Method for performing wraparound motion compensation

Abstract

This disclosure provides a method for performing wraparound motion compensation. The method may include receiving a first wraparound motion compensation flag, where a second wraparound motion compensation flag is associated with a picture, determining whether the first wraparound motion compensation flag is enabled, and in response to determining that the first wraparound motion compensation flag is enabled, receiving a wraparound motion compensation offset, where the wraparound motion compensation offset is associated with the picture, and performing wraparound motion compensation on the picture according to the first wraparound motion compensation flag and the wraparound motion compensation offset.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0001] This disclosure claims priority and the benefit of priority to U.S. Provisional Patent Application No. 62 / 949,396, filed on December 17, 2019. The provisional application is hereby incorporated by reference in its entirety herein.

[0002] Technical Field

[0002] This disclosure generally relates to video processing, and more particularly, to methods and systems for performing wraparound motion compensation.

Background Art

[0003] Background

[0003] Video is a set of static pictures (or "frames") that capture visual information. To reduce memory storage and transmission bandwidth, video can be compressed before storage or transmission and restored before display. The compression process is usually referred to as encoding, and the restoration process is usually referred to as decoding. Most commonly, there are various video encoding formats that use standardized video encoding techniques based on prediction, transformation, quantization, entropy encoding, and in - loop filtering. Video encoding standards such as the High Efficiency Video Coding (e.g., HEVC / H.265) standard, which specifies a particular video encoding format, the Versatile Video Coding (e.g., VVC / H.266), and the standard AVS standard have been developed by standardization organizations. As evolving video encoding techniques are successively adopted by video standards, the encoding efficiency of new video encoding standards becomes increasingly higher.

Summary of the Invention

Means for Solving the Problems

[0004] Summary of the Disclosure

[0004] Embodiments of the present disclosure provide a method for performing motion compensation. The method includes receiving a first wraparound motion compensation flag, where the first wraparound motion compensation flag is associated with a picture; determining whether the first wraparound motion compensation flag is valid; in response to determining that the first wraparound motion compensation flag is valid, receiving a wraparound motion compensation offset, where the wraparound motion compensation offset is associated with the picture; and performing wraparound motion compensation on the picture according to the first wraparound motion compensation flag and the wraparound motion compensation offset.

[0005]

[0005] Embodiments of the present disclosure further provide a system for performing motion compensation. The system includes a memory storing a set of instructions and a processor configured to execute the set of instructions to cause the system to receive a first wraparound motion compensation flag, where the first wraparound motion compensation flag is associated with a picture; determine whether the first wraparound motion compensation flag is valid; in response to determining that the first wraparound motion compensation flag is valid, receive a wraparound motion compensation offset, where the wraparound motion compensation offset is associated with the picture; and perform wraparound motion compensation on the picture according to the first wraparound motion compensation flag and the wraparound motion compensation offset.

[0006]

[0006] Embodiments of the present disclosure are non - transitory computer - readable media storing a set of instructions, the set of instructions being executable by one or more processors of a device to initiate a method for performing motion compensation on the device, the method comprising receiving a first wrap - around motion compensation flag, wherein the first wrap - around motion compensation flag is associated with a picture; determining whether the first wrap - around motion compensation flag is valid; in response to determining that the first wrap - around motion compensation flag is valid, receiving a wrap - around motion compensation offset, wherein the wrap - around motion compensation offset is associated with the picture; and performing wrap - around motion compensation on the picture according to the first wrap - around motion compensation flag and the wrap - around motion compensation offset. Further provided is a non - transitory computer - readable media.

[0007] Brief Description of the Drawings

[0007] Embodiments and various aspects of the present disclosure are illustrated in the following detailed description and the accompanying drawings. The various features shown in the figures are not drawn to scale.

Brief Description of the Drawings

[0008]

Figure 1

[0008] Shown is the structure of an exemplary video sequence according to some embodiments of the present disclosure.

Figure 2A

[0009] Shown is a schematic diagram of an exemplary encoding process according to some embodiments of the present disclosure.

Figure 2B

[0010] Shown is a schematic diagram of another exemplary encoding process according to some embodiments of the present disclosure.

Figure 3A

[0011] Shown is a schematic diagram of an exemplary decoding process according to some embodiments of the present disclosure.

Figure 3B

[0012] Shown is a schematic diagram of another exemplary decoding process according to some embodiments of the present disclosure.

Figure 4

[0013] FIG. 1 shows a block diagram of an exemplary apparatus for encoding or decoding video according to some embodiments of the present disclosure.

Figure 5A

[0014] FIG. 5 shows a schematic diagram of an exemplary blending operation for generating a reconfigured orthographic cylindrical projection according to some embodiments of the present disclosure.

Figure 5B

[0015] FIG. 9 shows a schematic diagram of an exemplary cropping operation for generating a reconfigured orthographic cylindrical projection according to some embodiments of the present disclosure.

Figure 6A

[0016] FIG. 13 shows a schematic diagram of an exemplary horizontal wrap-around motion compensation process for an orthographic cylindrical projection according to some embodiments of the present disclosure.

Figure 6B

[0017] FIG. 17 shows a schematic diagram of an exemplary horizontal wrap-around motion compensation process for a padded orthographic cylindrical projection according to some embodiments of the present disclosure.

Figure 7

[0018] FIG. 21 shows the syntax of an exemplary sequence parameter set for wrap-around motion compensation according to some embodiments of the present disclosure.

Figure 8

[0019] FIG. 25 shows the semantics of an exemplary sequence parameter set for wrap-around motion compensation according to some embodiments of the present disclosure.

Figure 9

[0020] FIG. 29 shows the syntax of an exemplary sequence parameter set for improved wrap-around motion compensation according to some embodiments of the present disclosure.

Figure 10

[0021] FIG. 33 shows the meaning of an exemplary sequence parameter set for improved wrap-around motion compensation according to some embodiments of the present disclosure.

Figure 11

[0022] FIG. 37 shows the meaning of an exemplary sequence parameter set for improved wrap-around motion compensation using the maximum picture width according to some embodiments of the present disclosure.

Figure 12

[0023] Examples of deriving the variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" according to some embodiments of the present disclosure are shown.

Figure 13

[0024] Examples of deriving sample positions used for motion compensation according to some embodiments of the present disclosure are shown.

Figure 14

[0025] Exemplary sequence parameter sets and picture parameter set syntax for wraparound motion compensation using wraparound motion compensation offsets within a picture parameter set according to some embodiments of the present disclosure are shown.

Figure 15

[0026] Exemplary sequence parameter sets and picture parameter set semantics for wraparound motion compensation using wraparound motion compensation offsets within a picture parameter set according to some embodiments of the present disclosure are shown.

Figure 16

[0027] Exemplary sequence parameter set syntax for improved wraparound motion compensation without wraparound motion compensation offsets according to some embodiments of the present disclosure is shown.

Figure 17

[0028] Exemplary picture parameter set syntax for improved wraparound motion compensation using wraparound motion compensation offsets according to some embodiments of the present disclosure is shown.

Figure 18

[0029] Exemplary sequence parameter sets and picture parameter set semantics for improved wraparound motion compensation using wraparound motion compensation offsets within a picture parameter set according to some embodiments of the present disclosure are shown.

Figure 19

[0030] Examples of deriving the variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" according to some embodiments of the present disclosure are shown.

Figure 20

[0031] Disclosed is the syntax of an exemplary sequence parameter set for improved wrap-around motion compensation without a wrap-around motion compensation offset within the sequence parameter set, according to some embodiments of the present disclosure.

Figure 21

[0032] Disclosed is the syntax of an exemplary picture parameter set for improved wrap-around motion compensation using a wrap-around motion control flag, according to some embodiments of the present disclosure.

Figure 22

[0033] Disclosed is the meaning of an exemplary sequence parameter set and picture parameter set for improved wrap-around motion compensation using a wrap-around control flag within the picture parameter set, according to some embodiments of the present disclosure.

Figure 23

[0034] Disclosed is the meaning of an exemplary sequence parameter set and picture parameter set for improved wrap-around motion compensation using a wrap-around control flag within the picture parameter set, according to some embodiments of the present disclosure.

Figure 24

[0035] Disclosed is an example of the derivation of the variable "PicRefWraparoundOffset", according to some embodiments of the present disclosure.

Figure 25

[0036] Disclosed is the meaning of an exemplary sequence parameter set and picture parameter set for improved wrap-around motion compensation using restrictions on the picture size, according to some embodiments of the present disclosure.

Figure 26

[0037] Disclosed is the meaning of an exemplary sequence parameter set for improved wrap-around motion compensation using the restrictions imposed on the variables "pic_width_max_in_luma_samples", "CtbSizeY", and "MinCbSizeY", according to some embodiments of the present disclosure.

Figure 27

[0038] Shows the meaning of an exemplary picture parameter set for improved wrap-around motion compensation using the restrictions imposed on the variable "pic_width_in_luma_samples" according to some embodiments of the present disclosure.

Figure 28

[0039] Shows a flowchart of an exemplary method for performing motion compensation according to some embodiments of the present disclosure.

Figure 29

[0040] Shows a flowchart of an exemplary method for performing motion compensation using a limited range for the sequence wrap-around motion compensation offset according to some embodiments of the present disclosure.

Figure 30

[0041] Shows a flowchart of an exemplary method for performing motion compensation using a picture associated with the sequence wrap-around motion compensation offset according to some embodiments of the present disclosure.

Figure 31

[0042] Shows a flowchart of an exemplary method for performing motion compensation using a limited maximum picture size according to some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Detailed Description

[0043] Next, reference is made in detail to exemplary embodiments illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like reference numerals in different drawings represent the same or similar elements unless otherwise indicated. The implementation forms shown in the following description of the exemplary embodiments do not represent all implementation forms according to the present disclosure. Rather, they are merely examples of apparatuses and methods according to aspects related to the present disclosure as recited in the appended claims. Specific aspects of the present disclosure are described in more detail below. In case of conflict with terms and / or definitions incorporated by reference, the terms and definitions provided in this specification shall prevail.

[0010]

[0044] The Joint Video Experts Team (JVET) of the ITU-T Video Coding Expert Group (ITU-T VCEG) and the ISO / IEC Moving Picture Expert Group (ISO / IEC MPEG) is currently developing the Versatile Video Coding (VVC / H.266) standard. The VVC standard aims to double the compression efficiency of its predecessor, the High Efficiency Video Coding (HEVC / H.265) standard. In other words, the goal of VVC is to achieve the same subjective quality as HEVC / H.265 using half the bandwidth.

[0011]

[0045] To achieve the same subjective quality as HEVC / H.265 using half the bandwidth, the Joint Video Experts Team (JVET) has been developing technologies beyond HEVC using the joint exploration model (JEM) reference software. Since the coding technology was incorporated into JEM, JEM has achieved substantially higher coding performance than HEVC. VCEG and MPEG have also officially started developing the next-generation video compression standard beyond HEVC.

[0012]

[0046] The VVC standard has been recently developed and continues to incorporate more coding technologies that bring better compression performance. VVC is based on the same hybrid video coding system that has been used in modern video compression standards such as HEVC, H.264 / AVC, MPEG2, H.263, etc.

[0013]

[0047] A video is a set of static pictures (or "frames") arranged in time series to store visual information. A video capture device (e.g., a camera) can be used to capture and store those pictures in time series, and a video playback device (e.g., a TV, computer, smartphone, tablet computer, video player, or any end-user terminal with a display function) can be used to display such pictures in time series. Also, depending on the application, the video capture device can transmit the captured video in real time to a video playback device (e.g., a computer with a monitor) for supervision, holding a meeting, or live broadcast, etc.

[0014]

[0048] In order to reduce the memory space and transmission bandwidth required by such applications, the video can be compressed. For example, the video can be compressed before storage and transmission and restored before display. Compression and restoration can be implemented by software executed by a processor (e.g., the processor of a general-purpose computer) or by special hardware. The module or circuit configuration for compression is generally referred to as an "encoder", and the module or circuit configuration for restoration is generally referred to as a "decoder". The encoder and decoder can be collectively referred to as a "codec". The encoder and decoder can be implemented as any of various suitable hardware, software, or combinations thereof. For example, the hardware implementation forms of the encoder and decoder can include circuit mechanisms such as one or more microprocessors, digital signal processors ("DSPs (digital signal processors)"), application-specific integrated circuits ("ASICs (application-specific integrated circuits)"), field-programmable gate arrays ("FPGAs (field-programmable gate arrays)"), discrete logic, or any combination thereof. The software implementation forms of the encoder and decoder can include program code, computer-executable instructions, firmware, or any suitable computer-implemented algorithm or process fixed in a computer-readable medium. Video compression and restoration can be implemented by various algorithms or standards such as MPEG-1, MPEG-2, MPEG-4, the H.26x series, or the like. Depending on the application, the codec can restore the video from a first encoding standard and re-compress the restored video using a second encoding standard. In this case, the codec can be referred to as a "transcoder".

