TW202406348A - Video coding method and apparatus thereof - Google Patents

Abstract

A method for coding video pictures by reordering a reference picture list (RPL) is provided. A video coder receives a RPL for a current coding tree unit (CTU) of a current picture. The RPL identifies a plurality of reference pictures. The video coder assigns indices to the plurality of reference pictures in the RPL of the current CTU. The video coder receives data to be encoded or decoded as a plurality of blocks of the current CTU. The video coder encodes or decodes the plurality of blocks of the CTU by using the assigned indices to select one or more reference pictures from the RPL to generate inter-predictions.

Description

Video encoding and decoding method and device

This disclosure relates generally to video codecs. In particular, the present disclosure relates to methods of encoding and decoding pixel blocks by using reference lists for inter prediction.

Unless otherwise indicated herein, the methods described in this section are not in the art within the scope of the claims listed below and are not included in this section and are not admitted as being in the art.

High-Efficiency Video Coding (HEVC for short) is an international video codec standard developed by the Joint Collaborative Team on Video Coding (JCT-VC for short). HEVC is based on a hybrid block-based motion compensation-like DCT transform coding and decoding architecture. The basic unit of compression, called the coding unit (CU), is a 2Nx2N square pixel block. Each CU can be recursively divided into four smaller CUs until a predetermined minimum size is reached. Each CU contains one or more prediction units (PU).

Versatile video coding (VVC) is the latest international video codec developed by the Joint Video Expert Team (JVET) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11 standard. The input video signal is predicted from a reconstructed signal derived from the codec picture region. The prediction residual signal is processed by block transform. The transform coefficients are quantized and entropy coded together with other ancillary information in the bitstream. The reconstructed signal is generated based on the prediction signal and the reconstructed residual signal obtained by inversely transforming the dequantized transform coefficients. The reconstructed signal is further processed by loop filtering to remove coding and decoding artifacts. The decoded pictures are stored in a frame buffer and used to predict future pictures in the input video signal.

In VVC, codec pictures are divided into non-overlapping square block areas represented by associated coding tree units (CTUs for short). Codec pictures can be represented by a collection of segments, each segment containing an integer number of CTUs. Individual CTUs in a segment are processed consecutively in a raster scan. Intra-prediction or inter-prediction can be used to decode bi-predictive (B) segments, where up to two motion vectors and reference indices are used to predict sample values for each block. Prediction (P) slices are decoded using intra prediction or inter prediction with at most one motion vector and reference index to predict sample values for each block. Intra (intra, or I) segments are decoded using only intra prediction pairs.

The CTU can be divided into one or more non-overlapping coding units (CUs) using a quadtree (QT) with a nested multi-type-tree (MTT) structure. to adapt to various local motion and texture features. A CU can be further partitioned into smaller CUs using one of five partitioning types: quadtree partitioning, vertical binary tree partitioning, horizontal binary tree partitioning, vertical center-side ternary tree partitioning, and horizontal center-side ternary tree partitioning.

Each CU contains one or more prediction units (prediction, PU for short). The prediction unit, together with the associated CU syntax, serves as the basic unit for sending prediction information. The specified prediction process is used to predict the values of relevant pixel samples within the PU. Each CU can contain one or more transform units (TUs for short) used to represent prediction residual blocks. The transform unit (TU) consists of a transform block (TB) of luma samples and two corresponding chroma sample transform blocks. Each TB corresponds to a residual block of samples from one color component. . Integer transforms are applied to transform blocks. The level values of the quantization coefficients are entropy encoded and decoded in the bit stream together with other auxiliary information. The terms coding tree block (CTB), coding block (CB), prediction block (PB), and transform block (TB) are defined to specify and CTU, CU, PU and TU are associated with a 2D array of samples of color components. Therefore, the CTU consists of a luma CTB, two chroma CTBs and related syntax elements. Similar relationships are valid for CU, PU and TU.

For each inter prediction CU, motion parameters consisting of motion vector, reference picture index and reference picture list usage index and additional information are used for inter prediction sample generation. Motion parameters can be sent explicitly or implicitly. When a CU is coded in skip mode, the CU is associated with a PU and has no significant residual coefficients, no coded motion vector delta or reference picture index. The merge mode is specified, and the motion parameters of the current CU are obtained from neighboring CUs, including spatial and temporal candidates, as well as the additional schedule introduced in VVC. Merge mode can be applied to any inter-predicted CU. An alternative to merge mode is explicit transmission of motion parameters, where motion vectors, corresponding reference picture indexes for each reference picture list and reference picture list usage flags and other required information are sent explicitly per CU.

The following summary is illustrative only and is not intended to be binding in any way. That is, the following summary is provided to introduce the concepts, highlights, benefits, and advantages of the novel and non-obvious techniques described herein. Select, but not all, embodiments are further described in the detailed description below. Accordingly, the following summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

Some embodiments of the present invention provide a method for decoding video pictures by reordering a reference picture list (RPL). The video codec receives the RPL of the current coding tree unit (CTU) of the current picture. RPL recognizes multiple reference pictures. The video codec assigns indices to multiple reference pictures in the RPL of the current CTU. The video codec receives data, which will be encoded or decoded into multiple blocks of the current CTU. The video codec selects one or more reference pictures from the RPL to generate inter prediction by encoding or decoding multiple blocks of the CTU using assigned indices.

In some embodiments, indexes are configured to multiple reference pictures in the RPL based on explicit signaling. In some embodiments, indexes are configured to multiple reference pictures in the RPL based on a history-based table recording the distribution of reference picture selections when encoding or decoding each CTU of the current picture.

In some embodiments, the video codec derives a representative MV of the current CTU and calculates the cost of multiple reference pictures. The cost of each reference picture is calculated based on (i) the neighboring samples of the current CTU and (ii) the reference samples in the reference picture identified by the representative MV, and based on the calculated cost, the index is assigned to the multiple based on the RPL. reference picture.

In some embodiments, the representative MV is derived from the MV used to reconstruct one or more blocks adjacent to the current CTU, and the representative MV may be a weighted MV used to reconstruct the MV of the block adjacent to the current CTU. average value. In some embodiments, the representative MV is derived from the MVs of one or more blocks in the current CTU, and the representative MV may be a weighted average of the MVs from one or more blocks in the current CTU. In some embodiments, the representative MV is derived from the temporal MV from the co-located CTU or reference picture CTU, and the representative MV may be a weighted average of the temporal MV from the co-located CTU or reference picture CTU. Representative MVs are derived from MVs inherited from neighboring positions of the current CTU. The video codec can use the motion vector predictor (MVP) of the block in the current CTU as the representative MV of the CTU.

