Minimum allowable quantization parameters for transform skip mode and palette mode in video coding

Abstract

A video encoder derives a minimum allowable basic quantization parameter for video data based on an input bit depth of the video data; determining a base quantization parameter for a block of video data based on the minimum allowable base quantization parameter; and quantizing the block of video data based on the basic quantization parameter. In a reciprocal manner, a video decoder derives a minimum allowable base quantization parameter for video data based on an input bit depth of the video data; determining a base quantization parameter for a block of video data based on the minimum allowable base quantization parameter; and inversely quantizing the block of video data based on the basic quantization parameter.

Description

[0001] This application is a divisional application of a patent application with an application date of July 1, 2020, an invention name of “Minimum allowable quantization parameter for transform skip mode and palette mode in video decoding” and application number of 202080047211.4.

[0002] This application claims priority to U.S. Application No. 16 / 917,051, filed on June 30, 2020, which claims priority to U.S. Provisional Application No. 62 / 869,236, filed on July 1, 2019, U.S. Provisional Application No. 62 / 870,999, filed on July 5, 2019, and U.S. Provisional Application No. 62 / 904,406, filed on September 23, 2019, the entire contents of each of the above applications are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to video encoding and video decoding. Background Art

[0004] Digital video capabilities may be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones (so-called "smart phones"), video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques (such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-TH.264 / MPEG-4 (Part 10, Advanced Video Coding (AVC)), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards). By implementing such video coding techniques, video devices may more efficiently send, receive, encode, decode, and / or store digital video information.

[0005] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction relative to reference samples in neighboring blocks in the same picture or temporal prediction relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0006] In some examples, a video decoder (e.g., an encoder and / or a decoder) may encode / decode video data in a transform skip mode. In transform skip mode, the video decoder does not apply a transform process to a block of residual data (i.e., skips the transform process). Therefore, for blocks decoded in transform skip mode, the residual data is not transformed and remains in the pixel domain. A residual block of video data decoded using a transform skip mode may also be referred to as an untransformed residual block (e.g., a transform unit of pixel domain video data). In transform skip mode, the video decoder may still apply quantization (at the video encoder) and inverse quantization (at the video decoder) to the untransformed residual block.

[0007] In other examples, the video decoder can use a palette mode to decode a block of video data. If the palette mode is used to decode a block of video data, the video decoder can use a small set of representative color values ​​to represent the pixel values ​​in the block. Such a set of representative color values ​​is called a palette. For pixels with values ​​close to the palette color, the video decoder decodes the palette index associated with the nearest palette color. For pixels with values ​​outside the palette, the video decoder decodes the pixel as an escape pixel and quantizes the actual pixel value.

[0008] In summary, the present disclosure describes techniques for determining and applying quantization parameters for video data decoded in palette mode using transform skip mode and / or escape mode. In some examples, when encoding and / or decoding a block of video data in transform skip mode, the quantization process is nearly lossless when the internal bit depth used in the decoding process is equal to the input material bit depth (e.g., the bit depth of the input video data) and when the base quantization parameter value is equal to 4. When the base QP value becomes less than 4, the quantization process may introduce rounding errors. Similar quantization errors may exist in palette mode decoding when decoding escaped pixels.

[0009] In order to avoid and / or reduce such rounding errors, the present disclosure proposes a technique for determining a minimum allowable quantization parameter (e.g., a minimum allowable basic quantization parameter). In some examples, the minimum allowable basic quantization parameter can be used for transform skip and / or palette decoding modes. The video decoder can determine the minimum allowable basic quantization parameter based on the input bit depth of the video data. The video decoder can then determine the basic quantization parameter for a particular block of the video data. If the determined basic quantization parameter for the block is less than the minimum allowable basic quantization parameter, the video decoder uses the minimum allowable basic quantization parameter instead. In this way, rounding errors are eliminated and / or reduced, and decoding efficiency is improved.

[0010] In one example, a method includes: deriving a minimum allowable basic quantization parameter for a block of the video data based on an input bit depth of the video data; determining a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and inverse quantizing the block of the video data based on the basic quantization parameter.

[0011] In another example, the present disclosure describes a device configured to decode video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in a circuit and in communication with the memory, the one or more processors configured to: derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and inverse quantize the block of video data based on the basic quantization parameter.

[0012] In another example, a device includes: a unit for deriving a minimum allowed basic quantization parameter for the video data based on an input bit depth of the video data; a unit for determining a basic quantization parameter for a block of the video data based on the minimum allowed basic quantization parameter; and a unit for inverse quantizing the block of video data based on the basic quantization parameter.

[0013] In another example, a computer-readable storage medium is encoded with instructions that, when executed, cause a programmable processor to: derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and inverse quantize the block of video data based on the basic quantization parameter.

[0014] In another example, the present disclosure describes a device configured to encode video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in a circuit and in communication with the memory, the one or more processors configured to: derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and quantize the block of video data based on the basic quantization parameter.

[0015] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0017] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0018] Figure 3 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0019] Figure 4 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0020] Figure 5 is a flow chart illustrating an example encoding method according to techniques of this disclosure.

[0021] Figure 6 is a flow chart illustrating an example decoding method according to techniques of this disclosure.

[0022] Figure 7 is a flow chart illustrating an example encoding method for determining a quantization parameter in accordance with techniques of this disclosure.

[0023] Figure 8 is a flow chart illustrating an example decoding method for determining a quantization parameter in accordance with techniques of this disclosure. DETAILED DESCRIPTION

[0024] In summary, the present disclosure describes techniques for determining and applying quantization parameters for video data decoded in palette mode using transform skip mode and / or escape mode. In some examples, when encoding and / or decoding a block of video data in transform skip mode, the quantization process is nearly lossless when the internal bit depth used in the decoding process is equal to the input material bit depth (e.g., the bit depth of the input video data) and when the base quantization parameter value is equal to 4. When the base QP value becomes less than 4, the quantization process may introduce rounding errors. Similar quantization errors may exist in palette mode decoding when decoding escaped pixels.

[0025] In order to avoid and / or reduce such rounding errors, the present disclosure proposes a technique for determining a minimum allowable quantization parameter (e.g., a minimum allowable basic quantization parameter). In some examples, the minimum allowable basic quantization parameter can be used for transform skip and / or palette decoding modes. The video decoder can determine the minimum allowable basic quantization parameter based on the input bit depth of the video data. The video decoder can then determine the basic quantization parameter for a particular block of the video data. If the determined basic quantization parameter for the block is less than the minimum allowable basic quantization parameter, the video decoder uses the minimum allowable basic quantization parameter instead. In this way, rounding errors are eliminated and / or reduced, and decoding efficiency is improved.

[0026] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of the present disclosure. In general, the techniques of the present disclosure relate to decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0027] like Figure 1As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides the video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 may include any of a wide variety of devices, including desktop computers, notebook computers (i.e., laptop computers), mobile devices, tablet computers, set-top boxes, telephone handsets such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0028] exist Figure 1 In the example of , the source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. The destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. According to the present disclosure, the video encoder 200 of the source device 102 and the video decoder 300 of the destination device 116 can be configured to apply a technique for determining and / or applying a quantization parameter for video data decoded using a transform skip mode or a palette mode. Therefore, the source device 102 represents an example of a video encoding device, and the destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or arrangements. For example, the source device 102 may receive video data from an external video source such as an external camera. Similarly, the destination device 116 may be docked with an external display device instead of including an integrated display device.