[0015]

[0049] The video encoding process can identify and maintain useful information that can be used to reconstruct a picture. If information ignored in the video encoding process cannot be fully reconstructed, the encoding process may be referred to as "non-reversible." Otherwise, it may be referred to as "reversible." Most encoding processes are non-reversible, which is a trade-off for reducing the required memory space and transmission bandwidth.

[0016]

[0050] Often, the useful information of a picture being encoded (referred to as the "current picture") includes changes with respect to a reference picture (e.g., a picture that has been previously encoded or reconstructed). Such changes can include changes in pixel position, brightness, or color. A change in the position of a group of pixels representing an object can reflect the movement of the object between the reference picture and the current picture.

[0017]

[0051] A picture encoded without referring to another picture (i.e., it is its own reference picture) is referred to as an "I picture." A picture encoded using a previous picture as a reference picture is referred to as a "P picture." A picture encoded using both a previous picture and a future picture as reference pictures (i.e., the reference is "bidirectional") is referred to as a "B picture."

[0018]

[0052] FIG. 1 shows the structure of an exemplary video sequence 100 according to some embodiments of the present disclosure. As shown in FIG. 1, the video sequence 100 can be a live video or a captured and archived video. The video 100 can be a real video, a computer-generated video (e.g., a computer game video), or a combination thereof (e.g., a real video with an augmented reality effect). The video sequence 100 can be input from a video capture device (e.g., a camera), a video archive including previously captured videos (e.g., video files stored in a storage device), or a video supply interface (e.g., a video broadcast transceiver) for receiving videos from a video content provider.

[0019]

[0053] As shown in FIG. 1, the video sequence 100 can include a series of pictures temporally arranged along a timeline, including pictures 102, 104, 106, and 108. Pictures 102 to 106 are consecutive, and there are additional pictures between pictures 106 and 108. In FIG. 1, picture 102 is an I picture, and its reference picture is picture 102 itself. Picture 104 is a P picture, and its reference picture is picture 102, as indicated by the arrow. Picture 106 is a B picture, and its reference pictures are pictures 104 and 108, as indicated by the arrows. Depending on the embodiment, the reference picture of a picture (e.g., picture 104) may not be the picture immediately before or after that picture. For example, the reference picture of picture 104 can be a picture before picture 102. The reference pictures of pictures 102 to 106 are merely examples, and it should be noted that the present disclosure does not limit the embodiments of the reference pictures to the examples shown in FIG. 1.

[0020]

[0054] Typically, due to the computational complexity of such tasks, video codecs do not encode or decode an entire picture at once. Rather, they can divide the picture into basic segments and encode or decode the picture segment by segment. Such basic segments are referred to in the present disclosure as basic processing units (“BPUs (basic processing unit)”). For example, the structure 110 in FIG. 1 shows an exemplary structure of a picture (e.g., any of pictures 102-108) of the video sequence 100. In structure 110, the picture is divided into 4×4 basic processing units, and their boundaries are shown as dashed lines. Depending on the embodiment, the basic processing unit may be referred to as a “macroblock” in some video coding standards (e.g., the MPEG family, H.261, H.263, or H.264 / AVC), or as a “coding tree unit” (“CTU (coding tree unit)”) in some other video coding standards (e.g., H.265 / HEVC or H.266 / VVC). The basic processing unit can have a variable size in the picture, such as 128×128, 64×64, 32×32, 16×16, 4×8, 16×32, etc., or any arbitrary shape and size of pixels. The size and shape of the basic processing unit can be selected based on a balance between the coding efficiency and the level of detail to be maintained in the basic processing unit for the picture.

[0021]

[0055] The basic processing unit can be a logical unit that can include groups of different types of video data stored in a computer memory (e.g., within a video frame buffer). For example, the basic processing unit of a color picture can include a luma component (Y) representing achromatic luminance information, one or more chroma components (e.g., Cb and Cr) representing color information, and associated syntax elements, where the luma and chroma components can have the same size of the basic processing unit. The luma and chroma components can be referred to as "coding tree blocks" ("CTB") in some video coding standards (e.g., H.265 / HEVC or H.266 / VVC). Any operation performed on the basic processing unit can be repeatedly performed on each of its luma and chroma components.

[0022]

[0056] Video coding has multiple processing stages, examples of which are shown in FIGS. 2A-2B and FIGS. 3A-3B. At each stage, the size of the basic processing unit may still be too large for processing, and thus, it can be further divided into segments referred to as "basic processing subunits" in the present disclosure. In some embodiments, the basic processing subunit may be referred to as a "block" in some video coding standards (e.g., the MPEG family, H.261, H.263, or H.264 / AVC), or as a "coding unit" ("CU") in some other video coding standards (e.g., H.265 / HEVC or H.266 / VVC). The basic processing subunit can have a size that is the same as or smaller than that of the basic processing unit. Similar to the basic processing unit, the basic processing subunit is also a logical unit that can include groups of different types of video data (e.g., Y, Cb, Cr, and related syntax elements) stored in a computer memory (e.g., within a video frame buffer). Any operation performed on the basic processing subunit can be repeatedly performed for each of its luma and chroma components. Note that such splitting can be performed to further levels as needed for processing. Also note that different stages can split the basic processing unit in different ways.

[0023]

[0057] For example, in the mode decision stage (an example of which is shown in FIG. 2B), the encoder can determine which prediction mode (e.g., intra-picture prediction or inter-picture prediction) to use for the basic processing unit, but the basic processing unit may be too large to make such a decision. The encoder can divide the basic processing unit into multiple basic processing subunits (e.g., CUs as in the case of H.265 / HEVC or H.266 / VVC) and determine the type of prediction for each individual basic processing subunit.

[0024]

[0058] As another example, in the prediction stage (an example is shown in FIGS. 2A - 2B), the coder can perform prediction operations at the level of a basic processing subunit (e.g., a CU). However, in some cases, the basic processing subunit may still be too large to process. The coder can further divide the basic processing subunit into smaller segments (e.g., called "prediction block" or "PB" in H.265 / HEVC or H.266 / VVC), and prediction operations can be performed at that level.

[0025]

[0059] As another example, in the transform stage (an example is shown in FIGS. 2A - 2B), the coder can perform transform operations for a residual basic processing subunit (e.g., a CU). However, in some cases, the basic processing subunit may still be too large to process. The coder can further divide the basic processing subunit into smaller segments (e.g., called "transform block" or "TB" in H.265 / HEVC or H.266 / VVC), and transform operations can be performed at that level. It should be noted that the same basic processing subunit division method may be different in the prediction stage and the transform stage. For example, in H.265 / HEVC or H.266 / VVC, the prediction blocks and transform blocks of the same CU may have different sizes and numbers.

[0026]

[0060] In the structure 110 of FIG. 1, the basic processing unit 112 is further divided into 3×3 basic processing subunits, and their boundaries are shown as dotted lines. Different basic processing units of the same picture may be divided into basic processing subunits in different ways.

[0027]

[0061] Depending on the implementation form, in order to bring parallel processing and error tolerance capabilities to video encoding and decoding, a picture can be divided into areas for processing, whereby the encoding or decoding process does not have to depend on information from any other area of the picture with respect to the picture area. In other words, each area of the picture can be processed independently. By doing so, the codec can process different areas of the picture in parallel, and therefore increase the encoding efficiency. Also, when the data of an area is damaged during processing or lost during network transmission, the codec can correctly encode or decode other areas of the same picture without relying on the damaged or lost data, and therefore bring an error tolerance capability. In some video encoding standards, a picture can be divided into different types of areas. For example, H.265 / HEVC and H.266 / VVC provide two types of areas: "slice" and "tile". It should also be noted that different pictures of video sequence 100 can have different partitioning methods for dividing the picture into areas.

[0028]

[0062] For example, in FIG. 1, structure 110 is divided into three areas 114, 116, and 118, and their boundaries are shown as solid lines inside structure 110. Area 114 includes four basic processing units. Each of areas 116 and 118 includes six basic processing units. It should be noted that the basic processing units, basic processing sub-units, and areas of structure 110 in FIG. 1 are merely examples, and the present disclosure does not limit its embodiments.

[0029]

[0063] Figure 2A shows a schematic diagram of an exemplary encoding process 200A according to some embodiments of the present disclosure. For example, the encoding process 200A shown in Figure 2A can be performed by an encoder. As shown in Figure 2A, the encoder can encode a video sequence 202 into a video bitstream 228 according to process 200A. Similar to the video sequence 100 in Figure 1, the video sequence 202 can include a set of pictures (referred to as "original pictures") arranged in chronological order. Similar to the structure 110 in Figure 1, each original picture of the video sequence 202 can be divided by the encoder into basic processing units, basic processing subunits, or regions for processing. Depending on the embodiment, the encoder can perform process 200A at the level of basic processing units for each original picture of the video sequence 202. For example, the encoder can perform process 200A in an iterative manner, in which case the encoder can encode a basic processing unit in one iteration of process 200A. Depending on the embodiment, the encoder can perform process 200A in parallel for regions (e.g., regions 114-118) of each original picture of the video sequence 202.

[0030]

[0064] In FIG. 2A, the coder can supply the basic processing unit of the original picture of video sequence 202 (referred to as "original BPU") to prediction stage 204 and generate prediction data 206 and prediction BPU 208. The coder can subtract prediction BPU 208 from the original BPU to generate residual BPU 210. The coder can supply residual BPU 210 to transformation stage 212 and quantization stage 214 to generate quantized transform coefficients 216. The coder can supply prediction data 206 and quantized transform coefficients 216 to binary coding stage 226 to generate video bitstream 228. Components 202, 204, 206, 208, 210, 212, 214, 216, 226, and 228 may be referred to as the "forward path". During process 200A, after quantization stage 214, the coder can supply quantized transform coefficients 216 to inverse quantization stage 218 and inverse transformation stage 220 to generate reconstructed residual BPU 222. The coder can add reconstructed residual BPU 222 to prediction BPU 208 to generate prediction reference 224, which is used in prediction stage 204 for the next iteration of process 200A. Components 218, 220, 222, and 224 of process 200A may be referred to as the "reconstruction path". The reconstruction path can be used to ensure that both the coder and the decoder use the same reference data for prediction.

[0031]

[0065] The coder can repeatedly perform process 200A to encode each original BPU of the original picture (within the forward path) and generate prediction reference 224 (within the reconstruction path) for encoding the next original BPU of the original picture. After encoding all the original BPUs of the original picture, the coder can proceed to encode the next picture in video sequence 202.

[0032]

[0066] Referring to process 200A, the coder can receive video sequence 202 generated by a video capture device (e.g., a camera). As used herein, the term "receive" can refer to receiving, inputting, acquiring, obtaining, getting, reading, accessing, or any act by any means for inputting data.

[0033]

[0067] In prediction stage 204, in the current iteration, the coder can receive the original BPU and prediction criterion 224, perform a prediction operation, and generate prediction data 206 and prediction BPU 208. Prediction criterion 224 can be generated from the reconstruction path of a previous iteration of process 200A. The purpose of prediction stage 204 is to reduce information redundancy by extracting prediction data 206, and prediction data 206 can be used to reconstruct the original BPU as prediction BPU 208 from prediction data 206 and prediction criterion 224.

[0034]

[0068] Ideally, prediction BPU 208 can be identical to the original BPU. However, due to non-ideal prediction and reconstruction operations, prediction BPU 208 generally differs slightly from the original BPU. To record such a difference, after generating prediction BPU 208, the coder can subtract it from the original BPU to generate residual BPU 210. For example, the coder can subtract the pixel values (e.g., grayscale values or RGB values) of prediction BPU 208 from the corresponding pixel values of the original BPU. Each pixel of residual BPU 210 can have a residual value as a result of such subtraction between the corresponding pixels of the original BPU and prediction BPU 208. Compared with the original BPU, prediction data 206 and residual BPU 210 can have fewer bits, but they can be used to reconstruct the original BPU without significant quality degradation. Therefore, the original BPU is compressed.

[0035]

[0069] To further compress the residual BPU 210, in the transformation stage 212, the coder can reduce the spatial redundancy of the residual BPU 210 by decomposing it into a set of two-dimensional "basis patterns", with each basis pattern associated with a "transformation coefficient". The basis patterns can have the same size (e.g., the size of the residual BPU 210). Each basis pattern can represent a frequency component of the change in the residual BPU 210 (e.g., the frequency of luminance change). None of the basis patterns can be reproduced from any combination (e.g., linear combination) of any other basis patterns. In other words, the decomposition can decompose the change in the residual BPU 210 into the frequency domain. Such a decomposition is similar to the discrete Fourier transform of a function, where in this case the basis patterns are similar to the basis functions of the discrete Fourier transform (e.g., trigonometric functions), and the transformation coefficients are similar to the coefficients associated with the basis functions.