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. Any changes, derivatives, and/or extensions based on the teachings described herein are within the scope of this disclosure. In some instances, well-known methods, processes, components and/or circuits related to one or more example embodiments disclosed herein may be described at a relatively high level without detail in order to avoid unnecessarily obscuring Aspects of the Teachings of the Present Disclosure. Ⅰ . Reference picture management

The video codec system uses multiple reference pictures to perform reference picture management for inter-frame prediction. Reference picture management manages the storage and removal of reference pictures in the decoded picture buffer (DPB), and places the reference pictures in the reference picture list (RPL) in the appropriate order. When a picture is referenced for inter prediction (either as a temporal reference or an inter-layer reference), the index in the RPL is used to select which picture in the DPB is being referenced. Reference picture management can use DPB and up to two RPLs. Reference picture management can also mark reference pictures as "for short-term reference", "for long-term reference" and "not for reference".

In the encoding and decoding process, the picture order count (POC) is a variable that is exported as an output order indicator and used as an identifier of the picture, including DPB management and reference picture management. In order to minimize the signaling overhead bit cost while maintaining robustness against data loss, the most significant bit (MSB) of the POC value may not be sent in the bit stream, since usually only the most significant bit (MSB) between POC values The difference is necessary for the correct operation of the encoding and decoding process.

The least significant bit (LSB) of the POC is used to derive the POC value and has the same value for all segments of the picture, in the picture header (PH) or slice header (SH) Send in. The POC MSB loop value can be sent in the PH to enable the POC value to be derived without tracking the POC MSB in a manner that relies on POC information from earlier encoded pictures. This allows, for example, a mix of intra random access pictures (IRAP) and non-IRAP pictures within an access unit (AU) in a multi-layer bitstream. POC LSB information can be sent for each picture (including instantaneous decoder refresh (IDR) pictures). POC LSB can be sent for IDR pictures, which saves some bits for IDR pictures. Sending POC LSB information of IDR pictures also helps merge IDR pictures and non-IDR pictures from different bit streams into a single codec picture.

In some embodiments, for all types of slices (eg, B, P, and I slices), two RPLs called List 0 (L0 or RPL 0) and List 1 (L1 or RPL 1) are sent directly and Exported without using RPL initialization or modification processing. In some embodiments, RPL is not based on reference picture sets or sliding windows plus memory management control operations.

Reference picture markers are directly based on RPL 0 and 1, indicating active and inactive entries in the RPL, where only active entries can be used in inter prediction of the current picture by the reference index.

Figures 1A-B illustrate various syntax structures related to reference picture management signaling included in sequence parameter set (SPS), picture parameter set (PPS), PH and SH and element. In the figure, syntax elements that are always present are shown in solid rectangles, while syntax elements that are conditionally present are shown in dashed rectangles. For RPL 0 and RPL 1 (if different from those of RPL 0), multiple predetermined candidate RPL syntax structures (e.g., ref_pic_list_struct(listIdx, rplsIdx) syntax structure) may be sent in the SPS to be passed in the PH or SH Quote them to use.

The syntax elements in the PPS indicate the default number of active entries for RPL 0 and RPL 1, a flag that controls the presence of RPL 1 syntax in the ref_pic_lists() structure, and a flag that specifies whether RPL information is contained in PH or SH. The information used to derive the two RPLs (i.e. the ref_pic_lists() structure) is sent in PH (if all fragments of the picture have the same RPL), or in SH. Instead of referencing the predetermined candidate RPL structure (identified by rpl_idx[i]), another RPL structure (i.e. the ref_pic_list_struct(i, sps_num_ref_pic_lists[i]) structure) can also be sent directly in the PH and SH.

Each RPL syntax structure includes information on the number of reference picture entries for a particular RPL. Reference picture entries in RPL are short-term reference picture entries, long-term reference picture entries or inter-layer reference picture entries. The default number of active entries for RPL 0 and RPL 1 is sent in PPS (i.e. pps_num_ref_idx_default_active_minus1[i]), and can be overridden in SH (using the syntax elements sh_num_ref_idx_active_override_flag and sh_num_ref_idx_active_minus1[i]). Ⅱ . Reordering the reference list

In some embodiments, a reference picture reordering method is used to allow block-level adaptation of the reference picture index configuration. Reference image reordering can be based on template matching cost. For uni-predictive AMVP mode, the reference pictures in List 0 and List 1 are interleaved to generate a joint list. For each hypothesis of the reference picture in the joint list, motion information can be derived accordingly, and template matching is performed to calculate the cost. The union list is reordered according to increasing template matching cost. The index of the selected reference picture in the reordered union list is sent in the bitstream. For bi-predictive AMVP mode, lists of reference picture pairs from List 0 and List 1 are generated and similarly reordered based on template matching cost. The index of the selected pair is sent in the bitstream.

In some embodiments, the results of the number of active reference pictures in a random access configuration are extended by setting the number of active reference pictures equal to the reported number of available reference pictures. In some embodiments, a template matching based block-level reference picture reordering method may be used. For uni-predictive AMVP mode, the reference pictures in List 0 and List 1 are interleaved to generate a joint list. For each hypothesis of the reference image in the joint list, template matching is performed to calculate the cost. The union list is reordered according to increasing template matching cost. The index of the selected reference picture in the reordered union list is sent in the bitstream. For bi-predictive AMVP mode, lists of reference picture pairs from List 0 and List 1 are generated and similarly reordered based on template matching cost. The index of the selected pair is sent in the bitstream.

In some embodiments, motion vector difference (MVD) sign prediction is applied to regular and affine AMVP modes. The derivation of predicted MVD symbols requires that the reference image be known. However, the reference picture reordering method requires the MVD to be known in this process. To solve this problem, the minimum template matching cost among all MVD symbol hypotheses is assigned to the reference picture hypothesis. The selected reference picture can then be determined by the decoded index and the reordered reference picture list. Thereafter MVD symbol prediction is performed by reusing the calculated template matching cost. For simplicity, in the case of bidirectional prediction, MVD symbol prediction in List 1 is only enabled when the MVD in List 0 is zero. Ⅲ . Reordering of reference picture list based on CTU

Some embodiments of the present disclosure provide a CTU-based reference picture list (RPL) reordering method. Specifically, when encoding and decoding a CTU, the reference picture list is implicitly or explicitly (via signaling) before encoding or decoding the first block of the CTU or the first AMVP or the first inter-frame block. Reorder. All blocks in a CTU use the same reordered reference picture. All blocks in a CTU use the same reference picture order. CTU-based reference picture ranking can be determined based on the template matching cost or SAD cost between the reconstructed sample adjacent to the current CTU and its corresponding reference sample (or prediction sample) in the reference picture.

