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WO2025119602A1 - Appareil, procédé et programme d'ordinateur pour le codage et le décodage de vidéo - Google Patents

Appareil, procédé et programme d'ordinateur pour le codage et le décodage de vidéo Download PDF

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Publication number
WO2025119602A1
WO2025119602A1 PCT/EP2024/082045 EP2024082045W WO2025119602A1 WO 2025119602 A1 WO2025119602 A1 WO 2025119602A1 EP 2024082045 W EP2024082045 W EP 2024082045W WO 2025119602 A1 WO2025119602 A1 WO 2025119602A1
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Prior art keywords
decoder
block
intra mode
mode derivation
sample data
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English (en)
Inventor
Ivan ZUPANCIC
Saverio BLASI
Jani Lainema
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Nokia Technologies Oy
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Nokia Technologies Oy
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/11—Selection of coding mode or of prediction mode among a plurality of spatial predictive coding modes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/42—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation
    • H04N19/423—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation characterised by memory arrangements
    • H04N19/426—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation characterised by memory arrangements using memory downsizing methods
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques

Definitions

  • the present invention relates to an apparatus, a method and a computer program for video coding and decoding.
  • DIMD decoder-side intra mode derivation
  • the DIMD information from the neighboring blocks can be used to generate a prediction for the current block, referred to as DIMD merge.
  • DIMD merge the DIMD information extracted from neighboring blocks is used to compute the intra prediction for the current block.
  • a new Merged Histogram of Gradients (MHoG) is computed for the current block based on the histograms of neighboring blocks.
  • HoG Merged Histogram of Gradients
  • histogram amplitudes for a block encoded with DIMD or DIMD merge need to be stored so that DIMD merge can use them if selected for a block later in the frame.
  • a method comprises decoding encoded samples of blocks of video sample data; determining at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; performing, for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; adjusting the decoder-side intra mode derivation parameters into a reduced precision; storing the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and forming an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction modes based on the stored adjusted decoder-side intra mode derivation parameters.
  • An apparatus comprises means for decoding encoded samples of blocks of video sample data; means for determining at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; means for performing, for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; means for adjusting the decoder-side intra mode derivation parameters into a reduced precision; means for storing the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and means for forming an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction modes based on the stored adjusted decoder-side intra mode derivation parameters.
  • the apparatus comprises means for applying an inverse adjustment process as a part of the merged decoder-side intra mode derivation process.
  • the apparatus comprises means for determining the inverse adjustment process based on a scaling factor used to scale decoder-side intra mode derivation parameters for at least one block.
  • the apparatus comprises means for storing a number of decoder-side intra mode derivation parameters for at least one coding unit.
  • the stored decoder-side intra mode derivation parameters comprise one or more of the following: a histogram of amplitudes, where one amplitude is determined and stored for each intra direction mode; a reduced set of determined modes formed of a subset of all possible intra direction modes; a reduced set of amplitudes, where each amplitude in the set corresponds to an amplitude determined during the DIMD process for a given intra direction mode; a set of weights, where each weight corresponds to the blending weight determined during the DIMD process for a given intra direction mode; the scaling factor.
  • the apparatus comprises means for storing the scaling factor using a greater number of bits than the other decoder-side intra mode derivation parameters.
  • the apparatus comprises means for scaling amplitude values into a predetermined range of values representable with a given number of bits.
  • the apparatus comprises means for normalizing the amplitude values.
  • the apparatus comprises means for clipping amplitude values into a predetermined range of values after the scaling and/or normalization. [0018] According to an embodiment, the apparatus comprises means for scaling values of the weights.
  • the scaling factor depends on the size of the second block of video sample data.
  • an apparatus comprising: at least one processor and at least one memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least: decode encoded samples of blocks of video sample data; determine at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; perform, for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; adjust the decoder-side intra mode derivation parameters into a reduced precision; store the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and form an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction
  • Figure 1 shows schematically an electronic device employing embodiments of the invention
  • Figure 2 shows schematically a user equipment suitable for employing embodiments of the invention
  • Figure 3 further shows schematically electronic devices employing embodiments of the invention connected using wireless and wired network connections;
  • Figures 4a and 4b show schematically an encoder and a decoder suitable for implementing embodiments of the invention;
  • Figure 5 shows a flow chart of a decoding method according to an embodiment
  • Figure 6 shows a schematic diagram of an example multimedia communication system within which various embodiments may be implemented.
  • Figure 1 shows a block diagram of a video coding system according to an example embodiment as a schematic block diagram of an exemplary apparatus or electronic device 50, which may incorporate a codec according to an embodiment of the invention.
  • Figure 2 shows a layout of an apparatus according to an example embodiment. The elements of Figs. 1 and 2 will be explained next.
  • the electronic device 50 may for example be a mobile terminal or user equipment of a wireless communication system. However, it would be appreciated that embodiments of the invention may be implemented within any electronic device or apparatus which may require encoding and decoding or encoding or decoding video images.
  • the apparatus 50 may comprise a housing 30 for incorporating and protecting the device.
  • the apparatus 50 further may comprise a display 32 in the form of a liquid crystal display.
  • the display may be any suitable display technology suitable to display an image or video.
  • the apparatus 50 may further comprise a keypad 34.
  • any suitable data or user interface mechanism may be employed.
  • the user interface may be implemented as a virtual keyboard or data entry system as part of a touch-sensitive display.
  • the apparatus may comprise a microphone 36 or any suitable audio input which may be a digital or analogue signal input.
  • the apparatus 50 may further comprise an audio output device which in embodiments of the invention may be any one of: an earpiece 38, speaker, or an analogue audio or digital audio output connection.
  • the apparatus 50 may also comprise a battery (or in other embodiments of the invention the device may be powered by any suitable mobile energy device such as solar cell, fuel cell or clockwork generator).
  • the apparatus may further comprise a camera capable of recording or capturing images and/or video.
  • the apparatus 50 may further comprise an infrared port for short range line of sight communication to other devices. In other embodiments the apparatus 50 may further comprise any suitable short range communication solution such as for example a Bluetooth wireless connection or a USB/firewire wired connection.
  • the apparatus 50 may comprise a controller 56, processor or processor circuitry for controlling the apparatus 50.
  • the controller 56 may be connected to memory 58 which in embodiments of the invention may store both data in the form of image and audio data and/or may also store instructions for implementation on the controller 56.
  • the controller 56 may further be connected to codec circuitry 54 suitable for carrying out coding and decoding of audio and/or video data or assisting in coding and decoding carried out by the controller.
  • the apparatus 50 may further comprise a card reader 48 and a smart card 46, for example a UICC and UICC reader for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.
  • a card reader 48 and a smart card 46 for example a UICC and UICC reader for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.
  • the apparatus 50 may comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example for communication with a cellular communications network, a wireless communications system or a wireless local area network.
  • the apparatus 50 may further comprise an antenna 44 connected to the radio interface circuitry 52 for transmitting radio frequency signals generated at the radio interface circuitry 52 to other apparatus(es) and for receiving radio frequency signals from other apparatus(es).
  • the apparatus 50 may comprise a camera capable of recording or detecting individual frames which are then passed to the codec 54 or the controller for processing.
  • the apparatus may receive the video image data for processing from another device prior to transmission and/or storage.
  • the apparatus 50 may also receive either wirelessly or by a wired connection the image for coding/decoding.
  • the structural elements of apparatus 50 described above represent examples of means for performing a corresponding function.
  • the system 10 comprises multiple communication devices which can communicate through one or more networks.
  • the system 10 may comprise any combination of wired or wireless networks including, but not limited to a wireless cellular telephone network (such as a GSM, UMTS, CDMA network etc.), a wireless local area network (WLAN) such as defined by any of the IEEE 802.x standards, a Bluetooth personal area network, an Ethernet local area network, a token ring local area network, a wide area network, and the Internet.
  • a wireless cellular telephone network such as a GSM, UMTS, CDMA network etc.
  • WLAN wireless local area network
  • the system 10 may include both wired and wireless communication devices and/or apparatus 50 suitable for implementing embodiments of the invention.
  • the system shown in Figure 3 shows a mobile telephone network 11 and a representation of the internet 28.