[0029] like Figure 1The system 100 shown is only one example. In general, any digital video encoding and / or decoding device can perform techniques for determining and / or applying quantization parameters for video data decoded using a transform skip mode or a palette mode. The source device 102 and the destination device 116 are only examples of such decoding devices, wherein the source device 102 generates decoded video data for transmission to the destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (e.g., encoding and / or decoding) of data. Therefore, the video encoder 200 and the video decoder 300 represent examples of decoding devices (specifically, video encoders and video decoders), respectively. In some examples, the source device 102 and the destination device 116 can operate in a substantially symmetrical manner, so that each of the source device 102 and the destination device 116 includes video encoding and decoding components. Therefore, the system 100 can support one-way or two-way video transmission between the source device 102 and the destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0030] Typically, video source 104 represents the source of video data (i.e., original, unencoded video data), and provides a series of pictures (also referred to as "frames") of the order of the video data to video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include a video capture device, such as a camera, a video archive unit containing previously captured original video, and / or a video feed interface for receiving video from a video content provider. As another alternative, video source 104 may generate computer graphics-based data as source video, or a combination of real-time video, archived video, and computer-generated video. In each case, video encoder 200 may encode captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange pictures from the received order (sometimes referred to as "display order") into a decoding order for decoding. Video encoder 200 may generate a bitstream comprising encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 to be received and / or retrieved by, for example, input interface 122 of destination device 116 .

[0031] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 can store original video data, for example, original video from the video source 104 and original decoded video data from the video decoder 300. In addition or alternatively, the memories 106, 120 can store software instructions that can be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although the memory 106 and the memory 120 are shown as separate from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 can also include internal memories for functionally similar or equivalent purposes. In addition, the memories 106, 120 can store, for example, encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memories 106, 120 can be allocated as one or more video buffers, for example, to store original decoded and / or encoded video data.

[0032] The computer-readable medium 110 may represent any type of medium or device capable of delivering the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to directly send the encoded video data to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. The output interface 108 may demodulate the transmission signal including the encoded video data according to a communication standard such as a wireless communication protocol, and the input interface 122 may demodulate the received transmission signal according to a communication standard such as a wireless communication protocol. The communication medium may include any wireless or wired communication medium, for example, a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form a portion of a packet-based network such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include a router, a switch, a base station, or any other device that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0033] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0034] In some examples, the source device 102 may output the encoded video data to a file server 114 or another intermediate storage device that may store the encoded video data generated by the source device 102. The destination device 116 may access the stored video data from the file server 114 via streaming or downloading. The file server 114 may be any type of server device capable of storing the encoded video data and sending the encoded video data to the destination device 116. The file server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. The destination device 116 may access the encoded video data from the file server 114 via any standard data connection (including an Internet connection). This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of the two suitable for accessing the encoded video data stored on the file server 114. The file server 114 and the input interface 122 may be configured to operate according to the following: a streaming protocol, a download transmission protocol, or a combination thereof.

[0035] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to a cellular communication standard (such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to other wireless standards (such as IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee TM ), Bluetooth TM Standards, etc.) to transmit data (such as encoded video data). In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing the functions assigned to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing the functions assigned to video decoder 300 and / or input interface 122.

[0036] The techniques of the present disclosure may be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (such as Dynamic Adaptive Streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0037] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information such as the following syntax elements defined by the video encoder 200 (which are also used by the video decoder 300): the syntax elements have values ​​that describe the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to the user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0038] Despite Figure 1 200 and 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including both audio and video in a common data stream. If applicable, the MUX-DEMUX units may follow the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0039] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device can store instructions for the software in a suitable non-transitory computer-readable medium, and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, and any of the encoders or decoders can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. The device including the video encoder 200 and / or the video decoder 300 can include an integrated circuit, a microprocessor, and / or a wireless communication device (such as a cellular phone).

[0040] Typically, the video encoder 200 and the video decoder 300 can perform block-based decoding of the picture. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 can decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding red, green, and blue (RGB) data for samples of a picture, the video encoder 200 and the video decoder 300 can decode luminance and chrominance components, wherein the chrominance components may include both red hue and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, a pre-processing unit and a post-processing unit (not shown) can perform these conversions.

[0041] In general, the present disclosure may relate to the decoding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding data for the picture. Similarly, the present disclosure may relate to the decoding of a block of a picture to include the process of encoding or decoding data for the block (e.g., prediction and / or residual decoding). The encoded video bitstream typically includes a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or a block should generally be understood as decoding the values ​​of the syntax elements used to form the picture or the block.

[0042] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as the video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video decoder may further partition the PU and TU. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0043] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video decoder (such as the video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). The video encoder 200 may partition the CTUs according to a tree structure (such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the separation between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0044] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also known as ternary tree (TT)) partitioning. A ternary tree or ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, the ternary tree or ternary tree partitioning divides the block into three sub-blocks without dividing the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0045] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the respective chroma components).

[0046] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures per HEVC. For purposes of explanation, a description of the techniques of the present disclosure is given with respect to QTBT segmentation. However, it should be understood that the techniques of the present disclosure may also be applied to video decoders configured to use quadtree segmentation or also use other types of segmentation.

[0047] In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or a CTB of samples of a monochrome picture or a picture coded using three separate color planes and syntax structures for coding the samples. A CTB can be an NxN block of samples (for some value of N) such that the division of components into CTBs is a partitioning. A component is an array or a single sample from one of the three arrays (one luma and two chroma) that make up a picture in a 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array that makes up a picture in a monochrome format. In some examples, a coding block is an MxN block of samples (for some values ​​of M and N) such that the division of a CTB into coding blocks is a partitioning.

[0048] Blocks (e.g., CTUs or CUs) may be grouped in a picture in various ways. As an example, a brick may refer to a rectangular area of ​​a CTU row within a particular tile in a picture. A tile may be a rectangular area of ​​a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular area of ​​a CTU having a height equal to the height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular area of ​​a CTU having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

[0049] In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. Tiles that are not partitioned into multiple bricks may also be referred to as bricks. However, bricks that are true subsets of tiles may not be referred to as tiles.

[0050] Tiles in a picture can also be arranged in slices. A slice can be an integer number of tiles of a picture that can be uniquely contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes a continuous sequence of multiple complete tiles or only complete tiles of one tile.

[0051] This disclosure may use "NxN" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, for example, 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxNCU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. In addition, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0052] The video encoder 200 encodes video data representing prediction and / or residual information and other information for a CU. The prediction information indicates how the CU will be predicted in order to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0053] In order to predict a CU, the video encoder 200 can generally form a prediction block for the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU based on data of a previously decoded picture, while intra-frame prediction generally refers to predicting a CU based on previously decoded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate a prediction block. The video encoder 200 can generally perform motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 can use the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean square difference (MSD), or other such difference calculations to calculate a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional prediction or bidirectional prediction to predict the current CU.