In the CTU-based reference list reordering method, reconstructed samples adjacent to the current CTU can be used to perform reference picture reordering. Figure 2 conceptually illustrates reconstructed samples used in CTU-based reference picture list reordering. In this figure, samples in the shaded area adjacent to the current CTU 200 can be used for CTU-based reference picture list reordering of the current CTU 200 . These adjacent reconstructed samples may be samples of blocks adjacent to the current CTU 200 . These adjacent blocks of CTU 200 may be blocks of CTU A, CTU B, and CTU D, which are CTUs adjacent to the current CTU 200 .

CTU 200 is associated with CTU-based RPL 240, which includes reference pictures A, B, C, and D. In some embodiments, the cost for sorting the RPL is the calculated difference between the reconstructed sample adjacent to the current CTU and its corresponding reference sample in a different reference picture of the RPL. These reference samples are located in reference blocks identified by the motion source of the current CTU, which may be representative MVs 220 of the current CTU 200 . The representative MV 220 of the current CTU 220 may be derived or determined from: adjacent reconstruction blocks in adjacent CTUs, one or more inter prediction blocks in the current CTU, one or more AMVP mode blocks in the current CTU , time MV in the same location picture or reference picture, history-based MV, or history-based motion information. The cost metric used to decide the order of reference pictures can be template matching cost, SAD cost or SATD cost, or SSE cost, or reconstructed samples adjacent to the current CTU with different reference pictures referenced/identified by the representative MV. Corresponding to other difference measures between reference samples.

Figure 3 conceptually illustrates reordering the reference picture list (RPL) of a CTU using its representative MV. For CTU 200, RPL 240 recognizes four reference pictures 301-304 (reference pictures A-D). Representative MVs 220 are used to locate reference blocks or samples in these reference pictures 301-304, and these reference blocks or samples are in turn used to calculate the costs of these reference pictures.

As shown, the current CTU 200 is located in the current picture 210. The adjacent samples or adjacent blocks 230 of the current CTU 200 will be used to calculate the TM cost. Representative MVs 220 of CTU 200 are derived for reordering RPL 240. Representative MVs 220 are used to identify reference blocks or reference samples 331-334 in different reference pictures 301-304. Reference blocks or reference samples 331 - 334 provide reference samples corresponding to adjacent samples 230 of the current CTU 200 .

The cost associated with the reference picture 301 (reference picture A) is calculated as the difference between the reference block/sample 331 and the neighboring sample/block 230 . The cost associated with the reference picture 302 (reference picture B) is calculated as the difference between the reference block/sample 332 and the adjacent sample/block 230 . The cost associated with the reference picture 303 (reference picture C) is calculated as the difference between the reference block/sample 333 and the adjacent sample/block 230 . The cost associated with the reference picture 304 (reference picture D) is calculated as the difference between the reference block/sample 334 and the adjacent sample/block 230 .

In this example, the cost calculated for reference picture B (reference picture 302) is the lowest among all reference pictures in RPL 240, so it is assigned a reordered index of 0. The cost calculated for reference picture C (reference picture 303) is the lowest among all reference pictures in RPL 240, so it is assigned a reordered index of 1. Reference picture D has the third lowest cost in RPL and is assigned index 2. Reference picture A has the fourth lowest cost in RPL and is assigned index 3, and so on.

In some embodiments, MVs or motion information from one or more adjacent reconstruction blocks in CTUs adjacent to the current CTU are used as representative MVs for the current CTU. In some embodiments, the MV or motion from the last N neighboring reconstruction blocks (N≥0) in neighboring CTUs is used as the representative MV for the current CTU. In some embodiments, MVs or motions from one or more adjacent reconstruction blocks in adjacent CTUs are weighted or averaged, and the weighted MV or averaged MV is used as the representative MV for the current CTU.

In some embodiments, the MV or motion from one or more blocks in the current CTU is used as the representative MV for the current CTU. In some embodiments, the MV or motion from one or more inter prediction blocks or one or more AMVP mode blocks in the current CTU is used as the representative MV for the current CTU.

In some embodiments, MVs or motions from the first N blocks (N≥0) in the current CTU are used as representative MVs for the current CTU. In some embodiments, the MV or motion from one or more blocks in the current CTU are weighted or averaged, and the weighted MV or averaged MV is used as the representative MV for the current CTU.

In some embodiments, the temporal MV from the co-located CTU or the temporal MV from the reference picture CTU is used as the representative MV of the current CTU. In some embodiments, the temporal MV from the co-located CTU or the temporal MV from the reference picture CTU is weighted or averaged, and the weighted MV or averaged MV is used as the representative MV of the current CTU.

In some embodiments, the MV(s) from neighboring positions of the current CTU are inherited as the representative MV of the current CTU. Figure 4 shows neighbor positions used in CTU-based reference list reordering. This figure shows the current CTU 400. Adjacent positions (such as A0, A1, A2, B0, B1, C0, C1 in the figure) can be adjacent CTUs or adjacent reconstruction blocks, and the adjacent reconstruction samples of the current CTU are used to determine the reference picture order. .

In some embodiments, history-based motion information or history-based MV is used as the representative MV of the current CTU.

In some embodiments, the reference picture reordering process is sent per frame or picture instead of per CTU. The reference picture list can be reordered based on explicit signaling or flags before encoding or decoding the current picture. The order of reference pictures can also be determined implicitly for each frame or picture.

In some embodiments, before encoding or decoding, a joint list (of reference pictures) for unidirectional prediction and a joint list (of reference pictures) for bidirectional prediction are formed, and then the reordering process is performed. The additional redundancy check processing to form the joint list is not processed, so more reference pictures can be inserted into the joint list.

In some embodiments, when motion vector difference (MVD) symbol derivation is enabled, reordering is performed before MVD symbol derivation. Since the symbol of MVD has not yet been decided, in order to determine the order of the reference picture list, the motion vector predictor (MVP) (as the representative MV of CTU) first determines the adjacent reconstructed block and the reference picture in RPL. Template matching cost or SATD cost between corresponding reference blocks.

In some embodiments, when the difference/cost between the current picture and the current reference picture is calculated, all MVPs from different reference pictures are scaled to the current reference picture.

In some embodiments, when encoding or decoding the current CTU, the order of reference pictures is determined based on the reference picture distribution of previously encoded and decoded CTUs. (Figure 5 shows the current CTU and the previous codec CTU in the current picture.) For example, the order of reference pictures in the current CTU depends on the reference picture distribution of one previous codec CTU. For another example, the order of reference pictures in the current CTU depends on the reference picture distribution of previously coded CTU lines. For another example, the history-based table records the distribution of reference picture selection when encoding or decoding each CTU, and the history-based table is used to sort the reference pictures of the current CTU.