  • Connectivity to the internet 28 may include, but is not limited to, long range wireless connections, short range wireless connections, and various wired connections including, but not limited to, telephone lines, cable lines, power lines, and similar communication pathways.
  • the example communication devices shown in the system 10 may include, but are not limited to, an electronic device or apparatus 50, a combination of a personal digital assistant (PDA) and a mobile telephone 14, a PDA 16, an integrated messaging device (IMD) 18, a desktop computer 20, a notebook computer 22.
  • PDA personal digital assistant
  • IMD integrated messaging device
  • the apparatus 50 may be stationary or mobile when carried by an individual who is moving.
  • the apparatus 50 may also be located in a mode of transport including, but not limited to, a car, a truck, a taxi, a bus, a train, a boat, an airplane, a bicycle, a motorcycle or any similar suitable mode of transport.
  • the embodiments may also be implemented in a set-top box; i.e. a digital TV receiver, which may/may not have a display or wireless capabilities, in tablets or (laptop) personal computers (PC), which have hardware or software or combination of the encoder/decoder implementations, in various operating systems, and in chipsets, processors, DSPs and/or embedded systems offering hardware/software based coding.
  • a set-top box i.e. a digital TV receiver, which may/may not have a display or wireless capabilities, in tablets or (laptop) personal computers (PC), which have hardware or software or combination of the encoder/decoder implementations, in various operating systems, and in chipsets, processors, DSPs and/or embedded systems offering hardware/software based coding.
  • Some or further apparatus may send and receive calls and messages and communicate with service providers through a wireless connection 25 to a base station 24.
  • the base station 24 may be connected to a network server 26 that allows communication between the mobile telephone network 11 and the internet 28.
  • the system may include additional communication devices and communication devices of various types.
  • the communication devices may communicate using various transmission technologies including, but not limited to, code division multiple access (CDMA), global systems for mobile communications (GSM), universal mobile telecommunications system (UMTS), time divisional multiple access (TDMA), frequency division multiple access (FDMA), transmission control protocol-internet protocol (TCP-IP), short messaging service (SMS), multimedia messaging service (MMS), email, instant messaging service (IMS), Bluetooth, IEEE 802.11 and any similar wireless communication technology.
  • CDMA code division multiple access
  • GSM global systems for mobile communications
  • UMTS universal mobile telecommunications system
  • TDMA time divisional multiple access
  • FDMA frequency division multiple access
  • TCP-IP transmission control protocol-internet protocol
  • SMS short messaging service
  • MMS multimedia messaging service
  • email instant messaging service
  • Bluetooth IEEE 802.11 and any similar wireless communication technology.
  • a communications device involved in implementing various embodiments of the present invention may communicate using various media including, but not limited to, radio, infrared, laser, cable connections, and any suitable connection.
  • a channel may refer either to a physical channel or to a logical channel.
  • a physical channel may refer to a physical transmission medium such as a wire
  • a logical channel may refer to a logical connection over a multiplexed medium, capable of conveying several logical channels.
  • a channel may be used for conveying an information signal, for example a bitstream, from one or several senders (or transmitters) to one or several receivers.
  • An MPEG-2 transport stream (TS), specified in ISO/LEC 13818-1 or equivalently in ITU-T Recommendation H.222.0, is a format for carrying audio, video, and other media as well as program metadata or other metadata, in a multiplexed stream.
  • a packet identifier (PID) is used to identify an elementary stream (a.k.a. packetized elementary stream) within the TS.
  • PID packet identifier
  • a logical channel within an MPEG-2 TS may be considered to correspond to a specific PID value.
  • Available media file format standards include ISO base media file format (ISO/IEC 14496-12, which may be abbreviated ISOBMFF) and file format for NAL unit structured video (ISO/IEC 14496-15), which derives from the ISOBMFF.
  • ISOBMFF ISO base media file format
  • ISO/IEC 14496-15 file format for NAL unit structured video
  • Video codec consists of an encoder that transforms the input video into a compressed representation suited for storage/transmission and a decoder that can uncompress the compressed video representation back into a viewable form.
  • a video encoder and/or a video decoder may also be separate from each other, i.e. need not form a codec.
  • encoder discards some information in the original video sequence in order to represent the video in a more compact form (that is, at lower bitrate).
  • Typical hybrid video encoders for example many encoder implementations of ITU-T H.263 and H.264, encode the video information in two phases. Firstly pixel values in a certain picture area (or “block”) are predicted for example by motion compensation means (finding and indicating an area in one of the previously coded video frames that corresponds closely to the block being coded) or by spatial means (using the pixel values around the block to be coded in a specified manner). Secondly the prediction error, i.e. the difference between the predicted block of pixels and the original block of pixels, is coded. This is typically done by transforming the difference in pixel values using a specified transform (e.g.
  • DCT Discrete Cosine Transform
  • inter prediction In temporal prediction, the sources of prediction are previously decoded pictures (a.k.a. reference pictures).
  • IBC intra block copy
  • inter-block-copy prediction prediction is applied similarly to temporal prediction but the reference picture is the current picture and only previously decoded samples can be referred in the prediction process.
  • Interlayer or inter-view prediction may be applied similarly to temporal prediction, but the reference picture is a decoded picture from another scalable layer or from another view, respectively.
  • inter prediction may refer to temporal prediction only, while in other cases inter prediction may refer collectively to temporal prediction and any of intra block copy, inter-layer prediction, and inter-view prediction provided that they are performed with the same or similar process than temporal prediction.
  • Inter prediction or temporal prediction may sometimes be referred to as motion compensation or motion-compensated prediction.
  • Motion compensation can be performed either with full sample or sub-sample accuracy.
  • motion can be represented as a motion vector with integer values for horizontal and vertical displacement and the motion compensation process effectively copies samples from the reference picture using those displacements.
  • motion vectors are represented by fractional or decimal values for the horizontal and vertical components of the motion vector.
  • a sub-sample interpolation process is typically invoked to calculate predicted sample values based on the reference samples and the selected sub-sample position.
  • the sub-sample interpolation process typically consists of horizontal filtering compensating for horizontal offsets with respect to full sample positions followed by vertical filtering compensating for vertical offsets with respect to full sample positions.
  • the vertical processing can be also be done before horizontal processing in some environments.
  • Inter prediction which may also be referred to as temporal prediction, motion compensation, or motion-compensated prediction, reduces temporal redundancy.
  • inter prediction the sources of prediction are previously decoded pictures.
  • Intra prediction utilizes the fact that adjacent pixels within the same picture are likely to be correlated.
  • Intra prediction can be performed in spatial or transform domain, i.e., either sample values or transform coefficients can be predicted. Intra prediction is typically exploited in intra coding, where no inter prediction is applied.
  • One outcome of the coding procedure is a set of coding parameters, such as motion vectors and quantized transform coefficients. Many parameters can be entropy-coded more efficiently if they are predicted first from spatially or temporally neighboring parameters. For example, a motion vector may be predicted from spatially adjacent motion vectors and only the difference relative to the motion vector predictor may be coded. Prediction of coding parameters and intra prediction may be collectively referred to as in-picture prediction.
  • FIGs. 4a and 4b show an encoder and a decoder suitable for employing embodiments of the invention.
  • a video codec consists of an encoder that transforms an input video into a compressed representation suited for storage/transmission and a decoder that can decompress the compressed video representation back into a viewable form.
  • the encoder discards and/or loses some information in the original video sequence in order to represent the video in a more compact form (that is, at lower bitrate).
  • An example of an encoding process is illustrated in Figure 4a.
  • Figure 4a illustrates an image to be encoded (I n ); a predicted representation of an image block (P' n ); a prediction error signal (D n ); a reconstructed prediction error signal (D' n ); a preliminary reconstructed image (I' n ); a final reconstructed image (R' n ); a transform (T) and inverse transform (T -1 ); a quantization (Q) and inverse quantization (Q 1 ); entropy encoding (E); a reference frame memory (RFM); inter prediction (Pinter); intra prediction (Pintra); mode selection (MS) and filtering (F).