[0054] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0055] To perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes, as well as planar modes and DC modes. Typically, the video encoder 200 selects an intra prediction mode that describes neighboring samples of the current block according to which the samples of the current block (e.g., a block of a CU) are to be predicted. Assuming that the video encoder 200 decodes the CTU and CU in raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0056] The video encoder 200 encodes data representing a prediction mode for the current block. For example, for an inter-frame prediction mode, the video encoder 200 may encode data representing which of the various available inter-frame prediction modes is used and motion information for the corresponding mode. For unidirectional or bidirectional inter-frame prediction, for example, the video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0057] After a prediction such as intra prediction or inter prediction of a block, the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in a transform domain rather than in a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0058] Although the above describes an example in which a transform is performed, in some examples, the transform may be skipped. For example, the video encoder 200 may implement a transform skip mode in which a transform operation is skipped. In an example in which the transform is skipped, the video encoder 200 may output coefficients corresponding to residual values ​​in the pixel domain instead of transform coefficients in the frequency domain. In the following description, the term "coefficient" should be interpreted as including coefficients corresponding to residual values ​​or transform coefficients generated from the result of the transform.

[0059] As described above, after any transform or skipping a transform (e.g., in a transform skip mode) to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all transform coefficients. For example, the video encoder 200 may round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0060] After quantization, the video encoder 200 may scan the transform coefficients (e.g., generated as a result of the transform or due to a transform skip), thereby generating a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In an example where the transform is skipped, the result of the scan may not be that the higher energy coefficients are at the front of the vector and the lower energy coefficients are at the back of the vector.

[0061] In some examples, the video encoder 200 may scan the quantized transform coefficients using a predefined scan order to produce a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode the values ​​of the syntax elements used to describe metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0062] In some examples, the video encoder 200 encodes the residual data in the TU. Depending on the expected characteristics of the residual data in the TU, the video encoder 200 can encode the TU in different modes (such as transform mode or transform skip mode), where different modes utilize different coefficient decoding schemes. Some coefficient decoding schemes utilize coefficient groups to encode TUs. A coefficient group is typically a subset of the coefficients in a TU. For example, the video encoder 200 can encode a 16x16 TU into four 4x4 coefficient groups.

[0063] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0064] The video encoder 200 may also generate syntax data (such as block-based syntax data, picture-based syntax data, and sequence-based syntax data) for the video decoder 300, for example, in a picture header, a block header, a slice header, or other syntax data (such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Likewise, the video decoder 300 may decode such syntax data to determine how to decode the corresponding video data.

[0065] In this way, the video encoder 200 can generate a bitstream, which includes the encoded video data, for example, a syntax element describing the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0066] In general, the video decoder 300 performs a process that is the reverse of the process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements for the bitstream in a manner substantially similar to, but reverse to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning a picture into CTUs, and partitioning each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTUs. The syntax elements may also define prediction and residual information for a block (e.g., CU) of video data.

[0067] The residual information may be represented by, for example, quantized coefficients (which represent residual values ​​in the pixel domain or transform coefficients in the frequency domain). The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce the residual block for the block. In an example where the video encoder 200 skips the transform operation (e.g., using a transform skip mode), the video decoder 300 may skip the inverse transform operation. That is, the video decoder 300 may also decode a block of video data using a transform skip mode. The video decoder 300 uses the signaled prediction mode (intra-frame prediction or inter-frame prediction) and the associated prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0068] According to the techniques of the present disclosure, video encoder 200 may be configured to: derive a minimum allowable basic quantization parameter for video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of video data based on the minimum allowable basic quantization parameter; and quantize the block of video data based on the basic quantization parameter. In a reciprocal manner, video decoder 300 may be configured to: derive a minimum allowable basic quantization parameter for video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of video data based on the minimum allowable basic quantization parameter; and inverse quantize the block of video data based on the basic quantization parameter.

[0069] In general, the present disclosure may involve "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the transmission of values ​​for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As described above, source device 102 may transmit the bitstream to destination device 116 in substantially real time or not in real time (such as may occur when storing syntax elements to storage device 112 for later retrieval by destination device 116).

[0070] Figure 2A and 2B1 is a conceptual diagram showing an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, while dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where, in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, since the quadtree node splits the block horizontally and vertically into 4 sub-blocks of equal size, there is no need to indicate the split type. Therefore, the video encoder 200 can encode the following, and the video decoder 300 can decode the following: syntax elements (such as split information) for the regional tree level (i.e., solid line) of the QTBT structure 130, and syntax elements (such as split information) for the prediction tree level (i.e., dashed line) of the QTBT structure 130. The video encoder 200 may encode video data (such as prediction and transform data) for a CU represented by a terminal leaf node of the QTBT structure 130 , and the video decoder 300 may decode the video data.

[0071] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes at the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, which indicates the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, which indicates the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, which indicates the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, which indicates the minimum allowed binary tree leaf node size).

[0072] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be segmented according to a quadtree segmentation. That is, the node of the first level is a leaf node (without child nodes) or has four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and a child node with a solid line branch. If the node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further segmented by the corresponding binary tree. The binary tree splitting of a node may be iterated until the node generated from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having a dotted line branch. The binary tree leaf node is called a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further segmentation. As discussed above, a CU may also be referred to as a "video block" or "block".

[0073] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luminance sample and two corresponding 64x64 chrominance samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate a quadtree leaf node. The quadtree leaf node can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the quadtree leaf node is 128x128, the leaf quadtree node will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the quadtree leaf node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. When a binary tree node has a width equal to MinBTSize (4 in this example), it means that no further vertical splitting is allowed. Similarly, a binary tree node with a height equal to MinBTSize means that no further horizontal splitting is allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0074] Figure 3 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 3It is provided for the purpose of explanation and should not be considered to limit the techniques generally illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes a video encoder 200 according to the techniques of VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure can be performed by video encoding devices configured for other video decoding standards.

[0075] exist Figure 3 In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any one or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 can be implemented in one or more processors or in processing circuits. For example, the units of the video encoder 200 can be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0076] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives the video data stored in the video data memory 230. DPB 218 can act as a reference picture memory, which stores reference video data for use when subsequent video data is predicted by the video encoder 200. Video data memory 230 and DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or a separate memory device. In various examples, video data memory 230 can be on chip with other components of the video encoder 200 (as shown), or off chip relative to those components.

[0077] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or to memory external to the video encoder 200 (unless specifically described as such). Rather, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data for a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0078] Shows Figure 4 The various units of the video encoder 200 are provided to help understand the operations performed by the video encoder 200. These units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with the operations that can be performed. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0079] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example in which the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store instructions (eg, object code) for software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0080] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve the picture of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be the original video data to be encoded.

[0081] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0082] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of a CTU into CUs, a prediction mode for a CU, a transform type for residual data of a CU, a quantization parameter for residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0083] The video encoder 200 may partition the picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0084] Typically, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). In order to inter-predict the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in the DPB 218). Specifically, the motion estimation unit 222 may calculate a value representing the degree of similarity of the potential reference block to the current block, for example, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0085] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the values ​​for the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0086] As another example, for intra prediction or intra prediction decoding, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of adjacent samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 can calculate the average of adjacent samples of the current block and generate a prediction block to include the resulting average for each sample of the prediction block.

