Patent Publication Number: US-2023135203-A1

Title: Video bitstream coding

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 16/721,246, filed Dec. 19, 2019, which is a continuation of U.S. patent application Ser. No. 15/885,687, filed Dec. 27, 2017, now U.S. Pat. No. 10,542,275, issued Jan. 21, 2020, which claims priority under 35 U.S.C. § 119(e) from earlier filed U.S. Provisional Patent Application No. 62/439,724, filed Dec. 28, 2016, from earlier filed U.S. Provisional Patent Application No. 62/440,379, filed Dec. 29, 2016, from earlier filed U.S. Provisional Patent Application No. 62/459,797, filed Feb. 16, 2017, from earlier filed U.S. Provisional Patent Application No. 62/482,178, filed Apr. 5, 2017, and from earlier filed U.S. Provisional Patent Application No. 62/522,420, filed Jun. 20, 2017, each of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The technical improvements in evolving video coding standards illustrate the trend of increasing coding efficiency to enable higher bit-rates, higher resolutions, and better video quality. The Joint Video Exploration Team is developing a new video coding scheme referred to as JVET. Similar to other video coding schemes like HEVC (High Efficiency Video Coding), JVET is a block-based hybrid spatial and temporal predictive coding scheme. However, relative to HEVC, JVET includes many modifications to bitstream structure, syntax, constraints, and mapping for the generation of decoded pictures. JVET has been implemented in Joint Exploration Model (JEM) encoders and decoders. 
     SUMMARY 
     The present disclosure provides a method of using planar mode to predict pixel values for a current coding unit (CU). The method includes calculating an intensity value of a bottom right neighboring pixel of the current CU. The bottom right intensity value can be used with an intensity value of a neighboring pixel from the row of horizontal boundary pixels on the upper side of the current CU to calculate intensity values for the neighboring pixels in a column along the right side of the current block. The bottom right intensity value can be used with a neighboring pixel from the column of vertical boundary pixels on the left side of the current CU to calculate intensity values for the neighboring pixels in a row along the lower side of the current block. The method further comprises calculating a first and second predictor and deriving a prediction pixel value from the first and second predictors, wherein a plurality of prediction pixel values make up a prediction block. 
     The present disclosure also provides an apparatus to predict pixel values for a current coding unit (CU) by way of the techniques disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details of the present invention are explained with the help of the attached drawings in which: 
         FIG.  1    depicts division of a frame into a plurality of Coding Tree Units (CTUs). 
         FIG.  2    depicts an exemplary partitioning of a CTU into Coding Units (CUs). 
         FIG.  3    depicts a quadtree plus binary tree (QTBT) representation of  FIG.  2   &#39;s CU partitioning. 
         FIG.  4    depicts a simplified block diagram for CU coding in a JVET encoder. 
         FIG.  5    depicts possible intra prediction modes for luma components in JVET. 
         FIG.  6    depicts a simplified block diagram for CU coding in a JVET decoder. 
         FIG.  7 A  depicts the horizontal predictor calculation. 
         FIG.  7 B  depicts a vertical predictor calculation. 
         FIG.  8    depicts an example of planar prediction plane with the JVET method that deviates from the flat plane. 
         FIG.  9    illustrates the planar prediction block generated based on equation (5), with the corner intensity values identical to an example in  FIG.  8   . 
         FIG.  10    depicts an embodiment of a computer system adapted and/or configured to process a method of CU coding. 
         FIG.  11    is a flow diagram that illustrates a method for performing the disclosed techniques. 
         FIG.  12    is a high-level view of a source device and destination device that may incorporate features of the systems and devices described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Digital video involves a large amount of data representing each and every frame of a digital video sequence, or series of frames, in an uncompressed manner. Transmitting uncompressed digital video across computer networks is usually limited by bandwidth limitations, and usually requires a large amount of storage space. Encoding the digital video may reduce both storage and bandwidth requirements. 
     Frames of a video sequence, or more specifically the coding tree units within each frame, can be encoded and decoded using JVET. JVET is a video coding scheme being developed by the Joint Video Exploration Team. Versions of JVET have been implemented in JEM (Joint Exploration Model) encoders and decoders. Similar to other video coding schemes like HEVC (High Efficiency Video Coding), JVET is a block-based hybrid spatial and temporal predictive coding scheme. 
     During coding with JVET, a frame is first divided into square blocks called Coding Tree Units (CTUs)  100 , as shown in  FIG.  1   .  FIG.  1    depicts division of a frame into a plurality of CTUs  100 . For example, CTUs  100  can be blocks of 128×128 pixels. A frame can be an image in a video sequence, which may include a plurality of frames. A frame can include a matrix, or set of matrices, with pixel values representing intensity measures in the image. The pixel values can be defined to represent color and brightness in full color video coding, where pixels are divided into three channels. For example, in a YCbCr color space pixels can have a luma value, Y, that represents gray level intensity in the image, and two chrominance values, Cb and Cr, that represent the extent to which color differs from gray to blue and red. In other embodiments, pixel values can be represented with values in different color spaces or models. The resolution of the video can determine the number of pixels in a frame. A higher resolution can mean more pixels and a better definition of the image, but can also lead to higher bandwidth, storage, and transmission requirements. 
       FIG.  2    depicts an exemplary partitioning of a CTU  100  into CUs  102 , which are the basic units of prediction in coding. Each CTU  100  in a frame can be partitioned into one or more CUs (Coding Units)  102 . CUs  102  can be used for prediction and transform as described below. Unlike HEVC, in JVET the CUs  102  can be rectangular or square, and can be coded without further partitioning into prediction units or transform units. The CUs  102  can be as large as their root CTUs  100 , or be smaller subdivisions of a root CTU  100  as small as 4×4 blocks. 
     In JVET, a CTU  100  can be partitioned into CUs  102  according to a quadtree plus binary tree (QTBT) scheme in which the CTU  100  can be recursively split into square blocks according to a quadtree, and those square blocks can then be recursively split horizontally or vertically according to binary trees. Parameters can be set to control splitting according to the QTBT, such as the CTU size, the minimum sizes for the quadtree and binary tree leaf nodes, the maximum size for the binary tree root node, and the maximum depth for the binary trees. 
     By way of a non-limiting example,  FIG.  2    shows a CTU  100  partitioned into CUs  102 , with solid lines indicating quadtree splitting and dashed lines indicating binary tree splitting. As illustrated, the binary splitting allows horizontal splitting and vertical splitting to define the structure of the CTU and its subdivision in to CUs. 
       FIG.  3    shows a QTBT block structure representation of  FIG.  2   &#39;s partitioning. To generate an encoded representation of a picture or image, the video encoder may generate a set of CTUs. in  FIG.  3   , quadtree root node represents the CTU  100 . To generate a coded CTU, the video encoder may recursively perform quadtree partitioning on the coding tree blocks of a CTU to divide the coding tree blocks into coding blocks (CB)s. Thus, as used herein, a video slice (e.g., a video frame or a portion of a video frame) may be partitioned into coding blocks, which may also be referred to as coding units, and each such coding unit may include blocks, such as luma blocks and chroma blocks, that are independently decoded. Thus, because JEM supports flexibility for CU partition shapes to better match local characteristics of video data, CUs may have non-square shapes and coding may take place at the CU level or at the luma or chroma block level within the CU. Reference is made herein to encoding or decoding a coding block, where a coding block represents a block of pixels that makes up a CU or coding blocks within the CU. 
     As shown in  FIG.  3   , each child node in a CTU  100  in the quadtree portion represents one of four square blocks split from a parent square block. The square blocks represented by the quadtree leaf nodes can then be divided zero or more times using binary trees, with the quadtree leaf nodes being root nodes of the binary trees, representing the parent coding unit that is partitioned into two child coding units. At each level of the binary tree portion, a block can be divided vertically or horizontally and symmetrically or asymmetrically. For example, a flag set to “0” may indicate that the block is symmetrically split horizontally, while a flag set to “1” may indicate that the block is symmetrically split vertically. 