  • Figure 4b illustrates a predicted representation of an image block (P' n ); a reconstructed prediction error signal (D' n ); a preliminary reconstructed image (I' n ); a final reconstructed image (R' n ); an inverse transform (T‘ 1 ); an inverse quantization (Q 1 ); an entropy decoding (E ); a reference frame memory (RFM); a prediction (either inter or intra) (P); and filtering (F).
  • pixel values in a certain picture area are predicted for example by motion compensation means (finding and indicating an area in one of the previously coded video frames that corresponds closely to the block being coded) or by spatial means (using the pixel values around the block to be coded in a specified manner).
  • the prediction error i.e. the difference between the predicted block of pixels and the original block of pixels. This is typically done by transforming the difference in pixel values using a specified transform (e.g. Discrete Cosine Transform (DCT) or a variant of it), quantizing the coefficients and entropy coding the quantized coefficients.
  • DCT Discrete Cosine Transform
  • Video codecs may also provide a transform skip mode, which the encoders may choose to use.
  • the prediction error is coded in a sample domain, for example by deriving a sample-wise difference value relative to certain adjacent samples and coding the sample-wise difference value with an entropy coder.
  • the phrase along the bitstream may be defined to refer to out-of-band transmission, signalling, or storage in a manner that the out-of-band data is associated with the bitstream.
  • the phrase decoding along the bitstream or alike may refer to decoding the referred out-of-band data (which may be obtained from out-of-band transmission, signalling, or storage) that is associated with the bitstream.
  • an indication along the bitstream may refer to metadata in a container file that encapsulates the bitstream.
  • the H.264/AVC standard was developed by the Joint Video Team (JVT) of the Video Coding Experts Group (VCEG) of the Telecommunications Standardization Sector of International Telecommunication Union (ITU-T) and the Moving Picture Experts Group (MPEG) of International Organisation for Standardization (ISO) / International Electrotechnical Commission (IEC).
  • JVT Joint Video Team
  • VCEG Video Coding Experts Group
  • MPEG Moving Picture Experts Group
  • ISO International Organization for Standardization
  • ISO International Electrotechnical Commission
  • the H.264/AVC standard is published by both parent standardization organizations, and it is referred to as ITU-T Recommendation H.264 and ISO/IEC International Standard 14496-10, also known as MPEG-4 Part 10 Advanced Video Coding (AVC).
  • AVC MPEG-4 Part 10 Advanced Video Coding
  • H.265/HEVC a.k.a. HEVC High Efficiency Video Coding
  • JCT-VC Joint Collaborative Team - Video Coding
  • the standard was published by both parent standardization organizations, and it is referred to as ITU-T Recommendation H.265 and ISO/IEC International Standard 23008-2, also known as MPEG-H Part 2 High Efficiency Video Coding (HEVC).
  • HEVC High Efficiency Video Coding
  • VVC Versatile Video Coding
  • MPEG Moving Picture Experts Group
  • VCEG Video Coding Experts Group
  • ITU International Telecommunication Union
  • bitstream and coding structures, and concepts of H.264/ AVC and HEVC are described in this section for providing background for a video encoder, decoder, encoding method, decoding method, and a bitstream structure, wherein the embodiments may be implemented.
  • Some of the key definitions, bitstream and coding structures, and concepts of H.264/ AVC are the same as in HEVC - hence, they are described below jointly.
  • bitstream syntax and semantics as well as the decoding process for error-free bitstreams are specified in H.264/ AVC and HEVC.
  • the encoding process is not specified, but encoders must generate conforming bitstreams.
  • Bitstream and decoder conformance can be verified with the Hypothetical Reference Decoder (HRD).
  • HRD Hypothetical Reference Decoder
  • the standards contain coding tools that help in coping with transmission errors and losses, but the use of the tools in encoding is optional and no decoding process has been specified for erroneous bitstreams.
  • the elementary unit for the input to an H.264/AVC or HEVC encoder and the output of an H.264/AVC or HEVC decoder, respectively, is a picture.
  • a picture given as an input to an encoder may also be referred to as a source picture, and a picture decoded by a decoded may be referred to as a decoded picture.
  • the source and decoded pictures are each comprised of one or more sample arrays, such as one of the following sets of sample arrays:
  • Luma and two chroma (YCbCr or YCgCo).
  • RGB Green, Blue and Red
  • Arrays representing other unspecified monochrome or tri-stimulus color samplings for example, YZX, also known as XYZ).
  • a picture may either be a frame or a field.
  • a frame comprises a matrix of luma samples and possibly the corresponding chroma samples.
  • a field is a set of alternate sample rows of a frame and may be used as encoder input, when the source signal is interlaced.
  • Chroma sample arrays may be absent (and hence monochrome sampling may be in use) or chroma sample arrays may be subsampled when compared to luma sample arrays.
  • Chroma formats may be summarized as follows:
  • each of the two chroma arrays has half the height and half the width of the luma array.
  • each of the two chroma arrays has the same height and half the width of the luma array.
  • each of the two chroma arrays has the same height and width as the luma array.
  • a partitioning may be defined as a division of a set into subsets such that each element of the set is in exactly one of the subsets.
  • a coding block may be defined as an NxN block of samples for some value of N such that the division of a coding tree block into coding blocks is a partitioning.
  • a coding tree block may be defined as an NxN block of samples for some value of N such that the division of a component into coding tree blocks is a partitioning.
  • a coding tree unit may be defined as a coding tree block of luma samples, two corresponding coding tree blocks of chroma samples of a picture that has three sample arrays, or a coding tree block of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples.
  • a coding unit may be defined as a coding block of luma samples, two corresponding coding blocks of chroma samples of a picture that has three sample arrays, or a coding block of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples.
  • a CU with the maximum allowed size may be named as LCU (largest coding unit) or coding tree unit (CTU) and the video picture is divided into non-overlapping LCUs.
  • a CU consists of one or more prediction units (PU) defining the prediction process for the samples within the CU and one or more transform units (TU) defining the prediction error coding process for the samples in the said CU.
  • PU prediction units
  • TU transform units
  • a CU consists of a square block of samples with a size selectable from a predefined set of possible CU sizes.
  • Each PU and TU can be further split into smaller PUs and TUs in order to increase granularity of the prediction and prediction error coding processes, respectively.
  • Each PU has prediction information associated with it defining what kind of a prediction is to be applied for the pixels within that PU (e.g. motion vector information for inter predicted PUs and intra prediction directionality information for intra predicted PUs).
  • Each TU can be associated with information describing the prediction error decoding process for the samples within the said TU (including e.g. DCT coefficient information). It is typically signalled at CU level whether prediction error coding is applied or not for each CU. In the case there is no prediction error residual associated with the CU, it can be considered there are no TUs for the said CU.
  • the division of the image into CUs, and division of CUs into PUs and TUs is typically signalled in the bitstream allowing the decoder to reproduce the intended structure of these units.
  • a picture can be partitioned in tiles, which are rectangular and contain an integer number of LCUs.
  • the partitioning to tiles forms a regular grid, where heights and widths of tiles differ from each other by one LCU at the maximum.
  • a slice is defined to be an integer number of coding tree units contained in one independent slice segment and all subsequent dependent slice segments (if any) that precede the next independent slice segment (if any) within the same access unit.
  • a slice segment is defined to be an integer number of coding tree units ordered consecutively in the tile scan and contained in a single NAL unit. The division of each picture into slice segments is a partitioning.
  • an independent slice segment is defined to be a slice segment for which the values of the syntax elements of the slice segment header are not inferred from the values for a preceding slice segment
  • a dependent slice segment is defined to be a slice segment for which the values of some syntax elements of the slice segment header are inferred from the values for the preceding independent slice segment in decoding order.
  • a slice header is defined to be the slice segment header of the independent slice segment that is a current slice segment or is the independent slice segment that precedes a current dependent slice segment
  • a slice segment header is defined to be a part of a coded slice segment containing the data elements pertaining to the first or all coding tree units represented in the slice segment.
  • the CUs are scanned in the raster scan order of LCUs within tiles or within a picture, if tiles are not in use. Within an LCU, the CUs have a specific scan order.
