, or more generically N.

To determine the new scaling matrix based on the set of default values, video decoder <NUM> may be configured to determine a predicted scaling matrix (e.g., ScalingMatrixDCPred above) based on the set of default values, receive delta values (e.g., scaling_list_dc_coef above) that represent differences between the predicted scaling matrix and the new scaling matrix, and determine the new scaling matrix based on the predicted scaling matrix and the delta values, using for example equation <NUM> above.

To determine that the set of scaling lists does not include the scaling list with the ID number, video decoder <NUM> may be configured to determine that the video data is coded without chroma components and determine that the ID number corresponds to a scaling list for a chroma component. To determine that the video data is coded without chroma components, video decoder <NUM> may receive a syntax element indicating that scaling lists are not included for chroma components. To determine that the set of scaling lists does not include the scaling list with the ID number, video decoder <NUM> may determine that the ID number divided by <NUM> has a remainder of <NUM> or <NUM>.

<FIG> is a block diagram illustrating an example video encoder <NUM> that may perform the techniques of this disclosure. <FIG> is provided for purposes of explanation and should not be considered limiting of the techniques as broadly exemplified and described in this disclosure. For purposes of explanation, this disclosure describes video encoder <NUM> according to the techniques of VVC (ITU-T H. <NUM>, under development), and HEVC (ITU-T H. However, the techniques of this disclosure may be performed by video encoding devices that are configured to other video coding standards.

In the example of <FIG>, video encoder <NUM> includes video data memory <NUM>, mode selection unit <NUM>, residual generation unit <NUM>, transform processing unit <NUM>, quantization unit <NUM>, inverse quantization unit <NUM>, inverse transform processing unit <NUM>, reconstruction unit <NUM>, filter unit <NUM>, decoded picture buffer (DPB) <NUM>, and entropy encoding unit <NUM>. Any or all of video data memory <NUM>, mode selection unit <NUM>, residual generation unit <NUM>, transform processing unit <NUM>, quantization unit <NUM>, inverse quantization unit <NUM>, inverse transform processing unit <NUM>, reconstruction unit <NUM>, filter unit <NUM>, DPB <NUM>, and entropy encoding unit <NUM> may be implemented in one or more processors or in processing circuitry. For instance, the units of video encoder <NUM> may be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor, ASIC, of FPGA. Moreover, video encoder <NUM> may include additional or alternative processors or processing circuitry to perform these and other functions.

The various units of <FIG> are illustrated to assist with understanding the operations performed by video encoder <NUM>. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide particular functionality and are preset on the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For instance, programmable circuits may execute software or firmware that cause the programmable circuits to operate in the manner defined by instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units may be distinct circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

Video encoder <NUM> may include arithmetic logic units (ALUs), elementary function units (EFUs), digital circuits, analog circuits, and/or programmable cores, formed from programmable circuits. In examples where the operations of video encoder <NUM> are performed using software executed by the programmable circuits, memory <NUM> (<FIG>) may store the instructions (e.g., object code) of the software that video encoder <NUM> receives and executes, or another memory within video encoder <NUM> (not shown) may store such instructions.

Mode selection unit <NUM> includes a motion estimation unit <NUM>, a motion compensation unit <NUM>, and an intra-prediction unit <NUM>. Mode selection unit <NUM> may include additional functional units to perform video prediction in accordance with other prediction modes. As examples, mode selection unit <NUM> may include a palette unit, an intra-block copy unit (which may be part of motion estimation unit <NUM> and/or motion compensation unit <NUM>), an affine unit, a linear model (LM) unit, or the like.

Video encoder <NUM> may partition a picture retrieved from video data memory <NUM> into a series of CTUs and encapsulate one or more CTUs within a slice. Mode selection unit <NUM> may partition a CTU of the picture in accordance with a tree structure, such as the QTBT structure or the quad-tree structure of HEVC described above. As described above, video encoder <NUM> may form one or more CUs from partitioning a CTU according to the tree structure. Such a CU may also be referred to generally as a "video block" or "block.

