CN116998150A - State transition for grid quantization in video coding and decoding - Google Patents

Abstract

In some embodiments, a video encoder or decoder reconstructs blocks of video by correlated quantization. The video encoder or decoder accesses the quantized elements within the block and processes the quantized elements according to an order corresponding to the block to generate corresponding dequantized elements. The processing includes obtaining a current quantized element from quantized elements of the block, and determining a current state for quantization based on a previous state for quantization of an element preceding the current quantized element and a state transition diagram selected from two state transition diagrams. The process also includes determining a quantizer of the current quantized element based on a current state of the current quantized element, and dequantizing the current quantized element based on the quantizer to generate a dequantized element. A video encoder or decoder reconstructs the block based on the dequantized elements.

Description

State transition of grid quantization in video encoding and decoding

Cross-references to related applications

This application claims the benefit of priority from U.S. Provisional Application No. 63/170,040, entitled "Improved State Transition Method for Trellis Quantization in Video Coding", filed on April 2, 2021, which is incorporated herein by reference in its entirety.

Technical field

The present disclosure relates generally to computer-implemented methods and systems for video processing. In particular, the present disclosure relates to trellis quantization for video codecs.

Background technique

The ubiquity of camera-enabled devices such as smartphones, tablets, and computers makes capturing video or images easier than ever. However, even short videos can be quite large in data size. Video codec technology (including video encoding and decoding) can compress video data into a smaller amount of data, allowing the storage and transmission of more types of videos. Video codecs are already used in a wide range of applications, such as digital television broadcasting, video transmission over the Internet and mobile networks, real-time applications (e.g., video chat, video conferencing), DVD and Blu-ray discs, and more. In order to reduce the storage space used to store videos and/or the network bandwidth consumption used to transmit videos, the efficiency of video encoding and decoding schemes needs to be improved.

Contents of the invention

Some embodiments relate to correlated quantization for video codecs. In one example, a method for reconstructing a block of a video includes processing a plurality of quantized elements within the block in a sequence to generate respective dequantized elements corresponding to the plurality of quantized elements. The processing includes obtaining a quantized element within the block from a plurality of quantized elements; a state for quantization based on a quantized element preceding the obtained quantized element and from a first state transition diagram and a second state transition diagram. Determine the state of the obtained quantized element for quantization from a state transition diagram selected in, wherein the first state transition diagram is different from the second state transition diagram; determine the obtained quantization based on the obtained state of the quantized element a quantizer for elements; and using this quantizer to quantize the obtained quantized elements to generate dequantized elements corresponding to the obtained quantized elements. The method also includes reconstructing the block based on respective dequantized elements corresponding to the plurality of quantized elements.

In another example, a non-transitory computer-readable medium has program code stored therein and executable by one or more processing devices to perform the following operations: sequentially process a plurality of blocks within a video quantized elements to generate respective dequantized elements corresponding to a plurality of quantized elements, the processing comprising: obtaining a quantized element within the block from the plurality of quantized elements; based on a previous quantization of the obtained quantized element The state of the element for quantization and the state transition diagram selected from the first state transition diagram and the second state transition diagram determine the obtained state of the element for quantization for quantization, wherein the first state transition diagram is different in the second state transition diagram; determining a quantizer for the obtained quantized element based on the state of the obtained quantized element; and using the quantizer to quantize the obtained quantized element to generate a quantized signal corresponding to the obtained quantized element. The dequantized element of the element. The operations also include reconstructing the block based on respective dequantized elements corresponding to the plurality of quantized elements.

In yet another example, a system includes a processing device and a non-transitory computer-readable medium capable of data transmission with the processing device. The processing device is configured to execute program code stored in the non-transitory computer-readable medium to perform the following operations: sequentially process a plurality of quantized elements within the video block to generate respective dequantizations corresponding to the plurality of quantized elements. The processing includes: obtaining a quantized element within the block from a plurality of quantized elements; a state for quantization based on the quantized element before the obtained quantized element and a transition diagram from the first state and the second state; The state transition diagram selected from the two state transition diagrams determines the state of the obtained quantized element for quantization, wherein the first state transition diagram is different from the second state transition diagram; based on the current state of the obtained quantized element determining a quantizer for the obtained quantized elements; and using the quantizer to quantize the obtained quantized elements to generate dequantized elements corresponding to the obtained quantized elements. The operations also include reconstructing the block based on respective dequantized elements corresponding to the plurality of quantized elements.

In another example, a method for encoding a block of video includes sequentially processing a plurality of elements within the block of video to generate respective quantized elements corresponding to the plurality of elements. The processing includes: obtaining one element within the block from a plurality of elements; a state for quantization based on an element before the obtained element and a state transition diagram selected from the first state transition diagram and the second state transition diagram, Determining a state of the obtained element for quantization, wherein the first state transition diagram is different from the second state transition diagram; determining a quantizer of the obtained element based on the current state of the obtained element; and quantizing using the quantizer the obtained element to generate a quantized element corresponding to the obtained element. The method also includes encoding respective quantized elements corresponding to the plurality of elements into a bitstream of the video.

In yet another example, a non-transitory computer-readable medium has program code stored therein and executable by one or more processing devices to: sequentially process multiple elements of a block of video , to generate respective quantized elements corresponding to the plurality of elements, the process including: obtaining an element within the block from the plurality of elements; a state for quantization based on the element before the obtained element and transitioning from the first state The state transition diagram selected in the diagram and the second state transition diagram determines the state of the obtained element for quantification, wherein the first state transition diagram is different from the second state transition diagram; determined based on the current state of the obtained element a quantizer for the obtained element; and quantizing the obtained element using this quantizer to generate a quantized element corresponding to the obtained element. The operations also include encoding respective quantized elements corresponding to the plurality of elements into the bitstream of the video.

A system includes a processing device and non-transitory computer-readable media capable of transmitting data to and from the processing device. The processing device is configured to execute program code stored in the non-transitory computer-readable medium to perform the following operations: process a plurality of elements of the video block in sequence to generate respective quantized elements corresponding to the plurality of elements, the processing including: obtaining an element within the block from a plurality of elements; determining the state transition diagram selected from the first state transition diagram and the second state transition diagram based on the state of the element before the obtained element for quantification. a state of the obtained element for quantization, wherein the first state transition diagram is different from the second state transition diagram; determining a quantizer of the obtained element based on the current state of the obtained element; and quantizing the obtained element using this quantizer elements to generate quantized elements corresponding to the obtained elements. The operations also include encoding respective quantized elements corresponding to the plurality of elements into the bitstream of the video.

These illustrative embodiments are mentioned not to limit or define the disclosure, but to provide examples to aid understanding of the disclosure. Additional embodiments are discussed and further description is provided in the Detailed Description.

Description of the drawings

The features, embodiments, and advantages of the present disclosure can be better understood by reading the following detailed description with reference to the accompanying drawings.

1 illustrates a block diagram of an example of a video encoder configured to implement embodiments presented in this disclosure.

2 illustrates a block diagram of an example of a video decoder configured to implement embodiments presented in this disclosure.

Figure 3 depicts an example of coding tree unit partitioning of images in a video according to some embodiments of the present disclosure.

Figure 4 depicts an example of coding unit partitioning of coding tree units according to some embodiments of the present disclosure.

Figure 5 depicts an example of a predetermined order for processing elements within a coding block.

Figure 6 depicts an example of two quantizers used for correlation quantization in existing video coding and decoding techniques.

Figure 7 depicts an example of a state transition diagram and associated state transition table for correlation quantization in accordance with some embodiments of the present disclosure.