[0087] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 can generate the residual block using residual differential pulse coding modulation (RDPCM) by calculating the difference between the sample values ​​in the residual block. In some examples, the residual generation unit 204 can be formed using one or more subtractor circuits that perform binary subtraction.

[0088] In an example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As noted above, the size of the CU may refer to the size of the luma coding block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra-frame prediction, and symmetrical PU sizes of 2Nx2N, 2NxN, Nx2N, NxN or similar sizes for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0089] In an example where mode selection unit 202 does not further partition a CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0090] For other video coding techniques (such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, to name a few examples), the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the coding technique. The video coder codes the pixels as escaped pixels and quantizes the actual pixel values. In such a mode, the mode selection unit 202 can provide these syntax elements to the entropy coding unit 220 for encoding.

[0091] In palette mode decoding, the palette unit 219 of the mode selection unit 202 may not generate a prediction block, but instead generate a syntax element indicating the manner in which the block is reconstructed based on the selected palette. For example, the palette unit 219 may encode the pixel values ​​of a block of video data using a small set of representative color values. Such a set of representative color values ​​is called a palette. For pixels with values ​​close to the palette color, the palette unit 219 may encode the palette index associated with the nearest palette color. For pixels with values ​​outside the palette, the palette unit 219 may encode such pixels as escape pixels. For escape pixels, the quantization unit 208 may quantize the actual pixel value.

[0092] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0093] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 may apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 may perform a variety of transforms on the residual block, for example, a primary transform and a secondary transform (such as a rotation transform). In some examples, the transform processing unit 206 does not apply a transform to the residual block. In some examples, when operating according to a transform skip mode, the video encoder 200 may bypass the transform processing unit 206. That is, no transform is performed on the pixel domain residual data. The pixel domain residual data is then processed by the quantization unit 208.

[0094] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. For a block decoded in a transform skip mode, the quantization unit 208 may quantize the coefficients in the coefficient block (e.g., a TU of pixel domain residual data) to produce a quantized coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause information loss, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients generated by the transform processing unit 206.

[0095] As will be explained in more detail below, the quantization unit 208 can be configured to quantize transform coefficients in a block encoded using a transform skip mode (e.g., a transform unit of pixel domain video data) using a minimum allowed basic quantization parameter. The quantization unit 208 can also quantize pixel values ​​decoded as escaped pixels in palette mode decoding using the minimum allowed basic quantization parameter. As will be explained in more detail below, the quantization unit 208 can be configured to: derive a minimum allowed basic quantization parameter for the video data based on the input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowed basic quantization parameter; and quantize the block of the video data based on the basic quantization parameter.

[0096] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block from the transform coefficient block. If the video encoder 200 uses a transform skip mode to encode the block, the inverse transform may be skipped. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0097] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edge of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0098] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In an example where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve the reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on the blocks of the subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0099] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode a quantized transform coefficient block from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on syntax elements as another example of video data to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0100] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required for reconstructing a block of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0101] The above operations are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a PU.

[0102] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Specifically, the MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0103] Video encoder 200 represents an example of a device configured to encode video data, the device comprising: a memory configured to store the video data; and one or more processing units implemented in circuits and configured to: derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and quantize the block of the video data based on the basic quantization parameter.

[0104] Figure 4 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 4 It is provided for the purpose of explanation and does not limit the techniques generally illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes a video decoder 300 according to the techniques of VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265). However, the techniques of this disclosure can be performed by a video decoding device configured for other video decoding standards.

[0105] exist Figure 4 In the example of , the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 134. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 134 can be implemented in one or more processors or in processing circuits. For example, the units of the video decoder 300 can be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0106] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include an addition unit that performs predictions according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0107] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. For example, the video bitstream may be obtained from computer readable medium 110 ( Figure 1) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. In addition, CPB memory 320 may store video data other than syntax elements of decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, and video decoder 300 may output decoded pictures, and / or use decoded pictures as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or a separate memory device. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0108] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to retrieve the decoded video data. That is, memory 120 may utilize CPB memory 320 to store data as discussed above. Likewise, when some or all of the functions of video decoder 300 are implemented in software to be executed by processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0109] Shows Figure 4 The various units shown in FIG. 3 are used to help understand the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 3 , fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with respect to the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0110] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0111] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to reproduce the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0112] Generally, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0113] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and, likewise, determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0114] According to the techniques of the present disclosure, as will be explained in more detail below, the inverse quantization unit 306 can be configured to use a minimum allowed basic quantization parameter to inverse quantize transform coefficients in a block encoded using a transform skip mode (e.g., a transform unit of pixel domain video data). The inverse quantization unit 306 can also use the minimum allowed basic quantization parameter to inverse quantize pixel values ​​decoded as escaped pixels in palette mode decoding. As will be explained in more detail below, the inverse quantization unit 306 can be configured to: derive a minimum allowed basic quantization parameter for the video data based on the input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowed basic quantization parameter; and inverse quantize the block of the video data based on the basic quantization parameter.

[0115] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block. For blocks decoded in transform skip mode, the inverse transform processing unit 308 may not perform an inverse transform and, in these decoding scenarios, may be considered as a pass-through unit that does not process or change the coefficient block.

[0116] As described above, in some examples, the video decoder 300 can use a palette decoding mode to decode the video data. For example, the palette unit 315 can decode the syntax elements indicating the manner in which the block is reconstructed based on the selected palette. For example, the palette unit 315 can use a small set of representative color values ​​(i.e., a palette) to decode the pixel values ​​of a block of video data. For pixels with values ​​close to the palette color, the palette unit 315 can decode the palette index associated with the nearest palette color. For pixels with values ​​outside the palette, the palette unit 315 can decode such pixels as escape pixels. That is, the palette unit 315 can receive a quantized version of the pixel value associated with the escape pixel. As described above, such escape pixel values ​​are inversely quantized by the inverse quantization unit 360.

[0117] In other examples, prediction processing unit 304 generates a prediction block based on the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax element can indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 can generally generate the prediction block in the same manner as described for motion compensation unit 224 ( Figure 3 )The inter-frame prediction process is performed in a manner substantially similar to that described in detail above.

[0118] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally generate a prediction block in the same manner as described with respect to the intra-prediction unit 226 ( Figure 3 The intra prediction process is performed in a substantially similar manner as described in the foregoing description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0119] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may reconstruct the current block by adding samples of the residual block to corresponding samples of the prediction block.

[0120] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0121] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in examples where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block in the DPB 314. In examples where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block in the DPB 314. As discussed above, the DPB 314 may provide reference information (such as samples of the current picture for intra-frame prediction and previously decoded pictures for subsequent motion compensation) to the prediction processing unit 304. In addition, the video decoder 300 may output a decoded picture (e.g., a decoded video) from the DPB 314 for use in, for example, Figure 1 Subsequent presentation on a display device such as display device 118.

[0122] In this way, the video decoder 300 represents an example of a video decoding device that includes: a memory configured to store video data; and one or more processing units implemented in circuits and configured to: derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and inverse quantize the block of the video data based on the basic quantization parameter.