     After quadtree splitting and binary tree splitting, the blocks represented by the QTBT&#39;s leaf nodes represent the final CUs  102  to be coded, such as coding using inter prediction or intra prediction. Inter-prediction exploits temporal redundancies between different frames. For example, temporally adjacent frames of video may include blocks of pixels that remain substantially the same. During encoding, a motion vector may interrelate movement of blocks of pixels in one frame to a block of correlating pixels in another frame. Thus, the system need not encode the block of pixels twice, but rather encode the block of pixels once and provide the motion vector to predict the correlated block of pixels. 
     For intra-prediction, a frame or portion of a frame may be encoded without reference to pixels in other frames. Instead, intra-prediction may exploit the spatial redundancies among blocks of pixels within a frame. For example, where spatially adjacent blocks of pixels have similar attributes, the coding process may reference a spatial correlation between adjacent blocks, exploiting the correlation by prediction of a target block based on prediction modes used in adjacent blocks. 
     For inter slices or slices or full frames coded with inter prediction, different partitioning structures can be used for luma and chroma components. For example, for an inter slice a CU  102  can have coding blocks for different color components, such as such as one luma CB and two chroma CBs. For intra slices or slices or full frames coded with intra prediction, the partitioning structure can be the same for luma and chroma components. Thus, each of the CTUs  100  may comprise a coding tree block of luma samples, corresponding coding tree blocks of chroma samples, and syntax structures used to code the samples of the coding tree blocks. A CTU may comprise a single coding tree block and the syntax structures used to code the samples. In either case, the CTU with coding blocks may be comprised within one or more coding units, as shown by  FIG.  2    and  FIG.  3   . 
       FIG.  4    depicts a simplified block diagram for CU coding in a JVET encoder. The main stages of video coding include partitioning to identify CUs  102  as described above, followed by encoding CUs  102  using prediction at  404  or  406 , generation of a residual CU  410  at  408 , transformation at  412 , quantization at  416 , and entropy coding at  420 . The encoder and encoding process illustrated in  FIG.  4    also includes a decoding process that is described in more detail below. 
     Given a current CU  102  (e.g., a CU prior to encoding; e.g., the original CU to be encoded for transmission in the bitstream by generating a prediction CU) the encoder can obtain a prediction CU  402  either spatially using intra prediction at  404  or temporally using inter prediction at  406 . The basic idea of prediction coding is to transmit a differential, or residual, signal between the original signal and a prediction for the original signal. At the receiver side, the original signal can be reconstructed by adding the residual and the prediction, as will be described below. Because the differential signal has a lower correlation than the original signal, fewer bits are needed for its transmission. 
     A sequence of coding units may make up a slice, and one or more slices may make up a picture. A slice may include one or more slice segments, each in its own NAL unit. A slice or slice segment may include header information for the slice or bitstream. 
     A slice, such as an entire picture or a portion of a picture, coded entirely with intra-predicted CUs can be an I slice that can be decoded without reference to other slices, and as such can be a possible point where decoding can begin. A slice coded with at least some inter-predicted CUs can be a predictive (P) or bi-predictive (B) slice that can be decoded based on one or more reference pictures. P slices may use intra-prediction and inter-prediction with previously coded slices. For example, P slices may be compressed further than the I-slices by the use of inter-prediction, but need the coding of a previously coded slice to code them. B slices can use data from previous and/or subsequent slices for its coding, using intra-prediction or inter-prediction using an interpolated prediction from two different frames, thus increasing the accuracy of the motion estimation process. In some cases P slices and B slices can also or alternately be encoded using intra block copy, in which data from other portions of the same slice is used. 
     As will be discussed below, the intra prediction or inter prediction can be performed based on reconstructed CUs  434  from previously coded CUs  102 , such as neighboring CUs  102  or CUs  102  in reference pictures. 
     When a CU  102  is coded spatially with intra prediction at  404 , an intra prediction mode can be found that best predicts pixel values of the CU  102  based on samples from neighboring CUs  102  in the picture. 
     When coding a CU&#39;s luma or chroma block components, the encoder can generate a list of candidate intra prediction modes. While HEVC had 35 possible intra prediction modes for luma components, in NET there are 67 possible intra prediction modes for luma components. These include a planar mode that uses a three-dimensional plane of values generated from neighboring pixels, a DC mode that uses values averaged from neighboring pixels, and the 65 directional modes shown in  FIG.  5    that use values copied from neighboring pixels along the indicated directions. 
     When generating a list of candidates intra prediction modes for a CU&#39;s luma block component, the number of candidate modes on the list can depend on the CU&#39;s size. The candidate list can include: a subset of HEVC&#39;s  35  modes with the lowest SATD (Sum of Absolute Transform Difference) costs; new directional modes added for NET that neighbor the candidates found from the HEVC modes; and modes from a set of six most probable modes (MPMs) for the CU  102  that are identified based on intra prediction modes used for previously coded neighboring blocks as well as a list of default modes. 
     When coding a CU&#39;s chroma block components, a list of candidate intra prediction modes can also be generated. The list of candidate modes can include modes generated with cross-component linear model projection from luma samples, intra prediction modes found for luma CBs in particular collocated positions in the chroma block, and chroma prediction modes previously found for neighboring blocks. The encoder can find the candidate modes on the lists with the lowest rate distortion costs, and use those intra prediction modes when coding the CU&#39;s luma and chroma components. Syntax can be coded in the bitstream that indicates the intra prediction modes used to code each CU  102 . 
     After the best intra prediction modes for a CU  102  have been selected, the encoder can generate a prediction CU  402  using those modes. When the selected modes are directional modes, a 4-tap filter can be used to improve the directional accuracy. Columns or rows at the top or left side of the prediction block can be adjusted with boundary prediction filters, such as 2-tap or 3-tap filters. 
     The prediction CU  402  can be smoothed further with a position dependent intra prediction combination (PDPC) process that adjusts a prediction CU  402  generated based on filtered samples of neighboring blocks using unfiltered samples of neighboring blocks, or adaptive reference sample smoothing using 3-tap or 5-tap low pass filters to process reference samples. 
     When a CU  102  is coded temporally with inter prediction at  406 , a set of motion vectors (MVs) can be found that points to samples in reference pictures that best predict pixel values of the CU  102 . Inter prediction exploits temporal redundancy between slices by representing a displacement of a block of pixels in a slice. The displacement is determined according to the value of pixels in previous or following slices through a process called motion compensation. Motion vectors and associated reference indices that indicate pixel displacement relative to a particular reference picture can be provided in the bitstream to a decoder, along with the residual between the original pixels and the motion compensated pixels. The decoder can use the residual and signaled motion vectors and reference indices to reconstruct a block of pixels in a reconstructed slice. 
     In JVET, motion vector accuracy can be stored at 1/16 pel, and the difference between a motion vector and a CU&#39;s predicted motion vector can be coded with either quarter-pel resolution or integer-pel resolution. 
     In JVET motion vectors can be found for multiple sub-CUs within a CU  102 , using techniques such as advanced temporal motion vector prediction (ATMVP), spatial-temporal motion vector prediction (STMVP), affine motion compensation prediction, pattern matched motion vector derivation (PMMVD), and/or bi-directional optical flow (BIO). 
     Using ATMVP, the encoder can find a temporal vector for the CU  102  that points to a corresponding block in a reference picture. The temporal vector can be found based on motion vectors and reference pictures found for previously coded neighboring CUs  102 . Using the reference block pointed to by a temporal vector for the entire CU  102 , a motion vector can be found for each sub-CU within the CU  102 . 
     STMVP can find motion vectors for sub-CUs by scaling and averaging motion vectors found for neighboring blocks previously coded with inter prediction, together with a temporal vector. 
     Affine motion compensation prediction can be used to predict a field of motion vectors for each sub-CU in a block, based on two control motion vectors found for the top corners of the block. For example, motion vectors for sub-CUs can be derived based on top corner motion vectors found for each 4×4 block within the CU  102 . 
     PMMVD can find an initial motion vector for the current CU  102  using bilateral matching or template matching. Bilateral matching can look at the current CU  102  and reference blocks in two different reference pictures along a motion trajectory, while template matching can look at corresponding blocks in the current CU  102  and a reference picture identified by a template. The initial motion vector found for the CU  102  can then be refined individually for each sub-CU. 
