Patent Description:
Intra prediction modes used in High Efficiency Video Coding (HEVC) and Versatile Video Coding (VVC) are illustrated in <FIG> and <FIG>, respectively. In HEVC, mode <NUM> is a horizontal mode, mode <NUM> is a vertical mode, and mode <NUM>, mode <NUM> and mode <NUM> are diagonal modes. An intra prediction scheme based on <NUM> directional modes has also been proposed to capture arbitrary edge directions presented in natural video, and this intra prediction scheme based on <NUM> directional modes is being studied for the development of WC.

In <FIG>, in HEVC, mode <NUM> and <NUM> indicate the same prediction direction. In <FIG>, in VVC, mode <NUM> and <NUM> indicate the same prediction direction.

As shown in <FIG> and <FIG>, all intra prediction modes are within <NUM> degrees in a top-right and a bottom-left direction, which are called conventional intra prediction modes in this document. Wide angles beyond the range of prediction directions covered by conventional intra prediction modes have been proposed, which are called wide angular intra prediction modes. Each wide-angular intra prediction direction is associated with one conventional intra prediction direction. Each wide-angular intra prediction direction and its associated intra prediction direction capture the same directionality, but use opposite sides of reference samples (left column or top row). The tool is signaled by sending a <NUM>-bit flag for those associated directions that have an available wide-angle "flip mode. " In the case of the <NUM>-direction angular intra prediction, the availability of new modes is limited to <NUM> directional modes closest to the <NUM>-degree diagonal top-right mode (i.e., mode <NUM> when <NUM> conventional intra modes are applied) and the bottom-left mode (i.e., mode <NUM> when <NUM> conventional intra modes are applied). The actual sample prediction process follows the one in HEVC or WC.

<FIG> illustrates the process for the hypothetical case of <NUM> HEVC directions and limiting the operation to two modes closest to the diagonal modes. In this example, if the block width is larger than the block height, mode <NUM> and mode <NUM> would have extra flags indicating whether to use the indicated mode or the flipped wide angular direction with mode <NUM> and mode <NUM>. In wide angular intra prediction (WAIP), whether mode <NUM> and mode <NUM> need flipping is not indicated by an extra flag in a bitstream, but rather is derived by block width and height. Besides, if mode <NUM> and mode <NUM> need flipping, mode <NUM> also needs flipping.

US Patent application <CIT> discloses a method for video coding and is particularly concerned with complexity reduction of signalling intra prediction modes. Of the initial <NUM> intra prediction modes, including <NUM> angular modes, <NUM> most probable modes are selected. <NUM> angular mode of the remaining <NUM> modes is excluded in order to obtain a remaining set of <NUM> modes which can be signalled by a <NUM>-bit fixed code. The mode to be excluded may be a mode neighbouring the bottom-left or top-right diagonal modes. Alternatively, other modes may be selected. The modes to be excluded are generally selected from among modes that are not included in the <NUM> modes for 4x4 PUs.

According to the invention, there are provided a method of controlling intra prediction for decoding or encoding of a video sequence as defined in claim <NUM>, an apparatus for controlling intra prediction for decoding or encoding of a video sequence as defined in claim <NUM> and a non-transitory computer-readable storage medium as defined in claim <NUM>.

<FIG> is a simplified block diagram of a communication system (<NUM>) according to embodiments. The communication system (<NUM>) may include at least two terminals (<NUM>-<NUM>) interconnected via a network (<NUM>). For unidirectional transmission of data, a first terminal (<NUM>) may code video data at a local location for transmission to the other terminal (<NUM>) via the network (<NUM>). The second terminal (<NUM>) may receive the coded video data of the other terminal from the network (<NUM>), decode the coded data and display the recovered video data.

<FIG> illustrates a second pair of terminals (<NUM>, <NUM>) provided to support bidirectional transmission of coded video that may occur, for example, during videoconferencing. For bidirectional transmission of data, each terminal (<NUM>, <NUM>) may code video data captured at a local location for transmission to the other terminal via the network (<NUM>). Each terminal (<NUM>, <NUM>) also may receive the coded video data transmitted by the other terminal, may decode the coded data and may display the recovered video data at a local display device.

