PDPC for intra prediction with perspectives

Abstract

Video coding may use position dependent pixel combination (PDPC) for intra prediction with perspectives. Prediction angles computed at the third, sixth, and twelfth pixels on the last row of the target block may be used to check angular scale values of 0, 1, and 2, respectively. A nonnegative scale factor may indicate application of normal PDPC. A negative scale factor may indicate application of gradient PDPC. Secondary reference samples may be localized for normal PDPC using inverse angles computed at the first 3, 6, or 12 target pixels on each row corresponding to angular scale values of 0, 1, or 2, respectively. The angle parameter at the secondary reference sample on the same row as the target pixel may be computed / used to localize the primary reference sample on the top reference array for gradient PDPC. The gradient between reference samples may be used to modify the initial prediction value.

Description

PDPC FOR INTRA PREDICTION WITH PERSPECTIVESCROSS-REFERENCE TO RELATED APPLICATOINS

[0001] The application claims the benefit of European Patent Application Number 23306661 .2, filed October 2, 2023, the contents of which are incorporated by reference in their entirety herein.BACKGROUND

[0002] Video coding systems may be used to compress digital video signals, e.g., to reduce the storage and / or transmission bandwidth needed for such signals. Video coding systems may include, for example, block-based, wavelet-based, and / or object-based systems.SUMMARY

[0003] Systems, methods, and instrumentalities are disclosed for performing video coding using position dependent pixel combination (PDPC) for intra prediction with perspectives. Prediction angles, which may be computed at the third, sixth, and twelfth pixels on the last row of the target block, may be used to check the angular scale values of 0, 1 , and 2, respectively. In some examples, a nonnegative value of a scale factor may indicate the application of a first type of PDPC (e.g., normal or usual PDPC), whereas a negative value of a scale factor may indicate the application of a second type of PDPC (e.g., gradient PDPC). In some examples (e.g., for the first type of PDPC), the secondary reference samples may be localized (e.g., for the first type of PDPC) using, for example, the inverse angles computed at the first 3, 6, or 12 target pixels on a (e.g., each) row corresponding to angular scale values of 0, 1 , or 2, respectively. In some examples (e.g., for the second type of PDPC), the angle parameter at the secondary reference sample on the same row as the target pixel may be computed and / or may be used to localize the primary reference sample on the top reference array. The gradient between the two reference samples may be used to modify the initial prediction value.

[0004] A video coding device (e.g., decoder or encoder) may implement a method for video coding. The decoder or encoder may predict a target block using a perspective intra prediction mode, wherein the target block is predicted using a perspective point. The decoder or encoder may apply a position dependent pixel combination (PDPC) scheme to a pixel associated with the perspective intra-predicted target block, wherein the PDPC scheme is applied based on a scale parameter value. The PDPC scheme may be applied if the perspective intra prediction mode is eligible for PDPC. The PDPC scheme may bea normal PDPC or a gradient PDPC. The PDPC scheme may be the normal PDPC when the scale parameter value is greater than zero. The PDPC scheme may be the gradient PDPC when the scale parameter value is less than zero.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0006] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0007] FIG. 1 C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0008] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0009] FIG. 2 illustrates an example video encoder.

[0010] FIG. 3 illustrates an example video decoder.

[0011] FIG. 4 illustrates an example of a system in which various aspects and examples may be implemented.

[0012] FIG. 5 illustrates an example of position dependent pixel combination (PDPC) for a vertical direction.

[0013] FIG. 6 illustrates an example of a PDPC process for positive vertical directions.

[0014] FIG. 7 illustrates an example of a gradient PDPC process for positive vertical directions.

[0015] FIG. 8 illustrates an example of perspective prediction of a target block in intra prediction.

[0016] FIG. 9 illustrates an example of intra prediction with perspective.

[0017] FIG. 10 illustrates an example of PDPC for perspective prediction.

[0018] FIG. 11 illustrates an example of gradient PDPC for perspective prediction.DETAILED DESCRIPTION

[0019] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings.

[0020] FIG. 1 A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT- Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0021] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a ON 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or a “STA”, may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0022] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the I nternet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will beappreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0023] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0024] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0025] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0026] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0027] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access, which may establish the air interface 116 using New Radio (NR).

[0028] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., a eNB and a gNB).

[0029] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0030] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1 A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106 / 115.

[0031] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 may provide call control, billing services, mobile location-based services,pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may be utilizing a NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0032] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0033] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0034] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0035] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, dataprocessing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0036] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0037] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0038] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.

[0039] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The nonremovable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In otherembodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0040] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0041] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0042] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0043] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0044] FIG. 1 C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0045] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0046] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0047] The CN 106 shown in FIG. 1 C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0048] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0049] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0050] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0051] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0052] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0053] In representative embodiments, the other network 112 may be a WLAN.

[0054] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.

[0055] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / ordetermined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0056] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0057] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0058] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 n, and 802.11 ac. 802.11 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control / Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0059] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11 n, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primarychannel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0060] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0061] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 1 16. The RAN 1 13 may also be in communication with the CN 115.

[0062] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0063] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0064] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without alsoaccessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode- Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0065] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E- UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0066] The CN 115 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0067] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users ofthe WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultrareliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) thatemploy other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0068] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0069] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0070] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0071] In view of Figures 1 A-1 D, and the corresponding description of Figures 1 A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0072] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / ordeployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or may performing testing using over-the-air wireless communications.

[0073] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a nondeployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0074] This application describes a variety of aspects, including tools, features, examples, models, approaches, etc. Many of these aspects are described with specificity and, at least to show the individual characteristics, are often described in a manner that may sound limiting. However, this is for purposes of clarity in description, and does not limit the application or scope of those aspects. Indeed, all of the different aspects may be combined and interchanged to provide further aspects. Moreover, the aspects may be combined and interchanged with aspects described in earlier filings as well.

[0075] The aspects described and contemplated in this application may be implemented in many different forms. FIGS. 5-11 described herein may provide some examples, but other examples are contemplated. The discussion of FIGS. 5-11 does not limit the breadth of the implementations. At least one of the aspects generally relates to video encoding and decoding, and at least one other aspect generally relates to transmitting a bitstream generated or encoded. These and other aspects may be implemented as a method, an apparatus, a computer readable storage medium having stored thereon instructions for encoding or decoding video data according to any of the methods described, and / or a computer readable storage medium having stored thereon a bitstream generated according to any of the methods described.

[0076] In the present application, the terms “reconstructed” and “decoded” may be used interchangeably, the terms “pixel” and “sample” may be used interchangeably, the terms “image,” “picture” and “frame” may be used interchangeably.

[0077] Various methods are described herein, and each of the methods comprises one or more steps or actions for achieving the described method. Unless a specific order of steps or actions is required for proper operation of the method, the order and / or use of specific steps and / or actions may be modified orcombined. Additionally, terms such as “first”, “second”, etc. may be used in various examples to modify an element, component, step, operation, etc., such as, for example, a “first decoding” and a “second decoding”. Use of such terms does not imply an ordering to the modified operations unless specifically required. So, in this example, the first decoding need not be performed before the second decoding, and may occur, for example, before, during, or in an overlapping time period with the second decoding.

[0078] Various methods and other aspects described in this application may be used to modify modules, for example, decoding modules, of a video encoder 200 and decoder 300 as shown in FIG. 2 and FIG. 3. Moreover, the subject matter disclosed herein may be applied, for example, to any type, format or version of video coding, whether described in a standard or a recommendation, whether preexisting or future-developed, and extensions of any such standards and recommendations. Unless indicated otherwise, or technically precluded, the aspects described in this application may be used individually or in combination.