     BIO can be used when inter prediction is performed with bi-prediction based on earlier and later reference pictures, and allows motion vectors to be found for sub-CUs based on the gradient of the difference between the two reference pictures. 
     In some situations, local illumination compensation (LIC) can be used at the CU level to find values for a scaling factor parameter and an offset parameter, based on samples neighboring the current CU  102  and corresponding samples neighboring a reference block identified by a candidate motion vector. In JVET, the LIC parameters can change and be signaled at the CU level. 
     For some of the above methods the motion vectors found for each of a CU&#39;s sub-CUs can be signaled to decoders at the CU level. For other methods, such as PMMVD and BIO, motion information is not signaled in the bitstream to save overhead, and decoders can derive the motion vectors through the same processes. 
     After the motion vectors for a CU  102  have been found, the encoder can generate a prediction CU  402  using those motion vectors. In some cases, when motion vectors have been found for individual sub-CUs, Overlapped Block Motion Compensation (OBMC) can be used when generating a prediction CU  402  by combining those motion vectors with motion vectors previously found for one or more neighboring sub-CUs. 
     When bi-prediction is used, JVET can use decoder-side motion vector refinement (DMVR) to find motion vectors. DMVR allows a motion vector to be found based on two motion vectors found for bi-prediction using a bilateral template matching process. In DMVR, a weighted combination of prediction CUs  402  generated with each of the two motion vectors can be found, and the two motion vectors can be refined by replacing them with new motion vectors that best point to the combined prediction CU  402 . The two refined motion vectors can be used to generate the final prediction CU  402 . 
     At  408 , once a prediction CU  402  has been found with intra prediction at  404  or inter prediction at  406  as described above, the encoder can subtract the prediction CU  402  from the current CU  102  find a residual CU  410 . 
     The encoder can use one or more transform operations at  412  to convert the residual CU  410  into transform coefficients  414  that express the residual CU  410  in a transform domain, such as using a discrete cosine block transform (DCT-transform) to convert data into the transform domain. WET allows more types of transform operations than HEVC, including DCT-II, DST-VII, DST-VII, DCT-VIII, DST-I, and DCT-V operations. The allowed transform operations can be grouped into sub-sets, and an indication of which sub-sets and which specific operations in those sub-sets were used can be signaled by the encoder. In some cases, large block-size transforms can be used to zero out high frequency transform coefficients in CUs  102  larger than a certain size, such that only lower-frequency transform coefficients are maintained for those CUs  102 . 
     In some cases, a mode dependent non-separable secondary transform (MDNSST) can be applied to low frequency transform coefficients  414  after a forward core transform. The MDNSST operation can use a Hypercube-Givens Transform (Hit) based on rotation data. When used, an index value identifying a particular MDNSST operation can be signaled by the encoder. 
     At  416 , the encoder can quantize the transform coefficients  414  into quantized transform coefficients  416 . The quantization of each coefficient may be computed by dividing a value of the coefficient by a quantization step, which is derived from a quantization parameter (QP). In some embodiments, the Qstep is defined as 2(QP−4)/6. Because high precision transform coefficients  414  can be converted into quantized transform coefficients  416  with a finite number of possible values, quantization can assist with data compression. Thus, quantization of the transform coefficients may limit a number of bits generated and sent by the transformation process. However, while quantization is a lossy operation, and the loss by quantization cannot be recovered, the quantization process presents a trade-off between quality of the reconstructed sequence and an amount of information needed to represent the sequence. For example, a lower QP value can result in better quality decoded video, although a higher amount of data may be required for representation and transmission. In contrast, a high QP value can result in lower quality reconstructed video sequences but with lower data and bandwidth needs. 
     NET may utilize variance-based adaptive quantization techniques, which allows every CU  102  to use a different quantization parameter for its coding process (instead of using the same frame QP in the coding of every CU  102  of the frame). The variance-based adaptive quantization techniques adaptively lower the quantization parameter of certain blocks while increasing it in others. To select a specific QP for a CU  102 , the CU&#39;s variance is computed. In brief, if a CU&#39;s variance is higher than the average variance of the frame, a higher QP than the frame&#39;s QP may be set for the CU  102 . If the CU  102  presents a lower variance than the average variance of the frame, a lower QP may be assigned. 
     At  420 , the encoder can find final compression bits  422  by entropy coding the quantized transform coefficients  418 . Entropy coding aims to remove statistical redundancies of the information to be transmitted. In NET, CABAC (Context Adaptive Binary Arithmetic Coding) can be used to code the quantized transform coefficients  418 , which uses probability measures to remove the statistical redundancies. For CUs  102  with non-zero quantized transform coefficients  418 , the quantized transform coefficients  418  can be converted into binary. Each bit (“bin”) of the binary representation can then be encoded using a context model. A CU  102  can be broken up into three regions, each with its own set of context models to use for pixels within that region. 
     Multiple scan passes can be performed to encode the bins. During passes to encode the first three bins (bin0, bin1, and bin2), an index value that indicates which context model to use for the bin can be found by finding the sum of that bin position in up to five previously coded neighboring quantized transform coefficients  418  identified by a template. 
     A context model can be based on probabilities of a bin&#39;s value being ‘0’ or ‘1’. As values are coded, the probabilities in the context model can be updated based on the actual number of ‘0’ and ‘1’ values encountered. While HEVC used fixed tables to re-initialize context models for each new picture, in NET the probabilities of context models for new inter-predicted pictures can be initialized based on context models developed for previously coded inter-predicted pictures. 
     The encoder can produce a bitstream that contains entropy encoded bits  422  of residual CUs  410 , prediction information such as selected intra prediction modes or motion vectors, indicators of how the CUs  102  were partitioned from a CTU  100  according to the QTBT structure, and/or other information about the encoded video. The bitstream can be decoded by a decoder as discussed below. In some embodiments, the encoder can save overhead in the bitstream by omitting information from the bitstream that indicates which intra prediction modes were used to encode CUs  102 , and the decoder can use template matching when decoding CUs  102  encoded with intra prediction. 
     In addition to using the quantized transform coefficients  418  to find the final compression bits  422 , the encoder can also use the quantized transform coefficients  418  to generate reconstructed CUs  434  by following the same decoding process that a decoder would use to generate reconstructed CUs  434 . Thus, once the transformation coefficients have been computed and quantized by the encoder, the quantized transform coefficients  418  may be transmitted to the decoding loop in the encoder. After quantization of a CU&#39;s transform coefficients, a decoding loop allows the encoder to generate a reconstructed CU  434  identical to the one the decoder generates in the decoding process. Accordingly, the encoder can use the same reconstructed CUs  434  that a decoder would use for neighboring CUs  102  or reference pictures when performing intra prediction or inter prediction for a new CU  102 . Reconstructed CUs  102 , reconstructed slices, or full reconstructed images or frames may serve as references for further prediction stages. 
     At the encoder&#39;s decoding loop (and see below, for the same operations in the decoder) to obtain pixel values for the reconstructed image, a dequantization process may be performed. To dequantize a frame, for example, a quantized value for each pixel of a frame is multiplied by the quantization step, e.g., (Qstep) described above, to obtain reconstructed dequantized transform coefficients  426 . For example, in the decoding process shown in  FIG.  4    in the encoder, the quantized transform coefficients  418  of a residual CU  410  can be dequantized at  424  to find dequantized transform coefficients  426 . If an MDNSST operation was performed during encoding, that operation can be reversed after dequantization. 
     At  428 , the dequantized transform coefficients  426  can be inverse transformed to find a reconstructed residual CU  430 , such as by applying a DCT to the values to obtain the reconstructed image. At  432  the reconstructed residual CU  430  can be added to a corresponding prediction CU  402  found with intra prediction at  404  or inter prediction at  406 , in order to find a reconstructed CU  434 . While in some embodiments the encoder can perform intra prediction at  404  as described above, in other embodiments the encoder can perform intra prediction template matching to generate a prediction CU  402  in the same way that a decoder would use template matching for intra prediction if information identifying the intra prediction mode used for the CU  102  is omitted from the bitstream. 