Figure 8 depicts an example of possible trellis paths employing trellis quantization to quantize multiple consecutive coefficients in a block in accordance with some embodiments of the present disclosure.

Figures 9A and 9B depict another example of possible trellis paths employing trellis quantization to quantize multiple consecutive coefficients in a block in accordance with some embodiments of the present disclosure.

Figure 10 depicts another example of a state transition diagram and associated state transition table for grid quantization in accordance with some embodiments of the present disclosure.

Figure 11 depicts an example of a possible grid path for using a two-state transition map to quantize multiple consecutive coefficients in a block in accordance with some embodiments of the present disclosure.

Figure 12 depicts another example of a possible grid path for using a two-state transition map to quantize multiple consecutive coefficients in a block in accordance with some embodiments of the present disclosure.

Figure 13 depicts an example of a process for encoding blocks of video using trellis quantization with a two-state transition map in accordance with some embodiments of the present disclosure.

Figure 14 depicts an example of a process for reconstructing blocks of video quantized using grid quantization with a two-state transition map in accordance with some embodiments of the present disclosure.

Figure 15 depicts an example of a computing system that may be used to implement some embodiments of the present disclosure.

Detailed ways

Various embodiments may provide trellis quantization for video codecs. As mentioned above, more and more video data are being generated, stored and transmitted, so it is beneficial to improve the encoding and decoding efficiency of video codec technology, which is beneficial to using less data to present the video without compromising the decoding efficiency. The visual quality of the video. One aspect of improving codec efficiency is to improve the quantization scheme of video codecs. The latest video codec standards, such as versatile video coding (VVC), have adopted grid quantization techniques such as correlation quantization.

In trellis quantization, more than one quantizer is available when quantizing elements (eg, residual pixel values or residual transform coefficients) within a coding block (or "block"). The quantizer used to quantize the current element depends on the value of the previous element in the encoding block. In some examples, the value of a previously quantized element is used to determine the quantization state used to quantize the current element, which in turn is used to determine the quantizer for the current element (hereinafter, the "quantization state used to quantize the element" is also referred to as is the "state of the element"). Since existing grid quantization methods use only one state transition graph, the quantization path along consecutive elements in a block is likely to follow a quantization path with a simple pattern. For example, a quantization path may indicate that multiple consecutive elements use the same scalar quantizer, or that two quantizers are used alternately for consecutive elements. These simple pattern quantization paths do not fully utilize grid quantization, which greatly weakens the advantages of grid quantization over scalar quantization, thereby reducing coding efficiency.

Various embodiments described in this disclosure address these issues by introducing a second state transition diagram and using two state transition diagrams when determining the state of an element of a coding block and selecting a quantizer for that element. The elements of the coding block may be the residuals after inter- or intra-prediction of the coding block. This element can be the transform coefficient of the residual in the frequency domain or the value of the residual in the pixel domain. When determining the quantization state used to select the quantizer for quantizing the current element, one of two state transition diagrams may be used. For example, these two state transition diagrams can be used in alternating mode, such that the first state transition diagram is used for N consecutive elements, the second state transition diagram is used for the next M consecutive elements, and so on. M and N are integer values, M can be equal to or less than N.

The following non-limiting examples are provided to introduce some embodiments. In one example, the quantizer for encoding the current element of the block is determined based on the quantization state used to quantize the current element. The quantization state used to quantize the current element is determined based on the quantization state of the previous element and whether the quantized value of the previous element belongs to one subset of quantized values rather than another subset. In some implementations, if the elements are transform coefficients in the frequency domain, the elements in the coding block are processed according to a predetermined order, such as from highest frequency to lowest frequency. In these examples, the video encoder or decoder determines the quantization state used to quantize the current element based on the elements preceding the current element and their corresponding quantization states according to a predetermined order and based on the state transition diagram.

The state transition diagram is determined by alternating between a primary state transition diagram and a secondary state transition diagram following an N+M repeating pattern. In other words, the primary state transition diagram can be used for N consecutive elements, and then the secondary state transition diagram is used for the next M consecutive elements. This pattern can be repeated until all elements in the block have been processed. N and M are integers, and N can be equal to M or greater than M. Both encoder and decoder use the same N, M and repeating pattern N+M. Compared with existing mesh quantization methods that only use a state transition diagram to determine the state of the current element, the proposed method avoids the quantized mesh paths being restricted to a limited number of simple paths, thereby being able to fully utilize the mesh. The advantages of lattice quantization over scalar quantization are used to improve coding efficiency.

The video encoder can quantize the current element using the selected quantizer, and then can encode the quantized elements for the encoding block into the bitstream of the video. On the decoder side or encoder side, when reconstructing a block for prediction purposes, the dequantization process may use the method described above to determine the quantization state of each quantized element in the block, and subsequently determine the quantizer. The determined quantizer can be used to dequantize the elements, and the elements of these dequantized blocks can then be used to reconstruct blocks of the video for display (at the decoder) or prediction of other blocks or images (at the encoder). encoder and decoder). The technology proposed by this disclosure can be an effective codec tool in various video codec standards.

Referring now to the drawings, FIG. 1 illustrates a block diagram of an example of a video encoder 100 configured to implement embodiments presented in this disclosure. In the example shown in Figure 1, video encoder 100 includes partitioning module 112, transform module 114, quantization module 115, inverse quantization module 118, inverse transform module 119, in-loop filter module 120, intra prediction module 126, frame inter prediction module 124, motion estimation module 122, decoded image buffer 130 and entropy encoding module 116.

The input to the video encoder 100 is an input video 102 that contains a sequence of images (also called frames or pictures). In a block-based video encoder, for each image, the video encoder 100 employs a partitioning module 112 to partition the image into blocks 104, and each block contains a plurality of pixels. A block may be a macroblock, coding tree unit, coding unit, prediction unit, and/or prediction block. An image can include blocks of different sizes, and different images of a video can have different block divisions. Different images may use different predictions (eg intra prediction or inter prediction or mixed intra and inter prediction) to encode each block.

Typically, the first picture of the video signal is an intra-coded picture, which is encoded using intra prediction only. Intra prediction mode predicts blocks of an image using only data encoded from the same image. Decoding intra-coded images can be done without information from other images. To perform intra prediction, video encoder 100 shown in FIG. 1 may employ intra prediction module 126. Intra-prediction module 126 is configured to generate an intra-prediction block (prediction block 134) using reconstructed samples from reconstructed neighboring blocks 136 in the same image. Intra prediction is performed based on the intra prediction mode selected for the block. Video encoder 100 then calculates the difference between original image block 104 and intra prediction block 134 . This difference is called the residual block 106.

To further remove redundancy from the block, the residual block 106 is transformed into the transform domain by transform module 114 by applying a transform to the samples in the block. Examples of transformations may include, but are not limited to, discrete cosine transform (DCT) or discrete sine transform (DST). The transformed values may be called transform coefficients representing the residual block in the transform domain. In some examples, the residual blocks may be quantized directly without being transformed by transform module 114. This is called transform skip mode.

Video encoder 100 may further quantize the transform coefficients using quantization module 115 to obtain quantized coefficients. Quantization involves dividing the sample by the quantization step, followed by rounding, while inverse quantization involves multiplying the quantized value by the quantization step. This quantization process is called scalar quantization. Quantization is used to reduce the dynamic range of video samples (transformed or untransformed) so that fewer bits are used to render the video samples.