[0079] Various numeric values are used in examples described the present application, such as target pixel locations (e.g., the third, sixth, and twelfth pixels on the last row of the target block), angular scale values of 0, 1 , and 2, the first 3, 6, or 12 target pixels on each row corresponding to angular scale values of 0, 1 , or 2, prediction modes [19-49], y= -1 ,0,1,...,(2*H-1), x= -1 ,0,1 ,...,(2*W-1), reference sample coordinates, target block sizes (e.g., 4x4, 64x64, 32x4), weight function wL values, constants, minimums, maximums, thresholds, multipliers, divisors, exponents, resolutions (e.g., 1 / 32, 1 / 64 of a pixel), ranges, etc. These and other specific values are for purposes of describing examples and the aspects described are not limited to these specific values.

[0080] FIG. 2 is a diagram showing an example video encoder. Variations of example encoder 200 are contemplated, but the encoder 200 is described below for purposes of clarity without describing all expected variations.

[0081] Before being encoded, the video sequence may go through pre-encoding processing (201), for example, applying a color transform to the input color picture (e.g., conversion from RGB 4:4:4 to YCbCr 4:2:0), or performing a remapping of the input picture components in order to get a signal distribution more resilient to compression (for instance using a histogram equalization of one of the color components). Metadata may be associated with the pre-processing, and attached to the bitstream.

[0082] In the encoder 200, a picture is encoded by the encoder elements as described below. The picture to be encoded is partitioned (202) and processed in units of, for example, coding units (CUs). Each unit is encoded using, for example, either an intra or inter mode. When a unit is encoded in an intra mode, it performs intra prediction (260). In an inter mode, motion estimation (275) and compensation (270) are performed. The encoder decides (205) which one of the intra mode or inter mode to use forencoding the unit, and indicates the intra / inter decision by, for example, a prediction mode flag. Prediction residuals are calculated, for example, by subtracting (210) the predicted block from the original image block.

[0083] The prediction residuals are then transformed (225) and quantized (230). The quantized transform coefficients, as well as motion vectors and other syntax elements, such as picture partitioning information, are entropy coded (245) to output a bitstream. The encoder can skip the transform and apply quantization directly to the non-transformed residual signal. The encoder can bypass both transform and quantization, i.e., the residual is coded directly without the application of the transform or quantization processes.

[0084] The encoder decodes an encoded block to provide a reference for further predictions. The quantized transform coefficients are de-quantized (240) and inverse transformed (250) to decode prediction residuals. Combining (255) the decoded prediction residuals and the predicted block, an image block is reconstructed. In-loop filters (265) are applied to the reconstructed picture to perform, for example, deblocking / SAO (Sample Adaptive Offset) / ALF (Adaptive Loop Filtering) filtering to reduce encoding artifacts. The filtered image is stored at a reference picture buffer (280).

[0085] FIG. 3 is a diagram showing an example of a video decoder. In example decoder 300, a bitstream is decoded by the decoder elements as described below. Video decoder 300 generally performs a decoding pass reciprocal to the encoding pass as described in FIG. 2. The encoder 200 also generally performs video decoding as part of encoding video data.

[0086] In particular, the input of the decoder includes a video bitstream, which may be generated by video encoder 200. The bitstream is first entropy decoded (330) to obtain transform coefficients, prediction modes, motion vectors, and other coded information. The picture partition information indicates how the picture is partitioned. The decoder may therefore divide (335) the picture according to the decoded picture partitioning information. The transform coefficients are de-quantized (340) and inverse transformed (350) to decode the prediction residuals. Combining (355) the decoded prediction residuals and the predicted block, an image block is reconstructed. The predicted block may be obtained (370) from intra prediction (360) or motion-compensated prediction (i.e., inter prediction) (375). In-loop filters (365) are applied to the reconstructed image. The filtered image is stored at a reference picture buffer (380). In some examples (e.g., for a given picture) the contents of the reference picture buffer 380 on the decoder 300 side may be identical to the contents of the reference picture buffer 280 on the encoder 200 side (e.g., for the same picture).

[0087] The decoded picture can further go through post-decoding processing (385), for example, an inverse color transform (e.g., conversion from YCbCr 4:2:0 to RGB 4:4:4) or an inverse remappingperforming the inverse of the remapping process performed in the pre-encoding processing (201). The post-decoding processing can use metadata derived in the pre-encoding processing and signaled in the bitstream. In an example, the decoded images (e.g., after application of the in-loop filters (365) and / or after post-decoding processing (385), if post-decoding processing is used) may be sent to a display device for rendering to a user.

[0088] FIG. 4 is a diagram showing an example of a system in which various aspects and examples described herein may be implemented. System 400 may be embodied as a device including the various components described below and is configured to perform one or more of the aspects described in this document. Examples of such devices, include, but are not limited to, various electronic devices such as personal computers, laptop computers, smartphones, tablet computers, digital multimedia set top boxes, digital television receivers, personal video recording systems, connected home appliances, and servers. Elements of system 400, singly or in combination, may be embodied in a single integrated circuit (IC), multiple ICs, and / or discrete components. For example, in at least one example, the processing and encoder / decoder elements of system 400 are distributed across multiple ICs and / or discrete components. In various examples, the system 400 is communicatively coupled to one or more other systems, or other electronic devices, via, for example, a communications bus or through dedicated input and / or output ports. In various examples, the system 400 is configured to implement one or more of the aspects described in this document.

[0089] The system 400 includes at least one processor 410 configured to execute instructions loaded therein for implementing, for example, the various aspects described in this document. Processor 410 can include embedded memory, input output interface, and various other circuitries as known in the art. The system 400 includes at least one memory 420 (e.g., a volatile memory device, and / or a non-volatile memory device). System 400 includes a storage device 440, which can include non-volatile memory and / or volatile memory, including, but not limited to, Electrically Erasable Programmable Read-Only Memory (EEPROM), Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), flash, magnetic disk drive, and / or optical disk drive. The storage device 440 can include an internal storage device, an attached storage device (including detachable and non-detachable storage devices), and / or a network accessible storage device, as non-limiting examples.

[0090] System 400 includes an encoder / decoder module 430 configured, for example, to process data to provide an encoded video or decoded video, and the encoder / decoder module 430 can include its own processor and memory. The encoder / decoder module 430 represents module(s) that may be included in a device to perform the encoding and / or decoding functions. As is known, a device can include one orboth of the encoding and decoding modules. Additionally, encoder / decoder module 430 may be implemented as a separate element of system 400 or may be incorporated within processor 410 as a combination of hardware and software as known to those skilled in the art.

[0091] Program code to be loaded onto processor 410 or encoder / decoder 430 to perform the various aspects described in this document may be stored in storage device 440 and subsequently loaded onto memory 420 for execution by processor 410. In accordance with various examples, one or more of processor 410, memory 420, storage device 440, and encoder / decoder module 430 can store one or more of various items during the performance of the processes described in this document. Such stored items can include, but are not limited to, the input video, the decoded video or portions of the decoded video, the bitstream, matrices, variables, and intermediate or final results from the processing of equations, formulas, operations, and operational logic.

[0092] In some examples, memory inside of the processor 410 and / or the encoder / decoder module 430 is used to store instructions and to provide working memory for processing that is needed during encoding or decoding. In other examples, however, a memory external to the processing device (for example, the processing device may be either the processor 410 or the encoder / decoder module 430) is used for one or more of these functions. The external memory may be the memory 420 and / or the storage device 440, for example, a dynamic volatile memory and / or a non-volatile flash memory. In several examples, an external non-volatile flash memory is used to store the operating system of, for example, a television. In at least one example, a fast external dynamic volatile memory such as a RAM is used as working memory for video encoding and decoding operations.