[0036]

[0070] Different transformation algorithms can use different basis patterns. For example, various transformation algorithms such as the discrete cosine transform, the discrete sine transform, or the like can be used in the transformation stage 212. The transformation in the transformation stage 212 is invertible. That is, the coder can recover the residual BPU 210 by means of the inverse operation of the transformation (referred to as "inverse transformation"). For example, to recover the pixels of the residual BPU 210, the inverse transformation can multiply the corresponding pixel values of the basis patterns by their respective associated coefficients and add the products to generate a weighted sum. For a video coding standard, both the coder and the decoder can use the same transformation algorithm (and thus the same basis patterns). Therefore, the coder can record only the transformation coefficients, and the decoder can reconstruct the residual BPU 210 from the transformation coefficients without receiving the basis patterns from the coder. Compared with the residual BPU 210, the transformation coefficients can have fewer bits, but they can be used to reconstruct the residual BPU 210 without significant quality degradation. Therefore, the residual BPU 210 is further compressed.

[0037]

[0071] The coder can further compress the transform coefficients in the quantization stage 214. In the transform process, different basis patterns can represent different change frequencies (e.g., luminance change frequencies). Since the human eye is generally more adept at recognizing low-frequency changes, the coder can ignore the information of high-frequency changes without causing significant quality degradation in decoding. For example, in the quantization stage 214, the coder can generate the quantized transform coefficients 216 by dividing each transform coefficient by an integer value (referred to as the "quantization parameter") and rounding the quotient to the nearest integer. After such an operation, some of the transform coefficients of the high-frequency basis pattern can be converted to 0, and the transform coefficients of the low-frequency basis pattern can be converted to smaller integers. The coder can ignore the quantized transform coefficients 216 with a value of 0, thereby further compressing the transform coefficients. The quantization process is also inversely operable. In this case, the quantized transform coefficients 216 can be reconstructed into transform coefficients in the inverse operation of quantization (referred to as "inverse quantization").

[0038]

[0072] Since the coder ignores the remainder of such division in the rounding operation, the quantization stage 214 can be non-invertible. Typically, the quantization stage 214 can contribute to the largest information loss in the process 200A. The greater the information loss, the fewer bits the quantized transform coefficients 216 may require. To obtain different information loss levels, the coder can use different values of the quantization parameter or any other parameter of the quantization process.

[0039]

[0073] In the binary encoding stage 226, the encoder can encode the predicted data 206 and the quantized transform coefficients 216 using binary encoding techniques such as, for example, entropy encoding, variable length encoding, arithmetic encoding, Huffman encoding, context adaptive binary arithmetic encoding, or any other reversible or irreversible compression algorithm. In some embodiments, in addition to the predicted data 206 and the quantized transform coefficients 216, the encoder can encode other information in the binary encoding stage 226, such as, for example, the prediction mode used in the prediction stage 204, the parameters of the prediction operation, the type of transform in the transform stage 212, the parameters of the quantization process (e.g., quantization parameters), the encoder control parameters (e.g., bitrate control parameters), or the like. The encoder can generate a video bitstream 228 using the output data of the binary encoding stage 226. In some embodiments, the video bitstream 228 can be further packetized for network transmission.

[0040]

[0074] Referring to the reconstruction path of process 200A, in the inverse quantization stage 218, the encoder can perform inverse quantization on the quantized transform coefficients 216 to generate reconstructed transform coefficients. In the inverse transform stage 220, the encoder can generate a reconstructed residual BPU 222 based on the reconstructed transform coefficients. The encoder can add the reconstructed residual BPU 222 to the predicted BPU 208 to generate a prediction reference 224 that will be used in the next iteration of process 200A.

[0041]

[0075] Note that other variations of process 200A can also be used to encode video sequence 202. Depending on the embodiment, the steps of process 200A can be performed in a different order by the encoder. Depending on the embodiment, one or more steps of process 200A can be combined into a single step. Depending on the embodiment, a single step of process 200A can be divided into multiple steps. For example, the transform step 212 and the quantization step 214 can be combined into a single step. Depending on the embodiment, process 200A can include additional steps. Depending on the embodiment, process 200A can omit one or more steps in FIG. 2A.

[0042]

[0076] FIG. 2B shows a schematic diagram of another exemplary encoding process 200B according to some embodiments of the present disclosure. As shown in FIG. 2B, process 200B can be modified from process 200A. For example, process 200B can be used by an encoder compliant with a hybrid video coding standard (e.g., the H.26x series). Compared to process 200A, the forward path of process 200B additionally includes a mode decision step 230 and divides the prediction step 204 into a spatial prediction step 2042 and a temporal prediction step 2044. The reconstruction path of process 200B additionally includes a loop filter step 232 and a buffer 234.

[0043]

[0077] Generally, prediction techniques can be classified into two types: spatial prediction and temporal prediction. Spatial prediction (e.g., intra-picture prediction or "intra prediction") can use pixels from one or more already-encoded adjacent BPUs within the same picture to predict the current BPU. That is, the prediction reference 224 in spatial prediction can include adjacent BPUs. Spatial prediction can reduce the inherent spatial redundancy of a picture. Temporal prediction (e.g., inter-picture prediction or "inter prediction") can use regions from one or more already-encoded pictures to predict the current BPU. That is, the prediction reference 224 in temporal prediction can include encoded pictures. Temporal prediction can reduce the inherent temporal redundancy of a picture.

[0044]

[0078] Referring to process 200B, within the forward path, the coder performs prediction operations at spatial prediction stage 2042 and temporal prediction stage 2044. For example, at spatial prediction stage 2042, the coder can perform intra prediction. For the original BPU of the picture being encoded, the prediction reference 224 can include one or more adjacent BPUs (within the forward path) that are encoded and (within the reconstruction path) reconstructed within the same picture. The coder can generate the predicted BPU 208 by extrapolating the adjacent BPUs. The extrapolation technique can include, for example, linear extrapolation or interpolation, polynomial extrapolation or interpolation, or the like. In some embodiments, the coder can perform the extrapolation at the pixel level, such as by extrapolating the value of the corresponding pixel for each pixel of the predicted BPU 208. The adjacent BPUs used for extrapolation can be located relative to the original BPU from various directions, such as the vertical direction (e.g., above the original BPU), the horizontal direction (e.g., to the left of the original BPU), the diagonal direction (e.g., bottom left, bottom right, top left, or top right of the original BPU), or any direction defined in the video coding standard being used. For intra prediction, the prediction data 206 can include, for example, the location (e.g., coordinates) of the adjacent BPUs used, the size of the adjacent BPUs used, the parameters of the extrapolation, the direction of the adjacent BPUs used relative to the original BPU, or the like.

[0045]

[0079] As another example, in the temporal prediction stage 2044, the coder can perform inter prediction. For the original BPU of the current picture, the prediction reference 224 can include one or more pictures (referred to as "reference pictures") that are coded (within the forward path) and reconstructed (within the reconstruction path). In some embodiments, the reference pictures can be coded and reconstructed for each BPU. For example, the coder can add the reconstructed residual BPU 222 to the prediction BPU 208 to generate a reconstructed BPU. When all the reconstructed BPUs of the same picture have been generated, the coder can generate the reconstructed picture as a reference picture. The coder can perform an operation of "motion estimation" to search for a matching region within a range of reference pictures (referred to as a "search window"). The location of the search window within the reference picture can be determined based on the location of the original BPU of the current picture. For example, the search window can be centered at a location within the reference picture that has the same coordinates as the original BPU within the current picture, and can be extended outward over a predetermined distance. When the coder identifies a region similar to the original BPU within the search window (e.g., by using a pixel-recursive algorithm, a block-matching algorithm, or the like), the coder can determine such a region as the matching region. The matching region can have dimensions that are different from those of the original BPU (e.g., smaller than, equal to, larger than, or of a different shape than the original BPU). Since the reference picture and the current picture are temporally separated within the timeline (as shown, for example, in FIG. 1), the matching region can be considered to "move" towards the location of the original BPU as time progresses. The coder can record such a direction and distance of motion as a "motion vector". When multiple reference pictures are used (e.g., as picture 106 in FIG. 1), the coder can search for a matching region for each reference picture and determine its associated motion vector. In some embodiments, the coder can weight the pixel values of the matching region of each matching reference picture.

[0046]

[0080] Motion estimation can be used to identify various types of motion, such as translation, rotation, zooming, or the like. For inter prediction, the prediction data 206 can include, for example, the location (e.g., coordinates) of the matching region, the motion vector associated with the matching region, the number of reference pictures, the weight associated with the reference pictures, or the like.

[0047]

[0081] To generate the prediction BPU 208, the coder can perform an operation of "motion compensation". Motion compensation can be used to reconstruct the prediction BPU 208 based on the prediction data 206 (e.g., motion vector) and the prediction reference 224. For example, the coder can move the matching region of the reference picture according to the motion vector, in which case the coder can predict the original BPU of the current picture. When multiple reference pictures are used (e.g., as picture 106 in FIG. 1), the coder can move the matching regions of the reference pictures according to their respective motion vectors and average the pixel values of the matching regions. In some embodiments, when the coder assigns weights to the pixel values of the matching regions of each matching reference picture, the coder can add the weighted sum of the pixel values to the moved matching regions.

[0048]

[0082] In some embodiments, inter prediction can be unidirectional or bidirectional. Unidirectional inter prediction can use one or more reference pictures in the same temporal direction with respect to the current picture. For example, picture 104 in FIG. 1 is a unidirectional inter prediction picture where the reference picture (i.e., picture 102) precedes picture 104. Bidirectional inter prediction can use one or more reference pictures in both temporal directions with respect to the current picture. For example, picture 106 in FIG. 1 is a bidirectional inter prediction picture where the reference pictures (i.e., pictures 104 and 108) are in both temporal directions with respect to picture 104.

[0049]

[0083] Referring still to the forward path of process 200B, after the spatial prediction stage 2042 and the temporal prediction stage 2044, at the mode decision stage 230, the coder can select a prediction mode (e.g., one of intra prediction or inter prediction) for the current iteration of process 200B. For example, the coder can perform rate-distortion optimization techniques. In this technique, the coder can select a prediction mode that minimizes the value of a cost function that depends on the bit rate of the candidate prediction modes and the distortion of the reconstructed reference picture under the candidate prediction modes. Depending on the selected prediction mode, the coder can generate the corresponding prediction BPU 208 and prediction data 206.

[0050]

[0084] In the reconstruction path of process 200B, when the intra prediction mode is selected in the forward path, after generating the prediction reference 224 (e.g., the currently encoded and reconstructed current BPU in the current picture), the coder can directly supply the prediction reference 224 to the spatial prediction stage 2042 for later use (e.g., for interpolation of the next BPU of the current picture). When the inter prediction mode is selected in the forward path, after generating the prediction reference 224 (e.g., the current picture in which all BPUs are encoded and reconstructed), the coder can supply the prediction reference 224 to the loop filter stage 232, where the coder can apply the loop filter to the prediction reference 224 to reduce or eliminate the distortion (e.g., blocking artifacts) introduced by inter prediction. The coder can apply various loop filter techniques, such as deblocking, sample adaptive offset, adaptive loop filter, or the like, in the loop filter stage 232. The loop-filtered reference picture can be stored in buffer 234 (or "decoded picture buffer") for later use (e.g., for use as an inter prediction reference picture for future pictures of video sequence 202). The coder can store one or more reference pictures in buffer 234 for use in the temporal prediction stage 2044. In some embodiments, the coder can encode the loop filter parameters (e.g., loop filter strength) together with the quantized transform coefficients 216, prediction data 206, and other information in the binary encoding stage 226.

[0051]

[0085] FIG. 3A shows a schematic diagram of an exemplary decoding process 300A according to some embodiments of the present disclosure. As shown in FIG. 3A, process 300A can be a restoration process corresponding to the compression process 200A in FIG. 2A. In some embodiments, process 300A can be similar to the reconstruction path of process 200A. A decoder can decode the video bitstream 228 into a video stream 304 according to process 300A. The video stream 304 can be very similar to the video sequence 202. However, due to information loss in the compression and restoration processes (e.g., the quantization stage 214 in FIGS. 2A-2B), generally, the video stream 304 is not identical to the video sequence 202. Similar to processes 200A and 200B in FIGS. 2A-2B, the decoder can perform process 300A at the level of a basic processing unit (BPU) for each picture encoded in the video bitstream 228. For example, the decoder can perform process 300A in an iterative manner, in which case the decoder can decode the basic processing unit in one iteration of process 300A. In some embodiments, the decoder can perform process 300A in parallel for each region (e.g., regions 114-118) of each picture encoded in the video bitstream 228.

[0052]

[0086] In FIG. 3A, the decoder can supply a portion of the video bitstream 228 associated with the basic processing unit of the encoded picture (referred to as the "encoded BPU") to the binary decoding stage 302. In the binary decoding stage 302, the decoder can decode the portion into prediction data 206 and quantization transform coefficients 216. The decoder supplies the quantization transform coefficients 216 to the inverse quantization stage 218 and the inverse transform stage 220 and can generate a reconstructed residual BPU 222. The decoder supplies the prediction data 206 to the prediction stage 204 and can generate a prediction BPU 208. The decoder can add the reconstructed residual BPU 222 to the prediction BPU 208 and generate a prediction reference 224. In some embodiments, the prediction reference 224 can be stored in a buffer (e.g., a decoded picture buffer in computer memory). The decoder can supply the prediction reference 224 to the prediction stage 204 to perform the prediction operation in the next iteration of process 300A.