     At  436 , one or more filters can be applied to the reconstructed data during the decoding process (in the encoder or, as described below, in the decoder), at either a picture level or CU level. For example, the encoder can apply a deblocking filter, a sample adaptive offset (SAO) filter, and/or an adaptive loop filter (ALF). The encoder&#39;s decoding process may implement filters to estimate and transmit to a decoder the optimal filter parameters that can address potential artifacts in the reconstructed image. Such improvements increase the objective and subjective quality of the reconstructed video. In deblocking filtering, pixels near a sub-CU boundary may be modified, whereas in SAO, pixels in a CTU  100  may be modified using either an edge offset or band offset classification. JVET&#39;s ALF can use filters with circularly symmetric shapes for each 2×2 block. An indication of the size and identity of the filter used for each 2×2 block can be signaled. 
     If reconstructed pictures are reference pictures, they can be stored in a reference buffer  438  for inter prediction of future CUs  102  at  406 . 
     During the above steps, JVET allows a content adaptive clipping operations to be used to adjust color values to fit between lower and upper clipping bounds. The clipping bounds can change for each slice, and parameters identifying the bounds can be signaled in the bitstream. 
       FIG.  6    depicts a simplified block diagram for CU coding in a JVET decoder. A JVET decoder can receive a bitstream, or bits,  602  containing information about encoded video data. The encoded video data may represent partitioned luma blocks and partitioned chroma blocks, where the chroma blocks may be partitioned and coded independently of the luma blocks. The decoder may determine the respective coding mode respective to the blocks within each CU  102 . 
     The bitstream can indicate how CUs  102  of a picture were partitioned from a CTU  100  according to a QTBT structure. The decoder may determine the tree structure as part of obtaining syntax elements from the bitstream. The tree structure may specify how the initial video block, such as a CTB, is partitioned into smaller video blocks, such as coding units. 
     As described herein, for each respective non-leaf node of the tree structure at each depth level of the tree structure, there are various splitting patterns for the respective non-leave node. By way of a non-limiting example, the bitstream can signal how CUs  102  were partitioned from each CTU  100  in a QTBT using quadtree partitioning, symmetric binary partitioning, and/or asymmetric binary partitioning. The video block corresponding to such respective non-leaf node may be partitioned into video blocks corresponding to the child nodes of the respective non-leaf node. 
     The bitstream can also indicate prediction information for the CUs  102  such as intra prediction modes or motion vectors. Bits  602  represent entropy encoded residual CUs. In some embodiments, syntax can be coded in the bitstream that indicates the intra prediction modes used to code each CU  102 . In some embodiments, the encoder can have omitted information in the bitstream about intra prediction modes used to encode some or all CUs  102  coded using intra prediction, and as such the decoder can use template matching for intra prediction 
     At  604  the decoder can decode the entropy encoded bits  602  using the CABAC context models signaled in the bitstream by the encoder. The decoder can use parameters signaled by the encoder to update the context models&#39; probabilities in the same way they were updated during encoding. 
     After reversing the entropy encoding at  604  to find quantized transform coefficients  606 , the decoder can dequantize them at  608  to find dequantized transform coefficients  610 . If an MDNSST operation was performed during encoding, that operation can be reversed by the decoder after dequantization. 
     At  612 , the dequantized transform coefficients  610  can be inverse transformed to find a reconstructed residual CU  614 . At  616 , the reconstructed residual CU  614  can be added to a corresponding prediction CU  626  found with intra prediction at  622  or inter prediction at  624 , in order to find a reconstructed CU  618 . In some embodiments, the decoder can find the prediction CU  626  using template matching for intra prediction. 
     At  620 , one or more filters can be applied to the reconstructed data, at a picture level or CU level, for example. For example, the decoder can apply a deblocking filter, a sample adaptive offset (SAO) filter, and/or an adaptive loop filter (ALF). As described above, the in-loop filters located in the decoding loop of the encoder may be used to estimate optimal filter parameters to increase the objective and subjective quality of a frame. These parameters are transmitted to the decoder to filter the reconstructed frame at  620  to match the filtered reconstructed frame in the encoder. 
     After reconstructed pictures have been generated by finding reconstructed CUs  618  and applying signaled filters, the decoder can output the reconstructed pictures as output video  628 . If reconstructed pictures are to be used as reference pictures, they can be stored in a reference buffer  630  for inter prediction of future CUs  102  at  624 . 
     In some embodiments, the bitstream received by a JVET decoder can include syntax identifying which intra prediction mode was used to encode a CU  102  with intra prediction, such that the decoder can directly use the signaled intra prediction mode at  622  to generate a prediction CU  626 . In some embodiments, such syntax can be omitted to save overhead by reducing the number of bits in the bitstream. In these embodiments, when the decoder is not provided with an indication of which intra prediction mode was used to encode a CU  102 , the decoder can use template matching for intra prediction at  622  to derive the intra prediction mode it should use to generate a prediction CU  626 . In some embodiments, an encoder can similarly use template matching for intra prediction at  404  when generating a prediction CU  402  to combine with a reconstructed residual CU  430  at  432  within its decoding loop. 
     As described herein, intra coding is a main tool for video compression. It utilizes the spatial neighbors of a pixel to create a predictor, from which a prediction residual between the pixel and its predictor is determined. Video encoder then compresses the residuals, resulting in the coding bitstream. The developing video coding standard, JVET, allows 67 possible intra prediction modes, including planar mode, DC mode, and 65 angular direction modes, as shown in  FIG.  5   . Each intra prediction mode has unique prediction generation method, based on either left-side neighbor or top-side neighbor. Each intra coding unit (CU) selects at least one intra prediction mode to be used, which needs to be signaled as overhead in bitstream. For example, where a single CU includes one luma coding block and two chroma coding blocks, each of the luma coding block and chroma coding block can have their own intra prediction mode. Thus, if signaled in the bitstream, multiple intra prediction modes may be identified. 
     Disclosed herein are various techniques to implement an improved intra prediction coding technique using a refined planar prediction. In embodiments, the neighboring pixels used in intra prediction are calculated more accurately, resulting in a more efficient and more accurate prediction of pixels within the current coding block. 
     Planar mode is often the most frequently used intra coding mode in HEVC and JVET. Planar mode is often suited for blocks with a smooth image whose pixel values gradually change with a small planar gradient.  FIGS.  7 A and  7 B  show the HEVC and JVET planar predictor generation process for a coding unit (block)  702  with height H=8 and width W=8, where the (0,0) coordinates corresponds to the top-left (TL) position  704  within the coding CU, where TL position  718  is a top left neighboring corner pixel. TR  706  denotes top right position and BL  708  denotes bottom left position. The dashed line  710  indicates interpolation and the dotted line  712  indicates replication.  FIG.  7 A  depicts the horizontal predictor calculation and  FIG.  7 B  depicts a vertical predictor calculation. 
     Planar mode in HEVC and JVET (HEVC Planar) generates a first order approximation of the prediction for a current coding unit (CU) by forming a plane based on the intensity values of the neighboring pixels. Due to a raster-scan coding order, the reconstructed left column neighboring pixels  714  and the reconstructed top row neighboring pixels  716  are available for a current coding block  702 , but not the right column neighboring pixels and the bottom row neighboring pixels. The planar predictor generation process sets the intensity values of all the right column neighboring pixels to be the same as the intensity value of the top right neighboring pixel  706 , and the intensity values of all the bottom row pixels to be the same as the intensity value of the bottom left neighboring pixel  708 . 
     Once the neighboring pixels surrounding a predicting block are defined, the horizontal and the vertical predictors (P h (x,y) and P v (x,y), respectively) for each pixel within the current coding block  702  are determined according to equations (1) and (2) below. 
         P   h ( x,y )=( W− 1− x )* R (−1, y )+( x+ 1)* R ( W,− 1)  (1)
 