  • the decoder reconstructs the output video by applying prediction means similar to the encoder to form a predicted representation of the pixel blocks (using the motion or spatial information created by the encoder and stored in the compressed representation) and prediction error decoding (inverse operation of the prediction error coding recovering the quantized prediction error signal in spatial pixel domain). After applying prediction and prediction error decoding means the decoder sums up the prediction and prediction error signals (pixel values) to form the output video frame.
  • the decoder (and encoder) can also apply additional filtering means to improve the quality of the output video before passing it for display and/or storing it as prediction reference for the forthcoming frames in the video sequence.
  • the filtering may for example include one more of the following: deblocking, sample adaptive offset (SAO), and/or adaptive loop filtering (ALF).
  • deblocking sample adaptive offset (SAO)
  • ALF adaptive loop filtering
  • H.264/AVC includes a deblocking
  • HEVC includes both deblocking and SAO.
  • the motion information is indicated with motion vectors associated with each motion compensated image block, such as a prediction unit.
  • Each of these motion vectors represents the displacement of the image block in the picture to be coded (in the encoder side) or decoded (in the decoder side) and the prediction source block in one of the previously coded or decoded pictures.
  • those are typically coded differentially with respect to block specific predicted motion vectors.
  • the predicted motion vectors are created in a predefined way, for example calculating the median of the encoded or decoded motion vectors of the adjacent blocks.
  • Another way to create motion vector predictions is to generate a list of candidate predictions from adjacent blocks and/or co-located blocks in temporal reference pictures and signalling the chosen candidate as the motion vector predictor.
  • this prediction information may be represented for example by a reference index of previously coded/ decoded picture.
  • the reference index is typically predicted from adjacent blocks and/or co-located blocks in temporal reference picture.
  • typical high efficiency video codecs employ an additional motion information coding/decoding mechanism, often called merging/merge mode, where all the motion field information, which includes motion vector and corresponding reference picture index for each available reference picture list, is predicted and used without any modification/correction.
  • predicting the motion field information is carried out using the motion field information of adjacent blocks and/or co-located blocks in temporal reference pictures and the used motion field information is signalled among a list of motion field candidate list filled with motion field information of available adjacent/co-located blocks.
  • Video coding standards and specifications may allow encoders to divide a coded picture to coded slices or alike. In-picture prediction is typically disabled across slice boundaries. Thus, slices can be regarded as a way to split a coded picture to independently decodable pieces. In H.264/AVC and HEVC, in-picture prediction may be disabled across slice boundaries.
  • slices can be regarded as a way to split a coded picture into independently decodable pieces, and slices are therefore often regarded as elementary units for transmission.
  • encoders may indicate in the bitstream which types of in-picture prediction are turned off across slice boundaries, and the decoder operation takes this information into account for example when concluding which prediction sources are available. For example, samples from a neighboring CU may be regarded as unavailable for intra prediction, if the neighboring CU resides in a different slice.
  • NAL Network Abstraction Layer
  • H.264/AVC and HEVC For transport over packet-oriented networks or storage into structured files, NAL units may be encapsulated into packets or similar structures.
  • a bytestream format has been specified in H.264/AVC and HEVC for transmission or storage environments that do not provide framing structures. The bytestream format separates NAL units from each other by attaching a start code in front of each NAL unit.
  • a NAL unit may be defined as a syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of an RBSP interspersed as necessary with emulation prevention bytes.
  • a raw byte sequence payload (RBSP) may be defined as a syntax structure containing an integer number of bytes that is encapsulated in a NAL unit.
  • An RBSP is either empty or has the form of a string of data bits containing syntax elements followed by an RBSP stop bit and followed by zero or more subsequent bits equal to 0.
  • NAL units consist of a header and pay load.
  • the NAL unit header indicates the type of the NAL unit [0079]
  • HEVC a two-byte NAL unit header is used for all specified NAL unit types.
  • the NAL unit header contains one reserved bit, a six-bit NAL unit type indication, a three-bit nuh_temporal_id_plusl indication for temporal level (may be required to be greater than or equal to 1) and a six-bit nuh layer id syntax element.
  • TID may be used to interchangeably with the Temporalld variable.
  • Temporalld 0 corresponds to the lowest temporal level.
  • the value of temporal_id_plusl is required to be non-zero in order to avoid start code emulation involving the two NAL unit header bytes.
  • the bitstream created by excluding all VCL NAL units having a Temporalld greater than or equal to a selected value and including all other VCL NAL units remains conforming.
  • a sub-layer or a temporal sub-layer may be defined to be a temporal scalable layer (or a temporal layer, TL) of a temporal scalable bitstream, consisting of VCL NAL units with a particular value of the Temporalld variable and the associated non-VCL NAL units, nuh layer id can be understood as a scalability layer identifier.
  • NAL units can be categorized into Video Coding Layer (VCL) NAL units and non- VCL NAL units.
  • VCL NAL units are typically coded slice NAL units.
  • VCL NAL units contain syntax elements representing one or more CU.
  • a non-VCL NAL unit may be for example one of the following types: a sequence parameter set, a picture parameter set, a supplemental enhancement information (SEI) NAL unit, an access unit delimiter, an end of sequence NAL unit, an end of bitstream NAL unit, or a filler data NAL unit.
  • SEI Supplemental Enhancement Information
  • Parameter sets may be needed for the reconstruction of decoded pictures, whereas many of the other non-VCL NAL units are not necessary for the reconstruction of decoded sample values.
  • Parameters that remain unchanged through a coded video sequence may be included in a sequence parameter set.
  • the sequence parameter set may optionally contain video usability information (VUI), which includes parameters that may be important for buffering, picture output timing, rendering, and resource reservation.
  • VUI video usability information
  • a sequence parameter set RBSP includes parameters that can be referred to by one or more picture parameter set RBSPs or one or more SEI NAL units containing a buffering period SEI message.
  • a picture parameter set contains such parameters that are likely to be unchanged in several coded pictures.
  • a picture parameter set RBSP may include parameters that can be referred to by the coded slice NAL units of one or more coded pictures.
  • a video parameter set may be defined as a syntax structure containing syntax elements that apply to zero or more entire coded video sequences as determined by the content of a syntax element found in the SPS referred to by a syntax element found in the PPS referred to by a syntax element found in each slice segment header.
  • a video parameter set RBSP may include parameters that can be referred to by one or more sequence parameter set RBSPs.
  • VPS resides one level above SPS in the parameter set hierarchy and in the context of scalability and/or 3D video.
  • VPS may include parameters that are common for all slices across all (scalability or view) layers in the entire coded video sequence.
  • SPS includes the parameters that are common for all slices in a particular (scalability or view) layer in the entire coded video sequence, and may be shared by multiple (scalability or view) layers.
  • PPS includes the parameters that are common for all slices in a particular layer representation (the representation of one scalability or view layer in one access unit) and are likely to be shared by all slices in multiple layer representations.
  • VPS may provide information about the dependency relationships of the layers in a bitstream, as well as many other information that are applicable to all slices across all (scalability or view) layers in the entire coded video sequence.
  • VPS may be considered to comprise two parts, the base VPS and a VPS extension, where the VPS extension may be optionally present.
  • Out-of-band transmission, signaling or storage can additionally or alternatively be used for other purposes than tolerance against transmission errors, such as ease of access or session negotiation.
  • a sample entry of a track in a file conforming to the ISO Base Media File Format may comprise parameter sets, while the coded data in the bitstream is stored elsewhere in the file or in another file.
  • the phrase along the bitstream (e.g.
  • indicating along the bitstream or along a coded unit of a bitstream (e.g. indicating along a coded tile) may be used in claims and described embodiments to refer to out-of-band transmission, signaling, or storage in a manner that the out-of-band data is associated with the bitstream or the coded unit, respectively.
  • decoding along the bitstream or along a coded unit of a bitstream or alike may refer to decoding the referred out-of-band data (which may be obtained from out-of-band transmission, signaling, or storage) that is associated with the bitstream or the coded unit, respectively.
  • a SEI NAL unit may contain one or more SEI messages, which are not required for the decoding of output pictures but may assist in related processes, such as picture output timing, rendering, error detection, error concealment, and resource reservation.
  • a coded picture is a coded representation of a picture.
  • a coded picture may be defined as a coded representation of a picture containing all coding tree units of the picture.