[0123] As described above, in some examples of HEVC range extension (Rext) and VVC, transform skip (TS) mode (which in some examples replaces transform with bit shifting) is allowed in transform units of size from 4x4 to 32x32 (for example, after VVC Test Model 3.0 (VTM3.0), TS mode is allowed for TU sizes greater than 4x4). Without using transform, the video encoder 200 and the video decoder 300 can be configured to apply quantization (and inverse quantization) and residual decoding to the TS mode in the pixel domain rather than the transform coefficient domain. Given a quantization parameter (QP), for a transform unit of size (w*h), the video encoder 200 and the video decoder 300 extract the residual d from the residual d ij (i=0...w-1, j=0...h-1) derive the quantized coefficients q for transform skip modeij (i=0…w-1,j=0…h-1), as shown below:

[0124] qij=(dij*qScale[baseQP%6]+(1<<(iQbit-1))>>iQbi,--(1)

[0125] in

[0126] qScale[x] = {26214, 23302, 20560, 18396, 16384, 14564}, x = 0, ..., 5 and - (2)

[0127]

[0128] The video encoder 200 and the video decoder 300 may derive the base QP (baseQP) in equation (3) from the input QP as follows:

[0129] baseQP=inputQP+6*(InternalBitdepth-8).

[0130] If the maximum allowed TU size is 32x32, then the minimum iQbit in equation (3) is equal to For an internal bit depth (InternalBitdepth) equal to the input material bit depth, quantization is almost lossless when the basic QP value is equal to 4. In this context, the internal bit depth is the bit depth at which the video encoder 200 and the video decoder 300 process the video data. The input material bit depth (input bitdepth) is the bit depth of the input video to be processed.

[0131] When the base QP value becomes smaller than 4, the quantization level may introduce rounding errors. Therefore, the present disclosure proposes to use QP limiting to limit the base QP to 4. On the other hand, when the input material bit depth is different from the internal bit depth, the limit on the base QP should preferably correspond to the lossless condition of the input material bit depth.

[0132] Similar problems may also occur when video data is decoded in palette mode, for example, in the HEVC screen content model (SCM) and VVC for screen content. If the palette mode is used for a coding unit (CU), the pixel values ​​in the CU are represented by a small set of representative color values. This set is called a palette. For pixels with values ​​close to the palette colors, the palette index is signaled. For pixels with values ​​outside the palette, escape symbols are used to represent the pixels, and the quantized pixel values ​​are directly signaled. The quantized coefficients for pixels decoded in escape mode are derived as shown in equation (1). The scaling array qScale[x] is derived as shown in equation (2), and iQbit is derived as follows:

[0133]

[0134] For values ​​of InternalBitdepth equal to the input material bit depth, quantization is almost lossless when the base QP value is equal to 4. The quantization level also introduces rounding errors when the base QP value becomes smaller than 4, as in the case of transform skip mode.

[0135] The present disclosure describes several techniques for addressing the QP-related issues described above. In one example, the video encoder 200 and the video decoder 300 may be configured to determine a QP value for a video block decoded using TS mode based on a restriction on a minimum base QP allowed in a TU decoded using transform skip mode and / or a restriction on escape mode decoded pixels in palette mode.

[0136] This disclosure describes the following techniques for deriving the minimum allowed base QP (min_baseQP) for transform skip mode and / or palette mode. In one example, the video encoder 200 and the video decoder 300 may be configured to clip the base QP used for quantization and inverse quantization in transform skip mode as follows:

[0137] baseQP=max(baseQP,min_baseQP)

[0138] In another example, the video encoder 200 and the video decoder 300 may be configured to determine the input QP using a limit (min_inputQP). The video encoder 200 and the video decoder 300 may be configured to determine the input QP as follows:

[0139] inputQP=max(inputQP,min_inputQP)

[0140] Therefore, in a general example of the present disclosure, the video encoder 200 may be configured to derive a minimum allowed basic quantization parameter (min_baseQP) for the video data. The video encoder 200 may also determine an initial value (baseQP) of a basic quantization parameter for a block of the video data using the above technique (e.g., baseQP=inputQP+6*(InternalBitdepth-8)) or another technique. The video encoder 200 may then determine an actual basic quantization parameter (baseQP) to be used for the block of the video data based on the minimum allowed basic quantization parameter (e.g., baseQP=max(baseQP,min_baseQP)). That is, the video encoder 200 may determine the basic quantization parameter as the maximum value of the initial value of the basic quantization parameter and the minimum allowed basic quantization parameter. The video encoder 200 may then quantize the block of the video data based on the basic quantization parameter.

[0141] In a reciprocal manner, the video decoder 300 may be configured to derive a minimum allowed basic quantization parameter (min_baseQP) for the video data. The video decoder 300 may also determine an initial value (baseQP) of a basic quantization parameter for a block of video data using the above technique (e.g., baseQP=inputQP+6*(InternalBitdepth-8)) or another technique. The video decoder 300 may then determine an actual basic quantization parameter (baseQP) to be used for the block of video data based on the minimum allowed basic quantization parameter (e.g., baseQP=max(baseQP,min_baseQP)). That is, the video decoder 200 may determine the basic quantization parameter as the maximum value of the initial value of the basic quantization parameter and the minimum allowed basic quantization parameter. The video decoder 300 may then inverse quantize the block of video data based on the determined basic quantization parameter.

[0142] In one example, the video encoder 200 and the video decoder 300 can be configured to limit the base QP to min_baseQP (eg, the base QP must be at least the minimum allowed base QP), which corresponds to the lossless condition of the input material bit depth (inputBitDepth). An example is shown below:

[0143] min_baseQP=4+6*(internalBitDepth-inputBitDepth)

[0144] For input QP, the values ​​corresponding to the lossless condition for the input material bit depth (inputBitDepth) are as follows:

[0145] min_inputQP=4-6*(inputBitDepth-8)

[0146] Thus, in one example of the present disclosure, the video encoder 200 may be configured to: derive a minimum allowable basic quantization parameter for the video data based on the input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and quantize the block of the video data based on the basic quantization parameter. Similarly, the video decoder 300 may be configured to: derive a minimum allowable basic quantization parameter for the video data based on the input bit depth of the video data; determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter; and inverse quantize the block of the video data based on the basic quantization parameter.

[0147] In the above examples, blocks of video data (e.g., transform units of pixel-domain video data) may be encoded and decoded using transform skip mode or an escape mode of palette mode. However, the techniques of the present disclosure may be used in any situation where rounding errors are generated using a base QP value that is too low.