Motion estimation unit <NUM> may form one or more motion vectors (MVs) that defines the positions of the reference blocks in the reference pictures relative to the position of the current block in a current picture. Motion estimation unit <NUM> may then provide the motion vectors to motion compensation unit <NUM>. For example, for uni-directional inter-prediction, motion estimation unit <NUM> may provide a single motion vector, whereas for bi-directional inter-prediction, motion estimation unit <NUM> may provide two motion vectors. Motion compensation unit <NUM> may then generate a prediction block using the motion vectors. For example, motion compensation unit <NUM> may retrieve data of the reference block using the motion vector. As another example, if the motion vector has fractional sample precision, motion compensation unit <NUM> may interpolate values for the prediction block according to one or more interpolation filters. Moreover, for bi-directional inter-prediction, motion compensation unit <NUM> may retrieve data for two reference blocks identified by respective motion vectors and combine the retrieved data, e.g., through sample-by-sample averaging or weighted averaging.

Mode selection unit <NUM> provides the prediction block to residual generation unit <NUM>. Residual generation unit <NUM> receives a raw, unencoded version of the current block from video data memory <NUM> and the prediction block from mode selection unit <NUM>. Residual generation unit <NUM> calculates sample-by-sample differences between the current block and the prediction block. The resulting sample-by-sample differences define a residual block for the current block. In some examples, residual generation unit <NUM> may also determine differences between sample values in the residual block to generate a residual block using residual differential pulse code modulation (RDPCM). In some examples, residual generation unit <NUM> may be formed using one or more subtractor circuits that perform binary subtraction.

In examples where mode selection unit <NUM> does not further partition a CU into PUs, each CU may be associated with a luma coding block and corresponding chroma coding blocks. As above, the size of a CU may refer to the size of the luma coding block of the CU. The video encoder <NUM> and video decoder <NUM> may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

For other video coding techniques such as an intra-block copy mode coding, an affine-mode coding, and linear model (LM) mode coding, as a few examples, mode selection unit <NUM>, via respective units associated with the coding techniques, generates a prediction block for the current block being encoded. In some examples, such as palette mode coding, mode selection unit <NUM> may not generate a prediction block, and instead generate syntax elements that indicate the manner in which to reconstruct the block based on a selected palette. In such modes, mode selection unit <NUM> may provide these syntax elements to entropy encoding unit <NUM> to be encoded.

Quantization unit <NUM> may quantize the transform coefficients in a transform coefficient block, to produce a quantized transform coefficient block. Quantization unit <NUM> may quantize transform coefficients of a transform coefficient block according to a QP value associated with the current block as well as using scaling matrices as described above. Video encoder <NUM> (e.g., via mode selection unit <NUM>) may adjust the degree of quantization applied to the transform coefficient blocks associated with the current block by adjusting the QP value associated with the CU. Quantization may introduce loss of information, and thus, quantized transform coefficients may have lower precision than the original transform coefficients produced by transform processing unit <NUM>.

Filter unit <NUM> may perform one or more filter operations on reconstructed blocks. For example, filter unit <NUM> may perform deblocking operations to reduce blockiness artifacts along edges of CUs. Operations of filter unit <NUM> may be skipped, in some examples.

Video encoder <NUM> stores reconstructed blocks in DPB <NUM>. For instance, in examples where operations of filter unit <NUM> are not needed, reconstruction unit <NUM> may store reconstructed blocks to DPB <NUM>. In examples where operations of filter unit <NUM> are needed, filter unit <NUM> may store the filtered reconstructed blocks to DPB <NUM>. Motion estimation unit <NUM> and motion compensation unit <NUM> may retrieve a reference picture from DPB <NUM>, formed from the reconstructed (and potentially filtered) blocks, to inter-predict blocks of subsequently encoded pictures. In addition, intra-prediction unit <NUM> may use reconstructed blocks in DPB <NUM> of a current picture to intra-predict other blocks in the current picture.

In some examples, operations performed with respect to a luma coding block need not be repeated for the chroma coding blocks. As one example, operations to identify a motion vector (MV) and reference picture for a luma coding block need not be repeated for identifying an MV and reference picture for the chroma blocks. Rather, the MV for the luma coding block may be scaled to determine the MV for the chroma blocks, and the reference picture may be the same. As another example, the intra-prediction process may be the same for the luma coding block and the chroma coding blocks.

Video encoder <NUM> represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to perform the techniques for signaling scaling lists as described herein.