In <FIG>, the terminals (<NUM>-<NUM>) may be illustrated as servers, personal computers and smart phones but the principles of embodiments are not so limited. Embodiments find application with laptop computers, tablet computers, media players and/or dedicated video conferencing equipment. The network (<NUM>) represents any number of networks that convey coded video data among the terminals (<NUM>-<NUM>), including for example wireline and/or wireless communication networks. For the purposes of the present discussion, the architecture and topology of the network (<NUM>) may be immaterial to the operation of embodiments unless explained herein below.

<FIG> is a diagram of a placement of a video encoder and a video decoder in a streaming environment, according to embodiments.

A streaming system may include a capture subsystem (<NUM>) that can include a video source (<NUM>), for example a digital camera, creating, for example, an uncompressed video sample stream (<NUM>). That sample stream (<NUM>), depicted as a bold line to emphasize a high data volume when compared to encoded video bitstreams, can be processed by an encoder (<NUM>) coupled to the camera (<NUM>). The encoder (<NUM>) can include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter as described in more detail below. The encoded video bitstream (<NUM>), depicted as a thin line to emphasize the lower data volume when compared to the sample stream, can be stored on a streaming server (<NUM>) for future use. One or more streaming clients (<NUM>, <NUM>) can access the streaming server (<NUM>) to retrieve copies (<NUM>, <NUM>) of the encoded video bitstream (<NUM>). A client (<NUM>) can include a video decoder (<NUM>), which decodes the incoming copy of the encoded video bitstream (<NUM>) and creates an outgoing video sample stream (<NUM>) that can be rendered on a display (<NUM>) or other rendering device (not depicted). In some streaming systems, the video bitstreams (<NUM>, <NUM>, <NUM>) can be encoded according to certain video coding/compression standards. Examples of those standards include ITU-T Recommendation H. Under development is a video coding standard informally known as VVC. The disclosed subject matter may be used in the context of VVC.

<FIG> is a functional block diagram of a video decoder (<NUM>) according to embodiments.

A receiver (<NUM>) may receive one or more codec video sequences to be decoded by the decoder (<NUM>); in the same or embodiments, one coded video sequence at a time, where the decoding of each coded video sequence is independent from other coded video sequences. The coded video sequence may be received from a channel (<NUM>), which may be a hardware/software link to a storage device, which stores the encoded video data. To combat network jitter, a buffer memory (<NUM>) may be coupled in between receiver (<NUM>) and entropy decoder / parser (<NUM>) ("parser" henceforth). When receiver (<NUM>) is receiving data from a store/forward device of sufficient bandwidth and controllability, or from an isosychronous network, the buffer (<NUM>) may not be needed, or can be small. For use on best effort packet networks such as the Internet, the buffer (<NUM>) may be required, can be comparatively large and can advantageously of adaptive size.

The video decoder (<NUM>) may include a parser (<NUM>) to reconstruct symbols (<NUM>) from the entropy coded video sequence. Categories of those symbols include information used to manage operation of the decoder (<NUM>), and potentially information to control a rendering device such as a display (<NUM>) that is not an integral part of the decoder but can be coupled to it, as was shown in <FIG>. The control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information (VUI) parameter set fragments (not depicted). The parser (<NUM>) may parse / entropy-decode the coded video sequence received. The coding of the coded video sequence can be in accordance with a video coding technology or standard, and can follow principles well known to a person skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and so forth. The parser (<NUM>) may extract from the coded video sequence, a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder, based upon at least one parameters corresponding to the group. The entropy decoder / parser may also extract from the coded video sequence information such as transform coefficients, quantizer parameter (QP) values, motion vectors, and so forth.