Quantization of intra-block coefficients/samples can be done independently, and this quantization method is used in some existing video compression standards, such as H.264 and HEVC. For an N×M block, some scan order can be used to convert the 2D coefficients of the block into a 1-D array for coefficient quantization and encoding and decoding. Quantization of coefficients within a block can exploit scan order information. For example, the quantization of a given coefficient in a block may depend on the state of previously quantized values along the scan order. To further improve encoding and decoding efficiency, more than one quantizer can be used. Which quantizer is used to quantize the current coefficient depends on the encoding and decoding information preceding the current coefficient along the scanning order. This quantification method is called correlation quantification.

The degree of quantization can be adjusted using the quantization step size. For example, with scalar quantization, different quantization steps can be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The quantization step size may be indicated by a quantization parameter (QP). Quantization parameters are provided in the encoded bitstream of the video so that the video decoder can access and apply the quantization parameters for decoding.

The quantized samples are then encoded by the entropy encoding module 116 to further reduce the size of the video signal. Entropy coding module 116 is configured to apply an entropy coding algorithm to the quantized samples. In some examples, the quantized samples are binarized into bins, and the encoding algorithm further compresses the bins into bits. Examples of binarization methods include, but are not limited to, combined truncated rice (TR) and k-th order Exp-Golomb (EGk) binarization, and k-th order Exp-Golomb binarization change. Examples of entropy coding algorithms include, but are not limited to, variable length coding (VLC) scheme, context adaptive VLC scheme (CAVLC), arithmetic coding scheme, binarization, context adaptive binary arithmetic coding (contextadaptive binary arithmetic coding, CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding or other entropy coding techniques . The entropy encoded data is then added to the encoded video 132 output bitstream.

As described above, reconstructed blocks 136 from neighboring blocks are used in intra prediction of blocks of an image. The process of generating the reconstructed block 136 of a block involves calculating the reconstructed residual of the block. The reconstructed residual may be determined by applying inverse quantization and inverse transform to the quantized residual of the block. The inverse quantization module 118 is configured to apply inverse quantization to the quantized samples to obtain dequantized coefficients. Inverse quantization module 118 applies the inverse of the quantization scheme applied by quantization module 115 by using the same quantization step size as quantization module 115 . The inverse transform module 119 is configured to apply an inverse transform of the transform applied by the transform module 114 to the dequantized samples, such as an inverse DCT or an inverse DST. The output of the inverse transform module 119 is the reconstructed residual of the block in the pixel domain. The reconstructed residual may be added to the predicted block 134 of the block to obtain the reconstructed block 136 in the pixel domain. For blocks with skipped transformations, the inverse transform module 119 is not applied to those blocks. The dequantized samples are the reconstructed residuals of the block.

Blocks in subsequent images of the first intra-predicted image may be encoded using inter-prediction or intra-prediction. In inter prediction, blocks in an image are predicted from one or more previously encoded video images. Video encoder 100 uses inter prediction module 124 to perform inter prediction. Inter prediction module 124 is configured to perform motion compensation on the block based on the motion estimate provided by motion estimation module 122 .

Motion estimation module 122 compares the current block 104 of the current image to the decoded reference image 108 to perform motion estimation. The decoded reference picture 108 is stored in the decoded picture buffer 130 . Motion estimation module 122 selects the reference block from the decoded reference image 108 that best matches the current block. Motion estimation module 122 further identifies an offset between the reference block's location (eg, x,y coordinates) and the current block's location. This offset is called a motion vector (MV) and is provided to the inter prediction module 124 together with the selected reference block. In some cases, multiple reference blocks are identified for the current block in multiple decoded reference images 108 . Accordingly, a plurality of motion vectors are generated and provided to the inter prediction module 124 along with the corresponding reference blocks.

Inter prediction module 124 performs motion compensation using motion vectors and other inter prediction parameters to generate predictions for the current block (ie, inter prediction block 134). For example, based on the motion vector, inter prediction module 124 may locate the prediction block pointed to by the motion vector in the corresponding reference image. If there is more than one prediction block, these prediction blocks are combined with some weights to generate prediction block 134 for the current block.

For inter-predicted blocks, video encoder 100 may subtract inter-predicted block 134 from block 104 to generate residual block 106 . The residual block 106 may be transformed, quantized, and entropy coded in the same manner as the residuals of intra-predicted blocks discussed above. Likewise, the reconstructed block 136 of the inter-predicted block may be obtained by inverse quantization, inverse transforming the residual and then combining with the corresponding prediction block 134 .

To obtain the decoded image 108 for motion estimation, the reconstructed block 136 is processed by the in-loop filter module 120 . In-loop filter module 120 is configured to smooth pixel transitions, thereby improving video quality. In-loop filter module 120 may be configured to implement one or more in-loop filters, such as a deblocking filter, or a sample-adaptive offset (SAO) filter, or an adaptive loop filter. (Adaptive loop filter, ALF) etc.

Figure 2 depicts an example of a video decoder 200 configured to implement embodiments presented in this disclosure. Video decoder 200 processes encoded video 202 in a bitstream and generates decoded images 208 . In the example shown in Figure 2, video decoder 200 includes entropy decoding module 216, inverse quantization module 218, inverse transform module 219, in-loop filter module 220, intra prediction module 226, inter prediction module 224, and decoded Image buffer 230.

Entropy decoding module 216 is configured to entropy decode encoded video 202 . Entropy decoding module 216 decodes the quantized coefficients, coding parameters including intra prediction parameters and inter prediction parameters, and other information. In some examples, entropy decoding module 216 decodes the bitstream of encoded video 202 into a binary representation and then converts the binary representation into quantization levels of coefficients. The entropy decoded coefficient levels are then inversely quantized by the inverse quantization module 218, and the inverse quantized coefficients are then inversely transformed to the pixel domain by the inverse transform module 219. The functions of the inverse quantization module 218 and the inverse transform module 219 are respectively similar to the inverse quantization module 118 and the inverse transform module 119 described above in FIG. 1 . The inverse-transformed residual blocks may be added to corresponding prediction blocks 234 to generate reconstructed blocks 236 . For blocks with skipped transformations, the inverse transform module 219 is not applied to those blocks. The dequantized samples generated by the inverse quantization module 118 are used to generate the reconstructed block 236 .

A prediction block 234 is generated for a specific block based on the prediction mode of the block. If the coding parameters of the block indicate that the block is intra-predicted, the reconstructed block 236 of the reference block in the same image may be fed into the intra-prediction module 226 to generate a predicted block 234 for the block. Predictive block 234 is generated by inter prediction module 224 if the coding parameters of the block indicate that the block is inter-predicted. The functions of intra prediction module 226 and inter prediction module 224 are similar to intra prediction module 126 and inter prediction module 124 of FIG. 1 , respectively.

As discussed above in Figure 1, inter prediction involves one or more reference pictures. Video decoder 200 generates decoded image 208 of the reference image by applying in-loop filter module 220 to the reconstructed blocks of the reference image. The decoded image 208 is stored in the decoded image buffer 230 for use by the inter prediction module 224 and also for output.