[0148] In a more specific example, in order to derive the minimum allowable basic quantization parameter for the video data based on the input bit depth of the video data, the video encoder 200 and the video decoder 300 are configured to derive the minimum allowable basic quantization parameter for the video data according to the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth). For example, the video encoder 200 and the video decoder 300 can be configured to derive the minimum allowable basic quantization parameter (min_baseQP) according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

[0149] In one example, the video encoder 200 and the video decoder 300 may be configured to limit the base QP to min_baseQP, which corresponds to the lossless condition of the internal bit depth (internalBitDepth). An example is shown below:

[0150] min_baseQP=4+6*(internalBitDepth-internalBitDepth)=4 For input QP, the values ​​corresponding to the lossless condition of internal bit depth (internalBitDepth) are as follows:

[0151] min_inputQP=4-6*(internalBitDepth-8)

[0152] In another example, the video encoder 200 and the video decoder 300 can be configured to limit the value of the base QP to min_baseQP (e.g., the base QP must be at least the minimum allowed base QP), which corresponds to the lossless condition of the input material bit depth (inputBitDepth). In this example, the value of the minimum allowed base QP depends on the maximum allowed TU size (Sb x Sb) for transform skip mode. An example is shown below:

[0153] min_baseQP=4+6*(internalBitDepth-inputBitDepth+log 2 Sb-5)

[0154] If the maximum allowed TU size for transform skipping is non-square, Sb is set to the maximum value between TU width and TU height. For input QP, the corresponding restrictions are as follows:

[0155] min_inputQP=4-6*(inputBitDepth-log 2 Sb-3)

[0156] In another example, the video encoder 200 and the video decoder 300 can be configured to limit the base QP to min_baseQP, which corresponds to the lossless condition of the internal bit depth (internalBitDepth). In this example, the value of the minimum allowed base QP depends on the maximum allowed TU size (Sb x Sb) for transform skip mode. An example is shown below:

[0157] min_baseQP=4+6*(internalBitDepth-internalBitDepth+log 2 Sb-5)=4+6*(log 2 Sb-5)

[0158] If the maximum allowed TU size for transform skipping is non-square, Sb is set to the maximum value between TU width and TU height. For input QP, the corresponding restrictions are as follows:

[0159] min_inputQP=4-6*(internalBitDepth-log 2 Sb-3)

[0160] Therefore, in another example of the present disclosure, the video encoder 200 and the video decoder 300 may be configured to derive a minimum allowed base quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode. In one example, the video encoder 200 and the video decoder 300 may be configured to derive a minimum allowed base quantization parameter (min_baseQP) based on the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth+log 2 Sb-5), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode. In another example, the video encoder 200 and the video decoder 300 can be configured to derive the minimum allowed basic quantization parameter (min_baseQP) according to the following function: min_baseQP=4+6*(internalBitDepth-internalBitDepth+log 2 Sb-5)=4+6*(log 2 Sb-5), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode.

[0161] In some examples, the video encoder 200 can be configured to signal the minimum allowed base QP or the minimum allowed input QP for transform skip mode and / or palette coding mode to the video decoder 300. The video encoder 200 can be configured to perform encoding and / or signaling of syntax elements in different ways. In one example, the video encoder 200 can be configured to directly signal the value of the minimum allowed base QP or input QP, i.e., min_baseQP or min_inputQP.

[0162] In other examples, the video encoder 200 may be configured to signal a delta QP value. In one example, the video encoder 200 may be configured to signal a min_baseQP minus a constant value. In another example, the video encoder 200 may be configured to signal a min_inputQP minus a constant value. In another example, the video encoder 200 may be configured to signal a QP difference between the original input QP and the minimum allowed input QP (e.g., signaling ΔQP=inputQP–min_inputQP or ΔQP=min_inputQP–inputQP). In another example, the video encoder 200 may be configured to signal a QP difference between the original base QP and the minimum allowed base QP, i.e., signaling ΔQP=baseQP–min_baseQP or ΔQP=min_baseQP–baseQP.

[0163] In another example of the present disclosure, the video encoder 200 may be configured to encode and signal a syntax element indicating inputBitDepth. The video decoder 300 may be configured to receive and decode such syntax elements. The video encoder 200 may encode the syntax elements in any syntax structure, including a sequence parameter set (SP). The video encoder 200 and the video decoder 300 may be configured to derive a minimum QP for a base QP or input QP using one or more of the techniques described above. Note that since the values ​​of inputBitDepth for luma and chroma components may be different, if chroma transform skip mode is supported, the video encoder 200 may be configured to perform separate signaling for luma and chroma minimum QPs for palette mode and transform skip mode.

[0164] In another example of the present disclosure, if the minimum QP limit is reached, the video encoder 200 and the video decoder 300 may be configured to apply lossless coding to the block (eg, as indicated by transquant_bypass_flag=1). When transquant_bypass_flag=1, the video encoder 200 and the video decoder 300 bypass the transform and quantization process.

[0165] Figure 5 2 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and 3 ), but it should be understood that other devices may be configured to perform the same Figure 5 A similar approach to the one used in this paper.

[0166] In this example, video encoder 200 initially predicts a current block (350). For example, video encoder 200 may form a prediction block for the current block. Video encoder 200 may then calculate a residual block for the current block (532). To calculate the residual block, video encoder 200 may calculate the difference between the original, unencoded block and the prediction block for the current block. Video encoder 200 may then transform and quantize coefficients of the residual block (354). For example, according to techniques of the present disclosure, video encoder 200 may be configured to: when encoding the residual block using transform skip mode or palette coding mode, perform a transform based on the residual block. Figure 7 The video encoder 200 may use a technique to determine a quantization parameter for quantizing the coefficients of the residual block. Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the coefficients (358). For example, the video encoder 200 may use CAVLC or CABAC to encode the coefficients. The video encoder 200 may then output the entropy coded data of the block (360).

[0167] Figure 6 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and 4 ), but it should be understood that other devices may be configured to perform the same Figure 6 A similar approach to the one used in this paper.

[0168] The video decoder 300 may receive entropy coded data for a current block (e.g., entropy coded prediction information and entropy coded data for coefficients of a residual block corresponding to the current block) (370). The video decoder 300 may entropy decode the entropy coded data to determine prediction information for the current block and reproduce coefficients of the residual block (372). The video decoder 300 may predict the current block (374), for example, by calculating a prediction block for the current block using an intra-frame or inter-frame prediction mode indicated by the prediction information of the current block. The video decoder 300 may then inverse scan the reproduced coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the coefficients to produce a residual block (378). For example, according to the techniques of the present disclosure, the video decoder 300 may be configured to: when decoding a residual block using a transform skip mode or a palette decoding mode, perform inverse quantization and inverse transform according to the inverse quantization and inverse transform modes. Figure 8 The technique of determining the quantization parameter used to inversely quantize the coefficients of the residual block. Finally, the video decoder 300 can decode the current block by combining the prediction block and the residual block (380).

[0169] Figure 7 is a flow chart illustrating an example encoding method for determining a quantization parameter in accordance with techniques of this disclosure. Figure 7 The techniques of the present invention may be performed by one or more components of the video encoder 200, including the quantization unit 208. In one example, the quantization unit 208 may be configured to derive a minimum allowable basic quantization parameter for the video data based on an input bit depth of the video data (400). The quantization unit 208 may encode a syntax element indicating the input bit depth (402). The quantization unit 208 may also determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter (404), and quantize the block of the video data based on the basic quantization parameter (406).