[0093] The input to the elements of system 400 may be provided through various input devices as indicated in block 445. Such input devices include, but are not limited to, (i) a radio frequency (RF) portion that receives an RF signal transmitted, for example, over the air by a broadcaster, (ii) a Component (COMP) input terminal (or a set of COMP input terminals), (iii) a Universal Serial Bus (USB) input terminal, and / or (iv) a High Definition Multimedia Interface (HDMI) input terminal. Other examples, not shown in FIG. 4, include composite video.

[0094] In various examples, the input devices of block 445 have associated respective input processing elements as known in the art. For example, the RF portion may be associated with elements suitable for (i) selecting a desired frequency (also referred to as selecting a signal, or band-limiting a signal to a band of frequencies), (ii) downconverting the selected signal, (iii) band-limiting again to a narrower band of frequencies to select (for example) a signal frequency band which may be referred to as a channel in certain examples, (iv) demodulating the downconverted and band-limited signal, (v) performing error correction, and / or (vi) demultiplexing to select the desired stream of data packets. TheRF portion of various examples includes one or more elements to perform these functions, for example, frequency selectors, signal selectors, band-limiters, channel selectors, filters, downconverters, demodulators, error correctors, and demultiplexers. The RF portion can include a tuner that performs various of these functions, including, for example, downconverting the received signal to a lower frequency (for example, an intermediate frequency or a near-baseband frequency) or to baseband. In one set-top box example, the RF portion and its associated input processing element receives an RF signal transmitted over a wired (for example, cable) medium, and performs frequency selection by filtering, downconverting, and filtering again to a desired frequency band. Various examples rearrange the order of the above-described (and other) elements, remove some of these elements, and / or add other elements performing similar or different functions. Adding elements can include inserting elements in between existing elements, such as, for example, inserting amplifiers and an analog-to-digital converter. In various examples, the RF portion includes an antenna.

[0095] The USB and / or HDMI terminals can include respective interface processors for connecting system 400 to other electronic devices across USB and / or HDMI connections. It is to be understood that various aspects of input processing, for example, Reed-Solomon error correction, may be implemented, for example, within a separate input processing IC or within processor 410 as necessary. Similarly, aspects of USB or HDMI interface processing may be implemented within separate interface ICs or within processor 410 as necessary. The demodulated, error corrected, and demultiplexed stream is provided to various processing elements, including, for example, processor 410, and encoder / decoder 430 operating in combination with the memory and storage elements to process the data stream as necessary for presentation on an output device.

[0096] Various elements of system 400 may be provided within an integrated housing, Within the integrated housing, the various elements may be interconnected and transmit data therebetween using suitable connection arrangement 425, for example, an internal bus as known in the art, including the I nter-IC (I2C) bus, wiring, and printed circuit boards.

[0097] The system 400 includes communication interface 450 that enables communication with other devices via communication channel 460. The communication interface 450 can include, but is not limited to, a transceiver configured to transmit and to receive data over communication channel 460. The communication interface 450 can include, but is not limited to, a modem or network card and the communication channel 460 may be implemented, for example, within a wired and / or a wireless medium.

[0098] Data is streamed, or otherwise provided, to the system 400, in various examples, using a wireless network such as a Wi-Fi network, for example IEEE 802.11 (IEEE refers to the Institute of Electrical and Electronics Engineers). The Wi-Fi signal of these examples is received over thecommunications channel 460 and the communications interface 450 which are adapted for Wi-Fi communications. The communications channel 460 of these examples is typically connected to an access point or router that provides access to external networks including the Internet for allowing streaming applications and other over-the-top communications. Other examples provide streamed data to the system 400 using a set-top box that delivers the data over the HDMI connection of the input block 445. Still other examples provide streamed data to the system 400 using the RF connection of the input block 445. As indicated above, various examples provide data in a non-streaming manner. Additionally, various examples use wireless networks other than Wi-Fi, for example a cellular network or a Bluetooth® network.

[0099] The system 400 can provide an output signal to various output devices, including a display 475, speakers 485, and other peripheral devices 495. The display 475 of various examples includes one or more of, for example, a touchscreen display, an organic light-emitting diode (OLED) display, a curved display, and / or a foldable display. The display 475 may be for a television, a tablet, a laptop, a cell phone (mobile phone), or other device. The display 475 can also be integrated with other components (for example, as in a smart phone), or separate (for example, an external monitor for a laptop). The other peripheral devices 495 include, in various examples, one or more of a stand-alone digital video disc (or digital versatile disc) (DVD, for both terms), a disk player, a stereo system, and / or a lighting system. Various examples use one or more peripheral devices 495 that provide a function based on the output of the system 400. For example, a disk player performs the function of playing the output of the system 400.

[0100] In various examples, control signals are communicated between the system 400 and the display 475, speakers 485, or other peripheral devices 495 using signaling such as AV. Link, Consumer Electronics Control (CEC), or other communications protocols that enable device-to-device control with or without user intervention. The output devices may be communicatively coupled to system 400 via dedicated connections through respective interfaces 470, 480, and 490. Alternatively, the output devices may be connected to system 400 using the communications channel 460 via the communications interface 450. The display 475 and speakers 485 may be integrated in a single unit with the other components of system 400 in an electronic device such as, for example, a television. In various examples, the display interface 470 includes a display driver, such as, for example, a timing controller (T Con) chip.

[0101] The display 475 and speakers 485 can alternatively be separate from one or more of the other components, for example, if the RF portion of input 445 is part of a separate set-top box. In various examples in which the display 475 and speakers 485 are external components, the output signal may beprovided via dedicated output connections, including, for example, HDMI ports, USB ports, or COMP outputs.

[0102] The examples may be carried out by computer software implemented by the processor 410 or by hardware, or by a combination of hardware and software. As a non-limiting example, the examples may be implemented by one or more integrated circuits. The memory 420 may be of any type appropriate to the technical environment and may be implemented using any appropriate data storage technology, such as optical memory devices, magnetic memory devices, semiconductor-based memory devices, fixed memory, and removable memory, as non-limiting examples. The processor 410 may be of any type appropriate to the technical environment, and can encompass one or more of microprocessors, general purpose computers, special purpose computers, and processors based on a multi-core architecture, as non-limiting examples.

[0103] Various implementations involve decoding. “Decoding”, as used in this application, can encompass all or part of the processes performed, for example, on a received encoded sequence in order to produce a final output suitable for display. In various examples, such processes include one or more of the processes typically performed by a decoder, for example, entropy decoding, inverse quantization, inverse transformation, and differential decoding. In various examples, such processes also, or alternatively, include processes performed by a decoder of various implementations described in this application, for example, predicting a target block using a perspective intra prediction mode, wherein the target block is predicted using a perspective point, applying a PDPC scheme to a pixel associated with the perspective intra-predicted target block, wherein the PDPC scheme is applied based on a scale parameter value, etc.

[0104] As further examples, in one example “decoding” refers only to entropy decoding, in another example “decoding” refers only to differential decoding, and in another example “decoding” refers to a combination of entropy decoding and differential decoding. Whether the phrase “decoding process” is intended to refer specifically to a subset of operations or generally to the broader decoding process will be clear based on the context of the specific descriptions and is believed to be well understood by those skilled in the art.