Referring now to Figure 3, Figure 3 depicts an example of coding tree unit partitioning of images in a video according to some embodiments of the present disclosure. As discussed above in Figures 1 and 2, in order to encode the image of the video, the image is divided into blocks, for example, Coding Tree Unit (CTU) 302 in VVC as shown in Figure 3. For example, CTU 302 may be a block of 128x128 pixels. CTUs are processed according to a sequence such as that shown in Figure 3. In some examples, as shown in Figure 4, each CTU 302 in the image can be divided into one or more coding units (Coding Units, CUs) 402, and one or more CUs can be used for prediction and transformation. Depending on the encoding scheme, the CTU 302 may be divided into CUs 402 in different ways. For example, in VVC, a CU 402 may be rectangular or square, and may be encoded without further partitioning into prediction units or transformation units. Each CU 402 may be as large as its root CTU 302, or as small as the 4x4 blocks into which the CTU 302 root block is subdivided. As shown in Figure 4, dividing the CTU 302 into CUs 402 in VVC may be a quad-tree partition, a binary tree partition, or a ternary tree partition. In Figure 4, the solid line represents quadtree segmentation, and the dashed line represents binary tree segmentation.

Relevant quantification

As discussed above in Figures 1 and 2, quantization is used to reduce the dynamic range of elements of blocks, including transform blocks and transform skip blocks in a video signal, thereby using fewer bits to render the video signal. In some examples, before quantization, the elements at the position of the block are called coefficients. After quantization, the quantized values of the coefficients are called quantization levels or levels. Quantization usually consists of steps of dividing by the quantization step size and subsequent rounding, while inverse quantization consists of steps of multiplying the quantization step size. This quantization process is also called scalar quantization. Quantization of intra-block coefficients can be performed independently, and this independent quantization method is used in some existing video compression standards, such as H.264, HEVC, etc. In other examples, correlated quantization is employed, such as in VVC.

For N×M blocks, some scan order can be used to convert the 2-D coefficients of the block into 1-D arrays for coefficient quantization and encoding and decoding, and the same scan order is used for encoding and decoding. FIG. 5 shows an example of encoding blocks with a predetermined scanning order for processing coefficients of the encoding blocks. In this example, the encoding block 500 has a size of 8×8, and processing starts at the lower right corner of position L ₀ and ends at the upper left corner L ₆₃ . If block 500 is a transformed block, the predetermined sequence shown in Figure 5 starts with the highest frequency and ends with the lowest frequency. In some examples, processing (eg, quantization) of a block begins with the first non-zero element of the block according to a predetermined scan order. For example, if the coefficients at positions L ₀ -L ₁₇ are all zero, and the coefficient at L ₁₈ is non-zero, then quantization starts with the coefficient at L ₁₈ and quantizes each coefficient after L ₁₈ in scan order. In correlated quantization, the quantization of intra-block coefficients may exploit scan order information. For example, it may depend on the state of previous quantization levels along the scan order.

Furthermore, to further improve coding efficiency, more than one quantizer (eg, two quantizers) is used in correlated quantization. For example, quantization methods using two quantizers and a trellis structure have been developed, such as trellis coded quantization (TCQ) and dependent quantization (DQ) in VVC. Typically, when using grid-based quantization, the input signal can be quantized by different quantizers. The use of a specific quantizer for the current signal depends on the previous quantization results of the current signal and is controlled by the paths that make up the trellis structure and are therefore encoded by these paths. When the quantization result of the current signal satisfies a predetermined condition, the path in the grid quantization allocates a quantizer for quantizing the next signal. When quantizing the next signal, there are often multiple paths leading to different quantizers. A Viterbi-like algorithm can be used to select a specific grid path that provides the smallest rate distortion measurement between the input and the quantized output of the entire sequence. The collective effect of grid quantization usually results in better overall performance of the signal sequence compared to using only one scalar quantizer.

Figure 6 shows an example of correlated quantization, where two quantizers are used, namely Q0 and Q1. The quantization step size Δ is determined by the quantization factor embedded in the bit stream. Ideally, the quantizer used to quantize the current coefficients can be specified explicitly. However, the signaling overhead for specifying the quantizer reduces codec efficiency. A possible alternative is to use a trellis structure instead of explicit signaling, i.e. the quantizer of the current coefficient can be determined and derived from the information of the quantization level of the previous coefficient. For example, a trellis structure with a four-state model can be used, and the parity of the quantization levels of previous coefficients can be used to guide the trellis path and control state transitions to ultimately decide which quantizer will be used to quantize the current coefficient.

Table 1 Related quantified state transition diagram

Switching between the two scalar quantizers (Q0 and Q1) is achieved through a state machine with four states. Table 1 shows an example of a state transition diagram. The status of the coefficient can be one of four different values: 0, 1, 2, and 3. The state of the current coefficient may be uniquely determined by the parity of the quantization level immediately preceding the current coefficient in the encoding/decoding scan order. At the beginning of quantization on the encoding side or inverse quantization on the decoding side of a block, the state is set to a default value, such as 0. These coefficients are quantized or dequantized in a predetermined scanning order (ie, in the same order in which they are entropy decoded). After one coefficient is quantized or dequantized, the process moves to the next coefficient according to the scan order. The next coefficient becomes the new current coefficient, and the coefficient just processed becomes the previous coefficient. The state _i of the new current coefficient is determined according to Table 1, where k _i-1 represents the value of the quantization level of the previous coefficient. The index i represents the position of the coefficient or quantization level along the scan order. Note that in this example the state only depends on the state of the previous coefficient _i-1 , and the parity of the stage k _i-1 of the previous coefficient at position i-1 (k _i-1 &1) . The status update process can be formulated as

State _i = stateTransTable [state _i-1 ] [k _i-1 &1] (1)

where stateTransTable represents the table shown in Table 1, and operator & specifies the bitwise AND operator in two's complement arithmetic. Optionally, state transitions can be specified without a lookup table, as follows:

State _i = (32040>>((state _i-1 <<2)+((k _i-1 &1)<<1)))&3 (2)

Among them, the 16-bit value 32040 specifies the state transition diagram. The state uniquely determines the scalar quantizer used. In one example, if the state of the current coefficient is equal to 0 or 1, then the scalar quantizer Q0 shown in Figure 6 is used. Otherwise (state equals 2 or 3), the scalar quantizer Q1 shown in Figure 6 is used.

The correlation quantization depicted by Figure 6 and Table 1 can be extended to a more general form as shown in Figure 7, where subset A and subset B are disjoint subsets and include all levels generated using quantizer Q0, and Set C and subset D are disjoint subsets and include all stages generated using quantizer Q1. Stages generated using quantizer Q0 can belong to either subset A or subset B, but not both. Similarly, a stage generated using quantizer Q1 can belong to either subset C or subset D, but not both. For example, subset A may include all odd quantized values generated using quantizer Q0, and subset B may include all even quantized values generated using quantizer Q0. Similarly, subset C may include all odd quantized values generated using quantizer Q1, and subset B may include all even quantized values generated using quantizer Q1. Other ways of dividing the quantized values generated using quantizer Q0 or Q1 into two subsets can also be used.

In grid-based quantization, quantization stages control state transitions, and the quantizer for the current coefficient is adjusted by the quantization stage of the previous coefficient. Typically, there are two subsets of quantization levels at Q0 or Q1. If the probability of falling into the quantization level of one subset is stronger than that of another subset, the overall quantization quality of the signal sequence may not be optimal. For example, when using Q0, two consecutive quantization levels for any input signal in the sequence can always have one level from subset A and another level from subset B, or when using Q1, any input signal in the sequence The two consecutive quantization levels are one level from subset C and another level from subset D. In this case, the system has the best chance of selecting a grid path that provides better overall quantization quality for the entire sequence than using just one scalar quantizer. This is illustrated in Figure 8, where any input coefficient between _Cn and Cn ₊₈ always has 8 possible paths from Q0 and Q1 onwards to the next coefficient. The grid path representing the minimum value of the predefined cost measure is selected among all possible grid paths, which is shown in Figure 8 as path 802. Such paths can be identified by calculating the cost measure after quantification for each level and identifying the next path that minimizes the cost measure to the cost measure determined by the current level.