[0053]

[0087] The decoder can iteratively perform process 300A to decode each encoded BPU of the encoded picture and generate a prediction reference 224 for encoding the next encoded BPU of the encoded picture. After decoding all the encoded BPUs of the encoded picture, the decoder can output the picture to the video stream 304 for display and proceed to decode the next encoded picture in the video bitstream 228.

[0054]

[0088] In the binary decoding stage 302, the decoder can perform the inverse operation of the binary encoding technique (e.g., entropy encoding, variable-length encoding, arithmetic encoding, Huffman encoding, context-adaptive binary arithmetic encoding, or any other reversible compression algorithm) used by the encoder. According to some embodiments, in addition to the predicted data 206 and the quantized transform coefficients 216, the decoder can also decode other information in the binary decoding stage 302, such as, for example, the prediction mode, the parameters of the prediction operation, the type of transform, the parameters of the quantization process (e.g., quantization parameters), the encoder control parameters (e.g., bitrate control parameters), or the like. According to some embodiments, when the video bitstream 228 is transmitted in the form of packets through a network, the decoder can depacketize the video bitstream 228 before supplying it to the binary decoding stage 302.

[0055]

[0089] FIG. 3B shows a schematic diagram of another exemplary decoding process 300B according to some embodiments of the present disclosure. As shown in FIG. 3B, the process 300B can be changed from the process 300A. For example, the process 300B can be used by a decoder compliant with a hybrid video encoding standard (e.g., the H.26x series). Compared with the process 300A, the process 300B additionally divides the prediction stage 204 into a spatial prediction stage 2042 and a temporal prediction stage 2044, and additionally includes a loop filter stage 232 and a buffer 234.

[0056]

[0090] In process 300B, for the encoding basic processing unit (referred to as the "current BPU") of the encoded picture being decoded (referred to as the "current picture"), the prediction data 206 decoded by the decoder from the binary decoding stage 302 can include various types of data depending on which prediction mode was used by the encoder to encode the current BPU. For example, when intra prediction was used by the encoder to encode the current BPU, the prediction data 206 can include an intra prediction, parameters of the intra prediction operation, or a prediction mode indicator (e.g., a flag value) indicating the like. The parameters of the intra prediction operation can include, for example, the location (e.g., coordinates) of one or more adjacent BPUs used as references, the size of the adjacent BPUs, the parameters of extrapolation, the direction of the adjacent BPUs with respect to the original BPU, or the like. As another example, when inter prediction was used by the encoder to encode the current BPU, the prediction data 206 can include an inter prediction, parameters of the inter prediction operation, or a prediction mode indicator (e.g., a flag value) indicating the like. The parameters of the inter prediction operation can include, for example, the number of reference pictures associated with the current BPU, the weights respectively associated with the reference pictures, the location (e.g., coordinates) of one or more matching regions in each reference picture, one or more motion vectors respectively associated with the matching regions, or the like.

[0057]

[0091] Based on the prediction mode indicator, the decoder can determine whether to perform spatial prediction (e.g., intra prediction) in the spatial prediction stage 2042 or temporal prediction (e.g., inter prediction) in the temporal prediction stage 2044. Details of performing such spatial or temporal prediction are described in FIG. 2B and will not be repeated here. After performing such spatial or temporal prediction, the decoder can generate the predicted BPU 208. As described in FIG. 3A, the decoder can add the predicted BPU 208 and the reconstructed residual BPU 222 to generate the prediction reference 224.

[0058]

[0092] In process 300B, the decoder can supply the prediction criterion 224 to the spatial prediction stage 2042 or the temporal prediction stage 2044 for performing the prediction operation in the next iteration of process 300B. For example, when the current BPU is decoded using intra prediction in the spatial prediction stage 2042, after generating the prediction criterion 224 (e.g., the decoded current BPU), the decoder can directly supply the prediction criterion 224 to the spatial prediction stage 2042 for later use (e.g., for extrapolation of the next BPU of the current picture). When the current BPU is decoded using inter prediction in the temporal prediction stage 2044, after generating the prediction criterion 224 (e.g., the reference pictures in which all BPUs are decoded), the coder can supply the prediction criterion 224 to the loop filter stage 232 to reduce or eliminate distortion (e.g., blocking artifacts). The decoder can apply the loop filter to the prediction criterion 224 in the manner as described in FIG. 2B. The loop-filtered reference picture can be stored in the buffer 234 (e.g., the decoded picture buffer in the computer memory) for later use (e.g., for use as an inter prediction reference picture for future encoded pictures of the video bitstream 228). The decoder can store one or more reference pictures in the buffer 234 for use in the temporal prediction stage 2044. In some embodiments, when the prediction mode indicator of the prediction data 206 indicates that inter prediction was used to encode the current BPU, the prediction data can further include loop filter parameters (e.g., loop filter strength).

[0059]

[0093] FIG. 4 is a block diagram of an exemplary apparatus 400 for encoding or decoding video according to some embodiments of the present disclosure. As shown in FIG. 4, the apparatus 400 can include a processor 402. When the processor 402 executes the instructions described herein, the apparatus 400 can become a special machine for video encoding or decoding. The processor 402 can be any kind of circuitry having the ability to manipulate or process information. For example, the processor 402 can be a central processing unit (or "CPU (central processing unit)"), a graphics processing unit (or "GPU (graphics processing unit)"), a neural processing unit ("NPU (neural processing unit)"), a microcontroller unit ("MCU (microcontroller unit)"), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a programmable logic array (PLA), a programmable array logic (PAL), a generic array logic (GAL), a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a system on chip (SoC), an application-specific integrated circuit (ASIC), or any number of any combination of the like. Depending on the embodiment, the processor 402 can also be a set of processors grouped as a single logical component. For example, as shown in FIG. 4, the processor 402 can include a plurality of processors, including processor 402a, processor 402b, and processor 402n.

[0060]

[0094] Device 400 can also include a memory 404 configured to store data (e.g., a set of instructions, computer code, intermediate data, or the like). For example, as shown in FIG. 4, the stored data can include program instructions (e.g., program instructions for implementing the steps in processes 200A, 200B, 300A, or 300B), as well as data for processing (e.g., video sequence 202, video bitstream 228, or video stream 304). The processor 402 can access (e.g., via bus 410) the program instructions and the data for processing, execute the program instructions, and perform operations or computations on the data for processing. The memory 404 can include a high-speed random access storage device or a non-volatile storage device. In some embodiments, the memory 404 can include any number of any combination of random access memory (RAM), read-only memory (ROM), optical disk, magnetic disk, hard drive, solid state drive, flash drive, security digital (SD) card, memory stick, compact flash (CF) card, or the like. The memory 404 can also be a group of memories grouped as a single logical component (not shown in FIG. 4).

[0061]

[0095] The bus 410 can be a communication device that transfers data between internal components of the device 400, such as an internal bus (e.g., a CPU-memory bus), an external bus (e.g., a universal serial bus port, a peripheral component interconnect express port), or the like.

[0062]

[0096] To facilitate explanation without creating ambiguity, the processor 402 and other data processing circuits are collectively referred to as "data processing circuits" in this disclosure. The data processing circuits can be implemented entirely as hardware, or as a combination of software, hardware, or firmware. Additionally, the data processing circuits can be a single stand-alone module or can be fully or partially combined with any other component of the device 400.

[0063]

[0097] The device 400 can further include a network interface 406 for providing wired or wireless communication with a network (e.g., the Internet, an intranet, a local area network, a mobile communication network, or the like). In some embodiments, the network interface 406 can include any number of any combination of a network interface controller (NIC), a radio frequency (RF) module, a transponder, a transceiver, a modem, a router, a gateway, a wired network adapter, a wireless network adapter, a Bluetooth® adapter, an infrared adapter, a near-field communication ("NFC") adapter, a cellular network chip, or the like.

[0064]

[0098] In some embodiments, the device 400 can further include a peripheral interface 408 for providing connection to one or more peripheral devices. As shown in FIG. 4, the peripheral devices can include, but are not limited to, a cursor control device (e.g., a mouse, a touchpad, or a touch screen), a keyboard, a display (e.g., a cathode ray tube display, a liquid crystal display, or a light emitting diode display), a video input device (e.g., a camera or an input interface communicatively coupled to a video archive), or the like.

[0065]

[0099] Note that the video codec (e.g., the codec that performs processes 200A, 200B, 300A, or 300B) can be implemented as any combination of any software or hardware modules within device 400. For example, some or all stages of processes 200A, 200B, 300A, or 300B can be implemented as one or more software modules of device 400, such as program instructions that can be loaded into memory 404. As another example, some or all stages of processes 200A, 200B, 300A, or 300B can be implemented as one or more hardware modules of device 400, such as special data processing circuits (e.g., FPGA, ASIC, NPU, or the like).

[0066]

[0100] In the quantization and inverse quantization functional blocks (e.g., quantization 214 and inverse quantization 218 in FIGS. 2A or 2B, inverse quantization 218 in FIGS. 3A or 3B), a quantization parameter (QP) is used to determine the amount of quantization (and inverse quantization) applied to the prediction residual. The initial QP value used for encoding a picture or slice can be signaled at a high level, for example, using the init_qp_minus26 syntax element within a Picture Parameter Set (PPS) and the slice_qp_delta syntax element within the slice header. Further, the QP value can be adapted at a local level for each CU using the delta QP value transmitted with the subdivision of the quantization group.

[0067]

[0101] The Equirectangular Projection (「ERP」) format is a common projection format used to represent 360-degree videos and images. The projection maps the meridians to vertical lines at regular intervals and the latitude circles to horizontal lines at regular intervals. Since the relationship between the position of an image pixel on the map and its corresponding geographical position on the sphere is particularly simple, ERP is one of the most common projections used for 360-degree videos and images.

[0068]

[0102] The algorithm description of projection format conversion and the video quality criteria output by JVET provide the introduction and coordinate conversion between ERP and the sphere. For the coordinate conversion from 2D to 3D, assuming the sampling position is (m, n), (u, v) can be calculated based on the following formulas. u = (m + 0.5) / W, 0 ≤ m < W Equation (1) v = (n + 0.5) / H, 0 ≤ n < H Equation (2)

[0069]

[0103] Next, the longitude and latitude (φ, θ) of the sphere can be calculated from (u, v) based on the following formulas. φ = (u - 0.5) × (2 × π) Equation (3) θ = (0.5 - v) × π Equation (4)

[0070]

[0104] The coordinates (X, Y, Z) can be calculated based on the following formulas. X = cos(θ)cos(φ) Equation (5) Y = sin(θ) Equation (6) Z = -cos(θ)sin(φ) Equation (7)

[0071]

[0105] For the coordinate conversion from 3D to 2D starting from (X, Y, Z), (φ, θ) can be calculated based on the following formulas. Then, (u, v) is calculated based on the formulas. Finally, (m, n) can be calculated based on the formulas. φ = tan -1 (-Z / X) Equation (8) θ = sin -1 (Y / (X 2 + Y 2 + Z 2 ) 1 / 2 ) Equation (9)

[0072]

[0106] To reduce seam artifacts in the reconstructed viewport that includes the left and right boundaries of the ERP picture, a new format called padded orthographic cylindrical projection (「PERP」) is provided by padding samples on each of the left and right sides of the ERP picture.

[0073]

[0107] When PERP is used to represent a 360-degree video, the PERP picture is encoded. After decoding, the reconstructed PERP is converted to the reconstructed ERP by blending the duplicated samples or cropping the padded area.

[0074]

[0108] FIG. 5A shows a schematic diagram of an exemplary blending operation for generating a reconstructed orthographic cylindrical projection according to some embodiments of the present disclosure. Unless otherwise specified, "recPERP" is used to denote the reconstructed PERP before post-processing, and "recERP" is used to denote the reconstructed ERP after post-processing. As shown in FIG. 5A, the duplicated samples of recPERP can be blended by applying a distance-based weighted average operation. For example, region A can be generated by blending region A1 with A2, and region B is generated by blending region B1 with B2.

[0075]

[0109] In the following description, the width and height of the unpadded recERP are denoted as "W" and "H", respectively. The left padding width and the right padding width are denoted as "P L " and "P R ", respectively. The total padding width is denoted as "P W ", and P W can be the sum of P L and P R . In some embodiments, recPERP can be converted to recERP by a blending operation. For example, for the samples recERP(j,i) in A, where i = [0, P R-1 and j = [0, H-1], recERP(j,i) can be determined according to the following equation. A = w × A1+(1 - w)×A2, where w is from P L / P w to 1 Equation (10) recERP(j,i) within A=(recPERP(j,i + P L )×(i + P L) + recPERP(j, i + P L+W ) × (P R-i ) + (P W >> 1)) / P W Equation (11)

[0076]

[0110] In some embodiments, for the sample recERP(j, i) in B, where i = [W - P L , W - 1] and j = [0, H - 1], recERP(j, i) can be determined according to the following equation. B = k × B1 + (1 - k) × B2, where k is from 0 to P L / P w Equation (12) recERP(j, i) within B = (recPERP(j, i + P L ) × (P R-i + W) + recPERP(j, i + P L-w ) × (i - W + P L ) + (P w >> 1)) / P W Equation (13)

[0077]

[0111] Figure 5B shows a schematic diagram of an exemplary cropping operation for generating a reconstructed orthographic cylindrical projection according to some embodiments of the present disclosure. As shown in Figure 5B, during the cropping process, the samples padded in recPERP can be directly discarded to obtain recERP. For example, the padded samples B1 and A2 may be discarded, the padded area A is equal to A1, and the padded area B is equal to B2.