[0105] Various implementations involve encoding. In an analogous way to the above discussion about “decoding”, “encoding” as used in this application can encompass all or part of the processes performed, for example, on an input video sequence in order to produce an encoded bitstream. In various examples, such processes include one or more of the processes typically performed by an encoder, for example, partitioning, differential encoding, transformation, quantization, and entropy encoding. In various examples, such processes also, or alternatively, include processes performed by an encoder of variousimplementations described in this application, for example, predicting a target block using a perspective intra prediction mode, wherein the target block is predicted using a perspective point, applying a PDPC scheme to a pixel associated with the perspective intra-predicted target block, wherein the PDPC scheme is applied based on a scale parameter value, etc.

[0106] As further examples, in one example “encoding” refers only to entropy encoding, in another example “encoding” refers only to differential encoding, and in another example “encoding” refers to a combination of differential encoding and entropy encoding. Whether the phrase “encoding process” is intended to refer specifically to a subset of operations or generally to the broader encoding process will be clear based on the context of the specific descriptions and is believed to be well understood by those skilled in the art.

[0107] Note that syntax elements as used herein, such as P(x,y) as a final prediction value, P_0(x,y) as an initial prediction value, R(-1 ,y) as a secondary reference sample, R(-1 ,-1) as a top left corner reference sample, wL as a weight function, R(-1 ,y’) as a secondary reference sample obtained by extending the prediction direction, y’ as a secondary reference sample, absInvAngle as an absolute value of the inverse angle associated with the prediction direction, A as the angle parameter associated with the prediction mode, R(x”,-1 ) as a predictor sample for the secondary reference sample R(-1 , y), Aoas a perspectiveAngle parameter the angle parameter predl ntraAngle, Aas the angle parameter at target pixel (x,y), Lmax, numCol, maxScale, tmpScale, etc. are descriptive terms. As such, they do not preclude the use of other syntax element names.

[0108] When a figure is presented as a flow diagram, it should be understood that it also provides a block diagram of a corresponding apparatus. Similarly, when a figure is presented as a block diagram, it should be understood that it also provides a flow diagram of a corresponding method / process.

[0109] The implementations and aspects described herein may be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method), the implementation of features discussed can also be implemented in other forms (for example, an apparatus or program). An apparatus may be implemented in, for example, appropriate hardware, software, and firmware. The methods may be implemented in, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable / personal digital assistants ("PDAs"), and other devices that facilitate communication of information between end-users.

[0110] Reference to “one example” or “an example” or “one implementation” or “an implementation”, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the example is included in at least one example. Thus, the appearances of the phrase “in one example” or “in an example” or “in one implementation” or “in an implementation”, as well any other variations, appearing in various places throughout this application are not necessarily all referring to the same example.

[0111] Additionally, this application may refer to “determining” various pieces of information. Determining the information can include one or more of, for example, estimating the information, calculating the information, predicting the information, or retrieving the information from memory. Obtaining may include receiving, retrieving, constructing, generating, and / or determining.

[0112] Further, this application may refer to “accessing” various pieces of information. Accessing the information can include one or more of, for example, receiving the information, retrieving the information (for example, from memory), storing the information, moving the information, copying the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0113] Additionally, this application may refer to “receiving” various pieces of information. Receiving is, as with “accessing”, intended to be a broad term. Receiving the information can include one or more of, for example, accessing the information, or retrieving the information (for example, from memory). Further, “receiving” is typically involved, in one way or another, during operations such as, for example, storing the information, processing the information, transmitting the information, moving the information, copying the information, erasing the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0114] It is to be appreciated that the use of any of the following ”, “and / or”, and “at least one of’, for example, in the cases of “A / B”, “A and / or B” and “at least one of A and B”, is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and / or C” and “at least one of A, B, and C”, such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as is clear to one of ordinary skill in this and related arts, for as many items as are listed.

[0115] Also, as used herein, the word “signal” refers to, among other things, indicating something to a corresponding decoder. Encoder signals may include, for example, pdpcFlag, prediction modes, etc. In this way, in an example the same parameter is used at both the encoder side and the decoder side. Thus, for example, an encoder can transmit (explicit signaling) a particular parameter to the decoder so that the decoder can use the same particular parameter. Conversely, if the decoder already has the particular parameter as well as others, then signaling may be used without transmitting (implicit signaling) to simply allow the decoder to know and select the particular parameter. By avoiding transmission of any actual functions, a bit savings is realized in various examples. It is to be appreciated that signaling may be accomplished in a variety of ways. For example, one or more syntax elements, flags, and so forth are used to signal information to a corresponding decoder in various examples. While the preceding relates to the verb form of the word “signal”, the word “signal” can also be used herein as a noun.

[0116] As will be evident to one of ordinary skill in the art, implementations may produce a variety of signals formatted to carry information that may be, for example, stored or transmitted. The information can include, for example, instructions for performing a method, or data produced by one of the described implementations. For example, a signal may be formatted to carry the bitstream of a described example. Such a signal may be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting may include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information that the signal carries may be, for example, analog or digital information. The signal may be transmitted over a variety of different wired or wireless links, as is known. The signal may be stored on, or accessed or received from, a processor-readable medium.

[0117] Many examples are described herein. Features of examples may be provided alone or in any combination, across various claim categories and types. Further, examples may include one or more of the features, devices, or aspects described herein, alone or in any combination, across various claim categories and types. For example, features described herein may be implemented in a bitstream or signal that includes information generated as described herein. The information may allow a decoder to decode a bitstream, the encoder, bitstream, and / or decoder according to any of the embodiments described. For example, features described herein may be implemented by creating and / or transmitting and / or receiving and / or decoding a bitstream or signal. For example, features described herein may be implemented a method, process, apparatus, medium storing instructions, medium storing data, or signal. For example, features described herein may be implemented by a TV, set-top box, cell phone, tablet, or other electronic device that performs decoding. The TV, set-top box, cell phone, tablet, or other electronic device may display (e.g., using a monitor, screen, or other type of display) a resulting image (e.g., animage from residual reconstruction of the video bitstream). The TV, set-top box, cell phone, tablet, or other electronic device may receive a signal including an encoded image and perform decoding.

[0118] Position dependent pixel combination (PDPC) in certain video coding techniques may be a post processing tool in intra prediction. PDPC may be used to remove discontinuities, which may arise, for example, from an initial intra prediction for the prediction modes having directions from the bottom-left corner towards the top-right corner of the block and vice versa. Different types of PDPC or PDPC schemes (e.g., a normal PDPC or a gradient PDPC) may be applied, for example, depending on the prediction direction and / or the target block size. For example, prediction directions having (e.g., all required) secondary reference samples available may undergo normal PDPC, whereas other PDPC- eligible modes may undergo gradient PDPC. This check may be implemented, for example, by computing an angular scale parameter involving the block’s size and the inverse angle parameter associated with the prediction direction. In some examples (e.g., intra prediction with perspectives), the prediction direction at a target pixel may be a variable quantity, meaning the usual computation of the angular scale parameter may not work. The application of PDPC with eligible prediction modes in perspective intra prediction may be determined, for example, based on an algorithm, which is described herein.

[0119] As described herein, PDPC may be applied for intra prediction with perspectives. Prediction angles, which may be computed at the third, sixth, and twelfth pixels on the last row of the target block, may be used to check the angular scale values of 0, 1 , and 2, respectively. In some examples, a nonnegative value of a scale factor may indicate the application of a first type of PDPC (e.g., normal or usual PDPC), whereas a negative value of a scale factor may indicate the application of a second type of PDPC (e.g., gradient PDPC). In some examples (e.g., for the first type of PDPC), the secondary reference samples may be localized (e.g., for the first type of PDPC) using, for example, the inverse angles computed at the first 3, 6, or 12 target pixels on a (e.g., each) row corresponding to angular scale values of 0, 1 , or 2, respectively. In some examples (e.g., for the second type of PDPC), the angle parameter at the secondary reference sample on the same row as the target pixel may be computed and / or may be used to localize the primary reference sample on the top reference array. The gradient between the two reference samples may be used to modify the initial prediction value.