Any of the previously proposed methods may be implemented in the encoder and/or decoder. For example, any of the proposed methods may be implemented in a predictor derivation module of the encoder and/or a predictor derivation module of the decoder. Alternatively, any of the proposed methods may be implemented as circuitry coupled to a predictor derivation module of the encoder and/or a predictor derivation module of the decoder to provide information required by the predictor derivation module. Ⅳ . Video encoder example

Figure 6 illustrates an example video encoder 600 that may implement a CTU-based reference picture list. As shown, video encoder 600 receives an input video signal from video source 605 and encodes the signal into a bit stream 695. Video encoder 600 has several components or modules for encoding signals from video source 605, including at least some components selected from the following: transform module 610, quantization module 611, inverse quantization module 614, inverse transform Module 615, intra estimation module 620, intra prediction module 625, motion compensation module 630, motion estimation module 635, loop filter 645, reconstructed picture buffer 650, MV buffer 665, MV prediction Module 675 and entropy encoder 690. Motion compensation module 630 and motion estimation module 635 are part of inter prediction module 640.

In some embodiments, modules 610-690 are modules of software instructions executed by one or more processing units (eg, processors) of a computing device or electronic device. In some embodiments, the modules 610-690 are hardware circuit modules implemented by one or more integrated circuits (ICs) of the electronic device. Although modules 610-690 are shown as individual modules, some modules may be combined into a single module.

Video source 605 provides a raw video signal, which represents the pixel data of each video frame without compression. The subtractor 608 calculates the difference between the original video pixel data of the video source 605 and the predicted pixel data 613 from the motion compensation module 630 or the intra prediction module 625 as the prediction residual 609 . Transform module 610 converts the difference values (or residual pixel data or residual signal) into transform coefficients (eg, by performing a discrete cosine transform or DCT). The quantization module 611 quantizes the transform coefficients into quantized data (or quantized coefficients) 612, which is encoded into a bit stream 695 by the entropy encoder 690.

The inverse quantization module 614 dequantizes the quantized data (or quantized coefficients) 612 to obtain transform coefficients, and the inverse transform module 615 performs an inverse transform on the transform coefficients to generate a reconstructed residual 619 . The reconstructed residual 619 is added to the predicted pixel data 613 to produce reconstructed pixel data 617 . In some embodiments, the reconstructed pixel data 617 is temporarily stored in a line buffer (line buffer not shown) for intra prediction and spatial MV prediction. The reconstructed pixels are filtered by loop filter 645 and stored in reconstructed picture buffer 650. In some embodiments, the reconstructed picture buffer 650 is a memory external to the video encoder 600 . In some embodiments, the reconstructed picture buffer 650 is an internal memory of the video encoder 600 .

The intra estimation module 620 performs intra prediction based on the reconstructed pixel data 617 to generate intra prediction data. The intra prediction data is provided to an entropy encoder 690 to be encoded into a bit stream 695 . The intra prediction data is also used by the intra prediction module 625 to generate predicted pixel data 613 .

The motion estimation module 635 performs inter prediction by generating MVs to reference pixel data of previously decoded frames stored in the reconstructed picture buffer 650 . These MVs are provided to the motion compensation module 630 to generate predicted pixel data.

Rather than encoding the complete actual MV in the bitstream, video encoder 600 uses MV prediction to generate a predicted MV, and the difference between the MV used for motion compensation and the predicted MV is encoded as residual motion. The data is stored in bit stream 695.

The MV prediction module 675 generates a predicted MV based on the reference MV generated for encoding the previous video frame, ie, the motion compensation MV used to perform motion compensation. The MV prediction module 675 obtains the reference MV from the previous video frame from the MV buffer 665 . The video encoder 600 stores the MV generated for the current video frame in the MV buffer 665 as a reference MV for generating a predicted MV.

The MV prediction module 675 uses the reference MV to create predicted MVs. The predicted MV can be calculated by spatial MV prediction or temporal MV prediction. The difference between the predicted MV and the motion compensated MV (MC MV) of the current frame (residual motion data) is encoded in the bit stream 695 by the entropy encoder 690 .

Entropy encoder 690 encodes various parameters and data into bit stream 695 by using entropy coding and decoding techniques such as context-adaptive binary arithmetic coding (CABAC) or Huffman coding. The entropy encoder 690 encodes various header elements, flags along with the quantized transform coefficients 612 and residual motion data as syntax elements into the bit stream 695. The bit stream 695 is then stored in a storage device or transmitted to the decoder via a communication medium such as a network.

The loop filter 645 performs a filtering or smoothing operation on the reconstructed pixel data 617 to reduce coding and decoding artifacts, especially at the boundaries of pixel blocks. In some embodiments, the filtering operations performed by the loop filter 645 include a deblock filter (DBF), a sample adaptive offset (SAO), and/or an adaptive loop. Filter (adaptive loop filter, ALF for short).

Figure 7 illustrates a portion of video encoder 600 that implements a CTU-based or frame-based reference picture list. Specifically, this figure shows the components of inter prediction module 640 of video encoder 600. As shown, the inter prediction module 640 obtains candidate motion vectors from the MV buffer 665 and searches the contents of the reconstructed picture buffer 650 to generate predicted pixel data 613 through motion compensation.

The inter prediction module 640 includes a motion compensation module 630, a motion estimation module 635, a representative MV selector 705, a reference picture list reordering module 710, and a reference picture list (RPL) of the current CTU or frame. )730.

The representative MV selector 705 obtains candidate motion vectors from the MV buffer 665 to derive or select a representative MV for the current CTU or frame. Representative MV selector 705 may derive or select representative MVs from: MVs used to reconstruct one or more blocks adjacent to the current CTU, or MVs from one or more blocks in the current CTU, or from The temporal MV of the co-located CTU or reference picture CTU, or the MV inherited from the adjacent position of the current CTU, or the motion vector predictor (MVP) of the block in the current CTU.

The RPL reordering module 720 uses the selected or derived representative MVs (from 705 ) to calculate a template matching (TM) cost associated with the reference picture in the RPL 730 . In some embodiments, the cost associated with each reference picture in RPL 730 is based on (i) neighboring samples or neighboring blocks of the current CTU and (ii) corresponding reference samples in the reference picture identified by the representative MV The difference between them is measured to determine. (Neighbor samples and reference samples are obtained from reconstructed picture buffer 650.) Based on the calculated cost, RPL reordering module 720 assigns indices to reference pictures in RPL 730.

Motion estimation module 635 performs motion estimation to provide one or more motion vectors to motion compensation module 630 to perform motion compensation. The motion estimation module 635 also sends the selected motion vector to the entropy encoder using the index assigned to the reference picture in the RPL 730 .