The parser (<NUM>) may perform entropy decoding / parsing operation on the video sequence received from the buffer (<NUM>), so to create symbols (<NUM>). The parser (<NUM>) may receive encoded data, and selectively decode particular symbols (<NUM>). Further, the parser (<NUM>) may determine whether the particular symbols (<NUM>) are to be provided to a Motion Compensation Prediction unit (<NUM>), a scaler / inverse transform unit (<NUM>), an Intra Prediction unit (<NUM>), or a loop filter unit (<NUM>).

Beyond the functional blocks already mentioned, decoder (<NUM>) can be conceptually subdivided into a number of functional units as described below.

The scaler / inverse transform unit (<NUM>) receives quantized transform coefficient as well as control information, including which transform to use, block size, quantization factor, quantization scaling matrices, etc. as symbol(s) (<NUM>) from the parser (<NUM>). It can output blocks comprising sample values that can be input into aggregator (<NUM>).

In some cases, the intra picture prediction unit (<NUM>) generates a block of the same size and shape of the block under reconstruction, using surrounding already reconstructed information fetched from the current (partly reconstructed) picture (<NUM>).

In such a case, a Motion Compensation Prediction unit (<NUM>) can access reference picture memory (<NUM>) to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols (<NUM>) pertaining to the block, these samples can be added by the aggregator (<NUM>) to the output of the scaler / inverse transform unit (in this case called the residual samples or residual signal) so to generate output sample information. The addresses within the reference picture memory form where the motion compensation unit fetches prediction samples can be controlled by motion vectors, available to the motion compensation unit in the form of symbols (<NUM>) that can have, for example X, Y, and reference picture components. Motion compensation also can include interpolation of sample values as fetched from the reference picture memory when sub-sample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.

Video compression technologies can include in-loop filter technologies that are controlled by parameters included in the coded video bitstream and made available to the loop filter unit (<NUM>) as symbols (<NUM>) from the parser (<NUM>), but can also be responsive to meta-information obtained during the decoding of previous (in decoding order) parts of the coded picture or coded video sequence, as well as responsive to previously reconstructed and loop-filtered sample values.

Once a coded picture is fully reconstructed and the coded picture has been identified as a reference picture (by, for example, parser (<NUM>)), the current reference picture (<NUM>) can become part of the reference picture buffer (<NUM>), and a fresh current picture memory can be reallocated before commencing the reconstruction of the following coded picture.

The video decoder (<NUM>) may perform decoding operations according to a predetermined video compression technology that may be documented in a standard, such as ITU-T Rec. The coded video sequence may conform to a syntax specified by the video compression technology or standard being used, in the sense that it adheres to the syntax of the video compression technology or standard, as specified in the video compression technology document or standard and specifically in the profiles document therein.

In embodiments, the receiver (<NUM>) may receive additional (redundant) data with the encoded video. Additional data can be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and so on.

<FIG> is a functional block diagram of a video encoder (<NUM>) according to embodiments.

The encoder (<NUM>) may receive video samples from a video source (<NUM>) (that is not part of the encoder) that may capture video image(s) to be coded by the encoder (<NUM>).

The video source (<NUM>) may provide the source video sequence to be coded by the encoder (<NUM>) in the form of a digital video sample stream that can be of any suitable bit depth (for example: <NUM> bit, <NUM> bit, <NUM> bit,. <NUM> Y CrCB, RGB,. ) and any suitable sampling structure (for example Y CrCb <NUM>:<NUM>:<NUM>, Y CrCb <NUM>:<NUM>:<NUM>).

According to embodiments, the encoder (<NUM>) may code and compress the pictures of the source video sequence into a coded video sequence (<NUM>) in real time or under any other time constraints as required by the application. Enforcing appropriate coding speed is one function of Controller (<NUM>). Controller controls other functional units as described below and is functionally coupled to these units. Parameters set by controller can include rate control related parameters (picture skip, quantizer, lambda value of rate-distortion optimization techniques,. A person skilled in the art can readily identify other functions of controller (<NUM>) as they may pertain to video encoder (<NUM>) optimized for a certain system design.