[0120] PDPC may be used in intra prediction to smooth out luminance discontinuities close to a reference array that may arise after the initial prediction. The discontinuities may occur, for example, in the planar mode, the DC mode, and / or (e.g., all) directional prediction modes that may be associated with prediction directions below and / or including the (e.g., purely) horizontal mode, and / or prediction directions to the right of and / or including the (e.g., purely) vertical mode. PDPC may not be applied withprediction modes that are associated with directions from the (e.g., purely) horizontal to purely vertical in clockwise direction (e.g., prediction modes [19-49] in WC and ECM), for example, because these prediction modes point towards the bottom-right directions. Perspective prediction (e.g., as described herein) may be applied (e.g., only) in the case of directional modes.

[0121] FIG. 5 illustrates an example of PDPC for a (e.g., purely) vertical direction, as may be implemented in video coding techniques, for example, in VVC and / or ECM. In an example, H and W may denote the height and the width of a target block for intra prediction. The reference array on top of the block may have (2W+1) samples and the reference array on the left may have (2H+1) samples, e.g., with the top-left corner sample in common. The reference arrays are illustrated in FIG. 5. As shown in FIG. 5, R(-1,y), y= -1,0,1,...,(2*H-1) may denote the reference samples on the left and R(x,-1), x= -1 ,0,1 , ...,(2*W- 1) may denote the reference samples on the top with R(-1 ,-1) as the top left corner reference sample.

[0122] PDPC may be performed for the (e.g., purely) vertical mode (e.g., mode 50 in WC and / or ECM), for example, by adding a weighted value of the gradient. The weighted value of the gradient may be computed at the left reference pixel on the same row as a target pixel, to the initial prediction value, for example, in accordance with Eq. (1):P(x,y) = Cl ip (P_0(x, y) + (wL * (R(-1 ,y) - R(-1 ,-1 )) + 32) » 6) (1 ) where, for example, P(x,y) may be the final prediction value at pixel (x,y); P_0(x,y) may be the initial prediction value at pixel (x,y), which may be equal to the primary reference sample R(x,-1); R(-1 ,y) may be the secondary reference sample on the same row; R(-1 ,-1) may be the top left corner reference sample; and wL may be the weight function. The weight function wL may be computed, for example, in accordance with Eq. (2): wL = 32 » (2*x » scale) (2) where the scale in Eq. (2) may be computed, for example, in accordance with Eq. (3): scale = (Log2(H) + Log2(W) - 2) » 2 (3)

[0123] The scale parameter may have a positive integer value, for example, in the range of 0-2. For example, the scale parameter may have a value of zero (0) for a target block size of 4x4, a value of two (2) for a target block size of 64x64, and a value in the range of 0-2 for (e.g., all) other block sizes inbetween 4x4 and 64x64. The scale factor may determine how quickly the weight function wL decays down to zero (0) moving away from the left edge of a block towards the right.

[0124] Table 1 shows an example of the number of columns over which the weight function wL may have positive values for different scale factor values. As shown in Table 1 , the number of columns processed by PDPC may depend on the scale value, which may depend on the target block size. For example, (e.g., only) 3 or 6 or 12 (e.g., 3 « scale ) columns may be processed by PDPC in the (e.g., purely) vertical mode. The original prediction value (P_0(x,y) in Eq. (1) may remain unchanged for the remaining (e.g., unprocessed) columns, e.g., with wL equal to zero (0). The remaining columns may not be processed in PDPC, for example, to avoid unnecessary multiplications by zero (0).Table 1 - Example of number of columns or rows processed in PDPC and the corresponding weights

[0125] A PDPC operation may add a gradually decaying weighted value of the gradient (e.g., computed on the left reference array) to the initial prediction value as we move away from the left edge towards the right of the block. A clipping operation may be used, for example, because the resulting value is not guaranteed to lie in the dynamic range of the signal component.

[0126] A weighting function may be chosen (e.g., in VVC and / or ECM), for example, so that the weights, as shown in Table 1 , are powers of two (2). The PDPC operation in Eq. (1) may, therefore, be performed with bit-shifts, avoiding multiplications.

[0127] Prediction along the (e.g., purely) horizontal direction (e.g., mode 18 in WC and ECM) may perform PDPC analogously, for example, except that rows, instead of columns, at the top edge of a block are processed. The scale factor may be computed, for example, (e.g., exactly) in the same manner. The number of rows at the top that are processed may be given, for example, as (3 « scale). The initial predictions in remaining rows may remain unchanged. The weighting function values may decay from top towards bottom as moving along a column. The gradient computed on the top reference array may be propagated downwards in a gradually decaying manner, for example, by adding to the initial prediction values based on the left reference array.

[0128] PDPC may be performed similarly for predictions along positive vertical directions (e.g., mode > 50 in VVC and ECM), for example, by changing the initial prediction value. However, a weighted sum with a secondary reference sample may be obtained instead of adding a weighted value of the gradient to the initial prediction value. The secondary reference sample may be localized, for example, by extending the prediction direction and finding the intersecting point with the secondary reference array on the left, as illustrated by example in FIG. 6.

[0129] FIG. 6 illustrates an example of a (e.g., normal) PDPC process (e.g., in VVC and / or ECM) for positive vertical directions. A secondary reference sample may be used to modify the first predicted value.

[0130] The PDPC operation may be performed, for example, in accordance with Eq. (4):P(x,y) = P_0(x, y) + (wL * (R(-1 ,y’) - P_0(x,y)) + 32) » 6 (4) where, for example, P(x,y) may be the final prediction value at pixel (x,y); P_0(x,y) may be the initial prediction value at pixel (x,y), which may be equal to the primary reference sample R(x’,-1 ); R(-1 ,y’) may be the secondary reference sample obtained by extending the prediction direction; and wL may be the weight function wL. The weight function wL may be computed, for example, in accordance with Eq. (5): wL = 32 » (2*x » scale) (5)

[0131] The co-ordinate of the secondary reference sample may be computed, for example, in accordance with Eq. (6): y’ = 1 + y + (((1 + x)*abslnvAngle + 256) » 9) (6) where absInvAngle may denote the absolute value of the inverse angle associated with the prediction direction. The parameter absInvAngle may be derived from the angle parameter predlntraAngle associated with the prediction mode, for example, in accordance with Eq. (7 A) or (7B) as follows: absInvAngle = round((512*32) / A) (e.g., for (1 / 32) sample resolution of prediction direction) (7A) absInvAngle = round((512*64) / A) (e.g., for (1 / 64) sample resolution of prediction direction) (7B)where A may denote the angle parameter associated with the prediction mode (e.g., A = predl ntraAngle). In an example, a clipping operation may not be implemented, since the final prediction value is a weighted sum of the initial prediction value and the secondary reference sample value.

[0132] The initial prediction value may remain unchanged, when wL is equal to zero. The clipping operation may performed on (e.g., only) the first (3 « scale) columns, as in the case of PDPC for the (e.g., purely) vertical mode. Table 1 provided herein shows an example of the number of columns processed and weights for the samples on different columns.