         P   v ( x,y )=( H− 1− y )* R ( x,− 1)+( y+ 1)* R (−1, H )  (2)
         Where:   R(x,y) denotes the intensity value of the reconstructed neighboring pixel   at (x,y) coordinate,   W is block width, and   H is block height.       

     As depicted in  FIG.  7 A , a horizontal predictor is interpolated from referencing reconstructed reference sample Ly  722 , a pixel in the left column neighboring pixels  714 , that is at the same y-coordinate as the current sample C  724 , and referencing sample Ty  726  which is a copy of previously reconstructed sample TR  718  that is adjacent to the top-right pixel of the coding unit. Thus, the horizontal predictor is calculated using linear interpolation between a value of a respective horizontal boundary pixel and a value of a vertical boundary pixel. 
     As depicted in  FIG.  7 B , a vertical predictor is interpolated from reconstructed sample Tx  728  from the top row neighboring pixels at the same x-coordinate as the current prediction pixel C and referencing sample Lx  730  which is a copy of the previously reconstructed sample BL  708 , a neighboring left pixel that is adjacent to the bottom left sample of the coding unit. Thus, the vertical predictor is calculated using liner interpolation between a value of a respective vertical boundary pixel and a value of a horizontal boundary value. 
     Once the horizontal and vertical predictor is determined for a coding unit pixel, the final predictor can be determined. For each pixel in a coding block, the final planar predictor, P(x,y), is the intensity value that may be computed by averaging the horizontal and vertical predictors according to equation (3), with certain adjustments in embodiments in which the current CU or coding block is non-square. 
         P ( x,y )=( H*P   h ( x,y )+ W*P   v ( x,y ))/(2* H*W )  (3)
 