Some video encoders operate in what a person skilled in the art readily recognizes as a "coding loop. " As an oversimplified description, a coding loop can consist of the encoding part of an encoder (<NUM>) ("source coder" henceforth) (responsible for creating symbols based on an input picture to be coded, and a reference picture(s)), and a (local) decoder (<NUM>) embedded in the encoder (<NUM>) that reconstructs the symbols to create the sample data that a (remote) decoder also would create (as any compression between symbols and coded video bitstream is lossless in the video compression technologies considered in the disclosed subject matter). That reconstructed sample stream is input to the reference picture memory (<NUM>). As the decoding of a symbol stream leads to bit-exact results independent of decoder location (local or remote), the reference picture buffer content is also bit exact between local encoder and remote encoder. This fundamental principle of reference picture synchronicity (and resulting drift, if synchronicity cannot be maintained, for example because of channel errors) is well known to a person skilled in the art.

The operation of the "local" decoder (<NUM>) can be the same as of a "remote" decoder (<NUM>), which has already been described in detail above in conjunction with <FIG>. Briefly referring also to <FIG>, however, as symbols are available and en/decoding of symbols to a coded video sequence by entropy coder (<NUM>) and parser (<NUM>) can be lossless, the entropy decoding parts of decoder (<NUM>), including channel (<NUM>), receiver (<NUM>), buffer (<NUM>), and parser (<NUM>) may not be fully implemented in local decoder (<NUM>).

As part of its operation, the source coder (<NUM>) may perform motion compensated predictive coding, which codes an input frame predictively with reference to one or more previously-coded frames from the video sequence that were designated as "reference frames. " In this manner, the coding engine (<NUM>) codes differences between pixel blocks of an input frame and pixel blocks of reference frame(s) that may be selected as prediction reference(s) to the input frame.

The local video decoder (<NUM>) may decode coded video data of frames that may be designated as reference frames, based on symbols created by the source coder (<NUM>). When the coded video data may be decoded at a video decoder (not shown in <FIG>), the reconstructed video sequence typically may be a replica of the source video sequence with some errors. The local video decoder (<NUM>) replicates decoding processes that may be performed by the video decoder on reference frames and may cause reconstructed reference frames to be stored in the reference picture cache (<NUM>). In this manner, the encoder (<NUM>) may store copies of reconstructed reference frames locally that have common content as the reconstructed reference frames that will be obtained by a far-end video decoder (absent transmission errors).

That is, for a new frame to be coded, the predictor (<NUM>) may search the reference picture memory (<NUM>) for sample data (as candidate reference pixel blocks) or certain metadata such as reference picture motion vectors, block shapes, and so on, that may serve as an appropriate prediction reference for the new pictures.

The controller (<NUM>) may manage coding operations of the video coder (<NUM>), including, for example, setting of parameters and subgroup parameters used for encoding the video data.

The entropy coder translates the symbols as generated by the various functional units into a coded video sequence, by loss-less compressing the symbols according to technologies known to a person skilled in the art as, for example Huffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (<NUM>) may buffer the coded video sequence(s) as created by the entropy coder (<NUM>) to prepare it for transmission via a communication channel (<NUM>), which may be a hardware/software link to a storage device that may store the encoded video data.

The controller (<NUM>) may manage operation of the encoder (<NUM>). For example, pictures often may be assigned as one of the following frame types:.

Source pictures commonly may be subdivided spatially into a plurality of sample blocks (for example, blocks of <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, or <NUM> × <NUM> samples each) and coded on a block-by-block basis. Pixel blocks of P pictures may be coded non-predictively, via spatial prediction or via temporal prediction with reference to one previously coded reference pictures. Blocks of B pictures may be coded non-predictively, via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

The video coder (<NUM>) may perform coding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. In its operation, the video coder (<NUM>) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence.

In embodiments, the transmitter (<NUM>) may transmit additional data with the encoded video. The video coder (<NUM>) may include such data as part of the coded video sequence. Additional data may comprise temporal/spatial/SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, Supplementary Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, and so on.