[0078]

[0112] According to some embodiments, horizontal wrap-around motion compensation can be used to improve the encoding performance of ERP. For example, horizontal wrap-around motion compensation can be used in the VVC standard as a 360-degree specific encoding tool designed to improve the visual quality of 360-degree videos reconstructed in the ERP format or the PERP format. In conventional motion compensation, when a motion vector references samples that exceed the picture boundary of the reference picture, iterative padding is applied to derive the values of the samples that exceed the boundary by copying from the nearest neighbor on the corresponding picture boundary. In the case of 360-degree videos, this method of iterative padding is not appropriate and may cause visual artifacts called "seam artifacts" in the reconstructed viewport video. Since 360-degree videos are captured on a sphere and inherently have no "boundary", reference samples outside the boundary of the reference picture in the projection area can be obtained from neighboring samples within the sphere area. In the case of common projection formats, since it involves not only 2D-to-3D and 3D-to-2D coordinate conversions but also sample interpolation for fractional sample positions, it may be difficult to derive the corresponding neighboring samples within the sphere area. This problem can be solved for the left and right boundaries of the ERP or PERP projection format because the sphere neighborhood outside the left picture boundary can be obtained from samples inside the right picture boundary and vice versa. Considering the wide use of the ERP or PERP projection format and the relatively ease of implementation, horizontal wrap-around motion compensation has been adapted to the VVC to improve the visual quality of 360-degree videos encoded in the ERP or PERP projection format.

[0079]

[0113] FIG. 6A shows a schematic diagram of an exemplary horizontal wrap-around motion compensation process for orthographic cylindrical projection according to some embodiments of the present disclosure. As shown in FIG. 6A, when a portion of the reference block is outside the left (or right) boundary of the reference picture within the projection area, instead of iterative padding, the "out-of-bounds" portion can be taken from the corresponding sphere neighborhood located within the reference picture with respect to the right (or left) boundary of the projection area. In some embodiments, iterative padding is used only for the upper and lower picture boundaries.

[0080]

[0114] FIG. 6B shows a schematic diagram of an exemplary horizontal wrap-around motion compensation process for padded orthographic cylindrical projection according to some embodiments of the present disclosure. As shown in FIG. 6B, horizontal wrap-around motion compensation can be combined with non-standard padding methods that are often used in 360-degree video coding. In some embodiments, this is achieved by signaling a high-level syntax element that indicates the wrap-around motion compensation offset, which can be set to the ERP picture width prior to padding. This syntax can be used to adjust the position of the horizontal wrap-around accordingly. In some embodiments, this syntax is not affected by a specific amount of padding at the left or right picture boundary. As a result, this syntax can naturally support asymmetric padding of the ERP picture, where the left padding and the right padding are different. In some embodiments, the wrap-around motion compensation can be determined according to the following formula.

Equation

[0081]

[0115] Horizontal wrap-around motion compensation can provide more significant information for motion compensation when the reference samples are outside the left and right boundaries of the reference picture. Under 360-degree video common test conditions, this tool can improve the compression performance not only regarding rate distortion but also regarding the reduced seam artifacts and subjective quality of the reconstructed 360-degree video. Horizontal wrap-around motion compensation can also be used in other single-plane projection formats with a constant sampling density in the horizontal direction, such as adjusted equirectangular projection.

[0082]

[0116] In some embodiments, restrictions are imposed on the wrap-around motion compensation offset. The value of the offset can be derived from the range of (CtbSizeY / MinCbSizeY + 2) to (pic_width_in_luma_samples / MinCbSizeY). Here, the variable "CtbSizeY" refers to the luma size of the coding tree block ("CTB"), the variable "MinCbSizeY" refers to the minimum size of the luma coded block, and the variable "pic_width_in_luma_samples" refers to the picture width in luma samples, which is unnecessary in actual applications but introduces a burden to hardware implementations and avoids wrap-around repetitions.

[0083]

[0117] Figure 7 shows the syntax of an exemplary sequence parameter set for wrap-around motion compensation according to some embodiments of the present disclosure. As shown in Figure 5, in VVC (e.g., VVC Draft 7), for wrap-around motion compensation, a valid flag "sps_ref_wraparound_enabled_flag" and an offset "sps_ref_wraparound_offset_minus1" can be signaled in the sequence parameter set ("PPS").

[0084]

[0118] Figure 8 shows the meaning of an exemplary sequence parameter set for wrap-around motion compensation according to some embodiments of the present disclosure. It should be understood that the meaning shown in Figure 8 may correspond to the syntax shown in Figure 7. As shown in Figure 8, in some embodiments, "sps_ref_wraparound_enabled_flag" may indicate whether horizontal wrap-around motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wrap-around motion compensation is applied, and a value of 0 may indicate that horizontal wrap-around motion compensation is not applied. In some embodiments, when the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1), the value of sps_ref_wraparound_enabled_flag is equal to 0, in which case "pic_width_in_luma_samples" is the value of "pic_width_in_luma_samples" in any PPS that references the SPS.

[0085]

[0119] According to some embodiments, as shown in FIG. 8, "sps_ref_wraparound_offset_minus1" + 1 may indicate an offset used to calculate the horizontal wraparound position in units of "MinCbSizeY" luma samples. According to some embodiments, the value of ref_wraparound_offset_minus1 is in the range from (CtbSizeY / MinCbSizeY) + 1 to (pic_width_in_luma_samples / MinCbSizeY) - 1, where pic_width_in_luma_samples is the value of pic_width_in_luma_samples in any PPS that references the SPS.

[0086]

[0120] There are some problems with the syntax shown in FIG. 7 and the meaning shown in FIG. 8. In particular, "sps_ref_wraparound_enabled_flag" and "sps_ref_wraparound_offset_minus1" are syntax elements signaled in the SPS, but there are compliance constraints that depend on all of the "pic_width_in_luma_samples" signaled on the PPS. The SPS is a higher-level syntax than the PPS, and generally a higher-level syntax should not reference a lower-level syntax, so there can be problems with restricting the value of an SPS syntax element value by the syntax elements in all related PPSs. Further, according to some embodiments, wraparound motion compensation is controlled at the sequence level, but changes in picture size are permitted in the VVC draft (e.g., VVC draft 7). At the same time, "sps_ref_wraparound_enabled_flag" can be true only when the widths of all pictures in the sequence that reference the SPS meet the constraint conditions. Therefore, even if only one frame does not meet the size conditions, wraparound motion compensation cannot be used. This means that the benefit of wraparound motion compensation for the entire sequence can be lost due to one frame.

[0087]

[0121] Additionally, in some embodiments, "sps_ref_wraparound_offset_minus1" is from (CtbSizeY / MinCbSizeY)+1 to (pic_width_in_luma_samples / MinCbSizeY)-1. Therefore, the minimum value signaled in the bitstream for sps_ref_wraparound_offset_minus1 is (CtbSizeY / MinCbSizeY)+1, which may not be a 0 value. Generally, the larger the value, the more bits are required for signaling than for smaller values. As a result, it is not efficient to signal a syntax element having a range of values that does not start from 0.

[0088]

[0122] Embodiments of the present disclosure provide an improved method for solving the above-described problems. FIG. 9 shows the syntax of an exemplary sequence parameter set for improved wraparound motion compensation according to some embodiments of the present disclosure. In some embodiments, the signaling overhead of the wraparound motion compensation ("MC") offset can be saved. To save bits specified for the wraparound motion compensation offset, (CtbSizeY / MinCbSizeY)+2 can be subtracted from the wraparound motion compensation offset before it is signaled. As a result, the minimum value of this syntax element can be 0.

[0089]

[0123] FIG. 10 shows the meaning of an exemplary sequence parameter set for improved wraparound motion compensation according to some embodiments of the present disclosure. As shown in FIG. 10, changes from the previous VVC are shown in italics. It should be understood that the meaning shown in FIG. 10 may correspond to the syntax shown in FIG. 9.

[0090]

[0124] According to some embodiments, as shown in FIG. 10, "sps_ref_wraparound_enabled_flag" may indicate whether horizontal wraparound motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wraparound motion compensation is applied, and a value of 0 may indicate that horizontal wraparound motion compensation is not applied. According to some embodiments, when the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1), the value of "sps_ref_wraparound_enabled_flag" is equal to 0.

[0091]

[0125] According to some embodiments, as shown in FIG. 10, "sps_ref_wraparound_offset" + (CtbSizeY / MinCbSizeY) + 2 may indicate an offset used to calculate the horizontal wraparound position in units of "MinCbSizeY" luma samples. The value of "sps_ref_wraparound_offset" may be in the range from 0 to (pic_width_in_luma_samples / MinCbSizeY) - (CtbSizeY / MinCbSizeY) - 2. Here, pic_width_in_luma_samples is the value of pic_width_in_luma_samples in any PPS that refers to the SPS.

[0092]

[0126] As described above, another problem with the conventional design is that, even if one picture in the video sequence has dimensions that violate the compliance requirements, the wrap-around MC is disabled for all pictures in the video sequence. In some embodiments, the constraints on the syntax element values are removed. The control flag sps_ref_wraparound_enabled_flag for wrap-around motion compensation is first signaled in the SPS. In some embodiments, when sps_ref_wraparound_enabled_flag is true, the offset value sps_ref_wraparound_offset_minus1 is signaled.

[0093]

[0127] FIG. 11 shows the meaning of an exemplary sequence parameter set for improved wrap-around motion compensation using the maximum picture width, according to some embodiments of the present disclosure. As shown in FIG. 11, changes from the previous VVC are shown in italics, and the proposed deleted meanings are further shown with a strikethrough.

[0094]

[0128] In some embodiments, as shown in FIG. 11, "sps_ref_wraparound_enabled_flag" may indicate whether horizontal wrap-around motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wrap-around motion compensation may be applied to inter prediction, and a value of 0 may indicate that horizontal wrap-around motion compensation is not applied.

[0095]

[0129] In some embodiments, as shown in FIG. 11, "sps_ref_wraparound_offset_minus1" + 1 may indicate the maximum value of the offset used to calculate the horizontal wrap-around position in "MinCbSizeY" luma sample units. In some embodiments, the value of "sps_ref_wraparound_offset_minus1" is in the range including (CtbSizeY / MinCbSizeY) + 1 to (pic_width_max_in_luma_samples / MinCbSizeY) - 1.

[0096]

[0130] According to some embodiments, "pic_width_max_in_luma_samples" is the maximum width in luma samples of each decoded picture that refers to the SPS.

[0097]

[0131] According to some embodiments, for each picture of the sequence, two variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" may be defined. FIG. 12 shows an example of deriving the variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" according to some embodiments of the present disclosure. As shown in FIG. 12, "pic_width_in_luma_samples" may refer to the width of the picture that refers to the PPS in which "pic_width_in_luma_samples" is signaled.

[0098]

[0132] According to some embodiments, as shown in FIG. 12, the variable "PicRefWraparoundEnableFlag" may be used to determine whether wraparound MC can be effective for the current picture. For example, when the value of "PicRefWraparoundEnableFlag" indicates that wraparound MC can be effective for the current picture, the offset "PicRefWraparoundOffset" is used in the motion compensation process.

[0099]

[0133] FIG. 13 shows an example of deriving the sample positions used for motion compensation according to some embodiments of the present disclosure. As shown in FIG. 13, the sample position (xInt i , yInt i ) refers to the sample position before wraparound, and the sample position (xInt i , yInt i) can be determined. In some embodiments, the variable "picW" is equal to the variable "pic_width_in_luma_samples". In some embodiments, the functions "ClipH" and "Clip3" can be executed according to the expressions shown in FIG. 13.

[0100]

[0134] In some embodiments, the wrap-around motion compensation control flag may also be signaled in the SPS, but the wrap-around motion compensation offset is signaled in the PPS rather than the SPS. FIG. 14 shows an exemplary sequence parameter set and picture parameter set syntax for wrap-around motion compensation using the wrap-around motion compensation offset within the picture parameter set according to some embodiments of the present disclosure. As shown in FIG. 14, changes from the previous VVC are shown in italics, and proposed deleted syntax is further shown with a strikethrough. In some embodiments, as shown in FIG. 14, "sps_ref_wraparound_enabled_flag" is signaled in the SPS and "pps_ref_wraparound_offset_minus1" is signaled in the PPS.