[0133] In some examples, although the weighting function in Eq. (5) may have the same form as Eq. (2) in PDPC for the (e.g., purely) vertical mode, the scale parameter may be computed in a different manner for Eq. (5) and Eq. (2). In some examples of PDPC, the scale parameter may be computed as shown in Eq. (3) using (e.g., only) the height and the width of a target block (e.g., as shown again in Eq.(8): scale = (Log2(H) + Log2(W) - 2) » 2) (8)

[0134] However, there may be an issue with the formulation in Eq. (3) and Eq. (8), for example, because of the finite length of the reference array on the left. With some prediction directions, even if the wL value is non-zero, there may not be a sufficient number of samples on the left reference array to localize the secondary reference samples for (e.g., all) the target pixels in the first (3 « scale) columns. The issue may be avoided by computing the scale parameter, for example, in accordance with Eq. (9) as follows: scale = min(2, Log2(height) - (Log2(3 * absInvAngle - 2) - 8)) (9)

[0135] The example formulation shown in Eq. (9) may guarantee that the secondary reference samples are available for (e.g., all) target pixels in the first (3«scale) columns. The formulation in Eq.(9) is based on the size of the block (e.g., to be precise, the height of the target block for the vertical modes) and the prediction angle while limiting the maximum number of columns to 12 (e.g., for a maximum value of the scale as 2). Eq. (9) may be derived, for example, by computing the number of samples on the last row of a target block that can have secondary reference samples available for a given prediction direction and then computing the scale so that (3 « scale) would fit in that length while limiting the maximum scale value to two (2).

[0136] A scale parameter computed in accordance with Eq. (9) may have (e.g., only) three nonnegative values (e.g., 0, 1 , and 2), which may correspond to the number of columns (e.g., 3, 6, and 12columns) processed in the PDPC, for example, with the respective weights given in Table 1 . In contrast with a scale parameter computed in accordance with Eq. (3) or Eq. (8), for some angles, a scale parameter computed in accordance with Eq. (9) may (e.g., also) have negative integral values. A negative value may imply that, for the given prediction mode, there may not be enough secondary reference samples available even for the first three columns. The secondary reference array may be too short for the given prediction direction. For example, for directions close to the (e.g., purely) vertical direction. A gradient PDPC operation may be performed in this case, e.g., instead of the normal PDPC. A gradient PDPC operation may be performed in a manner similar to the prediction with the (e.g., purely) vertical mode, but the gradient may be computed along the prediction direction considered, as shown by example in FIG. 7.

[0137] FIG. 7 illustrates an example of a gradient PDPC process (e.g., in WC and ECM) for positive vertical directions. A weighted value of the gradient may be computed at the secondary reference sample on the left reference array on the same row as the target pixel. The weighted value of the gradient may be used to modify the initial prediction value, e.g., added to the initial prediction value.

[0138] The gradient PDPC may modify the initial prediction value P_0(x,y), for example, in accordance with Eq. (10) as follows:P(x,y) = Cl ip (P_0(x, y) + (wL * (R(-1 ,y) - R(x”,-1 )) + 32) » 6) (10) where, for example, P(x,y) may be the final prediction value at pixel (x,y); P_0(x,y) may be the initial prediction value at pixel (x,y), which may be equal to the primary reference sample R(x’,-1); R(-1 ,y) may be the secondary reference sample on the same row as the target pixel; R(x”,-1) may be the predictor sample for the secondary reference sample R(-1 ,y); and wL may be the weight function computed, for example, in accordance with Eq. (11): wL = 32 » (2*x » scale)) (11 )The scale value in Eq. (11) may be computed, for example, in accordance with Eq. (12): scale = (Log 2 (H) + Log2(W) - 2) » 2) (12)

[0139] The final computed value may be clipped to the dynamic range of the signal component, which may be similar to the PDPC process in the case of (e.g., purely) vertical mode. Table 1 shows an example of the number of columns getting processed along with the respective weight values for different scale parameter values.

[0140] The type of PDPC applied for a given a target block size may depend on the prediction mode. Gradient PDPC may be applied, for example, if / when the prediction direction gets closer to the vertical direction. Normal PDPC may be applied, for example, if / when otherwise. The type of PDPC may (e.g., similarly) depend on the block size for a given eligible prediction direction. Normal PDPC may be replaced with gradient PDPC as the block size gets smaller, for example, as there may not be sufficient secondary reference samples. There may be a specified or configured relationship between block size, prediction mode, and / or the scale parameter in PDPC.

[0141] PDPC may be performed analogously for positive horizontal directions (e.g., 2 <= mode < 18, or mode < 0 in WC and / or ECM), except that rows at the top edge of a block instead of columns are processed. Normal PDPC or gradient PDPC may be applied, for example, depending on the value of the scale parameter. The scale parameter may be computed, for example, in accordance with Eq. (13): scale = min(2, Log2(width) - (Log2(3 * absInvAngle - 2) - 8)) (13)

[0142] Normal PDPC may be applied to the top (3 « scale) rows of the target block, for example, if scale is non-negative. The scale value may be recomputed if the scale is negative. For example, scale may be recomputed, for example, in accordance with Eq. (14): scale = (Log 2 (H) + Log2(W) - 2) » 2 (14)Gradient PDPC may be applied to the top (3 « scale) rows of the target block. The weights used for different rows (e.g., in either case) may be the same as given in Table 1. The initial predictions in the remaining rows may remain unchanged.

[0143] For some blocks, the actual number of columns or rows available may be smaller than (3 « scale). For example, for a block of size 32x4, the scale computed according to the foregoing example may be equal to one (1), indicating that six (6) columns may be processed with vertical modes. However, the maximum number of columns for this block is four (4). Therefore (e.g., in WC and / or ECM), thenumber of columns or rows processed by PDPC or gradient PDPC may be given as min ((3« scale), L), where L = W or L = H depending on if the prediction direction is vertical or horizontal.

[0144] FIG. 8 illustrates an example of perspective prediction of a target block in intra prediction. Target pixels in a row or column may have different prediction directions. The perspective point in the example shown in FIG. 8 is on top of the block.

[0145] In perspective intra prediction, a target block may be predicted using a perspective point, as shown by example in FIG. 8. A perspective point may be, for example, the intersection point of the prediction direction (e.g., associated with a mode) at the center of a target block with a straight line parallel to a side of the block at an offset distance. For vertical prediction modes, the line may be horizontal at offset distance dy . For horizontal modes, the line may be vertical at offset distance dx. Offset distances dx and dy may be referred to as the horizontal and vertical perspective distances, respectively. For a vertical angular mode, the corresponding perspective prediction may be referred to as vertical. For a horizontal prediction, the corresponding perspective prediction may be referred to as horizontal. Examples described herein consider (e.g., only) the perspective points on top and left of the block, for example, because these are the (e.g., only) situations that can lead to intensity discontinuities at the left or top edge of a target block.

[0146] A difference (e.g., the primary difference) between the normal prediction and the prediction with perspective is that the prediction direction along a row or a column may be variable in the latter case. The angle parameter predl ntraAngle (e.g., as may be defined in VVC and / or ECM) may be a function of the location of a target pixel. The terms perspectiveAngle and predl ntraAngleArray(x,y) may be used to distinguish between the two prediction types. The term perspectiveAngle may refer to the original predl ntraAngle. The term predl ntraAngleArray(x,y) may refer to the angle parameter at the pixel position (x,y).