Intra mode selection in intra prediction will now be described in detail. For coding or signaling of intra prediction modes, a set of most probable modes (MPMs) is established. A flag may be used to signal if a current intra prediction mode belongs to the set of MPMs. If yes, an index is signaled to indicate which of the MPMs matches the current intra prediction mode. Otherwise, a coding of remaining modes (non-MPMs) uses fixed-length coding or variable-length coding. Thus, a bit-length representing an MPM may be shorter (e.g., <NUM>-bit) than that representing a non-MPM mode.

According to the invention, one or more intra prediction modes are removed when a total number (a total amount) of intra prediction modes (a sum of a number of MPMs and a number of remaining modes) exceeds an allowed number (an allowed amount).

In embodiments, one or two directional modes may be excluded from <NUM> directional modes respectively corresponding to angular prediction directions. For example, when a total number (total amount) of intra prediction modes is <NUM>, while a number of MPMs is <NUM>, two directional modes may be excluded from the <NUM> directional modes. In another example, when the total number of intra prediction modes is <NUM>, while the number of MPMs is <NUM>, one directional mode may be excluded from the <NUM> directional modes. Thus, a coding of non-MPMs may use fixed-length coding, and a bit-length representing a non-MPM mode may be, e.g., <NUM>-bit for <NUM> non-MPM modes.

<FIG>, <FIG>, <FIG> and <FIG> are diagrams of candidate modes for exclusion from intra prediction modes, according to examples not falling under the scope of the invention as claimed.

Referring to <FIG>, an immediate mode (<NUM>) (top circled mode) to the left of a vertical mode (<NUM>) (top bolded arrow) and/or an immediate mode (<NUM>) (left circled mode) on top of a horizontal mode (<NUM>) (left bolded arrow) may be excluded.

Referring to <FIG>, an immediate mode (<NUM>) (top circled mode) to the right of the vertical mode (<NUM>) (top bolded arrow) and/or an immediate mode (<NUM>) (left circled mode) below the horizontal mode (<NUM>) (left bolded arrow) may be excluded.

Referring to <FIG>, a second immediate mode (<NUM>) (top circled mode) to the left of the vertical mode (<NUM>) (top bolded arrow) and/or a second immediate mode (<NUM>) (left circled mode) on top of the horizontal mode (<NUM>) (left bolded arrow) may be excluded.

Referring to <FIG>, a second immediate mode (<NUM>) (top circled mode) to the right of the vertical mode (<NUM>) (top bolded arrow) and/or a second immediate mode (<NUM>) (left circled mode) below the horizontal mode (<NUM>) (left bolded arrow) may be excluded.

Referring to <FIG>, a number of directional modes shown is not <NUM>, but is used to illustrate directional modes relative to the horizontal and vertical modes that may be excluded.

In examples not forming part of the invention as claimed, neighboring directional modes next to furthest diagonal modes (a top right corner mode, a bottom left corner mode and/or a top left corner mode) can also be candidate modes for exclusion from intra prediction modes According to the invention, the furthest diagonal modes are candidate modes for exclusion from intra prediction modes.

For example, referring to <FIG>, modes <NUM>, <NUM> and <NUM> respectively corresponding to the bottom left corner mode, the top left corner mode and the top right corner mode may be excluded.

<FIG> is a flowchart illustrating a method (<NUM>) of controlling intra prediction for decoding or encoding of a video sequence, according to embodiments. In some implementations, one or more process blocks of <FIG> may be performed by the decoder (<NUM>). In some implementations, one or more process blocks of <FIG> may be performed by another device or a group of devices separate from or including the decoder (<NUM>), such as the encoder (<NUM>).

Referring to <FIG>, in a first block (<NUM>), the method (<NUM>) includes obtaining intra prediction modes comprising directional modes respectively corresponding to angular prediction directions, a first amount of one or more of the directional modes being excluded from the intra prediction modes based on a second amount of the intra prediction modes and a third amount of most probable modes (MPMs).

In a second block (<NUM>), the method (<NUM>) includes selecting, as the MPMs, two or more of the intra prediction modes from which the one or more of the directional modes are excluded.