Figure 8 conceptually illustrates a process 800 for encoding pixel blocks using a CTU-based reference picture list. In some embodiments, one or more processing units (eg, processors) of a computing device implementing encoder 600 perform process 800 by executing instructions stored in a computer-readable medium. In some embodiments, an electronic device implementing encoder 600 performs process 800.

The video encoder receives (at block 810) a reference picture list (RPL) for the current coding tree unit (CTU) of the current picture. RPL recognizes multiple reference pictures.

The video encoder assigns (at block 820) indices to multiple reference pictures in the RPL of the current CTU. In some embodiments, indexes are configured to multiple reference pictures in the RPL based on explicit signaling. In some embodiments, an index is configured to a plurality of reference pictures in the RPL based on a history-based table recording the distribution of reference picture selections when encoding or decoding each CTU of the current picture.

In some embodiments, the video encoder derives a representative motion vector (MV) of the current CTU and calculates the cost of multiple reference pictures. The cost of each reference picture is calculated based on (i) the neighboring samples of the current CTU and (ii) the reference samples in the reference picture identified by the representative MV, and based on the calculated cost, the index is assigned to the multiple based on the RPL. reference picture.

In some embodiments, the representative MV is derived from the MV used to reconstruct one or more blocks adjacent to the current CTU, and the representative MV may be a weighted MV used to reconstruct the MV of the block adjacent to the current CTU. average. In some embodiments, the representative MV is derived from the MVs of one or more blocks in the current CTU, and the representative MV may be a weighted average of the MVs from one or more blocks in the current CTU. In some embodiments, the representative MV is derived from the temporal MV from the co-located CTU or reference picture CTU, and the representative MV may be a weighted average of the temporal MV from the co-located CTU or reference picture CTU. Representative MVs are derived from MVs inherited from neighboring positions of the current CTU. The video encoder can use the motion vector predictor (MVP) of the block in the current CTU as the representative MV of the CTU.

The video encoder receives (at block 830) data that will be encoded into blocks of the current CTU. The video encoder selects one or more reference pictures from the RPL to generate inter predictions for the blocks of the current CTU by encoding the blocks of the CTU using the assigned index (at block 840). Ⅳ . Sample video decoder

In some embodiments, the encoder may send (or generate) one or more syntax elements in the bitstream such that the decoder may parse the one or more syntax elements from the bitstream.

Figure 9 illustrates an example video decoder 900 that may implement a CTU-based or frame-based reference picture list. As shown in the figure, the video decoder 900 is an image decoding or video decoding circuit that receives a bit stream 995 and decodes the content of the bit stream into pixel data of a video frame for display. Video decoder 900 has several components or modules for decoding bit stream 995, including some components selected from the following: inverse quantization module 911, inverse transform module 910, intra prediction module 925, motion compensation module 930, loop filter 945, decoded picture buffer 950, MV buffer 965, MV prediction module 975 and parser 990. Motion compensation module 930 is part of inter prediction module 940 .

In some embodiments, modules 910-990 are modules of software instructions executed by one or more processing units (eg, processors) of a computing device. In some embodiments, modules 910-990 are hardware circuit modules implemented by one or more ICs of an electronic device. Although modules 910-990 are shown as individual modules, some modules may be combined into a single module.

A parser 990 (or entropy decoder) receives the bitstream 995 and performs initial parsing according to the syntax defined by the video encoding or image encoding standard. Parsed syntax elements include various header elements, flags, and quantization data (or quantization coefficients) 912 . The parser 990 parses out various syntax elements by using entropy coding and decoding techniques such as context-adaptive binary arithmetic coding (ABAC) or Huffman encoding.

The inverse quantization module 911 dequantizes the quantized data (or quantized coefficients) 912 to obtain transform coefficients, and the inverse transform module 910 inversely transforms the transform coefficients 916 to generate a reconstructed residual signal 919 . The reconstructed residual signal 919 is added to the predicted pixel data 913 from the intra prediction module 925 or the motion compensation module 930 to generate decoded pixel data 917 . The decoded pixel data is filtered by loop filter 945 and stored in decoded picture buffer 950. In some embodiments, the decoded picture buffer 950 is a memory external to the video decoder 900 . In some embodiments, the decoded picture buffer 950 is an internal memory of the video decoder 900 .

Intra prediction module 925 receives intra prediction data from bitstream 995 and, accordingly, generates predicted pixel data 913 from decoded pixel data 917 stored in decoded picture buffer 950 . In some embodiments, decoded pixel data 917 is also stored in a line buffer (not shown) for intra prediction and spatial MV prediction.

In some embodiments, the contents of picture buffer 950 are decoded for display. The display device 955 either obtains the contents of the decoded image buffer 950 for direct display, or obtains the contents of the decoded image buffer to a display buffer. In some embodiments, the display device receives pixel values from decoded picture buffer 950 via pixel transfer.

The motion compensation module 930 generates predicted pixel data 913 from the decoded pixel data 917 stored in the decoded picture buffer 950 according to the motion compensated MV (MC MV). These motion compensated MVs are decoded by adding the residual motion data received from bit stream 995 to the predicted MV received from MV prediction module 975 .

The MV prediction module 975 generates predicted MVs based on reference MVs generated for decoding previous video frames (eg, motion compensation MVs used to perform motion compensation). The MV prediction module 975 obtains the reference MV of the previous video frame from the MV buffer 965 . The video decoder 900 stores the motion compensated MV generated for decoding the current video frame in the MV buffer 965 as a reference MV for generating the predicted MV.

Loop filter 945 performs a filtering or smoothing operation on decoded pixel data 917 to reduce encoding and decoding artifacts, particularly at pixel block boundaries. In some embodiments, the filtering or smoothing operations performed by the loop filter 945 include a deblock filter (DBF), a sample adaptive offset (SAO), and/or an adaptive loop. Adaptive loop filter (ALF).

Figure 10 illustrates portions of a video decoder 900 that implements a CTU-based or frame-based reference picture list. Specifically, this figure illustrates the components of the inter prediction module 940 of the video decoder 900 . As shown, the inter prediction module 940 obtains candidate motion vectors from the contents of the MV buffer 965 and the decoded picture buffer 950 to generate predicted pixel data 913 through motion compensation.

The inter prediction module 940 includes a motion compensation module 930, a motion decoder 1035, a representative MV selector 1005, a reference picture list reordering module 1010, and a reference picture list (RPL) 1030 for the current CTU or frame.