[0147] FIG. 9 illustrates an example of intra prediction with perspective. The predictor for a target pixel may be the reference sample lying in the direction joining the target pixel with the perspective point. In FIG. 9, the angle parameter for the target pixel at position (x,y) is derived. While the example illustration in FIG. 9 shows a vertical prediction mode, the case may be analogous for a horizontal mode when the perspective point is on the left of the block. As shown in FIG. 9, let W and H denote the width and height of the target block, respectively. Let d denote the perspective height, that is, the vertical distance of the perspective point from the top edge of the target block. Division operations may be avoided, for example, by assuming that d is a power of 2. For a vertical mode, d = k * H , where k = 2n, n = 0, 1, . . Kmax. Kmax may be a preset integer. For a horizontal mode, d = k * W, where k = 2n,n = 0, 1, . . Kmax. Let A(x, y) denote the predl ntraAngleArray(x,y) value at (x, ). Let Aodenote the perspectiveAngle parameter, which may be the same as the angle parameter associated with prediction mode.

[0148] The angle parameter at target pixel (x, y) may be computed, for example, in accordance with Eq. (15):A(x, y) = A(x, 0) * (d / (d + y)) (15) where A(x, 0) may denote the angle parameter in the first row, but in the same column as the target pixel. A(x, 0) may be computed, for example, in accordance with Eq. (16):where s may be equal to five (5) or six (6), for example, depending on if the sample resolution of prediction direction is 1 / 32 or 1 / 64 of a pixel, respectively. A value of predl ntraAngleArray(x,y) may be computed, for example, as described in Eq. (15) or Eq. (16). The predictor samples may (e.g., then) be identified and interpolated, for example, similar (e.g., identical) to identification and interpolation in WC or ECM.

[0149] PDPC for perspective intra prediction may be implemented. A perspective prediction may be eligible for PDPC, for example, if the prediction directions at the left reference array (for vertical perspective prediction) or at the top reference (for horizontal perspective prediction) are nonnegative. PDPC may be applied (e.g., after the initial prediction), for example, if the perspective point is on top of a block and to the right of and including the left reference line (for vertical perspective prediction), or on the left of a block and below and including the top reference line (for horizontal perspective prediction). A reference line may refer to a straight line passing through the corresponding reference array. This condition may be mathematically expressed, for example, in accordance with Expression (17) or Expression (18):A0* (tf + 2 * d) > (W « s) (17)where Aomay be the perspectiveAngle value. The value of s may be equal to five (5) or six (6), for example, depending on if the sample resolution of angular direction is 1 / 32 or 1 / 64 of a pixel, respectively. PDPC can be applied (e.g., after the initial perspective prediction), for example, if the perspectiveAngle satisfies the condition in Expression (17) or Expression (18).

[0150] FIG. 10 illustrates an example of PDPC for perspective prediction FIG. 10illustrates the PDPC (e.g., normal PDPC) applied in the case of vertical perspective prediction. As shown in FIG. 10, the initial prediction values in (3 « scale) columns may be modified, for example, in accordance with Eq. (19):P(x,y) = P_0(x, y) + (wL * (R(-1 ,y’) - P_0(x,y)) + 32) » 6 (19) where P(x,y) may be the final perspective prediction value at pixel (x,y), P_0(x,y) may be the initial perspective prediction value at pixel (x,y), which may be equal to the primary reference sample R(x’,-1), R(-1 ,y’) may be the secondary reference sample obtained by extending the prediction direction at pixel (x,y), and wL may be the weight function, which may be computed, for example, in accordance with Eq. (20): wL = 32 » (2*x » scale) (20)The scale parameter may be computed, for example, such that the secondary reference samples are available for (e.g., all) target pixels in the first (3 « scale) columns of the target block. A weight function may be selected. In an example, the wight function may be similar to a weight function used in WC and ECM for easier adaptability of PDPC with perspective prediction. In an example, a weight function may be of a positive decreasing function type.

[0151] The location of the secondary reference sample R(-1 ,y’) may be computed, for example, in accordance with Eq. (21): y’ = 1 + y + (((1 + x)*abslnvAngle + 256) » 9 (21)The value of absInvAngle may be computed, for example, in accordance with Eq. (22A):absInvAngle = round((512 * 32) / A(x,y)), for (1 / 32) sample resolution (22A) or Eq. (22B): absInvAngle = round((512 * 64) / A(x,y)), for (1 / 64) sample resolution (22B)

[0152] A difference between the PDPC in normal intra prediction and the PDPC in perspective intra prediction is the localization of the secondary reference sample. In PDPC with normal intra prediction, the reference sample may be localized using the angle parameter associated with the mode (e.g., Ao). In PDPC with perspective intra prediction, the reference sample may be localized using the angle parameter at the target pixel (e.g., A(x,y)). The PDPC with normal intra prediction may be thought of as a special case of the PDPC with perspective prediction with A(x,y) = Aofor (e.g., all) target pixel locations (x,y).

[0153] The scale parameter, which may be computed for PDPC with absInvAngle corresponding to the angle parameter Ao, may be computed differently, for example, because the prediction angle in perspective prediction may depend on the coordinates of a target pixel. An algorithm is provided herein for scale factor computation.

[0154] It may be observed from FIG. 8 that the prediction angle becomes less positive moving along a row towards the right, which may be stated as follows: A(x,y) >= A(x+1,y), for (e.g., all) (x,y). It may also be observed from FIG. 8 that the prediction angle becomes less positive moving down a column, which may be stated as follows: A(x,y) >= A(x,y+1), for (e.g., all) (x,y). These two observations may be valid for PDPC-eligible vertical perspective modes and / or for PDPC-eligible horizontal perspective modes.

[0155] A PDPC with a general weighting function, denoted as l / l / (x), may have one or more of the following properties: (i) l / l / (x) is positive having values in the range (0, 32); (ii) l / l / (x) is non-increasing, e.g., l / l / (x) >= W(x+1); and / or (iii) l / l / (x) = 0, for x >= Lmax. Lmax may be the maximum number of columns that can undergo PDPC processing.

[0156] The two observations related to FIG. 8 indicate that a determination may be made whether a secondary reference sample is available, for example, by checking on the last row of a block starting from the Lmax-th column. Availability of the secondary reference for a (e.g., any) target pixel on the last row may provide the availability for (e.g., all) other pixels to the left of it. Availability of the secondary reference for a (e.g., any) target pixel on the last row may also provide the availability of secondary referencesamples for (e.g., all) target pixels on the rows above the last row up to and including the column on which the check was satisfied. The number of columns on which the PDPC can be applied when in perspective prediction may be determined, for example, by the following logic or algorithm expressed as pseudocode:1. Initialization: numCol = 0S = bit resolution for prediction direction (either 5 or 6) x= Lmax-1 ;2. do if A(x,H-1) > 0 absInvAngle = (512 * (1«S)) I A((x, H-1); if (((1 +x)* absInvAngle + 256) » 9) <= H break; else x = x - 1 ; while x >= 0; numCol = 1 +x;If numCol is greater than 0, normal PDPC can be applied over numCol columns

[0157] The weighting function may be considered to be based on the scale parameter, for example, as indicated in Eq. (23): wL = 32 » (2*x » scale) (23)Similar to the foregoing algorithm, the availability of the secondary reference sample may be checked for the largest scale value first. The scale value may (e.g., then) decrease if the sample is not available. The process may be repeated until the scale reaches zero (0). The following logic or algorithm expressed as pseudocode may implement the process:1. initialization: scale = -1;S = bit resolution for prediction direction (either 5 or 6);K = maxScale, where maxScale is the maximum scale value.2. do if A((3«K) - 1, H-1) > absInvAngletmpScale = min(maxScale, Log2(H) - (Log2(3 * absInvAngle - 2) - 8)); if tmpScale >= K-1 , break; elseK = K - 1 ; while K >= 0 scale = tmpScale;3. If scale >= 0, apply normal PDPC with computed scale.