In a third block (<NUM>), the method (<NUM>) includes selecting, for decoding the video sequence, one of the intra prediction modes from which the one or more of the directional modes are excluded.

The one or more of the directional modes excluded from the intra prediction modes may include an immediate mode left of a vertical mode corresponding to a vertical prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include an immediate mode above a horizontal mode corresponding to a horizontal prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include an immediate mode right of a vertical mode corresponding to a vertical prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include an immediate mode below a horizontal mode corresponding to a horizontal prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include a second immediate mode left of a first immediate mode that is left of a vertical mode corresponding to a vertical prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include a second immediate mode above a first immediate mode that is above a horizontal mode corresponding to a horizontal prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include a second immediate mode right of a first immediate mode that is right of a vertical mode corresponding to a vertical prediction direction, among the directional modes.

The one or more of the directional modes excluded from the intra prediction modes may include a second immediate mode below a first immediate mode that is below a horizontal mode corresponding to a horizontal prediction direction, among the directional modes.

According to the invention, the one or more of the directional modes excluded from the intra prediction modes include any one or any combination of a top right corner mode, a bottom left corner mode and a top left corner mode respectively corresponding to a top right corner direction, a bottom left corner direction and a top left corner direction, among the directional modes.

The first amount of the one or more of the directional modes is excluded from the intra prediction modes so that a sum of the third amount of the MPMs and a fourth amount of remaining modes that are not the MPMs is less than or equal to an allowed amount.

Two or more of the blocks of the method (<NUM>) of <FIG> may be performed in parallel.

Further, the proposed methods may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In an example, the one or more processors execute a program that is stored in a non-transitory computer-readable medium to perform one or more of the proposed methods.

<FIG> is a simplified block diagram of an apparatus (<NUM>) for controlling intra prediction for decoding or encoding of a video sequence, according to embodiments.

Referring to <FIG>, the apparatus (<NUM>) includes obtaining code (<NUM>), first selecting code (<NUM>) and second selecting code (<NUM>).

The obtaining code (<NUM>) is configured to cause the at least one processor to obtain intra prediction modes comprising directional modes respectively corresponding to angular prediction directions, a first amount of one or more of the directional modes being excluded from the intra prediction modes based on a second amount of the intra prediction modes and a third amount of most probable modes (MPMs).

The first selecting code (<NUM>) is configured to cause the at least one processor to select, as the MPMs, two or more of the intra prediction modes from which the one or more of the directional modes are excluded.

The second selecting code (<NUM>) is configured to cause the at least one processor to select, for decoding the video sequence, one of the intra prediction modes from which the one or more of the directional modes are excluded.

In examples not falling under the scope of the claims, the one or more of the directional modes excluded from the intra prediction modes may include any one or any combination of an immediate mode left of a vertical mode corresponding to a vertical prediction direction, among the directional modes, an immediate mode above a horizontal mode corresponding to a horizontal prediction direction, among the directional modes, an immediate mode right of the vertical mode, among the directional modes, and an immediate mode below the horizontal mode, among the directional modes.

In examples not falling under the scope of the claims, the one or more of the directional modes excluded from the intra prediction modes comprises any one or any combination of a second immediate mode left of a first immediate mode that is left of a vertical mode corresponding to a vertical prediction direction, among the directional modes, a second immediate mode above a first immediate mode that is above a horizontal mode corresponding to a horizontal prediction direction, among the directional modes, a second immediate mode right of a first immediate mode that is right of the vertical mode, among the directional modes, and a second immediate mode below a first immediate mode that is below the horizontal mode, among the directional modes.

According to the invention, the one or more of the directional modes excluded from the intra prediction modes includes any one or any combination of a top right corner mode, a bottom left corner mode and a top left corner mode respectively corresponding to a top right corner direction, a bottom left corner direction and a top left corner direction, among the directional modes.

The first amount of the one or more of the directional modes is excluded from the intra prediction modes so that a sum of the third amount of the MPMs and a fourth amount of remaining modes that are not the MPMs less than or equal to an allowed amount.

<FIG> is a diagram of a computer system (<NUM>) suitable for implementing embodiments.