  • an access unit (AU) may be defined as a set of NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain at most one picture with any specific value of nuh layer id.
  • an access unit may also contain non-VCL NAL units. Said specified classification rule may for example associate pictures with the same output time or picture output count value into the same access unit.
  • a bitstream may be defined as a sequence of bits, in the form of a NAL unit stream or a byte stream, that forms the representation of coded pictures and associated data forming one or more coded video sequences.
  • a first bitstream may be followed by a second bitstream in the same logical channel, such as in the same file or in the same connection of a communication protocol.
  • An elementary stream (in the context of video coding) may be defined as a sequence of one or more bitstreams.
  • the end of the first bitstream may be indicated by a specific NAL unit, which may be referred to as the end of bitstream (EOB) NAL unit and which is the last NAL unit of the bitstream.
  • EOB NAL unit is required to have nuh layer id equal to 0.
  • a coded video sequence is defined to be a sequence of consecutive access units in decoding order from an IDR access unit, inclusive, to the next IDR access unit, exclusive, or to the end of the bitstream, whichever appears earlier.
  • a coded video sequence may be defined, for example, as a sequence of access units that consists, in decoding order, of an IRAP access unit with NoRaslOutputFlag equal to 1, followed by zero or more access units that are not IRAP access units with NoRaslOutputFlag equal to 1, including all subsequent access units up to but not including any subsequent access unit that is an IRAP access unit with NoRaslOutputFlag equal to 1.
  • An IRAP access unit may be defined as an access unit in which the base layer picture is an IRAP picture.
  • NoRaslOutputFlag is equal to 1 for each IDR picture, each BLA picture, and each IRAP picture that is the first picture in that particular layer in the bitstream in decoding order, is the first IRAP picture that follows an end of sequence NAL unit having the same value of nuh layer id in decoding order.
  • HandleCraAsBlaFlag may be set to 1 for example by a player that seeks to a new position in a bitstream or tunes into a broadcast and starts decoding and then starts decoding from a CRA picture.
  • HandleCraAsBlaFlag is equal to 1 for a CRA picture, the CRA picture is handled and decoded as if it were a BLA picture.
  • a coded video sequence may additionally or alternatively (to the specification above) be specified to end, when a specific NAL unit, which may be referred to as an end of sequence (EOS) NAL unit, appears in the bitstream and has nuh layer id equal to 0.
  • EOS end of sequence
  • a group of pictures (GOP) and its characteristics may be defined as follows.
  • a GOP can be decoded regardless of whether any previous pictures were decoded.
  • An open GOP is such a group of pictures in which pictures preceding the initial intra picture in output order might not be correctly decodable when the decoding starts from the initial intra picture of the open GOP.
  • pictures of an open GOP may refer (in inter prediction) to pictures belonging to a previous GOP.
  • An HEVC decoder can recognize an intra picture starting an open GOP, because a specific NAL unit type, CRA NAL unit type, may be used for its coded slices.
  • a closed GOP is such a group of pictures in which all pictures can be correctly decoded when the decoding starts from the initial intra picture of the closed GOP. In other words, no picture in a closed GOP refers to any pictures in previous GOPs.
  • a closed GOP may start from an IDR picture.
  • a closed GOP may also start from a BLA W RADL or a BLA N LP picture.
  • An open GOP coding structure is potentially more efficient in the compression compared to a closed GOP coding structure, due to a larger flexibility in selection of reference pictures.
  • a Decoded Picture Buffer may be used in the encoder and/or in the decoder. There are two reasons to buffer decoded pictures, for references in inter prediction and for reordering decoded pictures into output order. As H.264/AVC and HEVC provide a great deal of flexibility for both reference picture marking and output reordering, separate buffers for reference picture buffering and output picture buffering may waste memory resources. Hence, the DPB may include a unified decoded picture buffering process for reference pictures and output reordering. A decoded picture may be removed from the DPB when it is no longer used as a reference and is not needed for output.
  • the reference picture for inter prediction is indicated with an index to a reference picture list.
  • the index may be coded with variable length coding, which usually causes a smaller index to have a shorter value for the corresponding syntax element.
  • two reference picture lists (reference picture list 0 and reference picture list 1) are generated for each bi-predictive (B) slice, and one reference picture list (reference picture list 0) is formed for each inter-coded (P) slice.
  • a reference picture index may be coded by an encoder into the bitstream is some inter coding modes or it may be derived (by an encoder and a decoder) for example using neighboring blocks in some other inter coding modes.
  • HEVC comprises 35 intra prediction modes, including a DC, a planar, and 33 angular (directional) prediction modes.
  • the DC and the planar mode are targeted at flat areas (i.e., the DC mode representing a block whose pixel values are constant across the block) or areas with few structure (i.e., the planar mode representing a block with pixel values gradually changing with a small planar gradient).
  • the angular modes provide directional prediction in a very granular way.
  • Motion parameter types or motion information may include but are not limited to one or more of the following types: an indication of a prediction type (e.g. intra prediction, uni-prediction, bi-prediction) and/or a number of reference pictures; an indication of a prediction direction, such as inter (a.k.a.
  • interlayer prediction inter- view prediction
  • view synthesis prediction VSP
  • intercomponent prediction which may be indicated per reference picture and/or per prediction type and where in some embodiments inter-view and view-synthesis prediction may be jointly considered as one prediction direction
  • an indication of a reference picture type such as a short-term reference picture and/or a long-term reference picture and/or an inter-layer reference picture (which may be indicated e.g. per reference picture) a reference index to a reference picture list and/or any other identifier of a reference picture (which may be indicated e.g.
  • a horizontal motion vector component (which may be indicated e.g. per prediction block or per reference index or alike); a vertical motion vector component (which may be indicated e.g. per prediction block or per reference index or alike); one or more parameters, such as picture order count difference and/or a relative camera separation between the picture containing or associated with the motion parameters and its reference picture, which may be used for scaling of the horizontal motion vector component and/or the vertical motion vector component in one or more motion vector prediction processes (where said one or more parameters may be indicated e.g.
  • coordinates of a block to which the motion parameters and/or motion information applies e.g. coordinates of the top-left sample of the block in luma sample units; extents (e.g. a width and a height) of a block to which the motion parameters and/or motion information applies.
  • MMVD Merge with MVD
  • DIMD Decoder-side intra mode derivation
  • the intra mode of the current block is determined using directionality of the texture of the neighboring reconstructed samples located in a template region at top, top-left, and left sides of the current block.
  • two (or more) intra modes and their corresponding weight factors are derived first.
  • predictors are generated for the intra modes, and also for the Planar mode.
  • the final prediction for the current block is generated by combining these predictors by means of sample-wise or uniform weighting, using the derived weights.
  • DIMD directionality of texture is derived for each neighboring sample in the template region, using 3x3 neighboring samples of that sample.
  • the derivation is performed in several steps.
  • the horizontal and vertical direction strengths (Dx and Dy) are calculated using 3x3 neighboring samples of the training sample.
  • the corresponding region on the Intra prediction mode (angle) is determined using sign of Dx and Dy.
  • the ratio of Dx/Dy is calculated, and the corresponding angle index is determined using the ratio value and a table that maps the ratio to proper angle index.
  • the final intra mode for said training sample is determined using the region and derived angle.
  • the amplitude (or importance) of the intra mode is derived as the sum of absolute values of Dx and Dy.
  • the intra mode (corresponding to a given directionality) and its corresponding amplitude are derived as above for each training sample. These are then collected into a histogram of gradients, namely a histogram collecting for each intra mode the cumulative amplitude of all neighboring samples with the directionality. Finally, two or more intra modes are derived from the histogram of gradients, by finding the dominant intra modes, i.e. the modes corresponding to the highest amplitudes in the histogram. These modes are used to compute different predictors. Finally, these predictors are blended together to compute the final DIMD prediction for the current block. The blending may be performed using weighted average.
  • the weights of each DIMD intra mode are determined based on the histogram amplitudes, where higher amplitudes may correspond to higher weights.
  • a fixed weight is typically assigned to the planar mode, which is blended together with the determined intra modes to form the final DIMD prediction.
  • the DIMD information from the neighboring blocks can be used to generate a prediction for the current block, referred to as DIMD merge.