[0158] As indicated, the foregoing algorithm checks the scale value with the angle parameters at the 12th, 6th, and 3rdpixels on the last row of the block sequentially if it is greater than or equal to 2, 1 , or 0, respectively. PDPC may be performed if the check is verified. PDPC may be performed (e.g., as explained herein) with the computed scale value. Gradient PDPC may be applied (e.g., as explained below), for example, if the scale has a negative value.

[0159] FIG. 11 illustrates an example of gradient PDPC for perspective prediction. Gradient PDPC may be implemented (e.g., as described herein). The predictor sample for the secondary reference sample R(-1 ,y) may be computed, for example, using the prediction direction computed at (-1 ,y). The gradient may (e.g., then) be computed, as shown by example in FIG. 11 . The initial perspective prediction may be modified, for example, in accordance with Eq. (24):P(x,y) = Cl ip (P_0(x, y) + (wL * (R(-1 ,y) - R(x”,-1 )) + 32) » 6) (24) where, for example, P(x,y) may be the final perspective prediction value at pixel (x,y),P_0(x,y) may be the initial perspective prediction value at pixel (x,y), which may be equal to the primary reference sample R(x’,-1), R(-1 ,y) may be the secondary reference sample on the same row as the target pixel, R(x”,-1) may be the perspective predictor sample for the secondary reference sample R(-1 ,y), and wL may be the weight function, which may be computed, for example, in accordance with Eq. (25): wL = 32 » (2*x » scale) (25)The scale value in Eq. (25) may be computed, for example, in accordance with Eq. (26): scale = (Log2(H) + Log2(W) - 2) » 2 (26)

[0160] A PDPC or a gradient PDPC may be performed analogously for horizontal perspective predictions, except that rows instead of columns at the top edge of a block are processed. The scaleparameter for PDPC may be computed using the prediction angles on the last column of a block at positions (3«scale). The normal PDPC may be applied, for example, if the scale value is positive. The gradient PDPC may be applied, for example, if the scale value is not positive. The number of columns or rows processed by PDPC or gradient PDPC in perspective prediction (e.g., similar to PDPC and gradient PDPC with normal prediction) may be given, for example, as min((3« scale), L), where L = W or L = H depending on if the prediction direction is vertical or horizontal.

[0161] Various examples are described herein related to application scenarios for the PDPC algorithm with perspective intra prediction. A video codec may support intra prediction with directional prediction modes.

[0162] In some examples, the encoder and the decoder (e.g., codec) may support perspective intra prediction, e.g., as described herein. The PDPC alone (e.g., with gradient PDPC is disabled) or PDPC and the gradient PDPC may be applied to an initial prediction at a pixel in a target block depending on the scale parameter value, for example, if a perspective prediction mode is eligible for PDPC.

[0163] In some examples, the encoder and the decoder (e.g., codec) support perspective intra prediction, e.g., as described herein. PDPC or gradient PDPC (e.g., as described herein) may be applied (e.g., optionally applied) to an initial prediction at a pixel in a target block. The option may be implemented with a flag (e.g., pdpcFlag). For example, a value of one (1) for the flag may indicate the application of PDPC or gradient PDPC and a value of zero (0) may indicate that neither PDPC nor gradient PDPC is applied. The flag may be used (e.g., only) for the modes eligible for PDPC.

[0164] In some examples, the encoder and the decoder (e.g., codec) support perspective intra prediction, e.g., as described herein. PDPC may not be applied after the initial perspective intra prediction. PDPC or gradient PDPC may be applied in the case of normal intra prediction. The encoder and the decoder (e.g., codec) may (e.g., additionally and / or alternatively) support perspective intra prediction, e.g., as described herein. PDPC applied to the perspective prediction may be similar to the PDPC applied in the normal prediction.

[0165] In some examples, except the secondary reference samples may be interpolated with higher precision in PDPC than the nearest neighbor interpolation, or the predictors for the secondary reference samples may be interpolated with higher precision than the linear interpolation. For example, a cubic interpolation may be performed whenever the secondary reference sample in PDPC, or a predictor for a secondary reference sample in gradient PDPC, does not coincide with a reference sample.

[0166] In some examples, the application of PDPC or gradient PDPC may be deactivated if the left neighbor block (e.g., for vertical modes) or top neighbor block (e.g., for horizontal modes) is not available.

[0167] PDPC for intra prediction with perspectives may provide one or more advantages. The described PDPC algorithm may be used with perspective intra prediction. The prediction model may generate better predictions in sequences having perspectives, which may lead to higher compression efficiency, e.g., compared to using only perspective prediction.

[0168] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media.Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMS1 . A device for video coding, the device comprising: a processor configured to: predict a target block using a perspective intra prediction mode, wherein the target block is predicted using a perspective point; and apply a position dependent pixel combination (PDPC) scheme to a pixel associated with the perspective intra-predicted target block, wherein the PDPC scheme is applied based on a scale parameter value.

2. The device of claim 1 , wherein the processor is further configured to: determine that the perspective intra prediction mode is eligible for PDPC; and based on the determination that the perspective intra prediction mode is eligible for PDPC, determine that PDPC is applied.

3. The device of claim 1 or 2, wherein the PDPC scheme is a normal PDPC scheme or a gradient PDPC scheme.

4. The device of any of claims 1 to 3, wherein the PDPC scheme is the normal PDPC if the scale parameter is greater than or equal to zero, and wherein the PDPC scheme is the gradient PDPC if the scale parameter value is less than zero.

5. The device of any of claims 1 to 4, wherein the processor is further configured to: obtain an indication that indicates whether to apply a normal PDPC scheme or a gradient PDPC scheme.

6. The device of any of claims 1 to 5, wherein the processor is further configured to: determine whether a left neighbor block is available, wherein the PDPC scheme application to the pixel is based on the determination of whether the left neighbor block is available.

7. The device of any of claims 1 to 6, wherein the processor is further configured to: determine whether a top neighbor block is available, wherein the PDPC scheme application to the pixel is based on the determination of whether the top neighbor block is available.

8. The device for video coding of any of claims 1 to 7, wherein the device is a video decoder or a video encoder.

9. A method for video coding, the method comprising: predicting a target block using a perspective intra prediction mode, wherein the target block is predicted using a perspective point; and applying a position dependent pixel combination (PDPC) scheme to a pixel associated with the perspective intra-predicted target block, wherein the PDPC scheme is applied based on a scale parameter value.

10. The method of claim 9, wherein the method further comprises: determining that the perspective intra prediction mode is eligible for PDPC; and based on the determination that the perspective intra prediction mode is eligible for PDPC, determining that PDPC is applied.11 . The method of claim 9 or 10, wherein the PDPC scheme is a normal PDPC scheme or a gradient PDPC scheme.

12. The method of any of claims 9 to 11 , wherein the PDPC scheme is the normal PDPC if the scale parameter is greater than or equal to zero, and wherein the PDPC scheme is the gradient PDPC if the scale parameter value is less than zero.

13. The method of any of claims 9 to 12, wherein the method further comprises: obtaining an indication that indicates whether to apply a normal PDPC scheme or a gradient PDPC scheme.

14. The method of any of claims 9 to 13, wherein the method further comprises: determining whether a left neighbor block is available, wherein the PDPC scheme application to the pixel is based on the determination of whether the left neighbor block is available.

15. The method of any of claims 9 to 14, wherein the method further comprises: determining whether a top neighbor block is available, wherein the PDPC scheme application to the pixel is based on the determination of whether the top neighbor block is available.

16. The method of any of claims 9 to 15, wherein the device is a video decoder or a video encoder.

Images