The representative MV selector 1005 obtains candidate motion vectors from the MV buffer 965 to derive or select a representative MV for the current CTU or frame. The representative MV selector 1005 may derive or select representative MVs from: MVs used to reconstruct one or more blocks adjacent to the current CTU, or MVs from one or more blocks in the current CTU, or from The temporal MV of the co-located CTU or reference picture CTU, or the MV inherited from the adjacent position of the current CTU, or the motion vector predictor (MVP) of the block in the current CTU.

The RPL re-ranking module 1020 uses the selected or derived representative MVs (from 1005) to calculate the template matching (TM) cost associated with the reference picture in the RPL 1030. In some embodiments, the cost associated with each reference picture in RPL 1030 is based on (i) neighboring samples or neighboring blocks of the current CTU and (ii) corresponding reference samples in the reference picture identified by the representative MV The difference between them is measured to determine. (Neighbor samples and reference samples are obtained from the decoded picture buffer 950.) Based on the calculated cost, the RPL reordering module 1020 assigns an index to the reference picture in the RPL 1030.

Entropy decoder 990 receives signaling indicating motion information for the current block and relays the motion information to motion decoder 1035 as MVs for motion compensation (MC MVs). Motion decoder 1035 may use one or more indices provided by entropy decoder 990 to identify one or more reference pictures in RPL 1030. The compensation module 930 performs motion compensation MV according to the MC using prediction samples obtained from the decoded picture buffer 950. The obtained prediction samples are samples of the identified reference pictures.

Figure 11 conceptually illustrates a process 1100 for decoding blocks using a CTU-based reference picture list. In some embodiments, one or more processing units (eg, processors) of a computing device implementing decoder 900 perform process 1100 by executing instructions stored in a computer-readable medium. In some embodiments, an electronic device implementing decoder 900 performs process 1100 .

The video decoder receives (at block 1110) a reference picture list (RPL) for the current codec tree unit (CTU) of the current picture. RPL recognizes multiple reference pictures.

The video decoder assigns (at block 1120) indices to multiple reference pictures in the RPL of the current CTU. In some embodiments, indexes are assigned to multiple reference pictures in the RPL based on explicit signaling. In some embodiments, indexes are assigned to multiple reference pictures in the RPL based on a history-based table that records the distribution of reference picture selections when decoding or decoding each CTU of the current picture.

In some embodiments, the video decoder derives a representative motion vector (MV) of the current CTU and calculates the cost of multiple reference pictures. The cost of each reference picture is calculated based on (i) the neighboring samples of the current CTU and (ii) the reference samples in the reference picture identified by the representative MV, and based on the calculated cost, the index is assigned to the multiple based on the RPL. reference picture.

In some embodiments, the representative MV is derived from the MV used to reconstruct one or more blocks adjacent to the current CTU, and the representative MV may be a weighted MV used to reconstruct the MV of the block adjacent to the current CTU. average. In some embodiments, the representative MV is derived from the MVs of one or more blocks in the current CTU, and the representative MV may be a weighted average of the MVs from one or more blocks in the current CTU. In some embodiments, the representative MV is derived from the temporal MV from the co-located CTU or reference picture CTU, and the representative MV may be a weighted average of the temporal MV from the co-located CTU or reference picture CTU. Representative MVs are derived from MVs inherited from neighboring positions of the current CTU. The video decoder may use the motion vector predictor (MVP) of the block in the current CTU as the representative MV of the CTU.

The video decoder receives (at block 1130) data which will be decoded into blocks of the current CTU. The video decoder reconstructs (at block 1140) the blocks of the CTU by selecting one or more reference pictures from the RPL using the assigned index to generate inter predictions of the blocks of the current CTU. The decoder may then provide the reconstructed current block for display as part of the reconstructed current picture. Ⅵ . Example electronic system

Many of the above features and applications are implemented as software processes specified as a set of instructions recorded on a computer-readable storage medium (also referred to as a computer-readable medium). When these instructions are executed by one or more computing or processing units (eg, one or more processors, processor cores, or other processing units), they cause the processing unit to perform the actions indicated in the instructions. Examples of computer-readable media include, but are not limited to, compact disc read-only memory (CD-ROM), flash memory drives, random-access memory (RAM) chips, Hard drive, erasable programmble read-only memory (EPROM), electrically erasable proagrammble read-only memory (EEPROM), etc. . Computer-readable media does not include carrier waves and electronic signals transmitted over wireless or wired connections.

In this specification, the term "software" is intended to include firmware that resides in read-only memory or applications stored in magnetic memory that can be read into memory for processing by a processor. Furthermore, in some embodiments, multiple software inventions may be implemented as sub-portions of a larger program while retaining distinct software inventions. In some embodiments, multiple software inventions may also be implemented as separate programs. Finally, any combination of individual programs that together implement the software inventions described herein is within the scope of this disclosure. In some embodiments, a software program, when installed to run on one or more electronic systems, defines one or more specific machine implementations that process and perform the operations of the software program.

Figure 12 conceptually illustrates an electronic system 1200 implementing some embodiments of the present disclosure. Electronic system 1200 may be a computer (eg, desktop computer, personal computer, tablet computer, etc.), telephone, PDA, or any other type of electronic device. Such electronic systems include various types of computer-readable media and interfaces for various other types of computer-readable media. Electronic system 1200 includes bus 1205, processing unit 1210, graphics-processing unit (GPU) 1215, system memory 1220, network 1225, read-only memory 1230, permanent storage device 1235, input device 1240 and Output device 1245.

Bus 1205 collectively represents all system, peripheral, and chipset busses of the numerous internal devices that are communicatively connected to electronic system 1200 . For example, bus 1205 communicatively connects processing unit 1210 to GPU 1215, read-only memory 1230, system memory 1220, and persistent storage 1235.

The processing unit 1210 obtains instructions to be executed and data to be processed from these various memory units in order to perform the processes of the present disclosure. In different embodiments, the processing unit may be a single processor or a multi-core processor. Some instructions are passed to and executed by the GPU 1215. GPU 1215 may offload various computations or supplement the image processing provided by processing unit 1210.

Read-only memory (ROM) 1230 stores static data and instructions used by the processing unit 1210 and other modules of the electronic system. On the other hand, the permanent storage device 1235 is a read-write storage device. This device is a non-volatile storage unit that stores instructions and data even when the electronic system 1200 is turned off. Some embodiments of the present disclosure use large-capacity memory devices (such as magnetic disks or optical disks and their corresponding disk drives) as the permanent storage device 1235 .