Depending on the definition of subsets, sometimes even the best quantization level from one subset of Q0 or Q1 may still be significantly lower than the level from another subset of the same quantizer. For example, if subset B and subset D are each defined to have only one specific level (eg, a level equal to 1), then the remaining levels in Q0 or Q1 are put into subset A or subset C respectively. This configuration works better in grid quantization when the input signal has small values. However, when the input signal is large and its corresponding quantization level is much greater than 1, the unique quantization level in subset B or subset D is less effective than using a level from another subset (i.e., subset A or subset C). Level 1 typically generates large quantization distortion and therefore significantly larger rate distortion (RD) cost measurements. Therefore, in this case, it is unlikely that subset B of Q0 or subset D of Q1 will contribute a grid path segment to the final optimal grid path selected for the sequence of input signals. In other words, state transitions caused by the previous level falling in subset B or subset D are rare, and state transitions are mainly dominated by the previous level falling in subset A or subset C. Figure 9A shows a grid quantization example where, for input signals between Cn ₊₂ to Cn ₊₈ , the best stage generation from subset A or subset C is better than subset B or D1 from Q0 The RD cost measure of any level in subset D is much smaller than the RD cost measure. Therefore, the best grid path will be selected from the four paths (paths 902-908). The dashed lines in Figure 9A represent paths generated by subset B or subset D that have significantly larger RD cost measures relative to those of paths 902-908. As a way to simplify and speed up the process of selecting the grid path with the smallest RD cost measure, the dashed path in Figure 9A may be omitted as shown in Figure 9B.

Compared to Figure 8, Figures 9A and 9B have fewer possible Q0 and Q1 combinations for selecting the best path between Cn+2 to Cn+8 with minimal RD cost measurements. Furthermore, the four paths remaining in Figures 9A and 9B are simple paths: one using only scalar quantizer Q0, one using scalar quantizer Q1, and the other two simply alternating between Q0 and Q1. Therefore, the advantages of grid quantization over scalar quantization are significantly diminished in this example.

To avoid always using the same pattern for selecting quantizers for continuous signals in grid quantization, one can take advantage of using a two-state transition map. First, a second state transition diagram is created by exchanging the control signals for each state in the original state transition diagram. As an example, the second state transition diagram shown in FIG. 10 may be created for the original state transition diagram shown in FIG. 7 . In Figure 7, state _S0 will proceed to state _S0 or state _S2 when the previous quantization level k _i-1 is from subset A or subset B respectively. However, in Figure 10, state _S0 will proceed to state _S2 or state _S0 when the previous quantization level k _i-1 is from subset A or subset B respectively. The other states in Figures 7 and 10 have similar relationships. The second map can be used to replace the first map during grid quantization of the sequence of input signals. For example, the use of two graphs can be described by a repeating pattern of N+M. where N represents the number of consecutive signals quantized with the first state transition diagram, followed by M consecutive signals quantized with the second state transition diagram. The scheme of changing the state transition diagram is not limited to the above-mentioned N+M mode. Note that the same pattern used in the quantization process is also used in the inverse quantization process. This can be achieved by encoding the actual N and M used and adding the encoded N and M to the bitstream. This way, the decoder can extract the N and M values from the bitstream to perform inverse quantization using the same N+M pattern.

In one embodiment, the second state transition diagram shown in FIG. 10 is used as a supplement to the first state transition diagram shown in FIG. 7 . In other words, most state transitions are still performed by following the first diagram, and the second diagram is used to "break" long quantization paths, where the same quantizer is used for multiple consecutive signals. Figure 11 shows the new state transition of Figure 9A when the two graphs alternate in fixed patterns N=2 and M=1 after Cn ₊₁ . As shown in the figure, the second diagram shown in Figure 10 is only used in the state transitions of C _n+3 and C _n+6 , and the remaining state transitions still follow the original diagram shown in Figure 7. As can be seen from Figure 11, the two long paths in Figures 9A and 9B no longer exist in Figure 11.

In another embodiment, the second state transition diagram shown in Figure 10 alternates with the first state transition diagram shown in Figure 7 such that the two diagrams are used equally. Figure 12 shows the new state transition of Figure 9 when the two maps alternate with N=2 and M=2 after _Cn . In this example, each plot is used for only two consecutive signals at a time. As shown in Figure 12, the switching of the state transition diagram occurs at Cn ₊₂ , Cn ₊₄ and Cn ₊₆ . The original diagram shown in Figure 7 is used in the state transitions at C _n , C _n+1 , C _n+4 , C _n+5 and C _n+8 , and at C _n+2 , C _n+3 , C The second diagram shown in Figure 10 is used for the state transitions at _n+6 and C _n+7 . The two long paths in Figure 9 no longer exist in Figure 12.

It should be noted that although the first state transition diagram described above is the diagram shown in FIG. 7 and the second state transition diagram is the diagram shown in FIG. 10 , other settings may also be adopted. For example, the diagram shown in FIG. 10 or other diagrams can be used as the first state transition diagram, and the diagram shown in FIG. 7 or other diagrams can be used as the second state transition diagram. A repeating alternating N+M pattern of two-state transition diagrams can be started from any element of the block. Before using the dual state transition diagram, one of the state transition diagrams can be used as described above for correlation quantification. For example, a repeating alternating N+M pattern can be applied to a certain set of elements within a block (from the start element to the end element) or to all elements in the block that need to be quantized. Whether the alternation pattern applies to all elements or a group of elements can be indicated by incorporating a flag signal into the bitstream of the video at the slice level, image level, or sequence level. If the alternating pattern is applied to a group of elements, the start and end elements can also be indicated using flags in the bitstream of the video at the slice level, picture level or sequence level. In this way, alternating patterns can be applied in the same way to blocks in a strip, image, or sequence. Similarly, a repeating alternating N+M pattern can also be applied to a specific image by starting after a specific image and ending at another specific image. The start image and the end image may be indicated using flag signals in the bitstream of the video. In other examples, the alternating pattern is applied to an entire sequence within a group of pictures (GOP). One or more flag signals in the bitstream may be used to indicate whether the alternating pattern applies to the entire sequence in the GOP or to a portion of the sequence.

Figure 13 depicts an example of a process 1300 for encoding blocks of video via trellis quantization with a two-state transition map, in accordance with some embodiments of the present disclosure. One or more computing devices (eg, a computing device implementing video encoder 100) implements the operations depicted in Figure 13 by executing suitable program code (eg, program code implementing quantization module 115). For purposes of illustration, process 1300 is described with reference to some examples depicted in the accompanying drawings. However, other implementations are possible.

At block 1302, process 1300 involves accessing an encoded block (or blocks) of a video signal. The block may be part of an image of the input video, such as encoding unit 402 discussed in Figure 4, or any type of block that is processed as a unit by the video encoder when performing quantization.

At block 1304, which includes processes 1306-1312, process 1300 involves processing each element in the block according to a predetermined scan order of the block (eg, the scan order shown in Figure 5) to generate quantized elements. The elements of a coding block can be the residual after inter- or intra-prediction. This element can be the transform coefficient of the residual in the frequency domain or the value of the residual in the pixel domain.