  • DIMD merge the DIMD information extracted from neighboring blocks is used to compute the intra prediction for the current block.
  • a new Merged Histogram of Gradients (MHoG) is computed for the current block based on the histograms of neighboring blocks. Neighboring blocks encoded with DIMD or with DIMD merge are considered.
  • neighboring blocks may also be considered.
  • neighboring blocks that are not encoded with DIMD or DIMD merge may be considered.
  • the computation of the Merged Histogram of Gradients may depend on the intra-prediction mode used to encode that neighboring block.
  • an intra-prediction directional mode can be considered, where such mode may be computed using template-based techniques.
  • an intra-prediction directional mode can be considered, where such mode may be computed using template-based techniques. Such mode also be computed, for example, by locating the block pointed by the block vector used in IBC and/or IntraTMP, and then extracting the intra-prediction mode of that block.
  • the computation of the Merged Histogram of Gradients may depend on the intraprediction mode used to select the transform for that block.
  • a combination of both DIMD, DIMD Merge and or other block candidates can be considered to compute the MHoG.
  • the MHoG is used to compute intra-prediction modes and weights, as in conventional DIMD.
  • the directional modes and their weights corresponding to the highest amplitudes in the MHoG are selected, and the corresponding predictors are blended as in conventional DIMD.
  • DIMD merge When using DIMD merge, a number of parameters need to be stored for a block encoded with DIMD or DIMD merge so that DIMD merge can use them for the computation of the MHoG, if selected for a block later in the frame. For example, the histogram amplitudes may be stored. However, this may cause additional memory overhead. This can be partially compensated by storing only a limited number of highest amplitudes, together with the corresponding intra-prediction modes. Nevertheless, even if the reduced number of amplitudes is stored in the full range precision, it may already represent a bottleneck for the codec implementation, especially for the hardware implementations of both the encoder and the decoder.
  • a method comprises decoding (500) encoded samples of blocks of video sample data; determining (502) at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; performing (504), for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; adjusting (506) the decoder-side intra mode derivation parameters into a reduced precision; storing (508) the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and forming (510) an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction modes based on the stored adjusted decoder-side intra mode derivation parameters
  • the method produces an intra-prediction for a given block using intra-prediction, where the prediction for the current (second) block is obtained by means of blending a number of predictors obtained with determined intra-prediction modes using determined weights, where the intra prediction modes and weights used to predict the current block are determined by using a Decoder side Intra Mode Derivation (DIMD) process applied to at least a first (neighboring) block and the information used to derive intra prediction modes and weights is stored in reduced precision.
  • DIMD Decoder side Intra Mode Derivation
  • said adjusting the decoder-side intra mode derivation parameters into a reduced precision comprises one or more of scaling, normalizing and/or clipping.
  • the amplitudes of DIMD or DIMD merge histograms are stored using reduced precision (e.g. 16 bits or less).
  • the reduced precision of the amplitudes can be achieved, for example, by means of scaling the amplitude values to fit into a range that can be represented with a given number of bits, normalizing the amplitude values and/or clipping the amplitude values into a given range.
  • the method comprises applying an inverse adjustment process as a part of the merged decoder-side intra mode derivation process.
  • the histogram amplitude from the neighboring block which has been adjusted, e.g. scaled and/or normalized before the storage, is re-adjusted with an inverse factor to restore to the original range of values prior to using it to generate the MHoG.
  • the method comprises determining the inverse adjustment process based on a scaling factor used to scale decoder-side intra mode derivation parameters for at least one block.
  • the method comprises storing a number of decoder-side intra mode derivation parameters for at least one coding unit (CU).
  • CU coding unit
  • DIMD merge requires a number of DIMD parameters to be stored in memory for certain Coding Units (CUs) during the decoding process, so that these can be fetched when computing the DIMD merge process by a CU that uses DIMD merge.
  • CUs Coding Units
  • the stored decoder-side intra mode derivation parameters comprise one or more of the following: a histogram of amplitudes, where one amplitude is determined and stored for each intra direction mode; a reduced set of determined modes formed of a subset of all possible intra direction modes; a reduced set of amplitudes, where each amplitude in the set corresponds to an amplitude determined during the DIMD process for a given intra direction mode; a set of weights, where each weight corresponds to the blending weight determined during the DIMD process for a given intra direction mode; the scaling factor.
  • the DIMD merge parameters may be stored for a given CU alongside the conventional DIMD parameters.
  • the DIMD merge parameters may be stored for a given CU that uses DIMD merge instead of the conventional DIMD parameters.
  • a single set of parameters is stored per CU, hence reducing the memory requirements for that CU.
  • Each amplitude may be determined during a DIMD process by means of accumulating individual sample amplitudes determined for each sample within the template formed of already reconstructed samples in the surrounding of the current block.
  • Each individual amplitude may be computed by means of applying a given filter to the template.
  • the magnitude of the final amplitude depends on both the individual sample magnitude as well as the number of samples in the template.
  • different parameters can also be stored for a block encoded with DIMD or DIMD merge so that DIMD merge can use them for the computation of the MHoG if selected for a block later in the frame.
  • the DIMD weights used during the blending process to compute the final DIMD prediction for the current block may be stored.
  • the method comprises scaling values of the weights.
  • the DIMD weights used during the blending process may be scaled.
  • the method comprises normalizing the amplitude values.
  • clipping is applied to the amplitude values, it may introduce loss as high amplitude values would be lost. For that reason, amplitudes can be normalized prior to clipping.
  • the normalization factor may be determined based on the number of reference samples within the DIMD template.
  • the size of the DIMD template may be approximated in various ways. For example, the size of the DIMD template can be approximated with the sum of the width and the height of the block. As another example, the size of the DIMD template can be approximated with the product of the width and the height of the block, i.e. the area of the block.
  • the number of reference sample positions within the DIMD template may also be approximated in various ways.
  • the number of reference sample positions can be approximated with the maximum of the width and the height of the block max(W, H), where W and H are the width and the height of the block, respectively.
  • the number of reference sample positions can be approximated with the minimum of the width and the height of the block min(W, H).
  • the number of reference sample positions can be approximated with the maximum of the width and the height of the block multiplied by a factor if the width and the height of the block are equal.
  • the number of reference sample positions can be approximated with the maximum of the width and the height of the block multiplied by a factor if the ratio of the larger and the smaller side of the block does not exceed a given value (e.g. 2 or more).
  • the method comprises storing the scaling factor using a greater number of bits than the other decoder-side intra mode derivation parameters.
  • the method comprises scaling amplitude values into a predetermined range of values representable with a given number of bits.
  • the histogram amplitudes may require additional scaling to fit into the range that can be represented with a given number of bits. As an example, if the histogram amplitudes are stored using 8 bits, the values can be in the range from 0 to 255. As another example, if the histogram amplitudes are stored using 6 bits, the values can be in the range from 0 to 63. In a further example, if normalizing or scaling with the powers of 2, the division can be replaced with the bit shifting operation.
  • the method comprises clipping amplitude values into a predetermined range of values.
  • a clipping operation i.e. a sequence of ceiling and flooring operations
  • the amplitude values can be clipped within a given range, so as to assume values that are representable with a limited number of bits.
  • an amplitude can be clipped to values between 0 and 65535 in order to be stored with no loss of information using an unsigned integer data type with 16 bits precision.
  • a value can be clipped into an interval [0, 2 N -1], where N is the number of bits used to store the final value.
  • a value can be clipped into an interval [1, 2 N -1], where N is the number of bits used to store the final value.
  • the amplitude values after normalization, scaling, and/or clipping can be stored separately or combined by means of bit masking operations and stored as a single value. As an example, if 5 or less histogram amplitudes are stored using 6 bits, they can be combined into a single value represented with at least 30 bits.
  • a a ! - n ⁇ s
  • a is the original amplitude
  • n is the normalization factor
  • s is the scaling factor
  • a' is the normalized amplitude
  • a clipping operation can be applied as: where a" is the clipped normalized amplitude, and min is the minimum interval value for the clipping.
  • n and s are the powers of two
  • a given normalization factor can be stored alongside the amplitudes.
  • the normalization factor may be stored at a higher precision than the amplitudes.