[0170] Figure 8 is a flow chart illustrating an example decoding method for determining a quantization parameter in accordance with techniques of this disclosure. Figure 8 The techniques of the invention may be performed by one or more components of the video decoder 300, including the inverse quantization unit 306. In one example, the inverse quantization unit 306 may be configured to decode a syntax element indicating an input bit depth of the video data (450). The inverse quantization unit 306 may then derive a minimum allowable basic quantization parameter for the video data based on the input bit depth of the video data (452). The inverse quantization unit 306 may also determine a basic quantization parameter for a block of the video data based on the minimum allowable basic quantization parameter (454), and inverse quantize the block of the video data based on the basic quantization parameter (456).

[0171] Additional illustrative examples of the disclosure are described below.

[0172] Example 1 - A method of decoding video data, the method comprising: deriving a minimum allowable basic quantization parameter for a block of video data decoded using a transform skip mode; limiting a basic quantization parameter for the block of video data based on the minimum allowable basic quantization parameter; and applying the basic quantization parameter to the block of video data.

[0173] Example 2 - The method of Example 1, wherein the block of video data is a transform unit of pixel-domain video data.

[0174] Example 3 - The method of Example 1, wherein deriving the minimum allowed base quantization parameter comprises deriving the minimum allowed base quantization parameter (min_baseQP) according to the following equation: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

[0175] Example 4 - The method of Example 1, wherein deriving the minimum allowed base quantization parameter comprises deriving the minimum allowed base quantization parameter (min_baseQP) according to the following equation: min_baseQP=4+6*(internalBitDepth-internalBitDepth)=4.

[0176] Example 5 - The method of Example 1, wherein deriving the minimum allowed base quantization parameter comprises: deriving the minimum allowed base quantization parameter (min_baseQP) according to the following equation: min_baseQP = 4 + 6 * (internalBitDepth - inputBitDepth + log 2 Sb-5), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode.

[0177] Example 6 - The method of Example 1, wherein deriving the minimum allowed basic quantization parameter comprises: deriving the minimum allowed basic quantization parameter (min_baseQP) according to the following equation: min_baseQP = 4 + 6 * (internalBitDepth - internalBitDepth + log 2 Sb-5)=4+6*(log 2 Sb-5), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode.

[0178] Example 7 - The method of Example 1, further comprising: decoding a syntax element indicating the minimum allowed base quantization parameter.

[0179] Example 8 - A method of decoding video data, the method comprising: deriving a minimum allowable input quantization parameter for a block of video data decoded using a transform skip mode; limiting the input quantization parameter for the block of video data based on the minimum allowable input quantization parameter; and applying the input quantization parameter to the block of video data.

[0180] Example 9 —The method of Example 8, wherein the block of video data is a transform unit of pixel-domain video data.

[0181] Example 10 - The method of Example 8, wherein deriving the minimum allowed input quantization parameter comprises deriving the minimum allowed input quantization parameter (min_inputQP) according to the following equation: min_inputQP=4-6*(inputBitDepth-8).

[0182] Example 11 - The method of Example 8, wherein deriving the minimum allowed input quantization parameter comprises deriving the minimum allowed input quantization parameter (min_inputQP) according to the following equation: min_inputQP=4-6*(internalBitDepth-8).

[0183] Example 12 - The method of Example 8, wherein deriving the minimum allowed input quantization parameter comprises: deriving the minimum allowed input quantization parameter (min_inputQP) according to the following equation: min_inputQP = 4-6*(inputBitDepth-log 2 Sb-3), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode.

[0184] Example 13 - The method of Example 8, wherein deriving the minimum allowed input quantization parameter comprises: deriving the minimum allowed input quantization parameter (min_inputQP) according to the following equation: min_inputQP = 4-6*(internalBitDepth-log 2 Sb-3), where Sb is the width or height of the maximum allowed transform unit size for transform skip mode.

[0185] Example 14 - The method of Example 8, further comprising: decoding a syntax element indicating the minimum allowed input quantization parameter.

[0186] Example 15 - The method according to any combination of Examples 1-14, further comprising: decoding a syntax element indicating the input bit depth (inputBitDepth).

[0187] Example 16 - The method of any combination of Examples 1-14, further comprising: performing lossless decoding on the block when the minimum allowed base quantization parameter is reached.

[0188] Example 17 - A method according to any of Examples 1-16, wherein decoding includes decoding.

[0189] Example 18 - A method according to any of Examples 1-16, wherein decoding includes encoding.

[0190] Example 19 - An apparatus for decoding video data, the apparatus comprising one or more units for performing the method according to any of Examples 1-18.

[0191] Example 20 - The apparatus of Example 19, wherein the one or more units include one or more processors implemented in a circuit.

[0192] Example 21 - The apparatus of any one of Examples 19 and 20, further comprising: a memory for storing the video data.

[0193] Example 22 - The apparatus of any of Examples 19-21, further comprising: a display configured to display the decoded video data.

[0194] Example 23 - A device according to any of Examples 19-22, wherein the device includes one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0195] Example 24 - A device according to any of Examples 19-23, wherein the device includes a video decoder.

[0196] Example 25 - A device according to any of Examples 19-24, wherein the device includes a video encoder.

[0197] Example 26 - A computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform a method according to any of Examples 1-18.

[0198] It is to be appreciated that, according to examples, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary to implement the techniques). In addition, in some examples, actions or events may be performed concurrently rather than sequentially, such as through multithreading, interrupt handling, or multiple processors.

[0199] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium or a communication medium, the communication medium including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-temporary tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, codes, and / or data structures for implementing the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0200] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is appropriately referred to as a computer-readable medium. For example, if a coaxial cable, optical fiber cable, twisted pair, digital subscriber line (DSL) or wireless technology (e.g., infrared, radio and microwave) is used to transmit instructions from a website, server or other remote source, then the coaxial cable, optical fiber cable, twisted pair, DSL or wireless technology (e.g., infrared, radio and microwave) is included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals or other temporary media, but are instead directed to non-temporary tangible storage media. As used herein, disks and optical disks include compact disks (CDs), laser optical disks, optical disks, digital versatile disks (DVDs), floppy disks and blue-ray disks, wherein disks usually copy data magnetically, while optical disks use lasers to optically copy data. Combinations of the above should also be included within the scope of computer-readable media.

[0201] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuitry" as used herein may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. In addition, the techniques may be implemented entirely in one or more circuits or logic elements.

[0202] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize the functional aspects of a device configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. Specifically, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and / or firmware.

[0203] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: deriving a minimum allowed basic quantization parameter for the video data based on an input bit depth of the video data; determining a base quantization parameter for a block of the video data based on the minimum allowed base quantization parameter; as well as The block of video data is inverse quantized based on the base quantization parameter.

2. The method according to claim 1, further comprising: A syntax element indicating the input bit depth is decoded.

3. The method according to claim 1, wherein: The block of video data is a transform unit of pixel domain video data, the method further comprising: The inverse quantized transform unit of pixel-domain video data is decoded using a transform skip mode or an escape mode of a palette mode.

4. The method according to claim 1, wherein: Derivation of the minimum allowed base quantization parameter for the video data based on the input bit depth of the video data comprises: The minimum allowed basic quantization parameter for the video data is derived from an internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth).