The components shown in <FIG> for computer system (<NUM>) are examples in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in embodiments of a computer system (<NUM>).

Input human interface devices may include one or more of (only one of each depicted): keyboard (<NUM>), mouse (<NUM>), trackpad (<NUM>), touch screen (<NUM>), data-glove (<NUM>), joystick (<NUM>), microphone (<NUM>), scanner (<NUM>), camera (<NUM>).

Such human interface output devices may include tactile output devices (for example tactile feedback by the touch-screen (<NUM>), data-glove (<NUM>), or joystick (<NUM>), but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers (<NUM>), headphones (not depicted)), visual output devices (such as screens (<NUM>) to include cathode ray tube (CRT) screens, liquid-crystal display (LCD) screens, plasma screens, organic light-emitting diode (OLED) screens, each with or without touch-screen input capability, each with or without tactile feedback capability-some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual-reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted). A graphics adapter (<NUM>) generates and outputs images to the touch-screen (<NUM>).

Computer system (<NUM>) can also include interface(s) to one or more communication networks (<NUM>). Networks (<NUM>) can for example be wireless, wireline, optical. Networks (<NUM>) can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, and so on. Examples of networks (<NUM>) include local area networks such as Ethernet, wireless LANs, cellular networks to include global systems for mobile communications (GSM), third generation (<NUM>), fourth generation (<NUM>), fifth generation (<NUM>), Long-Term Evolution (LTE), and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain networks (<NUM>) commonly require external network interface adapters that attached to certain general purpose data ports or peripheral buses ((<NUM>)) (such as, for example universal serial bus (USB) ports of the computer system (<NUM>); others are commonly integrated into the core of the computer system (<NUM>) by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface (<NUM>) into a smartphone computer system). Using any of these networks (<NUM>), computer system (<NUM>) can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbus to certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks (<NUM>) and network interfaces (<NUM>) as described above.

Aforementioned human interface devices, human-accessible storage devices, and network interfaces (<NUM>) can be attached to a core (<NUM>) of the computer system (<NUM>).

The core (<NUM>) can include one or more Central Processing Units (CPU) (<NUM>), Graphics Processing Units (GPU) (<NUM>), specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) (<NUM>), hardware accelerators (<NUM>) for certain tasks, and so forth. These devices, along with Read-only memory (ROM) (<NUM>), Random-access memory (RAM) (<NUM>), internal mass storage such as internal non-user accessible hard drives, solid-state drives (SSDs), and the like (<NUM>), may be connected through a system bus (<NUM>). Architectures for a peripheral bus include peripheral component interconnect (PCI), USB, and the like.

Transitional data can also be stored in RAM (<NUM>), whereas permanent data can be stored for example, in the internal mass storage (<NUM>).

The media and computer code can be those specially designed and constructed for the purposes of embodiments, or they can be of the kind well known and available to those having skill in the computer software arts.

Claim 1:
A method of controlling intra prediction for decoding or encoding of a video sequence, the method being performed by at least one processor, and the method comprising:
obtaining (<NUM>) intra prediction modes comprising directional modes respectively corresponding to angular prediction directions, a first amount of one or more of the directional modes being excluded from the intra prediction modes based on a second amount of the intra prediction modes and a third amount of most probable modes, MPMs;
selecting (<NUM>), as the MPMs, two or more of the intra prediction modes from which the one or more of the directional modes are excluded; and
selecting (<NUM>), for decoding the video sequence, one of the intra prediction modes from which the one or more of the directional modes are excluded,
wherein the one or more of the directional modes excluded from the intra prediction modes comprises any one or any combination of a top right corner mode, a bottom left corner mode, and a top left corner mode respectively corresponding to a top right corner direction, a bottom left corner direction, and a top left corner direction, among the directional modes, and
wherein the first amount of the one or more of the directional modes is excluded from the intra prediction modes so that a sum of the third amount of the MPMs and a fourth amount of remaining modes that are not the MPMs is less than or equal to an allowed amount.