[0101]

[0135] FIG. 15 shows the meaning of an exemplary sequence parameter set and picture parameter set for wrap-around motion compensation using the wrap-around motion compensation offset within the picture parameter set according to some embodiments of the present disclosure. As shown in FIG. 15, changes from the previous VVC are shown in italics, and proposed deleted meanings are further shown with a strikethrough. It should be understood that the meanings shown in FIG. 15 may correspond to the syntax shown in FIG. 14.

[0102]

[0136] According to some embodiments, as shown in FIG. 15, "sps_ref_wraparound_enabled_flag" may indicate whether horizontal wraparound motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wraparound motion compensation is applied, and a value of 0 may indicate that horizontal wraparound motion compensation is not applied.

[0103]

[0137] According to some embodiments, as shown in FIG. 15, "pps_ref_wraparound_offset_minus1" + 1 may indicate an offset used to calculate the horizontal wraparound position in units of "MinCbSizeY" luma samples. According to some embodiments, when "sps_ref_wraparound_enabled_flag" is equal to 0 or the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1), "pps_ref_wraparound_offset_minus1" is equal to 0. In other cases, the value of "pps_ref_wraparound_offset_minus1" is within the range including (CtbSizeY / MinCbSizeY) + 1 to (pic_width_in_luma_samples / MinCbSizeY) - 1.

[0104]

[0138] According to some embodiments, for each picture in a sequence, two variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" may be defined. According to some embodiments, "PicRefWraparoundEnableFlag" may be determined as shown in FIG. 12. According to some embodiments, "PicRefWraparoundOffset" may be determined as "pps_ref_wraparound_offset_minus1" + 1.

[0105]

[0139] According to some embodiments, during the decoding process, "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" can be used for wraparound motion compensation. For example, the sample positions (xInt i , yInt i ) used for motion compensation can be derived in the manner shown in FIG. 13. As shown in FIG. 13, according to some embodiments, the variable "picW" may be equal to "pic_width_in_luma_samples".

[0106]

[0140] According to some embodiments, the wraparound motion compensation control flag can also be signaled, but the wraparound motion compensation offset is signaled in the PPS rather than the SPS. Further, "pps_ref_wraparound_offset" can also indicate the use of wraparound motion compensation for the picture referring to the PPS. FIG. 16 shows the syntax of an exemplary sequence parameter set for improved wraparound motion compensation without a wraparound motion compensation offset according to some embodiments of the present disclosure. As shown in FIG. 16, the changes from the previous VVC are shown in italics, and the proposed deleted syntax is further shown with a strikethrough. As shown in FIG. 14, "sps_ref_wraparound_enabled_flag" can be signaled in the SPS.

[0107]

[0141] Figure 17 shows the syntax of an exemplary picture parameter set for improved wrap-around motion compensation using wrap-around motion compensation offsets according to some embodiments of the present disclosure. As shown in Figure 17, changes from the previous VVC are shown in italics. It should be understood that the PPS shown in Figure 17 may correspond to the SPS shown in Figure 16. As shown in Figure 17, "pps_ref_wraparound_offset" may be signaled in the PPS. In some embodiments, "pps_ref_wraparound_offset" signaled in the PPS may also indicate the use of wrap-around motion compensation for the picture that references the PPS. In other words, the coder may disable wrap-around motion compensation at the PPS level by setting pps_ref_wraparound_offset to a special value.

[0108]

[0142] Figure 18 shows the meaning of an exemplary sequence parameter set and picture parameter set for improved wrap-around motion compensation using wrap-around motion compensation offsets within the picture parameter set according to some embodiments of the present disclosure. As shown in Figure 18, changes from the previous VVC are shown in italics, and the proposed removed meanings are shown with strikethrough. It should be understood that the meanings shown in Figure 18 may correspond to the syntax shown in Figures 16 and 17.

[0109]

[0143] In some embodiments, as shown in Figure 18, "sps_ref_wraparound_enabled_flag" may indicate whether horizontal wrap-around motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wrap-around motion compensation may be applied to inter prediction, and a value of 0 may indicate that horizontal wrap-around motion compensation is not applied.

[0110]

[0144] Depending on the embodiment, as shown in FIG. 18, "pps_ref_wraparound_offset" + 1 may indicate the offset value used to calculate the horizontal wraparound position in MinCbSizeY luma sample units. For example, when "pps_ref_wraparound_offset" is equal to 0, wraparound motion compensation is disabled. "pps_ref_wraparound_offset" is equal to 0 when "sps_ref_wraparound_enabled_flag" is equal to 0 or the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1). In other cases, the value of "pps_ref_wraparound_offset" is within the range including (CtbSizeY / MinCbSizeY) + 1 to (pic_width_in_luma_samples / MinCbSizeY) - 1.

[0111]

[0145] Depending on the embodiment, for each picture of the sequence, two variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" may be defined. FIG. 19 shows an example of the derivation of the variables "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" according to some embodiments of the present disclosure.

[0112]

[0146] Depending on the embodiment, during the decoding process, "PicRefWraparoundEnableFlag" and "PicRefWraparoundOffset" may be used for wraparound motion compensation. For example, the sample position (xInt i , yInt i ) used for motion compensation may be derived in the manner shown in FIG. 11. As shown in FIG. 11, depending on the embodiment, the variable "picW" may be equal to "pic_width_in_luma_samples".

[0113]

[0147] Depending on the embodiment, the syntax is changed. The wrap-around motion compensation control flag can still be signaled in the SPS, but the wrap-around motion compensation offset is signaled in the PPS rather than the SPS. Further, the PPS-level wrap-around motion compensation control flag can also be signaled. FIG. 20 shows the syntax of an exemplary sequence parameter set for improved wrap-around motion compensation without a wrap-around motion compensation offset in the sequence parameter set according to some embodiments of the present disclosure. As shown in FIG. 20, changes from the previous VVC are shown in italics, and the proposed deleted syntax is further shown with a strikethrough. As shown in FIG. 20, "sps_ref_wraparound_enabled_flag" can be signaled in the SPS.

[0114]

[0148] FIG. 21 shows the syntax of an exemplary picture parameter set for improved wrap-around motion compensation using a wrap-around control flag according to some embodiments of the present disclosure. As shown in FIG. 21, changes from the previous VVC are shown in italics. As shown in FIG. 21, "pps_ref_wraparound_enabled_flag" can be signaled in the PPS. Depending on the embodiment, when "pps_ref_wraparound_enabled_flag" is true (e.g., the value is equal to 1), "pps_ref_wraparound_offset" can be signaled.

[0115]

[0149] FIG. 22 shows the meaning of an exemplary sequence parameter set and picture parameter set for improved wrap-around motion compensation using a wrap-around control flag in the picture parameter set according to some embodiments of the present disclosure. As shown in FIG. 22, changes from the previous VVC are shown in italics, and the proposed deleted meaning is further shown with a strikethrough. It should be understood that the meaning shown in FIG. 22 can correspond to the syntax shown in FIGS. 20 and 21.

[0116]

[0150] According to some embodiments, as shown in FIG. 22, “sps_ref_wraparound_enabled_flag” may indicate whether horizontal wraparound motion compensation is applied to inter prediction. For example, a value of 1 may indicate that horizontal wraparound motion compensation may be applied to inter prediction, and a value of 0 may indicate that horizontal wraparound motion compensation is not applied.

[0117]

[0151] According to some embodiments, as shown in FIG. 22, “pps_ref_wraparound_enabled_flag” equal to 1 may indicate that horizontal wraparound motion compensation is applied in inter prediction. “pps_ref_wraparound_enabled_flag” equal to 0 may indicate that horizontal wraparound motion compensation is not applied. According to some embodiments, when “sps_ref_wraparound_enabled_flag” is equal to 0 or the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1), “pps_ref_wraparound_enabled_flag” is equal to 0.

[0118]

[0152] According to some embodiments, as shown in FIG. 22, there are alternative meanings for the sequence parameter set and the picture parameter set. FIG. 23 shows exemplary sequence parameter sets and picture parameter set meanings for improved wraparound motion compensation using wraparound control flags within the picture parameter set according to some embodiments of the present disclosure. As shown in FIG. 23, changes from the previous VVC are shown in italics, and proposed deleted meanings are further shown with a strikethrough. It should be understood that the meanings shown in FIG. 23 may correspond to the syntax shown in FIGS. 20 and 21.

[0119]

[0153] According to some embodiments, as shown in FIG. 23, a "pps_ref_wraparound_enabled_flag" equal to 1 may indicate that horizontal wraparound motion compensation is applied to inter prediction. A "pps_ref_wraparound_enabled_flag" equal to 0 may indicate that horizontal wraparound motion compensation is not applied. According to some embodiments, when "sps_ref_wraparound_enabled_flag" is equal to 0 or the value of (CtbSizeY / MinCbSizeY + 1) is greater than (pic_width_in_luma_samples / MinCbSizeY - 1), "pps_ref_wraparound_enabled_flag" is 0. In other cases, "pps_ref_wraparound_enabled_flag" is equal to 1.

[0120]

[0154] According to some embodiments, as shown in FIG. 23, "pps_ref_wraparound_offset" + (CtbSizeY / MinCbSizeY) + 2 may specify a value of an offset used to calculate a horizontal wraparound position in units of MinCbSizeY luma samples. According to some embodiments, the value of "pps_ref_wraparound_offset", if it exists, may be within a range including 0 to (pic_width_in_luma_samples / MinCbSizeY) - (CtbSizeY / MinCbSizeY) - 2.

[0121]

[0155] According to some embodiments, for each picture of a sequence, a variable "PicRefWraparoundOffset" may be defined. For example, "PicRefWraparoundOffset" may be derived as pps_ref_wraparound_offset_minus1 + 1.

[0122]

[0156] Depending on the embodiment, during the decoding process, the variables "pps_ref_wraparound_enabled_flag" and "PicRefWraparoundOffset" can be used for wraparound motion compensation. FIG. 24 shows an example of the derivation of the variable "PicRefWraparoundOffset" according to some embodiments of the present disclosure. As shown in FIG. 24, the variable "PicRefWraparoundOffset" can be derived according to the variables "pps_ref_wraparound_offset", "CtbSizeY", and "MinCbSizeY". Depending on the embodiment, the variable "PicRefWraparoundOffset" can also be used to determine a sample position (xInt i , yInt i ) similar to the sample position shown in FIG. 13 for use in motion compensation. As shown in FIG. 13, the variable "picW" may be equal to "pic_width_in_luma_samples".

[0123]

[0157] Depending on the embodiment, "sps_ref_wraparound_enabled_flag" may be removed, and "pps_ref_wraparound_enabled_flag" and "pps_ref_wraparound_offset" may be retained.

[0124]

[0158] Depending on the embodiment, the restrictions on the value ranges of "sps_ref_wraparound_enabled_flag" and "sps_ref_wraparound_offset_minus1" may be removed, and restrictions on the value ranges of the picture sizes signaled in the SPS and PPS may be added. Furthermore, there may be no change in the syntax. FIG. 25 shows the meaning of an exemplary sequence parameter set and picture parameter set for improved wraparound motion compensation using restrictions on picture size according to some embodiments of the present disclosure. As shown in FIG. 25, the changes from the previous VVC are shown in italics, and the proposed removed meanings are further shown with a strikethrough.

[0125]

[0159] According to an embodiment, as shown in FIG. 25, "pic_width_max_in_luma_samples" may indicate the maximum width in luma sample units of each decoded picture that refers to the SPS. According to an embodiment, "pic_width_max_in_luma_samples" may not be equal to 0 and may be an integer multiple of max(8, MinCbSizeY).

[0126]

[0160] According to an embodiment, as shown in FIG. 25, "pic_height_max_in_luma_samples" may indicate the maximum height in luma sample units of each decoded picture that refers to the SPS. According to an embodiment, "pic_height_max_in_luma_samples" may not be equal to 0 and may be an integer multiple of max(8, MinCbSizeY).

[0127]

[0161] According to an embodiment, as shown in FIG. 25, "sps_ref_wraparound_enabled_flag" equal to 1 may indicate that horizontal wraparound motion compensation is applied to inter prediction, and "sps_ref_wraparound_enabled_flag" equal to 0 may indicate that horizontal wraparound motion compensation is not applied.

[0128]

[0162] According to an embodiment, "sps_ref_wraparound_offset_minus1" + 1 may indicate the offset used to calculate the horizontal wraparound position in "MinCbSizeY" luma sample units. According to an embodiment, the value of "sps_ref_wraparound_offset_minus1" is (CtbSizeY / MinCbSizeY) + 1 or more.

[0129]

[0163] Depending on the embodiment, restrictions may be imposed on "pic_width_max_in_luma_samples", "[CtbSizeY]", and "MinCbSizeY". FIG. 26 shows the meaning of an exemplary sequence parameter set for improved wrap-around motion compensation using the restrictions imposed on the variables "pic_width_max_in_luma_samples", "CtbSizeY", and "MinCbSizeY" according to some embodiments of the present disclosure. As shown in FIG. 26, changes from the previous VVC are shown in italics, and proposed deleted meanings are further shown with strikethrough.