<FIG> is a block diagram illustrating an example video decoder <NUM> that may perform the techniques of this disclosure. <FIG> is provided for purposes of explanation and is not limiting on the techniques as broadly exemplified and described in this disclosure. For purposes of explanation, this disclosure describes video decoder <NUM> according to the techniques of VVC (ITU-T H. <NUM>, under development), and HEVC (ITU-T H. However, the techniques of this disclosure may be performed by video coding devices that are configured to other video coding standards.

In the example of <FIG>, video decoder <NUM> includes coded picture buffer (CPB) memory <NUM>, entropy decoding unit <NUM>, prediction processing unit <NUM>, inverse quantization unit <NUM>, inverse transform processing unit <NUM>, reconstruction unit <NUM>, filter unit <NUM>, and decoded picture buffer (DPB) <NUM>. Any or all of CPB memory <NUM>, entropy decoding unit <NUM>, prediction processing unit <NUM>, inverse quantization unit <NUM>, inverse transform processing unit <NUM>, reconstruction unit <NUM>, filter unit <NUM>, and DPB <NUM> may be implemented in one or more processors or in processing circuitry. For instance, the units of video decoder <NUM> may be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor, ASIC, of FPGA. Moreover, video decoder <NUM> may include additional or alternative processors or processing circuitry to perform these and other functions.

Prediction processing unit <NUM> includes motion compensation unit <NUM> and intra-prediction unit <NUM>. Prediction processing unit <NUM> may include additional units to perform prediction in accordance with other prediction modes. As examples, prediction processing unit <NUM> may include a palette unit, an intra-block copy unit (which may form part of motion compensation unit <NUM>), an affine unit, a linear model (LM) unit, or the like. In other examples, video decoder <NUM> may include more, fewer, or different functional components.

CPB memory <NUM> may store video data, such as an encoded video bitstream, to be decoded by the components of video decoder <NUM>. The video data stored in CPB memory <NUM> may be obtained, for example, from computer-readable medium <NUM> (<FIG>). CPB memory <NUM> may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Also, CPB memory <NUM> may store video data other than syntax elements of a coded picture, such as temporary data representing outputs from the various units of video decoder <NUM>. DPB <NUM> generally stores decoded pictures, which video decoder <NUM> may output and/or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory <NUM> and DPB <NUM> may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. CPB memory <NUM> and DPB <NUM> may be provided by the same memory device or separate memory devices. In various examples, CPB memory <NUM> may be on-chip with other components of video decoder <NUM>, or off-chip relative to those components.

Additionally or alternatively, in some examples, video decoder <NUM> may retrieve coded video data from memory <NUM> (<FIG>). That is, memory <NUM> may store data as discussed above with CPB memory <NUM>. Likewise, memory <NUM> may store instructions to be executed by video decoder <NUM>, when some or all of the functionality of video decoder <NUM> is implemented in software to be executed by processing circuitry of video decoder <NUM>.

The various units shown in <FIG> are illustrated to assist with understanding the operations performed by video decoder <NUM>. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Similar to <FIG>, fixed-function circuits refer to circuits that provide particular functionality and are preset on the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For instance, programmable circuits may execute software or firmware that cause the programmable circuits to operate in the manner defined by instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units may be distinct circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

Entropy decoding unit <NUM> may entropy decode syntax elements defining quantized transform coefficients of a quantized transform coefficient block, as well as transform information, such as a QP and/or transform mode indication(s). Inverse quantization unit <NUM> may use the QP and the scaling matrices associated with the quantized transform coefficient block to determine a degree of quantization and, likewise, a degree of inverse quantization for inverse quantization unit <NUM> to apply.

After inverse quantization unit <NUM> forms the transform coefficient block, inverse transform processing unit <NUM> may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit <NUM> may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

Filter unit <NUM> may perform one or more filter operations on reconstructed blocks. For example, filter unit <NUM> may perform deblocking operations to reduce blockiness artifacts along edges of the reconstructed blocks. Operations of filter unit <NUM> are not necessarily performed in all examples.

Video decoder <NUM> may store the reconstructed blocks in DPB <NUM>. For instance, in examples where operations of filter unit <NUM> are not performed, reconstruction unit <NUM> may store reconstructed blocks to DPB <NUM>. In examples where operations of filter unit <NUM> are performed, filter unit <NUM> may store the filtered reconstructed blocks to DPB <NUM>. As discussed above, DPB <NUM> may provide reference information, such as samples of a current picture for intra-prediction and previously decoded pictures for subsequent motion compensation, to prediction processing unit <NUM>. Moreover, video decoder <NUM> may output decoded pictures (e.g., decoded video) from DPB <NUM> for subsequent presentation on a display device, such as display device <NUM> of <FIG>.

