Quantization parameter signaling

Abstract

To provide a method, an apparatus, a computer program, and a computer program-based device for deriving and signaling a chroma QP (QPc) for high dynamic range (HDR) content.SOLUTION: Quantization parameter signaling mechanisms for both standard dynamic range (SDR) and HDR content in video coding are described using two approaches. The first approach is to send the user-defined Qpc table directly in the high-level syntax. This leads to more flexible and efficient QP control for future codec development and video content coding. A second approach is to signal the luma and chroma QPs independently. This eliminates the need for a Qpc table and eliminates the dependency of the chroma quantization parameter on the luma QP.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] This disclosure relates to deriving and signaling quantization parameters when encoding video signals, and more particularly to methods, apparatus, computer programs, and computer program-based devices for deriving and signaling luma and / or chroma quantization parameters of video signals.

[0002] Cross-reference of related applications This application claims priority to U.S. Provisional Patent Application No. 62 / 853,352, filed on 28 May 2019, which is incorporated herein by reference. [Background technology]

[0003] The quantization parameter (QP) is a type of parameter used in a video bitstream to adjust the quality and bitrate. Generally, a lower QP value set during encoding results in higher quality encoded video at the expense of consuming more bits, while a QP of 0 means no quantization. Conversely, a higher QP value results in lower quality encoded video and consumes fewer bits. Furthermore, the decoder uses the QP value when reconstructing video content from the encoded video.

[0004] Versatile Video Coding (VVC) is a standard developed by JVET (Joint Video Exploration Team) for encoding both standard dynamic range (SDR) and high dynamic range (HDR) content. In the current (2019) VVC specification, the signal transmission of quantization parameters for the lumen and chroma components is handled in different ways.

[0005] For the luma component, a delta quantization parameter (QP), which means the difference between consecutive quantization parameter values, is signaled and added to the initial QP value of each slice.

[0006] In the case of chroma, the chroma quantization parameter (Qpc) is derived from the luma QP with a chroma offset value (qPi) using a chroma quantization parameter table. As an example, Figure 1 shows a table (100) containing different values of Qpc as a function of the luma quantization parameter with the chroma offset qPi. The data shown in table (100) corresponds to a specific chroma format. According to the VVC standard, the chroma format is based on the variable chroma_format_idc in the range of 0 to 3. Table (100) corresponds to a chroma_format_idc value of 1 representing the 4:2:0 chroma format.

[0007] The table (100) in Figure 1 is inherited from the High Efficiency Video Coding (HEVC) standard and is designed only for SDR content. However, when HDR Perceptual Quantization (PQ) content was first discussed in JCT-VC, it was concluded that the default SDR Qpc table is not suitable for HDR content, as it leads to chroma artifacts at low bit rates, especially in achromatic regions. As a result, a non-normative encoder optimization using a variable called ChromaQPOffset was introduced into the HDR Common Test Conditions (CTC) for HDR PQ content. In general, to indicate the difference from the luma QP value, ChromaQPOffset is signaled in the picture parameter set (PPS), which indicates that a fixed value is used based on the input QP. However, the QP may vary across the picture, and a fixed offset may not be able to cope with this situation.

[0008] In the first version of HEVC, there were separate QP offsets for each of the two chroma components at the slice level. However, at the coding unit (CU) level, the delta QP was applied to all three components, with chroma passing through a mapping table based on the luma QP. In the Range Extensions (Rext) version, separate chroma QP control was introduced at the CU level via the respectively specified chroma QP offset lists for Cb and Cr.

[0009] <Quantization parameter derivation in the current VVC standard> In this process, the luma quantization parameter Qp' Y and the chroma quantization parameters Qp' Cb and Qp' Cr were derived. The initial value of the luma quantization parameter Qp for a slice Y is derived as follows: SliceQp Y =26+init_qp_minus26+slice_qp_delta qP Y_PREV represents the previous luma quantization parameter for the current coding unit. When the current quantization group is the first quantization group of a slice or brick, qP Y_PREV is set to SliceQpY. Otherwise, qP Y_PREV is set equal to the luma quantization parameter Qp of the last luma coding unit of the previous quantization group in decoding order Y .