  • a given normalization factor may be stored using an unsigned integer data type with 32 bits precision, and the amplitudes may be stored using precisions smaller than 32 bits.
  • a given amplitude when applying the DIMD merge process, may be scaled back to a predefined range by means of multiplying the stored amplitude by a given normalization factor.
  • the normalization factor may be determined based on characteristics of the current block.
  • the normalization factor may be determined based on characteristics of the neighboring block.
  • the normalization factor may be stored.
  • the scaling factor depends on the size of the second block of video sample data.
  • the size of the current block may at least partly have impact on the scaling factor.
  • An apparatus comprises means for decoding encoded samples of blocks of video sample data; means for determining at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; means for performing, for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; means for adjusting the decoder-side intra mode derivation parameters into a reduced precision; means for storing the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and means for forming an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction modes based on the stored adjusted decoder-side intra mode derivation parameters.
  • said adjusting the decoder-side intra mode derivation parameters into a reduced precision comprises one or more of scaling, normalizing and/or clipping.
  • the apparatus comprises means for applying an inverse adjustment process as a part of the merged decoder-side intra mode derivation process.
  • the apparatus comprises means for determining the inverse adjustment process based on a scaling factor used to scale decoder-side intra mode derivation parameters for at least one block.
  • the apparatus comprises means for storing a number of decoder-side intra mode derivation parameters for at least one coding unit.
  • the stored decoder-side intra mode derivation parameters comprise one or more of the following: a histogram of amplitudes, where one amplitude is determined and stored for each intra direction mode; a reduced set of determined modes formed of a subset of all possible intra direction modes; a reduced set of amplitudes, where each amplitude in the set corresponds to an amplitude determined during the DIMD process for a given intra direction mode; a set of weights, where each weight corresponds to the blending weight determined during the DIMD process for a given intra direction mode; the scaling factor.
  • the apparatus comprises means for storing the scaling factor using a greater number of bits than the other decoder-side intra mode derivation parameters.
  • the apparatus comprises means for scaling amplitude values into a predetermined range of values representable with a given number of bits. [0160] According to an embodiment, the apparatus comprises means for normalizing the amplitude values.
  • the apparatus comprises means for clipping amplitude values into a predetermined range of values after the scaling and/or normalization.
  • the apparatus comprises means for scaling values of the weights.
  • the scaling factor depends on the size of the second block of video sample data.
  • an apparatus comprising: at least one processor and at least one memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform at least: decode encoded samples of blocks of video sample data; determine at least one template region for at least a first block of video sample data, wherein the template region comprises a set of reconstructed samples at predetermined locations with respect to said first block of video sample data; perform, for the at least one template region, a decoder-side intra mode derivation process to obtain decoder-side intra mode derivation parameters; adjust the decoder-side intra mode derivation parameters into a reduced precision; store the adjusted decoder-side intra mode derivation parameters for at least said first block of video sample data; and form an intra prediction block for at least a second block of video sample data in accordance with a merged decoder-side intra mode derivation process, wherein the merged decoder-side intra mode derivation process includes determining intra prediction
  • said adjusting the decoder-side intra mode derivation parameters into a reduced precision comprises one or more of scaling, normalizing and/or clipping.
  • the apparatus comprises code configured to cause the apparatus to apply an inverse adjustment process as a part of the merged decoder-side intra mode derivation process.
  • the apparatus comprises code configured to cause the apparatus to determine the inverse adjustment process based on a scaling factor used to scale decoder-side intra mode derivation parameters for at least one block.
  • the apparatus comprises code configured to cause the apparatus to store a number of decoder-side intra mode derivation parameters for at least one coding unit.
  • the stored decoder-side intra mode derivation parameters comprise one or more of the following: a histogram of amplitudes, where one amplitude is determined and stored for each intra direction mode; a reduced set of determined modes formed of a subset of all possible intra direction modes; a reduced set of amplitudes, where each amplitude in the set corresponds to an amplitude determined during the DIMD process for a given intra direction mode; a set of weights, where each weight corresponds to the blending weight determined during the DIMD process for a given intra direction mode; the scaling factor.
  • the apparatus comprises code configured to cause the apparatus to store the scaling factor using a greater number of bits than the other decoder-side intra mode derivation parameters.
  • the apparatus comprises code configured to cause the apparatus to scale amplitude values into a predetermined range of values representable with a given number of bits.
  • the apparatus comprises code configured to cause the apparatus to normalize the amplitude values.
  • the apparatus comprises code configured to cause the apparatus to clip amplitude values into a predetermined range of values after the scaling and/or normalization.
  • the apparatus comprises code configured to cause the apparatus to scale values of the weights.
  • the scaling factor depends on the size of the second block of video sample data.
  • Such apparatuses may comprise e.g. the functional units disclosed in any of the Figures 1, 2, 4a, and 4b for implementing the embodiments.
  • Such an apparatus further comprises code, stored in said at least one memory, which when executed by said at least one processor, causes the apparatus to perform one or more of the embodiments disclosed herein.
  • FIG. 6 is a graphical representation of an example multimedia communication system within which various embodiments may be implemented.
  • a data source 1510 provides a source signal in an analog, uncompressed digital, or compressed digital format, or any combination of these formats.
  • An encoder 1520 may include or be connected with a preprocessing, such as data format conversion and/or filtering of the source signal.
  • the encoder 1520 encodes the source signal into a coded media bitstream. It should be noted that a bitstream to be decoded may be received directly or indirectly from a remote device located within virtually any type of network. Additionally, the bitstream may be received from local hardware or software.
  • the encoder 1520 may be capable of encoding more than one media type, such as audio and video, or more than one encoder 1520 may be required to code different media types of the source signal.
  • the encoder 1520 may also get synthetically produced input, such as graphics and text, or it may be capable of producing coded bitstreams of synthetic media. In the following, only processing of one coded media bitstream of one media type is considered to simplify the description. It should be noted, however, that typically real-time broadcast services comprise several streams (typically at least one audio, video and text sub-titling stream). It should also be noted that the system may include many encoders, but in the figure only one encoder 1520 is represented to simplify the description without a lack of generality. It should be further understood that, although text and examples contained herein may specifically describe an encoding process, one skilled in the art would understand that the same concepts and principles also apply to the corresponding decoding process and vice versa.
  • the coded media bitstream may be transferred to a storage 1530.
  • the storage 1530 may comprise any type of mass memory to store the coded media bitstream.
  • the format of the coded media bitstream in the storage 1530 may be an elementary self-contained bitstream format, or one or more coded media bitstreams may be encapsulated into a container file, or the coded media bitstream may be encapsulated into a Segment format suitable for DASH (or a similar streaming system) and stored as a sequence of Segments. If one or more media bitstreams are encapsulated in a container file, a file generator (not shown in the figure) may be used to store the one more media bitstreams in the file and create file format metadata, which may also be stored in the file.
  • the encoder 1520 or the storage 1530 may comprise the file generator, or the file generator is operationally attached to either the encoder 1520 or the storage 1530.
  • Some systems operate “live”, i.e. omit storage and transfer coded media bitstream from the encoder 1520 directly to the sender 1540.
  • the coded media bitstream may then be transferred to the sender 1540, also referred to as the server, on a need basis.
  • the format used in the transmission may be an elementary self-contained bitstream format, a packet stream format, a Segment format suitable for DASH (or a similar streaming system), or one or more coded media bitstreams may be encapsulated into a container file.
  • the encoder 1520, the storage 1530, and the server 1540 may reside in the same physical device or they may be included in separate devices.
  • the encoder 1520 and server 1540 may operate with live real-time content, in which case the coded media bitstream is typically not stored permanently, but rather buffered for small periods of time in the content encoder 1520 and/or in the server 1540 to smooth out variations in processing delay, transfer delay, and coded media bitrate.
  • the server 1540 sends the coded media bitstream using a communication protocol stack.
  • the stack may include but is not limited to one or more of Real-Time Transport Protocol (RTP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), Transmission Control Protocol (TCP), and Internet Protocol (IP).
  • RTP Real-Time Transport Protocol
  • UDP User Datagram Protocol
  • HTTP Hypertext Transfer Protocol
  • TCP Transmission Control Protocol
  • IP Internet Protocol
  • the server 1540 encapsulates the coded media bitstream into packets.