At block 1306, process 1300 involves retrieving the current element according to the scan order. If no element has been quantized for the current block, the current element will be the first element in the block according to the scan order. As discussed above in Figure 5, in some cases the video encoder performs quantization starting from the first non-zero element in the block according to the scan order. In these cases, the current element will be the first non-zero element in the block. If there are already quantized elements in the block, the current element will be the element after the last processed element in the scan order.

At block 1308, process 1300 involves determining the current state of the current element based on the states of elements preceding the current element and the state transition diagram. As described in detail in Figure 10-12, a state transition diagram can be selected from two alternative state transition diagrams. In some examples, the two state transition diagrams include the state transition diagram shown in FIG. 7 and the state transition diagram shown in FIG. 10 . The current state transition diagram can start from the first state transition diagram and then select from these two state transition diagrams such that before switching to the second state transition diagram, the first state transition diagram is used for N consecutive elements, and in Before switching back to the first state transition diagram, the second state transition diagram is used for M consecutive elements. where M and N are integer values, and M can be equal to N or less than N.

In one embodiment, the state transition diagram shown in FIG. 7 is a first state transition diagram, and the state transition diagram shown in FIG. 10 is a second state transition diagram. If the current element is the first element in the block, you can set a default state (for example, state 0). If the current element is the second element in the block, the first state transition diagram can be used together with the quantized value of the first element to determine the state. For example, according to the state transition diagram shown in Figure 7, if the quantized value of the first element belongs to subset A, and the state of the first element is S ₀ , then the current state of the current element is state S ₀ . Except switching the state transition diagram to the second state transition diagram after using the first state transition diagram for N consecutive elements and switching the state transition diagram back to the first state after using the second state transition diagram for M consecutive elements. Beyond transition diagrams, the state of any subsequent element of a block can be determined in a similar manner via a state transition diagram.

At block 1310, process 1300 involves determining a quantizer for the current element based on the state of the current element based on a mapping between states and quantizers. For example, if the state transition diagrams in Figures 7 and 10 are used to determine the current state of the current element, then the quantizer can be determined to be Q0 if the current state is S ₀ or S ₁ , and Q0 if the current state is S ₂ or S ₃ , then the quantizer can be determined as Q1. At block 1312, process 1300 involves quantizing the current element using the determined quantizer to generate a quantized element. At block 1314, process 1300 involves encoding the quantized elements (quantization levels) of the block for inclusion in the bitstream of the video. Encoding may include entropy encoding as discussed in Figure 1 above.

Figure 14 depicts an example of a process 1400 for reconstructing blocks of video via grid dequantization with a two-state transition map, in accordance with some embodiments of the present disclosure. One or more computing devices implement the operations depicted in Figure 14 by executing suitable program code. For example, a computing device implementing video encoder 100 may implement the operations depicted in FIG. 14 by executing the program code of inverse quantization module 118 . A computing device implementing video decoder 200 may implement the operations depicted in FIG. 14 by executing the program code of inverse quantization module 218. For purposes of illustration, process 1400 is described with reference to some examples depicted in the accompanying drawings. However, other implementations are possible.

At block 1402, process 1400 involves accessing a quantized element (quantization level) of a coded block of a video signal. The block may be part of an image of the input video, such as encoding unit 402 discussed in Figure 4, or any type of block that is processed as a unit by a video encoder or decoder when performing dequantization. For the encoder, the quantized elements can be obtained by quantizing the elements of the block. For the decoder, the quantized elements can be obtained by performing entropy decoding on a binary string parsed from the encoded bitstream of the video.

At block 1404 (including 1406-1412), process 1400 involves processing each quantized element of the block according to a predetermined scan order of the block (eg, the scan order shown in Figure 5) to generate dequantized elements. At block 1406, process 1400 involves retrieving the currently quantized element according to the scan order. If no quantized element in the current block has been dequantized, the currently quantized element will be the first quantized element of the block according to the scan order. As discussed above in Figure 5, in some cases the video encoder performs quantization starting from the first non-zero element in the block according to the scan order. In these cases, the first quantized element will be the first non-zero quantization level in the block. If there are elements in the block that have been dequantized, the currently quantized element will be the quantization level after the last dequantized element in the scan order.

At block 1408, process 1400 involves determining the current state of the current quantized element based on the state transition diagram and the state of the quantized element preceding the current element. As detailed in Figure 10-12, a state transition diagram can be selected from two alternative state transition diagrams. In some examples, the two state transition diagrams include the state transition diagram shown in FIG. 7 and the state transition diagram shown in FIG. 10 . The state transition diagram can start with the first state transition diagram and then select from these two state transition diagrams such that before switching to the second state transition diagram, the first state transition diagram is used for N consecutive elements, and before switching to Before the first state transition diagram, the second state transition diagram is used for M consecutive elements. where M and N are integer values, and M can be equal to N or less than N. In some examples, the values of M and N may be encoded in the bitstream of the video and transmitted to the decoder side.

In one embodiment, the state transition diagram shown in FIG. 7 is a first state transition diagram, and the state transition diagram shown in FIG. 10 is a second state transition diagram. If the currently quantized element is the first element in the block, a default state (e.g., state 0) can be set. If the currently quantized element is the second element in the block, the first state transition diagram may be used together with the quantized value of the first element to determine the state. For example, according to the state transition diagram shown in Figure 7, if the quantized value of the first element belongs to subset A, and the state of the first element is S ₀ , then the current state of the current element is state S ₀ . In addition to switching the state transition diagram to the second state transition diagram after using the first state transition diagram for N consecutive quantized elements and switching the state transition diagram after using the second state transition diagram for M consecutive quantized elements. Beyond the first state transition diagram, the state of any subsequent quantized elements of the block may be determined similarly.

At block 1410, process 1400 involves determining a quantizer for the currently quantized element based on the current state of the current element according to a mapping between states and quantizers. For example, if the state transition diagrams in Figures 7 and 10 are used to determine the current state of the currently quantized element, then the quantizer can be determined to be Q0 if the current state is _S0 or _S1 , and Q0 if the current state is S2 or S3, then the quantizer can be determined as Q1. At block 1412, process 1400 involves dequantizing the currently quantized element using the determined quantizer to generate dequantized elements. At block 1414, process 1400 involves reconstructing the block in the pixel domain based on the elements of the dequantized block. Reconstruction may include inverse transformation as discussed above in Figures 1 and 2. As described above in Figures 1 and 2, the reconstructed blocks can also be used by the encoder or decoder to perform intra or inter prediction on other blocks or images in the video. The reconstructed blocks can also be further processed to generate decoded blocks for display at the decoder side with other decoded blocks in the image.

It should be noted that state transition diagrams other than those shown in FIGS. 7 and 10 may be used during encoding and decoding of video. Furthermore, although in the above description, correlation quantization is applied to video encoding and decoding, the same technology can also be applied to image encoding and decoding. For example, as mentioned above, when compressing an image, the image can be divided into blocks, and the elements of each block (transformed or not) can be quantized. As mentioned above, decompression of an image can be performed by dequantizing the elements in each block.

Example of a computing system for implementing correlated quantization of video codecs

Any suitable computing system may be used to perform the operations described in this disclosure. For example, FIG. 15 depicts an example of a computing device 1500 that may implement video encoder 100 of FIG. 1 or video decoder 200 of FIG. 2 . In some embodiments, computing device 1500 may include processor 1512, memory 1514 coupled in data communication with processor 1512, and execute computer-executable program code and/or access information stored in memory 1514. Processor 1512 may include a microprocessor, application-specific integrated circuit ("ASIC"), state machine, or other processing device. Processor 1512 may include any number of processing devices (including one processing device). Such a processor may include, or may be in data communication with, a computer-readable medium storing instructions that, when executed by processor 1512, cause the processor to perform the operations described in this disclosure.