5. The method according to claim 4, wherein: Derivation of the minimum allowed basic quantization parameter for the video data according to the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) comprises: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

6. The method according to claim 4, wherein: Derivation of the minimum allowed basic quantization parameter for the video data according to the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) comprises: The minimum allowed basic quantization parameter for the video data is derived from the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and a maximum allowed transform unit size for transform skip mode.

7. The method according to claim 6, wherein: Derivation of the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode comprises: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth+log2Sb- 5), wherein Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

8. The method according to claim 6, wherein: Derivation of the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode comprises: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-internalBitDepth+ log2Sb-5)=4+6*(log2Sb-5), where Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

9. The method according to claim 1, wherein: Determining the base quantization parameter for the block of the video data based on the minimum allowed base quantization parameter comprises: determining an initial value of the basic quantization parameter; and The basic quantization parameter is determined as a maximum value of the initial value of the basic quantization parameter and the minimum allowed basic quantization parameter.

10. The method according to claim 1, further comprising: A picture including the block of the video data is displayed.

11. An apparatus configured to decode video data, the apparatus comprising: a memory configured to store the video data; as well as One or more processors implemented in circuitry and in communication with the memory, the one or more processors being configured to: deriving a minimum allowed basic quantization parameter for the video data based on an input bit depth of the video data; determining a base quantization parameter for a block of the video data based on the minimum allowed base quantization parameter; as well as The block of video data is inverse quantized based on the base quantization parameter.

12. The device according to claim 11, wherein The one or more processors are further configured to: A syntax element indicating the input bit depth is decoded.

13. The device according to claim 11, wherein: The block of video data is a transform unit of pixel domain video data, and wherein the one or more processors are further configured to: The inverse quantized transform unit of pixel-domain video data is decoded using a transform skip mode or an escape mode of a palette mode.

14. The device according to claim 11, wherein: To derive the minimum allowed base quantization parameter for the video data based on the input bit depth of the video data, the one or more processors are further configured to: The minimum allowed basic quantization parameter for the video data is derived from an internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth).

15. The device according to claim 14, wherein: To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth), the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

16. The device according to claim 14, wherein: To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth), the one or more processors are further configured to: The minimum allowed basic quantization parameter for the video data is derived from the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and a maximum allowed transform unit size for transform skip mode.

17. The device according to claim 16, wherein: To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode, the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth+log2Sb- 5), wherein Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

18. The device according to claim 16, wherein: To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode, the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-internalBitDepth+ log2Sb-5)=4+6*(log2Sb-5), where Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

19. The device according to claim 11, wherein: To determine the base quantization parameter for the block of the video data based on the minimum allowed base quantization parameter, the one or more processors are further configured to: Determining an initial value of the basic quantization parameter; as well as The basic quantization parameter is determined as a maximum value of the initial value of the basic quantization parameter and the minimum allowed basic quantization parameter.

20. The apparatus according to claim 11, further comprising: A display configured to display a picture comprising the block of the video data.

21. An apparatus configured to decode video data, the apparatus comprising: means for deriving a minimum allowed basic quantization parameter for said video data based on an input bit depth of said video data; means for determining a base quantization parameter for a block of the video data based on the minimum allowed base quantization parameter; as well as Means for inverse quantizing the block of video data based on the base quantization parameter.

22. The apparatus according to claim 21, further comprising: Means for decoding a syntax element indicating the input bit depth.

23. The device according to claim 21, wherein The block of video data is a transform unit of pixel domain video data, the apparatus further comprising: Unit for decoding an inverse quantized transform unit of pixel domain video data using a transform skip mode or an escape mode of a palette mode.

24. The device according to claim 21, wherein The means for deriving the minimum allowed basic quantization parameter for the video data based on the input bit depth of the video data comprises: Means for deriving the minimum allowed base quantization parameter for the video data from an internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth).

25. The device according to claim 24, wherein: The means for deriving the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) comprises: Unit for deriving the minimum allowed base quantization parameter (min_baseQP) according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

26. A non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors configured to decode video data to: deriving a minimum allowed basic quantization parameter for the video data based on an input bit depth of the video data; determining a base quantization parameter for a block of the video data based on the minimum allowed base quantization parameter; as well as The block of video data is inverse quantized based on the base quantization parameter.

27. The non-transitory computer-readable storage medium of claim 26, wherein: The instructions further cause the one or more processors to: A syntax element indicating the input bit depth is decoded.

28. The non-transitory computer-readable storage medium of claim 26, wherein: The block of video data is a transform unit of pixel domain video data, and wherein the instructions further cause the one or more processors to: The inverse quantized transform unit of pixel-domain video data is decoded using a transform skip mode or an escape mode of a palette mode.

29. The non-transitory computer-readable storage medium of claim 26, wherein: To derive the minimum allowed base quantization parameter for the video data based on the input bit depth of the video data, the instructions further cause the one or more processors to: The minimum allowed basic quantization parameter for the video data is derived from an internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth).

30. The non-transitory computer-readable storage medium of claim 29, wherein: To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth), the instructions further cause the one or more processors to perform the following operations: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

31. An apparatus configured to encode video data, the apparatus comprising: a memory configured to store the video data; as well as One or more processors implemented in circuitry and in communication with the memory, the one or more processors being configured to: deriving a minimum allowed basic quantization parameter for the video data based on an input bit depth of the video data; determining a base quantization parameter for a block of the video data based on the minimum allowed base quantization parameter; as well as The block of video data is quantized based on the base quantization parameter.

32. The device according to claim 31, wherein The one or more processors are further configured to: A syntax element indicating the input bit depth is encoded.

33. The device according to claim 31, wherein The block of the video data is a transform unit of pixel domain video data, and wherein the one or more processors are further configured to: The block of the video data is encoded using a transform skip mode or an escape mode of a palette mode.

34. The device according to claim 31, wherein To derive the minimum allowed base quantization parameter for the video data based on the input bit depth of the video data, the one or more processors are further configured to: The minimum allowed basic quantization parameter for the video data is derived from an internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth).

35. The device according to claim 34, wherein To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth), the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth).

36. The device according to claim 34, wherein To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth), the one or more processors are further configured to: The minimum allowed basic quantization parameter for the video data is derived from the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and a maximum allowed transform unit size for transform skip mode.

37. The device according to claim 36, wherein To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode, the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-inputBitDepth+log2Sb- 5), wherein Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

38. The device according to claim 36, wherein To derive the minimum allowed basic quantization parameter for the video data based on the internal bit depth (internalBitDepth) minus the input bit depth (inputBitDepth) and the maximum allowed transform unit size for the transform skip mode, the one or more processors are further configured to: The minimum allowed base quantization parameter (min_baseQP) is derived according to the following function: min_baseQP=4+6*(internalBitDepth-internalBitDepth+ log2Sb-5)=4+6*(log2Sb-5), where Sb is the width or height of the maximum allowed transform unit size for the transform skip mode.

39. The device according to claim 31, wherein To determine the base quantization parameter for the block of the video data based on the minimum allowed base quantization parameter, the one or more processors are further configured to: Determining an initial value of the basic quantization parameter; as well as The basic quantization parameter is determined as a maximum value of the initial value of the basic quantization parameter and the minimum allowed basic quantization parameter.

40. The apparatus of claim 31 , further comprising: A camera is configured to capture a picture comprising the block of video data.

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