     The encoder may also signal a residual between the prediction coding unit and the current coding unit in the bitstream to the decoder. 
     Certain constraints with the current planar mode in WET may cause coding inefficiencies. For example, as described above, all the right column neighboring pixels are set to the same intensity value, which is the value of the top right neighboring pixel. Similarly, all the bottom row neighboring pixels are set to the same intensity value, which is the value of the bottom left neighboring pixel. Setting all right column pixels the same, and all bottom row pixels the same, conflicts with plane prediction assumption. Thus, these constraints cause the planar prediction block to deviate from an ideal flat plane.  FIG.  8    depicts an example of planar prediction plane with the NET method that deviates from the flat plane (TR denotes top right position and BL denotes bottom left position). 
     Disclosed herein are embodiments for deriving an intensity value of a bottom right neighboring pixel P(W,H) for a current coding block. In embodiments, a coding unit may be the smallest coding block(s) within a CTU that is coded. In embodiments, a coding unit may include luma and chroma coding blocks that are independently coded. The proposed techniques include computing an intensity value of the bottom right neighboring pixel (lifting), and then computing the intensity values of the bottom row and the right column neighboring pixels, using the derived intensity value of the bottom right neighboring pixel along with the intensity values of other corner neighboring pixels, such as the top right neighboring pixel and the bottom left neighboring pixel. It is noted that a corner pixel at coordinates x=0, y=0 within the coding block is different from the corner neighboring pixels (e.g., P(W,H)) which is outside the coding block. 
     An example of a lifting process is a weighted average of the top right and the bottom left neighboring pixels, as defined in equation (4). 
         P ( W,H )=( W*R ( W,− 1)+ H*R (−1, H ))/( H+W )  (4)
 
     Another example of lifting process is maintaining a flat plane based on the intensity value of the top left, the top right, and the bottom left neighboring pixels, as defined in equation (5). 
         P ( W,H )= R ( W,− 1)+ R (−1, H )− R (−1,−1)  (5)
 
       FIG.  9    illustrates the planar prediction block generated based on equation (5), with the corner intensity values identical to an example in  FIG.  8   . As shown, a flat planar prediction plane results from using equation (5) given the same three corner points as in  FIG.  8    (TR denotes top-right position, TL denotes top-left position and BL denotes bottom-left position). 
     With the derived intensity value of the bottom right neighboring pixel of P(W,H), the intensity values of the bottom row neighboring pixels, P b (x,H), and the right column neighboring pixels, P r (W,y), can be computed accordingly. One example of such computation follows linear interpolation according to equations (6) and (7). 
     
       
         
           
             
               
                 
                   
                     
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                   ( 
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     Once the neighboring pixels surrounding a current coding block are defined, the horizontal and the vertical predictors (P h (x,y) and P v (x,y), respectively) for each pixel within the coding block are determined according to equations (8) and (9) below. 
         P   h ( x,y )=( W− 1− x )* R (−1, y )+( x+ 1)* P   r ( W,y )  (8)
 
         P   v ( x,y )=( H− 1− y )* R ( x,− 1)+( y+ 1)* P   b ( x,H )  (9)
 
     Notice that in equations (8) and (9), P h (x,y) and P v (x,y) are shown as scaled up version of horizontal and vertical predictors. These factors will be compensated in the final predictor calculation step. 
     It may also be beneficial to use filtered version of neighboring pixels intensity, instead of actual neighboring pixel intensity for lifting part of the bottom right position adjustment. This is especially true when the coding content is noisy. An example of such filtering operation is described in equations (10) and (11). 
     
       
         
           
             
               
                 
                   
                     
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                   ( 
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     Another example of filtering operation is described in equations (10a) and (11a). 
     
       
         
           
             
               
                 
                   
                     
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     The filtering operation may be selectively employed based on whether neighboring pixels have already been filtered by other prior process (such as mode dependent intra smoothing in HEVC). In embodiments, when neighboring pixels have not been filtered by prior task, the filtering operation is used. Otherwise, the filtering operation is not used. 
     Alternatively, it may be beneficial to set top-right and bottom-left corner positions to be R(W−1, −1) and R (−1, H−1), respectively. In this situation, interpolation for intermediate predictors can be described as an example by equations (12)-(16). 
     
       
         
           
             
               
                 