Memory 1514 may include any suitable non-transitory computer-readable media. Computer-readable media may include any electronic, optical, magnetic, or other storage device capable of providing computer-readable instructions or other program code to the processor. Non-limiting examples of computer-readable media include disks, memory chips, ROM, RAM, ASICs, configured processors, optical storage, tape or other magnetic storage, or any other medium from which a computer processor can read instructions. Instructions may include processor-specific instructions generated by a compiler and/or interpreter from code written in any suitable computer programming language, including, for example, C, C++, C#, Visual Basic, Java, Python, Perl, JavaScript and ActionScript.

Computing device 1500 may also include bus 1516 . Bus 1516 may enable data communications connections between one or more components of computing device 1500 . Computing device 1500 may also include a number of external or internal devices, such as input or output devices. For example, computing device 1500 is shown having an input/output (“I/O”) interface 1518 that can receive input from one or more input devices 1520 or provide output to one or more output devices 1522 . One or more input devices 1520 and one or more output devices 1522 may be coupled to the I/O interface 1518 via data communications. Data communication coupling may be achieved by any suitable means (eg, connection via a printed circuit board, connection via cable, communication via wireless transmission, etc.). Non-limiting examples of input devices 1520 include a touch screen (e.g., one or more cameras for imaging the touch area or a pressure sensor for detecting changes in pressure caused by touch), a mouse, a keyboard, or a computing device that may be used to respond to The user's physical actions generate input events for any other device. Non-limiting examples of output devices 1522 include an LCD screen, an external monitor, speakers, or any other device that can be used to display or otherwise present output generated by the computing device.

Computing device 1500 may execute program code that configures processor 1512 to perform one or more operations described above in FIGS. 1-14. The program code may include video encoder 100 or video decoder 200. The program code may reside in memory 1514 or any suitable computer-readable medium, and may be executed by processor 1512 or any other suitable processor.

Computing device 1500 may also include at least one network interface device 1524. Network interface device 1524 may include any device or group of devices suitable for establishing wired or wireless data connections to one or more data networks 1528 . Non-limiting examples of network interface devices 1524 include Ethernet network adapters, modems, and the like. Computing device 1500 may transmit messages in the form of electronic or optical signals via network interface device 1524 .

General precautions

This article sets forth numerous details to provide a thorough understanding of the claimed subject matter. However, one skilled in the art will understand that the claimed subject matter may be practiced without these details. In other instances, methods, apparatus or systems known to one of ordinary skill have not been described in detail so as not to obscure claimed subject matter.

Unless specifically stated otherwise, it will be understood that throughout this specification, discussions utilizing similar terms such as "process," "compute," "calculate," "determine," and "identify" refer to the action or process of a computing device, such as the manipulation of a computing device. or one or more computers or one or more similar electronic computing devices that converts the electromagnetic data represented into actual electromagnetic data within the memory, registers or other information storage devices, transmission devices or display devices of the computing platform.

The system or systems discussed in this disclosure are not limited to any particular hardware architecture or configuration. A computing device may include components in any suitable arrangement to produce an output in response to one or more inputs. Suitable computing devices include general-purpose microprocessor-based computer systems that access stored software for programming computing systems ranging from general-purpose computing devices to special-purpose computing devices implementing one or more embodiments of the subject matter, or configuration. Any suitable programming, scripting, or other type of language or combination of languages may be used to implement the teachings contained in this disclosure in software used in programming or configuring a computing device.

Embodiments of the disclosed methods may be performed in operation of such computing devices. The order of the chunks presented in the examples above may vary - for example, the chunks may be reordered, combined and/or broken into sub-chunks. Some boxes or processes can be executed in parallel.

The use of "suitable for" or "configured to" herein means open and inclusive language that does not exclude equipment adapted or configured to perform additional tasks or steps. Furthermore, the use of "based on" is meant to be open and inclusive in that a process, step, calculation or other action "based on" one or more of the enumerated conditions or values may in practice be based on conditions other than the enumerated conditions or values. Additional conditions or values. The headings, lists, and numbering included in this disclosure are for convenience of interpretation only and are not meant to be limiting.

Although the subject matter has been described in detail with respect to specific embodiments thereof, it should be understood that modifications, variations, and equivalents to these embodiments can readily be devised by those skilled in the art upon gaining an understanding of the foregoing. Accordingly, it is to be understood that the present disclosure is presented for purposes of illustration and not limitation and is not intended to exclude the inclusion of such modifications, changes and/or additions to the subject matter that would be apparent to one of ordinary skill in the art.

Claims (40)