[0130]

[0164] Depending on the embodiment, restrictions may be imposed on "pic_width_in_luma_samples", which is signaled in the PPS. FIG. 27 shows the meaning of an exemplary picture parameter set for improved wrap-around motion compensation using the restrictions imposed on the variable "pic_width_in_luma_samples" according to some embodiments of the present disclosure. As shown in FIG. 27, changes from the previous VVC are shown in italics, and proposed deleted meanings are further shown with strikethrough.

[0131]

[0165] Depending on the embodiment, the method shown in FIGS. 9-11 may be combined with any of the methods shown in FIGS. 11-27. In order to reduce the signaling cost, since a special value is subtracted from the wrap-around motion compensation offset before the wrap-around motion compensation offset is signaled (e.g., the method shown in FIGS. 9-10), when the methods are combined, the range limitation of the wrap-around motion compensation offset signaled in the bitstream may also be changed. For example, the same special value may be subtracted from both the upper and lower limits. Further, if the lower limit after subtraction is 0, since it is guaranteed that the offset signaled in the bitstream is a non-negative value in the VVC standard (e.g., VVC draft 7), it may be removed.

[0132]

[0166] Embodiments of the present disclosure further provide a method for performing motion compensation. FIG. 28 shows a flowchart of an exemplary method for performing motion compensation according to some embodiments of the present disclosure. It should be understood that the method 28000 shown in FIG. 28 can be executed according to the syntax and semantics shown in FIGS. 9 and 10.

[0133]

[0167] In step S28010, a sequence of pictures is received. The sequence is associated with a sequence wrap-around motion compensation flag and a sequence wrap-around motion compensation offset. The minimum value for the sequence motion compensation wrap-around motion compensation offset is 0. For example, as shown in FIG. 9, in order to save the bits specified for the wrap-around motion compensation offset, (CtbSizeY / MinCbSizeY)+2 can be subtracted from the wrap-around motion compensation offset before the wrap-around motion compensation offset is signaled. As a result, the minimum value of this syntax element can be 0.

[0134]

[0168] In step S28020, it is determined whether the sequence wrap-around motion compensation flag is valid.

[0135]

[0169] In step S28030, in response to the sequence wrap-around motion compensation flag being valid, wrap-around motion compensation is performed on the pictures in the sequence of pictures according to the sequence wrap-around motion compensation offset. According to some embodiments, the motion compensation is performed according to the VVC standard.

[0136]

[0170] Embodiments of the present disclosure further provide a method for performing motion compensation with a limited range for sequence wrap-around motion compensation offset. FIG. 29 shows a flowchart of an exemplary method for performing motion compensation using a limited range for sequence wrap-around motion compensation offset according to some embodiments of the present disclosure. It should be understood that the method 29000 shown in FIG. 29 can be executed according to the meaning shown in FIG. 11.

[0137]

[0171] In step S29010, a sequence of pictures is received. The sequence is associated with a sequence wrap-around motion compensation flag and a sequence wrap-around motion compensation offset. The range for the sequence wrap-around motion compensation offset is limited according to the maximum width of the pictures in the sequence of pictures. For example, as shown in FIG. 11, "pic_width_max_in_luma_samples" may represent the maximum width in luma samples of each decoded picture referring to the SPS. The value of "sps_ref_wraparound_offset_minus1" can be within the range including (CtbSizeY / MinCbSizeY)+1 to (pic_width_max_in_luma_samples / MinCbSizeY)-1.

[0138]

[0172] In step S29020, it is determined whether the sequence wrap-around motion compensation flag is valid.

[0139]

[0173] In step S29030, in response to the sequence wrap-around motion compensation flag being valid, wrap-around motion compensation is performed on the pictures in the sequence of pictures according to the sequence wrap-around motion compensation offset. In some embodiments, the motion compensation is performed according to the VVC standard. In some embodiments, the wrap-around motion compensation may be performed on a plurality of pictures in the sequence of pictures, and the plurality of pictures may have different sizes. In some embodiments, the wrap-around motion compensation for a picture is performed according to the sequence wrap-around motion compensation offset in response to the picture wrap-around valid flag being valid. The picture wrap-around valid flag may be determined according to the sequence wrap-around motion compensation flag. For example, as shown in FIG. 12, the picture wrap-around valid flag may be determined from an expression including the variable "sps_ref_wraparound_enabled_flag".

[0140]

[0174] Embodiments of the present disclosure further provide a method for performing motion compensation using pictures associated with a sequence wrap-around motion compensation offset. FIG. 30 shows a flowchart of an exemplary method for performing motion compensation using pictures associated with a sequence wrap-around motion compensation offset according to some embodiments of the present disclosure. It should be understood that the method 30000 shown in FIG. 30 may be executed according to the syntax and semantics shown in FIGS. 14 and 15.

[0141]

[0175] In step S30010, a sequence of pictures is received. The sequence is associated with a sequence wrap-around motion compensation flag, and the pictures in the sequence are associated with a picture wrap-around motion compensation offset. For example, as shown in FIG. 14, a new variable "pps_ref_wraparound_offset" may be included in the picture parameter set.

[0142]

[0176] In step S30020, it is determined whether the sequence wrap-around motion compensation flag is valid.

[0143]

[0177] In step S30030, in response to the sequence wrap-around motion compensation flag being valid, wrap-around motion compensation is performed on the pictures in the picture sequence according to the sequence wrap-around motion compensation offset. In some embodiments, the motion compensation is performed according to the VVC standard. In some embodiments, the wrap-around motion compensation may be performed on a plurality of pictures in the picture sequence, and the plurality of pictures may have different sizes.

[0144]

[0178] In some embodiments, the wrap-around motion compensation for a picture is performed according to the sequence wrap-around motion compensation offset in response to the picture wrap-around enable flag being valid. The picture wrap-around enable flag may be determined according to the sequence wrap-around motion compensation flag. For example, as shown in FIG. 12, the picture wrap-around enable flag may be determined from an expression including the variable "sps_ref_wraparound_enabled_flag". In some embodiments, the minimum value of the picture wrap-around motion compensation offset is 0. For example, as shown in FIG. 18, the minimum value of the variable "pps_ref_wraparound_offset" may be 0.

[0145]

[0179] According to some embodiments, a picture is associated with a picture wrap-around motion compensation flag. Depending on whether the picture wrap-around motion compensation flag is valid, wrap-around motion compensation can be performed on the picture according to the picture wrap-around motion compensation offset. For example, as shown in FIG. 21, a new variable "pps_ref_wraparound_enabled_flag" may be added to the picture parameter set. As shown in FIG. 22, the variable "pps_ref_wraparound_enabled_flag" may indicate whether horizontal wrap-around motion compensation is applied at the picture level. According to some embodiments, depending on whether the picture wrap-around motion compensation flag is valid, the picture wrap-around motion compensation offset may be signaled.

[0146]

[0180] Embodiments of the present disclosure further provide a method for performing motion compensation with a limited maximum picture size. FIG. 31 shows a flowchart of an exemplary method for performing motion compensation using a limited maximum picture size according to some embodiments of the present disclosure. It should be understood that the method 31000 shown in FIG. 31 can be executed according to the meaning shown in FIG. 25.

[0147]

[0181] In step S31010, a sequence of pictures is received. The sequence is associated with a sequence wrap-around motion compensation flag, and the pictures in the sequence are associated with a picture wrap-around motion compensation offset.

[0148]

[0182] In step S31020, it is determined whether the sequence wrap-around motion compensation flag is valid.

[0149]

[0183] In step S31030, in response to the sequence wrap-around motion compensation flag being valid, wrap-around motion compensation is performed on the pictures in the sequence of pictures according to the sequence wrap-around motion compensation offset. The maximum size of the picture is limited to a minimum value according to the sequence wrap-around motion compensation offset. For example, as shown in FIG. 26, the maximum picture width can be determined according to an expression including "sps_ref_wraparound_offset_minus1". In some embodiments, the motion compensation is performed according to the VVC standard. In some embodiments, the wrap-around motion compensation may be performed on a plurality of pictures in the sequence of pictures, and the plurality of pictures may have different sizes. In some embodiments, the size of the picture is limited to a minimum value according to the sequence wrap-around motion compensation offset. For example, as shown in FIG. 27, the picture width can be determined according to an expression including "sps_ref_wraparound_offset_minus1".

[0150]

[0184] In some embodiments, a non-transitory computer-readable storage medium including instructions is also provided, and the instructions can be executed by a device (such as the encoder and decoder of the present disclosure) to perform the above-described method. Examples of common forms of non-transitory media include, for example, floppy (registered trademark) disks, flexible disks, hard disks, solid state drives, magnetic tapes, or any other magnetic data storage media, CD-ROMs, any other optical data storage media, any physical medium having a pattern of holes, RAMs, PROMs, and EPROMs, FLASH (registered trademark)-EPROMs or any other flash memory, NVRAMs, caches, registers, any other memory chips or cartridges, and networked versions of these. The device may include one or more processors (CPUs), an input / output interface, a network interface, and / or a memory.

[0151]

[0185] Note that relative terms in this specification, such as "first" and "second", are only used to distinguish an entity or operation from another entity or operation, and do not require or imply any actual relationship or order between these entities or operations. Further, the words "comprising", "having", "containing", and "including", and other similar forms, are equivalent in meaning and are intended to be open-ended in that an element or group of elements following any one of these words is not meant to be a limiting enumeration of such element or group of elements, or limited to only the enumerated element or group of elements.

[0152]

[0186] As used herein, unless otherwise specifically stated, the term "or" includes all possible combinations, except when the combination is infeasible. For example, if it is stated that a database may contain A or B, then, unless otherwise specifically stated or infeasible, the database may contain A, or B, or A and B. As a second example, if it is stated that a database may contain A, B, or C, then, unless otherwise specifically stated or infeasible, the database may contain A, B, or C, or A and B, A and C, or B and C, or A and B and C.

[0153]

[0187] It is understood that the above-described embodiments can be implemented by hardware, or software (program code), or a combination of hardware and software. When implemented by software, it can be stored in the above-described computer-readable medium. The software can perform the method of the present disclosure when executed by a processor. The computing unit and other functional units described in the present disclosure can be implemented by hardware, or software, or a combination of hardware and software. Those skilled in the art will also understand that a plurality of the above-described modules / units may be combined into one module / unit, and each of the above-described modules / units may be further divided into a plurality of sub-modules / sub-units.

[0154]

[0188] In the above specification, the embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. Specific adaptations and modifications of the above-described embodiments can be made. From the considerations of this specification and the practice of the invention disclosed herein, other embodiments may become apparent to those skilled in the art. The specification and examples are intended to be considered only as examples, and the true scope and spirit of the invention are indicated by the appended claims. Also, the arrangement of steps shown in the figures is merely for illustrative purposes and is not intended to be limited to any specific arrangement of steps. Therefore, those skilled in the art can understand that these steps can be performed in a different order while implementing the same method.

[0155]