                   
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     The execution of the sequences of instructions required to practice the embodiments can be performed by a computer system  1000  as shown in  FIG.  10   . In an embodiment, execution of the sequences of instructions is performed by a single computer system  1000 . According to other embodiments, two or more computer systems  1000  coupled by a communication link  1015  can perform the sequence of instructions in coordination with one another. Although a description of only one computer system  1000  will be presented below, however, it should be understood that any number of computer systems  1000  can be employed to practice the embodiments. 
     A computer system  1000  according to an embodiment will now be described with reference to  FIG.  10   , which is a block diagram of the functional components of a computer system  1000 . As used herein, the term computer system  1000  is broadly used to describe any computing device that can store and independently run one or more programs. 
     Each computer system  1000  can include a communication interface  1014  coupled to the bus  1006 . The communication interface  1014  provides two-way communication between computer systems  1000 . The communication interface  1014  of a respective computer system  1000  transmits and receives electrical, electromagnetic or optical signals, which include data streams representing various types of signal information, e.g., instructions, messages and data. A communication link  1015  links one computer system  1000  with another computer system  1000 . For example, the communication link  1015  can be a LAN, in which case the communication interface  1014  can be a LAN card, or the communication link  1015  can be a PSTN, in which case the communication interface  1014  can be an integrated services digital network (ISDN) card or a modem, or the communication link  1015  can be the Internet, in which case the communication interface  1014  can be a dial-up, cable or wireless modem. 
     A computer system  1000  can transmit and receive messages, data, and instructions, including program, i.e., application, code, through its respective communication link  1015  and communication interface  1014 . Received program code can be executed by the respective processor(s)  1007  as it is received, and/or stored in the storage device  1010 , or other associated non-volatile media, for later execution. 
     In an embodiment, the computer system  1000  operates in conjunction with a data storage system  1031 , e.g., a data storage system  1031  that contains a database  1032  that is readily accessible by the computer system  1000 . The computer system  1000  communicates with the data storage system  1031  through a data interface  1033 . A data interface  1033 , which is coupled to the bus  1006 , transmits and receives electrical, electromagnetic or optical signals, which include data streams representing various types of signal information, e.g., instructions, messages and data. In embodiments, the functions of the data interface  1033  can be performed by the communication interface  1014 . 
     Computer system  1000  includes a bus  1006  or other communication mechanism for communicating instructions, messages and data, collectively, information, and one or more processors  1007  coupled with the bus  1006  for processing information. Computer system  1000  also includes a main memory  1008 , such as a random-access memory (RAM) or other dynamic storage device, coupled to the bus  1006  for storing dynamic data and instructions to be executed by the processor(s)  1007 . The main memory  1008  also can be used for storing temporary data, i.e., variables, or other intermediate information during execution of instructions by the processor(s)  1007 . 
     The computer system  1000  can further include a read only memory (ROM)  1009  or other static storage device coupled to the bus  1006  for storing static data and instructions for the processor(s)  1007 . A storage device  1010 , such as a magnetic disk or optical disk, can also be provided and coupled to the bus  1006  for storing data and instructions for the processor(s)  1007 . 
     A computer system  1000  can be coupled via the bus  1006  to a display device  1011 , such as, but not limited to, a cathode ray tube (CRT) or a liquid-crystal display (LCD) monitor, for displaying information to a user. An input device  1012 , e.g., alphanumeric and other keys, is coupled to the bus  1006  for communicating information and command selections to the processor(s)  1007 . 
     According to one embodiment, an individual computer system  1000  performs specific operations by their respective processor(s)  1007  executing one or more sequences of one or more instructions contained in the main memory  1008 . Such instructions can be read into the main memory  1008  from another computer-usable medium, such as the ROM  1009  or the storage device  1010 . Execution of the sequences of instructions contained in the main memory  1008  causes the processor(s)  1007  to perform the processes described herein. In alternative embodiments, hard-wired circuitry can be used in place of or in combination with software instructions. Thus, embodiments are not limited to any specific combination of hardware circuitry and/or software. 
     The term “computer-usable medium,” as used herein, refers to any medium that provides information or is usable by the processor(s)  1007 . Such a medium can take many forms, including, but not limited to, non-volatile, volatile and transmission media. Non-volatile media, i.e., media that can retain information in the absence of power, includes the ROM  1009 , CD ROM, magnetic tape, and magnetic discs. Volatile media, i.e., media that cannot retain information in the absence of power, includes the main memory  1008 . Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise the bus  1006 . Transmission media can also take the form of carrier waves; i.e., electromagnetic waves that can be modulated, as in frequency, amplitude or phase, to transmit information signals. Additionally, transmission media can take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. In the foregoing specification, the embodiments have been described with reference to specific elements thereof. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the embodiments. For example, the reader is to understand that the specific ordering and combination of process actions shown in the process flow diagrams described herein is merely illustrative, and that using different or additional process actions, or a different combination or ordering of process actions can be used to enact the embodiments. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense 
     It should also be noted that the present invention can be implemented in a variety of computer systems. The various techniques described herein can be implemented in hardware or software, or a combination of both. Preferably, the techniques are implemented in computer programs executing on programmable computers that each include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. Program code is applied to data entered using the input device to perform the functions described above and to generate output information. The output information is applied to one or more output devices. Each program is preferably implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language can be a compiled or interpreted language. Each such computer program is preferably stored on a storage medium or device (e.g., ROM or magnetic disk) that is readable by a general or special purpose programmable computer for configuring and operating the computer when the storage medium or device is read by the computer to perform the procedures described above. The system can also be considered to be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner. Further, the storage elements of the exemplary computing applications can be relational or sequential (flat file) type computing databases that are capable of storing data in various combinations and configurations. 
       FIG.  11    is a flow diagram that illustrates a method for performing the disclosed techniques, but it should be understood that the techniques described herein with respect to the remaining figures similarly capture the methods available using the disclosed techniques. As illustrated in  FIG.  11   , the method at  1102  includes calculating an intensity value of a bottom right neighboring pixel of the current coding block, such as a coding unit or a luma or chroma block. At  1104 , the bottom right intensity value can be used with a neighboring pixel from the column of vertical boundary pixels on the left side of the current coding block to calculate intensity values for the neighboring pixels in a row along the lower side of the current block. At  1106 , the bottom right intensity value can be used with an intensity value of a neighboring pixel from the row of horizontal boundary pixels on the upper side of the current coding block to calculate intensity values for the neighboring pixels in a column along the right side of the current block. The method at  1108  and  1110  further comprises calculating a first and second predictor and, at  1112 , the method includes deriving a prediction pixel value from the first and second predictors, wherein a plurality of prediction pixel values make up a prediction block. 
       FIG.  12    is a high-level view of a source device  12  and destination device  10  that may incorporate features of the systems and devices described herein. As shown in  FIG.  12   , example video coding system  10  includes a source device  12  and a destination device  14  where, in this example, the source device  12  generates encoded video data. Accordingly, source device  12  may be referred to as a video encoding device. Destination device  14  may decode the encoded video data generated by source device  12 . Accordingly, destination device  14  may be referred to as a video decoding device. Source device  12  and destination device  14  may be examples of video coding devices. 