1. A method for reconstructing blocks of a video, the method comprising: Processing a plurality of quantized elements within the block in sequence to generate respective dequantized elements corresponding to the plurality of quantized elements, the processing comprising: Obtaining a quantized element within the block from the plurality of quantized elements; Determine the state of the obtained quantized element for quantization based on the state of the quantized element before the obtained quantized element and the state transition diagram selected from the first state transition diagram and the second state transition diagram. Quantized states, wherein the first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained quantized element based on the state of the obtained quantized element; and Quantize the obtained quantized elements using the quantizer to generate dequantized elements corresponding to the obtained quantized elements; and The block is reconstructed based on the respective dequantized element corresponding to the plurality of quantized elements. 2. The method of claim 1, wherein the plurality of quantized elements within the block comprise quantized pixels of the block or quantized transform coefficients of the block. 3. The method of claim 1, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternation mode in which, after switching to Before the second state transition diagram, the first state transition diagram is used for N consecutive quantized elements, and before switching to the first state transition diagram, the second state transition diagram is used for M consecutive Quantized elements, where M and N are integer values. 4. The method of claim 3, wherein the values of M and N are encoded in the bitstream of the video. 5. The method of claim 3, wherein the alternating pattern is applied to a sequence of images of the video comprising images or a part of the sequence of images comprising the images, the images comprising the blocks. 6. The method of claim 3, wherein M<N or M=N. 7. The method of claim 3, wherein the first state transition diagram includes: And the second state transition diagram includes: Where Si _, i=0,...,3 represents the element before the currently quantized element and the possible states of the currently quantized element, and k _i-1 represents the value of the element before the currently quantized element; Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer. 8. A non-transitory computer-readable medium having stored therein program code executable by one or more processing devices to perform the following operations: Processing a plurality of quantized elements within a block of video in sequence to generate respective dequantized elements corresponding to the plurality of quantized elements, the processing comprising: Obtaining a quantized element within the block from the plurality of quantized elements; Determine the state of the obtained quantized element for quantization based on the state of the quantized element before the obtained quantized element and the state transition diagram selected from the first state transition diagram and the second state transition diagram. Quantized states, wherein the first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained quantized element based on the current state of the obtained quantized element; and Quantize the obtained quantized elements using the quantizer to generate dequantized elements corresponding to the obtained quantized elements; and The block is reconstructed based on the respective dequantized element corresponding to the plurality of quantized elements. 9. The non-transitory computer-readable medium of claim 8, wherein the plurality of quantized elements within the block comprise quantized pixels of the block or quantized transform coefficients of the block. 10. The non-transitory computer-readable medium of claim 8, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternation pattern, in which mode, before switching to the second state transition diagram, the first state transition diagram is for N consecutive quantized elements, and before switching to the first state transition diagram, the second state transition diagram The graph is for M consecutive quantized elements, where M and N are integer values. 11. The non-transitory computer-readable medium of claim 10, wherein the values of M and N are encoded in the bitstream of the video. 12. The non-transitory computer-readable medium of claim 10, wherein the alternating pattern is applied to an image sequence of the video that includes an image or a portion of the image sequence that includes the image, the The image includes the blocks. 13. The non-transitory computer-readable medium of claim 10, wherein M<N or M=N. 14. The non-transitory computer-readable medium of claim 10, wherein the first state transition diagram includes: And the second state transition diagram includes: Where Si _, i=0,...,3 represents the element before the currently quantized element and the possible states of the currently quantized element, and k _i-1 represents the value of the element before the currently quantized element; Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer. 15. A system comprising: processing equipment; and A non-transitory computer-readable medium connected to the processing device by means of data communication and exchange, wherein the processing device is configured to execute program code stored in the non-transitory computer-readable medium to perform The following actions: Processing a plurality of quantized elements within a block of video in sequence to generate respective dequantized elements corresponding to the plurality of quantized elements, the processing comprising: Obtaining a quantized element within the block from the plurality of quantized elements; Determine the state of the obtained quantized element for quantization based on the state of the quantized element before the obtained quantized element and the state transition diagram selected from the first state transition diagram and the second state transition diagram. Quantized states, wherein the first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained quantized element based on the current state of the obtained quantized element; and Quantize the obtained quantized elements using the quantizer to generate dequantized elements corresponding to the obtained quantized elements; and The block is reconstructed based on the respective dequantized element corresponding to the plurality of quantized elements. 16. The system of claim 15, wherein the plurality of quantized elements within the block comprise quantized pixels of the block or quantized transform coefficients of the block. 17. The system of claim 15, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternation pattern, wherein in the alternation pattern, in Before switching to the second state transition diagram, the first state transition diagram is for N consecutive quantized elements, and before switching to the first state transition diagram, the second state transition diagram is for M consecutive quantized elements, where M and N are integer values, and M < N or M = N. 18. The system of claim 17, wherein the values of M and N are encoded in the bitstream of the video. 19. The system of claim 17, wherein the alternating pattern is applied to a sequence of images of the video comprising images or a part of the sequence of images comprising the images, the images comprising the blocks. 20. The system of claim 17, wherein the first state transition diagram includes: And the second state transition diagram includes: Where Si _, i=0,...,3 represents the element before the currently quantized element and the possible states of the currently quantized element, and k _i-1 represents the value of the element before the currently quantized element; Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer. 21. A method for encoding blocks of video, the method comprising: Processing a plurality of elements of the block of the video in sequence to generate respective quantized elements corresponding to the plurality of elements, the processing comprising: Obtain elements of the block from the plurality of elements; The state for quantization of the obtained element is determined based on the state for quantization of an element before the obtained element and a state transition diagram selected from the first state transition diagram and the second state transition diagram, wherein, The first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained element based on the current state of the obtained element; and Quantize the obtained elements using the quantizer to generate quantized elements corresponding to the obtained elements; and The respective quantized elements corresponding to the plurality of elements are encoded into a bitstream of the video. 22. The method of claim 21, wherein the plurality of elements of the block comprise pixels of the block or transform coefficients of the block. 23. The method of claim 21, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternation mode in which, after switching to Before the second state transition diagram, the first state transition diagram is used for N consecutive elements, and before switching to the first state transition diagram, the second state transition diagram is used for M consecutive elements, where M and N are integer values. 24. The method of claim 23, further comprising: The values of M and N are encoded into the video's bitstream. 25. The method of claim 23, wherein the alternating pattern is applied to a sequence of images of the video comprising images or a part of the sequence of images comprising the images, the images comprising the blocks. 26. The method of claim 23, wherein M≤N. 27. The method of claim 23, wherein the first state transition diagram includes: And the second state transition diagram includes: Where Si _, i=0,...,3 represents the element before the current element and the possible state of the current element, and k _i-1 represents the quantized value of the element before the current element; subset Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer. 28. A non-transitory computer-readable medium having stored therein program code executable by one or more processing devices to: Processing a plurality of elements of a block of video in sequence to generate respective quantized elements corresponding to the plurality of elements, the processing comprising: Obtain elements of the block from the plurality of elements; The state for quantization of the obtained element is determined based on the state for quantization of an element before the obtained element and a state transition diagram selected from the first state transition diagram and the second state transition diagram, wherein, The first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained element based on the current state of the obtained element; and Quantize the obtained elements using the quantizer to generate quantized elements corresponding to the obtained elements; and The respective quantized elements corresponding to the plurality of elements are encoded into a bitstream of the video. 29. The non-transitory computer-readable medium of claim 28, wherein elements associated with the block include pixels of the block or transform coefficients of the block. 30. The non-transitory computer-readable medium of claim 28, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternation pattern, in which mode, before switching to the second state transition diagram, the first state transition diagram is used for N consecutive elements, and before switching to the first state transition diagram, the second state transition diagram is used for M consecutive elements, where M and N are integer values. 31. The non-transitory computer-readable medium of claim 30, wherein the operations further comprise: The values of M and N are encoded into the video's bitstream. 32. The non-transitory computer-readable medium of claim 30, wherein M<N or M=N. 33. The non-transitory computer-readable medium of claim 30, wherein the alternating pattern is applied to an image sequence of the video that includes an image or a portion of the image sequence that includes the image, the The image includes the blocks. 34. The non-transitory computer-readable medium of claim 30, wherein the first state transition diagram includes: And the second state transition diagram includes: Where _Si , i=0,...,3 represents the element before the current element and the possible state of the current element, and k _i-1 represents the quantized value of the element before the current element; Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer. 35. A system comprising: processing equipment; and A non-transitory computer-readable medium connected to the processing device by means of data communication and exchange, wherein the processing device is configured to execute program code stored in the non-transitory computer-readable medium to perform The following actions: Processing a plurality of elements of a block of video in sequence to generate respective quantized elements corresponding to the plurality of elements, the processing comprising: Obtain elements of the block from the plurality of elements; The state for quantization of the obtained element is determined based on the state for quantization of an element preceding the obtained element and a state transition diagram selected from the first state transition diagram and the second state transition diagram, wherein, The first state transition diagram is different from the second state transition diagram; determining a quantizer for the obtained element based on the current state of the obtained element; and Quantize the obtained elements using the quantizer to generate quantized elements corresponding to the obtained elements; and The respective quantized elements corresponding to the plurality of elements are encoded into a bitstream of the video. 36. The system of claim 35, wherein the plurality of elements of the block include pixels of the block or transform coefficients of the block. 37. The system of claim 35, wherein the state transition diagram is selected from the first state transition diagram and the second state transition diagram according to an alternating mode in which, after switching to Before the second state transition diagram, the first state transition diagram is used for N consecutive elements, and before switching to the first state transition diagram, the second state transition diagram is used for M consecutive elements, where M and N are integer values, and M≤N. 38. The system of claim 37, wherein the operations further comprise: The values of M and N are encoded into the video's bitstream. 39. The system of claim 37, wherein the alternating pattern is applied to a sequence of images of the video comprising images, or a part of the sequence of images comprising the images, the images comprising the blocks. 40. The system of claim 37, wherein the first state transition diagram includes: And the second state transition diagram includes: Where Si _, i=0,...,3 represents the element before the current element and the possible state of the current element, and k _i-1 represents the quantized value of the element before the current element; subset Subset A and subset B are subsets of quantized values generated by the first quantizer; subset C and subset D are subsets of quantized values generated by the second quantizer.