[0189] The embodiments can be further described using the following clauses. 1. A method of performing motion compensation, receiving a first wraparound motion compensation flag, wherein the first wraparound motion compensation flag is associated with a picture, determining whether the first wraparound motion compensation flag is valid, Receiving a wraparound motion compensation offset in response to a determination that the first wraparound motion compensation flag is valid, wherein the wraparound motion compensation offset is associated with a picture, and performing motion compensation on a picture according to the first wraparound motion compensation flag and the wraparound motion compensation offset; A method comprising: 2. Receiving a second wraparound motion compensation flag, wherein the first wraparound motion compensation flag is associated with a set of pictures including the picture associated with the first wraparound motion compensation flag, and determining whether the second wraparound motion compensation flag is invalid; determining that the first wraparound motion compensation flag is also invalid in response to a determination that the second wraparound motion compensation flag is invalid; The method according to clause 1, further comprising: 3. Determining whether the first wraparound motion compensation flag is valid may include determining the picture width of the picture associated with the first wraparound motion compensation flag, and determining whether the first wraparound motion compensation flag is valid based on the picture width; The method according to clause 2, further comprising: 4. Determining whether the luma coding tree block size of the minimum coding block unit + 1 is greater than the picture width of the picture of the minimum coding block unit - 1, and determining that the first motion compensation flag is invalid in response to a determination that the luma coding tree block size of the minimum coding block unit + 1 is greater than the picture width of the picture of the minimum coding block unit - 1; The method according to clause 3, further comprising: 5. determining whether the second wraparound motion compensation flag is valid; in response to a determination that a second wrap-around motion compensation flag is valid, determining that a picture width of a picture is greater than or equal to a luma coding tree block size + an offset; The method according to any one of clauses 2 to 4, further comprising: 6. The method according to clause 5, further comprising, in response to a determination that a second wrap-around motion compensation flag is valid, determining that a luma coding tree block size + 1 of a minimum coding block unit is less than or equal to a picture width - 1 of a picture of the minimum coding block unit. 7. The method according to any one of clauses 2 to 6, wherein the second wrap-around motion compensation flag is signaled in a sequence parameter set, and the first wrap-around motion compensation flag and a wrap-around motion compensation offset are signaled in a picture parameter set. 8. The method according to any one of clauses 1 to 7, wherein motion compensation is performed according to a multi-purpose video coding standard. 9. The method according to any one of clauses 1 to 8, further comprising performing motion compensation for a plurality of pictures, wherein the plurality of pictures have different sizes. 10. performing motion compensation for a picture according to a wrap-around motion compensation offset, determining a second wrap-around motion compensation offset by adding an offset to a wrap-around motion compensation offset received from a bitstream; performing motion compensation for the picture according to the second wrap-around motion compensation offset; The method according to any one of clauses 1 to 9, further comprising: 11. A system for performing motion compensation, comprising: a memory storing a set of instructions; and a processor, wherein the processor Receiving first wraparound motion compensation, wherein a first wraparound motion compensation offset is associated with picture i, Determining whether a first wraparound motion compensation flag is valid, Receiving a wraparound motion compensation offset in response to a determination that the first wraparound motion compensation flag is valid, wherein the wraparound motion compensation offset is associated with a picture, Performing motion compensation on a picture according to the first wraparound motion compensation flag and the wraparound motion compensation offset, A system configured to execute a set of instructions to cause the system to perform the above. 12. The processor, Receiving a second wraparound motion compensation flag, wherein the second wraparound motion compensation flag is associated with a set of pictures including the picture associated with the first wraparound motion compensation flag, Determining whether the second wraparound motion compensation flag is invalid, Determining that the first wraparound motion compensation flag is also invalid in response to a determination that the second wraparound motion compensation flag is invalid, The system according to clause 11, further configured to execute a set of instructions to cause the system to perform the above. 13. The processor, Determining the picture width of the picture associated with the first wraparound motion compensation flag, Determining whether the first wraparound motion compensation flag is valid based on the picture width, The system according to clause 12, further configured to execute a set of instructions to cause the system to perform the above. 14. The processor, Determining whether the luma encoding tree block size + 1 of the minimum coding block unit is greater than the picture width - 1 of the picture of the minimum coding block unit, Determining that the first motion compensation flag is invalid in response to the determination that the luma encoding tree block size + 1 of the minimum coding block unit is greater than the picture width - 1 of the picture of the minimum coding block unit, The system according to clause 13, further configured to execute a set of instructions so as to cause the system to execute. 15. The processor Determining whether the second wrap-around motion compensation flag is valid, Determining that the picture width of the picture is equal to or greater than the luma encoding tree block size + offset in response to the determination that the second wrap-around motion compensation flag is valid, The system according to any one of clauses 12 to 14, further configured to execute a set of instructions so as to cause the system to execute. 16. The processor Determining that the luma encoding tree block size + 1 of the minimum coding block unit is less than or equal to the picture width - 1 of the picture of the minimum coding block unit in response to the determination that the second wrap-around motion compensation flag is valid The system according to clause 15, further configured to execute a set of instructions so as to cause the system to execute. 17. The second wrap-around motion compensation flag is signaled in the sequence parameter set, and the first wrap-around motion compensation flag and the wrap-around motion compensation offset are signaled in the picture parameter set. The system according to any one of clauses 12 to 16. 18. The processor Performing motion compensation on a plurality of pictures The system is further configured to execute a set of instructions so as to cause the system to execute, The system according to any one of clauses 11 to 17, wherein a plurality of pictures have different sizes. 19. The processor is determining a second wrap-around motion compensation offset by adding an offset to the wrap-around motion compensation offset received from the bitstream; performing motion compensation on the picture according to the second wrap-around motion compensation offset; The system according to any one of clauses 11 to 18, further configured to execute a set of instructions so as to cause the system to perform. 20. A non-transitory computer-readable medium storing a set of instructions, the set of instructions being executable by one or more processors of the device to cause the device to initiate a method of performing motion compensation, the method comprising: receiving a first wrap-around motion compensation flag, the first wrap-around motion compensation flag being associated with a picture within a set of pictures; determining whether the first wrap-around motion compensation flag is valid; receiving a wrap-around motion compensation offset in response to a determination that the first wrap-around motion compensation flag is valid, the wrap-around motion compensation offset being associated with the picture; performing motion compensation on the picture according to the first wrap-around motion compensation flag and the wrap-around motion compensation offset. A non-transitory computer-readable medium including the above. 21. The set of instructions includes determining the picture width of the picture associated with the first wrap-around motion compensation flag; determining whether the first wrap-around motion compensation flag is valid based on the picture width; A non-transitory computer-readable medium according to clause 20, executable by at least one processor of a computer system, for causing the computer system to further execute.

[0156]

[0190] Exemplary embodiments have been disclosed in the drawings and the specification. However, many modifications and changes can be made to these embodiments. Therefore, even if specific terms are adopted, they are merely used in the sense of a general description and are not used for the purpose of limitation.

Claims

1. A method of performing motion compensation by a decoder, comprising: receiving a first wrap-around motion compensation flag, wherein the first wrap-around motion compensation flag is associated with one or more pictures and signaled in a picture parameter set; determining whether the first wrap-around motion compensation flag is equal to a first value or equal to a second value; wherein the first wrap-around motion compensation flag equal to the first value indicates that horizontal wrap-around motion compensation is valid for the one or more pictures; wherein the first wrap-around motion compensation flag equal to the second value indicates that horizontal wrap-around motion compensation is invalid for the one or more pictures; receiving parameters associated with a wrap-around motion compensation offset in response to determining that the first wrap-around motion compensation flag is equal to the first value, wherein the wrap-around motion compensation offset is associated with the one or more pictures and signaled in the picture parameter set; receiving a second wrap-around motion compensation flag, wherein the second wrap-around motion compensation flag is associated with a sequence of pictures including the one or more pictures; determining whether the second wrap-around motion compensation flag is equal to the first value or equal to the second value; wherein the second wrap-around motion compensation flag equal to the first value indicates that horizontal wrap-around motion compensation is valid for the sequence of pictures; wherein the second wrap-around motion compensation flag equal to the second value indicates that horizontal wrap-around motion compensation is invalid for the sequence of pictures; determining that the first wrap-around motion compensation flag is also equal to the second value in response to determining that the second wrap-around motion compensation flag is equal to the second value; determining that a luma coded tree block size of a minimum luma coded block unit + 1 is less than or equal to a picture width - 1 of the one or more pictures of the minimum luma coded block unit in response to determining that the second wrap-around motion compensation flag is equal to the first value; decoding the one or more pictures according to the first wrap-around motion compensation flag and the parameter; A method comprising. **Claim 2** determining whether the first wrap-around motion compensation flag is equal to the first value or equal to the second value; determining a picture width of the one or more pictures; determining whether the first wrap-around motion compensation flag is equal to the first value or equal to the second value based on the picture width; The method according to claim 1, further comprising. **Claim 3** determining whether a luma coding tree block size + 1 of a minimum luma coding block unit is greater than a picture width - 1 of the one or more pictures of the minimum luma coding block unit; determining that the first wrap-around motion compensation flag is equal to the second value in response to a determination that a luma coding tree block size + 1 of the minimum luma coding block unit is greater than a picture width - 1 of the one or more pictures of the minimum luma coding block unit; The method according to claim 2, further comprising. **Claim 4** The method according to claim 1, wherein the second wrap-around motion compensation flag is signaled in a sequence parameter set. **Claim 5** decoding the one or more pictures according to the first wrap-around motion compensation flag and the parameter; determining an offset according to the parameter; decoding the one or more pictures according to the offset; The method according to claim 1, further comprising. **Claim 6** A method for storing a bitstream of a video, the method comprising: receiving a video sequence; encoding one or more pictures of the video sequence; generating a bitstream based on the encoded one or more pictures; storing the bitstream in a non-transitory computer-readable storage medium; including, wherein the encoding comprises: signaling a first wrap-around motion compensation flag in a picture parameter set, the first wrap-around motion compensation flag being associated with one or more pictures; determining whether the first wrap-around motion compensation flag is equal to a first value or equal to a second value; The first wrap-around motion compensation flag equal to the first value indicates that horizontal wrap-around motion compensation is effective for the one or more pictures, The first wrap-around motion compensation flag equal to the second value indicates that horizontal wrap-around motion compensation is ineffective for the one or more pictures, Signaling a parameter associated with a wrap-around motion compensation offset in response to a determination that the first wrap-around motion compensation flag is equal to the first value, wherein the wrap-around motion compensation offset is associated with the one or more pictures and is signaled in the picture parameter set, Signaling a second wrap-around motion compensation flag, wherein the second wrap-around motion compensation flag is associated with a sequence of pictures including the one or more pictures, Determining whether the second wrap-around motion compensation flag is equal to the first value or equal to the second value, The second wrap-around motion compensation flag equal to the first value indicates that horizontal wrap-around motion compensation is effective for the sequence of pictures, The second wrap-around motion compensation flag equal to the second value indicates that horizontal wrap-around motion compensation is ineffective for the sequence of pictures, Determining that the first wrap-around motion compensation flag is also equal to the second value in response to a determination that the second wrap-around motion compensation flag is equal to the second value, Determining that the luma coding tree block size of the minimum luma coding block unit + 1 is less than or equal to the picture width of the one or more pictures of the minimum luma coding block unit - 1 in response to the determination that the second wrap-around motion compensation flag is equal to the first value, Encoding the one or more pictures according to the first wrap-around motion compensation flag and the parameter, A method comprising.

7. Determining whether the first wrap-around motion compensation flag is equal to the first value or equal to the second value is Determining the picture width of the one or more pictures, determining whether the first wrap-around motion compensation flag is equal to the first value or the second value based on the picture width; The method according to claim 6, further comprising.

8. determining whether the luma coding tree block size of the minimum luma coding block unit + 1 is greater than the picture width of the one or more pictures of the minimum luma coding block unit - 1; determining that the first wrap-around motion compensation flag is equal to the second value in response to the determination that the luma coding tree block size of the minimum luma coding block unit + 1 is greater than the picture width of the one or more pictures of the minimum luma coding block unit - 1; The method according to claim 7, further comprising.

9. The method according to claim 6, wherein the second wrap-around motion compensation flag is signaled in a sequence parameter set.

10. decoding the one or more pictures according to the first wrap-around motion compensation flag and the parameters; determining an offset according to the parameters; encoding the one or more pictures according to the offset; The method according to claim 6, further comprising.

11. A method of performing motion compensation by an encoder, comprising: signaling a first wrap-around motion compensation flag in a picture parameter set, the first wrap-around motion compensation flag being associated with one or more pictures; determining whether the first wrap-around motion compensation flag is equal to a first value or a second value; the first wrap-around motion compensation flag equal to the first value indicating that horizontal wrap-around motion compensation is effective for the one or more pictures; the first wrap-around motion compensation flag equal to the second value indicating that horizontal wrap-around motion compensation is ineffective for the one or more pictures; signaling a parameter associated with a wrap-around motion compensation offset in response to the determination that the first wrap-around motion compensation flag is equal to the first value, the wrap-around motion compensation offset being associated with the one or more pictures and signaled in the picture parameter set; Signaling a second wrap-around motion compensation flag, wherein the second wrap-around motion compensation flag is associated with a sequence of pictures including the one or more pictures, Determining whether the second wrap-around motion compensation flag is equal to the first value or equal to the second value, The second wrap-around motion compensation flag equal to the first value indicates that horizontal wrap-around motion compensation is effective for the sequence of pictures, The second wrap-around motion compensation flag equal to the second value indicates that horizontal wrap-around motion compensation is ineffective for the sequence of pictures, Determining that the first wrap-around motion compensation flag is also equal to the second value in response to a determination that the second wrap-around motion compensation flag is equal to the second value, Determining that the luma coding tree block size + 1 of the minimum luma coding block unit is less than or equal to the picture width - 1 of the one or more pictures of the minimum luma coding block unit in response to a determination that the second wrap-around motion compensation flag is equal to the first value, Encoding the one or more pictures according to the first wrap-around motion compensation flag and the parameter, A method comprising.

12. Determining whether the first wrap-around motion compensation flag is equal to the first value or equal to the second value, Determining the picture width of the one or more pictures, Determining whether the first wrap-around motion compensation flag is equal to the first value or equal to the second value based on the picture width, The method according to claim 11, further comprising.

13. Determining whether the luma coding tree block size + 1 of the minimum luma coding block unit is greater than the picture width - 1 of the one or more pictures of the minimum luma coding block unit, Determining that the first wrap-around motion compensation flag is equal to the second value in response to a determination that the luma coding tree block size + 1 of the minimum luma coding block unit is greater than the picture width - 1 of the one or more pictures of the minimum luma coding block unit, The method according to claim 12, further comprising.

14. The method according to claim 11, wherein the second wrap-around motion compensation flag is signaled in a sequence parameter set. **Claim 15** decoding the one or more pictures according to the first wrap-around motion compensation flag and the parameter, determining an offset according to the parameter, encoding the one or more pictures according to the offset, The method according to claim 11, further comprising:

Images