     Destination device  14  may receive encoded video data from source device  12  via a channel  16 . Channel  16  may comprise a type of medium or device capable of moving the encoded video data from source device  12  to destination device  14 . In one example, channel  16  may comprise a communication medium that enables source device  12  to transmit encoded video data directly to destination device  14  in real-time. 
     In this example, source device  12  may modulate the encoded video data according to a communication standard, such as a wireless communication protocol, and may transmit the modulated video data to destination device  14 . The communication medium may comprise a 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 other equipment that facilitates communication from source device  12  to destination device  14 . In another example, channel  16  may correspond to a storage medium that stores the encoded video data generated by source device  12 . 
     In the example of  FIG.  12   , source device  12  includes a video source  18 , video encoder  20 , and an output interface  22 . In some cases, output interface  28  may include a modulator/demodulator (modem) and/or a transmitter. In source device  12 , video source  18  may include a source such as a video capture device, e.g., a video camera, a video archive containing previously captured video data, a video feed interface to receive video data from a video content provider, and/or a computer graphics system for generating video data, or a combination of such sources. 
     Video encoder  20  may encode the captured, pre-captured, or computer-generated video data. An input image may be received by the video encoder  20  and stored in the input frame memory  21 . The general-purpose processor  23  may load information from here and perform encoding. The program for driving the general-purpose processor may be loaded from a storage device, such as the example memory modules depicted in  FIG.  12   . The general-purpose processor may use processing memory  22  to perform the encoding, and the output of the encoding information by the general processor may be stored in a buffer, such as output buffer  26 . 
     The video encoder  20  may include a resampling module  25  which may be configured to code (e.g., encode) video data in a scalable video coding scheme that defines at least one base layer and at least one enhancement layer. Resampling module  25  may resample at least some video data as part of an encoding process, wherein resampling may be performed in an adaptive manner using resampling filters. 
     The encoded video data, e.g., a coded bit stream, may be transmitted directly to destination device  14  via output interface  28  of source device  12 . In the example of  FIG.  12   , destination device  14  includes an input interface  38 , a video decoder  30 , and a display device  32 . In some cases, input interface  28  may include a receiver and/or a modem. Input interface  38  of destination device  14  receives encoded video data over channel  16 . The encoded video data may include a variety of syntax elements generated by video encoder  20  that represent the video data. Such syntax elements may be included with the encoded video data transmitted on a communication medium, stored on a storage medium, or stored a file server. 
     The encoded video data may also be stored onto a storage medium or a file server for later access by destination device  14  for decoding and/or playback. For example, the coded bitstream may be temporarily stored in the input buffer  31 , then loaded in to the general-purpose processor  33 . The program for driving the general-purpose processor may be loaded from a storage device or memory. The general-purpose processor may use a process memory  32  to perform the decoding. The video decoder  30  may also include a resampling module  35  similar to the resampling module  25  employed in the video encoder  20 . 
       FIG.  12    depicts the resampling module  35  separately from the general-purpose processor  33 , but it would be appreciated by one of skill in the art that the resampling function may be performed by a program executed by the general-purpose processor, and the processing in the video encoder may be accomplished using one or more processors. The decoded image(s) may be stored in the output frame buffer  36  and then sent out to the input interface  38 . 
     Display device  38  may be integrated with or may be external to destination device  14 . In some examples, destination device  14  may include an integrated display device and may also be configured to interface with an external display device. In other examples, destination device  14  may be a display device. In general, display device  38  displays the decoded video data to a user. 
     Video encoder  20  and video decoder  30  may operate according to a video compression standard. ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) are studying the potential need for standardization of future video coding technology with a compression capability that significantly exceeds that of the current High Efficiency Video Coding HEVC standard (including its current extensions and near-term extensions for screen content coding and high-dynamic-range coding). The groups are working together on this exploration activity in a joint collaboration effort known as the Joint Video Exploration Team (WET) to evaluate compression technology designs proposed by their experts in this area. A recent capture of JVET development is described in the “Algorithm Description of Joint Exploration Test Model 5 (JEM 5)”, JVET-E1001-V2, authored by J. Chen, E. Alshina, G. Sullivan, J. Ohm, J. Boyce. 
     Additionally or alternatively, video encoder  20  and video decoder  30  may operate according to other proprietary or industry standards that function with the disclosed JVET features. Thus, other standards such as the ITU-T H.264 standard, alternatively referred to as MPEG-4, Part 10, Advanced Video Coding (AVC), or extensions of such standards. Thus, while newly developed for JVET, techniques of this disclosure are not limited to any particular coding standard or technique. Other examples of video compression standards and techniques include MPEG-2, ITU-T H.263 and proprietary or open source compression formats and related formats. 
     Video encoder  20  and video decoder  30  may be implemented in hardware, software, firmware or any combination thereof. For example, the video encoder  20  and decoder  30  may employ one or more processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, or any combinations thereof. When the video encoder  20  and decoder  30  are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder  20  and video decoder  30  may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device. 
     Aspects of the subject matter described herein may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer, such as the general-purpose processors  23  and  33  described above. Generally, program modules include routines, programs, objects, components, data structures, and so forth, which perform particular tasks or implement particular abstract data types. Aspects of the subject matter described herein may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. 
     Examples of memory include random access memory (RAM), read only memory (ROM), or both. Memory may store instructions, such as source code or binary code, for performing the techniques described above. Memory may also be used for storing variables or other intermediate information during execution of instructions to be executed by a processor, such as processor  23  and  33 . 
     A storage device may also store instructions, instructions, such as source code or binary code, for performing the techniques described above. A storage device may additionally store data used and manipulated by the computer processor. For example, a storage device in a video encoder  20  or a video decoder  30  may be a database that is accessed by computer system  23  or  33 . Other examples of storage device include random access memory (RAM), read only memory (ROM), a hard drive, a magnetic disk, an optical disk, a CD-ROM, a DVD, a flash memory, a USB memory card, or any other medium from which a computer can read. 
     A memory or storage device may be an example of a non-transitory computer-readable storage medium for use by or in connection with the video encoder and/or decoder. The non-transitory computer-readable storage medium contains instructions for controlling a computer system to be configured to perform functions described by particular embodiments. The instructions, when executed by one or more computer processors, may be configured to perform that which is described in particular embodiments. 
     Also, it is noted that some embodiments have been described as a process which can be depicted as a flow diagram or block diagram. Although each may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process may have additional steps not included in the figures. 
     Particular embodiments may be implemented in a non-transitory computer-readable storage medium for use by or in connection with the instruction execution system, apparatus, system, or machine. The computer-readable storage medium contains instructions for controlling a computer system to perform a method described by particular embodiments. The computer system may include one or more computing devices. The instructions, when executed by one or more computer processors, may be configured to perform that which is described in particular embodiments 
     As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. 
     Although embodiments have been disclosed herein in detail and in language specific to structural features and/or methodological acts above, it is to be understood that those skilled in the art will readily appreciate that many additional modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the invention. Moreover, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Accordingly, these and all such modifications are intended to be included within the scope of this invention construed in breadth and scope in accordance with the appended claims.