In this manner, video decoder <NUM> represents an example of a video decoding device including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to perform the techniques for signaling scaling lists as described herein.

<FIG> is a flowchart illustrating an example method for encoding a current block. The current block may comprise a current CU. Although described with respect to video encoder <NUM> (<FIG> and <FIG>), it should be understood that other devices may be configured to perform a method similar to that of <FIG>.

In this example, video encoder <NUM> initially predicts the current block (<NUM>). For example, video encoder <NUM> may form a prediction block for the current block. Video encoder <NUM> may then calculate a residual block for the current block (<NUM>). To calculate the residual block, video encoder <NUM> may calculate a difference between the original, unencoded block and the prediction block for the current block. Video encoder <NUM> may then transform the residual block and quantize transform coefficients of the residual block (<NUM>). Next, video encoder <NUM> may scan the quantized transform coefficients of the residual block (<NUM>). During the scan, or following the scan, video encoder <NUM> may entropy encode the transform coefficients (<NUM>). For example, video encoder <NUM> may encode the transform coefficients using CAVLC or CABAC. Video encoder <NUM> may then output the entropy encoded data of the block (<NUM>).

<FIG> is a flowchart illustrating an example method for decoding a current block of video data. The current block may comprise a current CU. Although described with respect to video decoder <NUM> (<FIG> and <FIG>), it should be understood that other devices may be configured to perform a method similar to that of <FIG>.

Video decoder <NUM> may receive entropy encoded data for the current block, such as entropy encoded prediction information and entropy encoded data for transform coefficients of a residual block corresponding to the current block (<NUM>). Video decoder <NUM> may entropy decode the entropy encoded data to determine prediction information for the current block and to reproduce transform coefficients of the residual block (<NUM>). Video decoder <NUM> may predict the current block (<NUM>), e.g., using an intra- or inter-prediction mode as indicated by the prediction information for the current block, to calculate a prediction block for the current block. Video decoder <NUM> may then inverse scan the reproduced transform coefficients (<NUM>), to create a block of quantized transform coefficients. Video decoder <NUM> may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (<NUM>). Video decoder <NUM> may ultimately decode the current block by combining the prediction block and the residual block (<NUM>).

Video decoder <NUM> determines a set of scaling lists for the video data (<NUM>), wherein each scaling list of the set of scaling lists is used to determine an associated scaling matrix in a set of scaling matrices, and wherein each scaling list and each associated scaling matrix determined has an associated ID number. Video decoder <NUM> determines that a new scaling list for the determined set of scaling lists is to be predicted from a reference scaling list, wherein the new scaling list corresponds to a new scaling matrix (<NUM>). Video decoder <NUM> receives a syntax element (<NUM>). Video decoder <NUM> determines an ID number based on the syntax element (<NUM>). In response to determining that the set of scaling lists does not include a scaling list with the ID number, video decoder <NUM> determines the new scaling matrix based on a set of default values (<NUM>). Video decoder <NUM> decodes the video data based on the new scaling matrix (<NUM>). Video decoder <NUM> outputs the decoded video data (<NUM>).

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the terms "processor" and "processing circuitry," as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein.

Claim 1:
A method of decoding video data, the method comprising:
determining a set of scaling lists for the video data, wherein each scaling list of the set of scaling lists is used to determine an associated scaling matrix in a set of scaling matrices, and wherein each scaling list and each associated scaling matrix has an associated identification (ID) number (<NUM>);
determining that a new scaling list for the set of scaling lists is to be predicted from a reference scaling list, wherein the new scaling list corresponds to a new scaling matrix (<NUM>);
receiving a syntax element (<NUM>);
determining an ID number based on the syntax element (<NUM>);
determining that the set of scaling lists does not include a scaling list with the ID number, wherein determining that the set of scaling lists does not include the scaling list with the ID number comprises determining that the ID number divided by <NUM> has a remainder of <NUM> or <NUM>;
in response to determining that the set of scaling lists does not include a scaling list with the ID number, determining the new scaling matrix based on a set of default values (<NUM>);
decoding the video data based on the new scaling matrix (<NUM>); and
outputting the decoded video data (<NUM>).