Other embodiments use off-mount storage devices (such as floppy disks, flash memory devices, etc., and their corresponding disk drives) as permanent storage devices. Like persistent storage device 1235, system memory 1220 is a read-write memory device. However, unlike the permanent storage device 1235, the system memory 1220 is a volatile read-write memory, such as a random access memory. System memory 1220 stores some instructions and data used by the processor during operation. In some embodiments, processes in accordance with the present disclosure are stored in system memory 1220, persistent storage device 1235, and/or read-only memory 1230. For example, according to some embodiments of the present disclosure, various memory units include instructions for processing multimedia clips. From these various memory units, the processing unit 1210 obtains instructions to be executed and data to be processed in order to perform the processing of some embodiments.

Bus 1205 also connects to input device 1240 and output device 1245 . Input device 1240 enables the user to communicate information and select commands to the electronic system. Input devices 1240 include alphanumeric keyboards and pointing devices (also known as "cursor control devices"), cameras (eg, webcams), microphones or similar devices for receiving voice commands, and the like. Output device 1245 displays images or output material generated by the electronic system. Output devices 1245 include printers and display devices, such as cathode ray tubes (CRT) or liquid crystal displays (LCD), as well as speakers or similar audio output devices. Some embodiments include devices used as input and output devices, such as touch screens.

Finally, as shown in Figure 12, bus 1205 also couples electronic system 1200 to network 1225 via a network interface card (not shown). In this manner, the computer may be part of a computer network, such as a local area network ("LAN"), a wide area network ("WAN"), or an intranet, or a network of multiple networks, such as the Internet. Electronic system 1200 Any or all components may be used in conjunction with the present disclosure.

Some embodiments include electronic components, such as microprocessors, storage devices, and memories that store computer program instructions on a machine-readable or computer-readable medium (also referred to as a computer-readable storage medium, machine-readable medium, or machine-readable medium). readable storage media). Some examples of such computer-readable media include RAM, ROM, read-only compact discs (CD-ROM), recordable compact discs (CD-R), rewritable discs compact discs (CD-RW for short), read-only digital versatile discs (e.g., DVD-ROM, double-layer DVD-ROM), various recordable/rewritable DVDs (e.g., DVD -RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SD card, mini SD card, micro SD card, etc.), magnetic and/or solid-state hard drives, read-only and recordable Blu-Ray ® optical discs, ultra-density optical discs, any other optical or magnetic media, and floppy disks. The computer-readable medium may store a computer program that is executable by at least one processing unit and includes a set of instructions for performing various operations. Examples of computer programs or computer code include machine code such as that produced by a compiler, as well as documents that include high-level code executed by a computer, electronic component, or microprocessor using an interpreter.

While the above discussion primarily relates to microprocessors or multi-core processors executing software, many of the above features and applications are performed by one or more integrated circuits, such as application specific integrated circuits (ASICs) or field programmable Design a field programmable gate array (FPGA for short). In some embodiments, such integrated circuits execute instructions stored on the circuit itself. Additionally, some embodiments execute software stored in a programmable logic device (PLD), ROM, or RAM device.

As used in this specification and any claim in this application, the terms "computer", "server", "processor" and "memory" refer to electronic or other technical equipment. These terms do not include persons or groups of people. For the purposes of this specification, the term display or display refers to display on an electronic device. As used in this specification and any claim claimed in this application, the terms "computer-readable medium," "computer-readable medium," and "machine-readable medium" are exclusively limited to tangible physical media that stores information in a computer-readable form. object. These terms do not include any wireless signals, wired download signals and any other short-lived signals.

Although the present disclosure has been described with reference to numerous specific details, those of ordinary skill in the art will recognize that the disclosure may be embodied in other specific forms without departing from the spirit of the disclosure. Additionally, many figures (including Figures 8 and 11) conceptually illustrate processing. The specific operations of these processes may not be performed in the exact sequence shown and described. Specific operations may not be performed in a continuous series of operations, and different specific operations may be performed in different embodiments. Furthermore, this processing can be implemented using several sub-processes or as part of a larger macro-process. Accordingly, one of ordinary skill in the art will understand that the present disclosure is not limited by the foregoing illustrative details, but rather by the scope of the appended claims. Additional information

The subject matter described herein sometimes represents different components that are contained within or connected to other different components. It will be understood that the structures described are examples only and may in fact be implemented by many other structures to achieve the same functionality, and conceptually any arrangement of components achieving the same functionality is in fact "related" , in order to achieve the required functions. Therefore, any two components, regardless of structure or intermediate components, that are combined to achieve a specific function are considered to be "interrelated" to achieve the required function. Likewise, any two associated components are considered to be "operably connected" or "operably coupled" to each other to achieve the specified functionality. Any two components that can be associated with each other are also said to be "operably coupled" with each other to achieve the specified functionality. Any two components that can be associated with each other are also said to be "operably coupled" with each other to achieve the specified functionality. Specific examples of operably connected components include, but are not limited to, physically pairable and/or physically interacting components, and/or wirelessly interactable and/or wirelessly interacting components, and/or logically interacting and/or logically interacting components. Interactive components.

Furthermore, with regard to the use of substantially any plural and/or singular term, one of ordinary skill in the art may convert the plural to the singular and/or from the singular to the plural depending on the context and/or application. For the sake of clarity, this disclosure expressly sets out different singular/plural arrangements.

In addition, those of ordinary skill in the art will understand that generally, terms used in the present invention, especially within the scope of the application, such as the subject matter of the scope of the application, are generally used as "open" terms, for example, "including" should be interpreted as "Including but not limited to", "have" should be understood as "at least have", "include" should be interpreted as "including but not limited to", etc. One of ordinary skill in the art will further understand that if a specific amount of claimed content is intended to be introduced, this will be explicitly stated within the claimed scope and, in the absence of such content, it will not be shown. For example, to aid understanding, the following patent claims may contain the phrases "at least one" and "one or a plurality" to introduce the content of the patent claims. However, the use of these phrases should not be construed as implying that the use of the indefinite article "a" or "an" to introduce the scope of the claim limits any particular patent scope. Even when the same claim includes the introductory phrase "one or plural" or "at least one", the indefinite article, such as "a" or "an", shall be construed to mean at least one or more, for The same holds true for the use of an explicit description to introduce the scope of a patent claim. Furthermore, even if an introductory reference to a particular number is expressly cited, one of ordinary skill in the art would recognize that such reference should be construed to mean the number cited, e.g., "two citations" without other modifications, means at least Two citations, or two or more citations. Furthermore, where an expression similar to "at least one of A, B, and C" is used, it is usually stated so that a person of ordinary skill in the art can understand the expression, for example, "the system includes at least one of A, B, and C" "At least one of" will include, but is not limited to, a system with A alone, a system with B alone, a system with C alone, a system with A and B, a system with A and C, a system with B and C, and/ Or a system with A, B and C etc. It will be further understood by those of ordinary skill in the art that any separated words and/or phrases represented by two or more alternative terms, whether in the specification, patent claims or drawings, should be understood as , including the possibility of one, one, or both of these terms. For example, "A or B" should be understood as the possibility of "A", or "B", or "A and B".