  • RTP Real-Time Transport Protocol
  • UDP User Datagram Protocol
  • HTTP Hypertext Transfer Protocol
  • TCP Transmission Control Protocol
  • IP Internet Protocol
  • the sender 1540 may comprise or be operationally attached to a "sending file parser" (not shown in the figure).
  • a sending file parser locates appropriate parts of the coded media bitstream to be conveyed over the communication protocol.
  • the sending file parser may also help in creating the correct format for the communication protocol, such as packet headers and payloads.
  • the multimedia container file may contain encapsulation instructions, such as hint tracks in the ISOBMFF, for encapsulation of the at least one of the contained media bitstream on the communication protocol.
  • the server 1540 may or may not be connected to a gateway 1550 through a communication network, which may e.g. be a combination of a CDN, the Internet and/or one or more access networks.
  • the gateway may also or alternatively be referred to as a middle-box.
  • the gateway may be an edge server (of a CDN) or a web proxy. It is noted that the system may generally comprise any number gateways or alike, but for the sake of simplicity, the following description only considers one gateway 1550.
  • the gateway 1550 may perform different types of functions, such as translation of a packet stream according to one communication protocol stack to another communication protocol stack, merging and forking of data streams, and manipulation of data stream according to the downlink and/or receiver capabilities, such as controlling the bit rate of the forwarded stream according to prevailing downlink network conditions.
  • the gateway 1550 may be a server entity in various embodiments.
  • the system includes one or more receivers 1560, typically capable of receiving, demodulating, and de-capsulating the transmitted signal into a coded media bitstream.
  • the coded media bitstream may be transferred to a recording storage 1570.
  • the recording storage 1570 may comprise any type of mass memory to store the coded media bitstream.
  • the recording storage 1570 may alternatively or additively comprise computation memory, such as random access memory.
  • the format of the coded media bitstream in the recording storage 1570 may be an elementary self-contained bitstream format, or one or more coded media bitstreams may be encapsulated into a container file. If there are multiple coded media bitstreams, such as an audio stream and a video stream, associated with each other, a container file is typically used and the receiver 1560 comprises or is attached to a container file generator producing a container file from input streams. Some systems operate “live,” i.e. omit the recording storage 1570 and transfer coded media bitstream from the receiver 1560 directly to the decoder 1580. In some systems, only the most recent part of the recorded stream, e.g., the most recent 10-minute excerption of the recorded stream, is maintained in the recording storage 1570, while any earlier recorded data is discarded from the recording storage 1570.
  • the coded media bitstream may be transferred from the recording storage 1570 to the decoder 1580. If there are many coded media bitstreams, such as an audio stream and a video stream, associated with each other and encapsulated into a container file or a single media bitstream is encapsulated in a container file e.g. for easier access, a file parser (not shown in the figure) is used to decapsulate each coded media bitstream from the container file.
  • the recording storage 1570 or a decoder 1580 may comprise the file parser, or the file parser is attached to either recording storage 1570 or the decoder 1580. It should also be noted that the system may include many decoders, but here only one decoder 1580 is discussed to simplify the description without a lack of generality.
  • the coded media bitstream may be processed further by a decoder 1580, whose output is one or more uncompressed media streams.
  • a Tenderer 1590 may reproduce the uncompressed media streams with a loudspeaker or a display, for example.
  • the receiver 1560, recording storage 1570, decoder 1580, and Tenderer 1590 may reside in the same physical device or they may be included in separate devices.
  • a sender 1540 and/or a gateway 1550 may be configured to perform switching between different representations e.g. for switching between different viewports of 360-degree video content, view switching, bitrate adaptation and/or fast start-up, and/or a sender 1540 and/or a gateway 1550 may be configured to select the transmitted representation(s). Switching between different representations may take place for multiple reasons, such as to respond to requests of the receiver 1560 or prevailing conditions, such as throughput, of the network over which the bitstream is conveyed. In other words, the receiver 1560 may initiate switching between representations.
  • a request from the receiver can be, e.g., a request for a Segment or a Subsegment from a different representation than earlier, a request for a change of transmitted scalability layers and/or sub-layers, or a change of a rendering device having different capabilities compared to the previous one.
  • a request for a Segment may be an HTTP GET request.
  • a request for a Subsegment may be an HTTP GET request with a byte range.
  • bitrate adjustment or bitrate adaptation may be used for example for providing so-called fast start-up in streaming services, where the bitrate of the transmitted stream is lower than the channel bitrate after starting or random-accessing the streaming in order to start playback immediately and to achieve a buffer occupancy level that tolerates occasional packet delays and/or retransmissions.
  • Bitrate adaptation may include multiple representation or layer up-switching and representation or layer down-switching operations taking place in various orders.
  • a decoder 1580 may be configured to perform switching between different representations e.g. for switching between different viewports of 360-degree video content, view switching, bitrate adaptation and/or fast start-up, and/or a decoder 1580 may be configured to select the transmitted representation(s).
  • Switching between different representations may take place for multiple reasons, such as to achieve faster decoding operation or to adapt the transmitted bitstream, e.g. in terms of bitrate, to prevailing conditions, such as throughput, of the network over which the bitstream is conveyed.
  • Faster decoding operation might be needed for example if the device including the decoder 1580 is multi-tasking and uses computing resources for other purposes than decoding the video bitstream.
  • faster decoding operation might be needed when content is played back at a faster pace than the normal playback speed, e.g. twice or three times faster than conventional real-time playback rate.
  • the encoder may have structure and/or computer program for generating the bitstream to be decoded by the decoder.
  • some embodiments have been described related to generating a prediction block as part of encoding. Embodiments can be similarly realized by generating a prediction block as part of decoding, with a difference that coding parameters, such as the horizontal offset and the vertical offset, are decoded from the bitstream than determined by the encoder.
  • user equipment may comprise a video codec such as those described in embodiments of the invention above. It shall be appreciated that the term user equipment is intended to cover any suitable type of wireless user equipment, such as mobile telephones, portable data processing devices or portable web browsers.
  • elements of a public land mobile network may also comprise video codecs as described above.
  • the various embodiments of the invention may be implemented in hardware or special purpose circuits, software, logic or any combination thereof.
  • some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
  • the embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware.
  • any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions.
  • the software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.
  • the memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture, as non-limiting examples.
  • Embodiments of the inventions may be practiced in various components such as integrated circuit modules.
  • the design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
  • Programs such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules.
  • the resultant design in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication.
  • a standardized electronic format e.g., Opus, GDSII, or the like

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

L'invention concerne un procédé consistant à : décoder des échantillons codés de blocs de données d'échantillon vidéo ; déterminer au moins une région de modèle pour au moins un premier bloc de données d'échantillon vidéo, la région de modèle comprenant un ensemble d'échantillons reconstruits à des zones prédéterminées par rapport audit premier bloc de données d'échantillon vidéo ; effectuer, pour ladite au moins une région de modèle, un processus de dérivation de mode intra côté décodeur pour obtenir des paramètres de dérivation de mode intra côté décodeur ; régler les paramètres de dérivation de mode intra côté décodeur en une précision réduite ; stocker les paramètres de dérivation de mode intra côté décodeur réglés pour au moins ledit premier bloc de données d'échantillon vidéo ; et former un bloc de prédiction intra pour au moins un second bloc de données d'échantillon vidéo conformément à un processus de dérivation de mode intra côté décodeur fusionné, le processus de dérivation de mode intra côté décodeur fusionné consistant à déterminer des modes de prédiction intra sur la base des paramètres de dérivation de mode intra côté décodeur réglés stockés.
PCT/EP2024/082045 2023-12-08 2024-11-12 Appareil, procédé et programme d'ordinateur pour le codage et le décodage de vidéo Pending WO2025119602A1 (fr)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025011822A1 (fr) * 2023-07-12 2025-01-16 Nokia Technologies Oy Améliorations de fusion de dérivation de mode intra côté décodeur

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WO2025011822A1 (fr) * 2023-07-12 2025-01-16 Nokia Technologies Oy Améliorations de fusion de dérivation de mode intra côté décodeur

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