It will be understood from the foregoing that various embodiments of the present invention have been described for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the various embodiments disclosed herein are not to be construed as limiting, and the true scope and claims are indicated by the claims.

200:Current CTU 210:Current picture 220: Representative MV 230: Adjacent samples/block 240:RPL 400:Current CTU 605:Video source 608:Subtractor 610:Transformation module 611:Quantization module 612: Transformation coefficient 613: Predict pixel data 614:Inverse quantization module 615:Inverse transformation module 616: Transformation coefficient 617:Reconstructed pixel data 619:Reconstruction residuals 620: Intra-frame estimation module 625: Intra prediction module 630: Motion compensation module 635: Motion estimation module 640: Inter-frame prediction module 645: Loop filter 650: Reconstruct image buffer 665:MV buffer 675:MV prediction module 695:Bit stream 705: Representative MV selector 720:RPL reordering module 730:RPL 800: Processing 810, 820, 830, 840: steps 900:Video decoder 910:Inverse transformation module 911:Inverse quantization module 912:Quantitative data 913: Predict pixel data 916: Transformation coefficient 917: Decode pixel data 919:Reconstruct the residual signal 925: Intra prediction module 930: Motion compensation module 940: Inter prediction module 950: Decode picture buffer 955:Display device 965:MV buffer 975:MV prediction module 990:Entropy decoder 995:bit stream 1005: Representative MV selector 1020:RPL reordering module 1030:RPL 1035:Motion decoder 1100: Processing 1110, 1120, 1130, 1140: steps 1200: Electronic systems 1205:Bus 1210: Processing unit 1215:GPU 1220:System memory 1225:Internet 1230: Read-only memory 1235:Permanent storage of equipment 1240:Input device 1245:Output device

The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this disclosure. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. Notably, the drawings are not necessarily to scale as certain components may be shown disproportionately large in actual implementations in order to clearly illustrate the concepts of the present disclosure. Figures 1A-B illustrate various syntax structures and elements related to reference picture management signaling. Figure 2 conceptually illustrates reconstructed samples used in coding tree unit (CTU) based reference picture list reordering. Figure 3 conceptually illustrates the use of the representative motion vector (MV) of the CTU to reorder the reference picture list (RPL) of the CTU. Figure 4 shows neighbor positions used in CTU-based reference list reordering. Figure 5 shows the current CTU and the previously codected CTU in the current picture. Figure 6 illustrates an example video encoder that may implement a CTU-based reference picture list. Figure 7 conceptually illustrates portions of a video encoder that implements a CTU-based reference picture list. Figure 8 conceptually illustrates the process of encoding pixel blocks using a CTU-based reference picture list. Figure 9 illustrates an example video decoder that may implement a CTU-based reference picture list. Figure 10 shows the part of the video decoder that implements the CTU-based reference picture list. Figure 11 conceptually illustrates the process of decoding a block of pixels using a CTU-based reference picture list. Figure 12 conceptually illustrates an electronic system for implementing some embodiments of the present disclosure.

200:Current CTU

210:Current picture

220: Representative MV

230: Adjacent samples/block

240:RPL

Claims (15)

A video coding and decoding method includes: receiving a reference picture list of a current codec tree unit of a current picture, the reference picture list identifying multiple reference pictures; Assign multiple indices to the reference pictures in the reference picture list of the current codec tree unit; Receive data to be encoded or decoded into blocks of the current codec tree unit; and Inter predictions are generated by selecting one or more reference pictures from the reference picture list by encoding or decoding the blocks of the current codec tree unit using the assigned indices. The video encoding and decoding method as described in claim 1, wherein the indices are assigned to the reference pictures in the reference picture list based on explicit signaling. The video encoding and decoding method as described in request item 1 further includes: Derive a representative motion vector for the current codec tree unit; and Computing a plurality of costs for the reference pictures, wherein the cost for each reference picture is based on (i) a plurality of neighboring samples of the current codec tree unit and (ii) a plurality of the reference pictures identified by the representative motion vectors. Reference samples are calculated, wherein the indices are assigned to the reference pictures in the reference picture list based on the calculated costs. The video encoding and decoding method of claim 3, wherein the representative motion vector is derived from a plurality of motion vectors used to reconstruct one or more blocks adjacent to the current encoding and decoding tree unit. The video coding and decoding method of claim 4, wherein the representative motion vector is a weighted average of the motion vectors used to reconstruct the blocks adjacent to the current codec tree unit. The video encoding and decoding method of claim 3, wherein the representative MV is derived from multiple motion vectors of one or more blocks in the current CTU. The video encoding and decoding method of claim 6, wherein the representative motion vector is a weighted average of the motion vectors of the one or more blocks in the current CTU. The video encoding and decoding method of claim 3, wherein the representative MV is derived from multiple temporal MVs from a co-located CTU or a reference picture CTU. The video encoding and decoding method of claim 8, wherein the representative MV is a weighted average of the temporal MVs from the co-located CTU or the reference picture CTU. The video encoding and decoding method as described in claim 3, wherein the representative MV is derived from multiple MVs inherited from multiple adjacent positions of the current CTU. The video encoding and decoding method as claimed in claim 3, wherein a motion vector predictor of a block in the current CTU is used as the representative MV of the CTU. The video encoding and decoding method as described in claim 3, wherein the adjacent samples of the current CTU are located in multiple CTUs adjacent to the current CTU. The video encoding and decoding method as described in claim 1, wherein indexes are assigned to the reference pictures in the reference picture list according to a history-based table, which is recorded in each of the current pictures. The distribution of multiple reference picture selections when the CTU performs encoding or decoding. An electronic device includes: a video codec circuit configured to perform the following operations, including: receiving a reference picture list of a current codec tree unit of a current picture, the reference picture list identifying a plurality of reference pictures; Assign multiple indices to the reference pictures in the reference picture list of the current codec tree unit; Receive data to be encoded or decoded into blocks of the current codec tree unit; and Inter predictions are generated by selecting one or more reference pictures from the reference picture list by encoding or decoding the blocks of the current codec tree unit using the assigned indices. A video decoding method includes: receiving a reference picture list of a current codec tree unit of a current picture, the reference picture list identifying a plurality of reference pictures; Assign multiple indices to the reference pictures in the reference picture list of the current codec tree unit; Receive data to be decoded into blocks of the current codec tree unit; and Inter predictions are generated by selecting one or more reference pictures from the reference picture list by reconstructing the blocks of the current codec tree unit using the assigned indices.