[0010] qP Y_PRED represents the predicted luma quantization parameter of the current coding unit. When the current quantization group is the first quantization group of a CTB row in a brick and the top coding unit is available, qP Y_PRED is set to the Qp of the top CU Y , otherwise, qP Y_PRED =(qP Y_A +qP Y_B +1)>>1 Here, if the left-hand coding block is not the first coding block of the left-hand quantization group, or if the left-hand coding block is unavailable, qP Y_A is qP Y_PREV If set to and the top coding block is not the first coding block of the top quantization group, or if the top coding block is unavailable, then qP Y_B is qP Y_PREV It will be set to this.

[0011] Variable Qp per coding unit Y This is derived as follows:

number

[0012] Luma quantization parameter Qp' Y This is derived as follows: Qp' Y = Qp Y +QpBdOffset Y If ChromaArrayType is not 0 and treeType is SINGLE_TREE or DUAL_TREE_CHROMA, the following applies: If treeType is equal to DUAL_TREE_CHROMA, the variable QpY is set to equal to the luminance quantization parameter QpY of the current luminance coding unit covering the luminance position (xCb + cbWidth / 2, yCb + cbHeight / 2). · Variable qP Cb and qP Cr This is derived as follows:

number

number

[0013] Current video content is not the same as the SDR content for which the original default SDR Qpc table was designed. For example, the luminous and chroma components of SDR and HDR content can be encoded using the Y'CbCr or ICtCp signal format. The situation is more complex for HDR content. HDR content may also be encoded using the HLG or PQ transfer characteristics. It would be beneficial to signal different chroma quantization parameters for different chroma component types and transfer characteristics. It may also be beneficial to signal different chroma quantization parameters for two different chroma components, such as Cb and Cr or Ct and Cp. It may also be beneficial to signal chroma quantization parameters in a content-dependent manner. The disclosed methods and apparatus address the above-mentioned problems and requirements.

[0014] The devices and methods disclosed herein provide solutions to the problem of deriving chroma QP (QPc) of HDR content. Furthermore, devices and methods for signaling such derived chroma QP for HDR are also disclosed. According to a first aspect of the disclosure, a method for decoding an encoded video bitstream is disclosed, the method comprising the steps of a) extracting a chroma quantization parameter (Qpc) table mapping chroma quantization parameters (Qp) having chroma QP offset values ​​qP(i) to corresponding chroma Qp values ​​Qpc(i), i) where "i" is an index of a table entry in the range from startID to endID, ii) startID is an integer greater than or equal to 1 and less than or equal to N, where N is the total number of Qpc table entries, and iii) endID is an integer greater than startID and greater than or equal to N. b) a step of generating a decoded output signal based on the extracted Qpc table and the encoded video bitstream, wherein the encoded bitstream includes a table identifier, in the first case the table identifier indicates the presence of a default table, and in the second case the encoded video bitstream further includes one or more elements signaled in high-level syntax, the one or more elements being encoded based on a) two or more chroma Qp values, or b) a combination of one or more chroma Qp values ​​and one or more chroma Qp with chroma offset values.

[0015] A second aspect of the present disclosure provides a method for decoding an encoded stream of a video signal, comprising: extracting a luma quantization parameter (Qps), a first chroma component Qps, and a second chroma component Qps from the encoded stream; and generating an output decoded video signal based on the extracted luma component, the first chroma component, and the second chroma component Qps, and the encoded video bitstream, wherein the encoded video stream comprises a plurality of elements signaled in high-level syntax, the plurality of elements being encoded based on a combination of the luma Qps, the first chroma component, and the second chroma component Qps, the first chroma component Qps being derived based on a predicted value of the first chroma component Qps and the bit depth of a first chroma component sample of the video signal, and the second chroma component Qps being derived based on a predicted value of the second chroma component Qps and the bit depth of a second chroma component sample of the video signal. [Brief explanation of the drawing]

[0016] [Figure 1] An example of a table containing different values ​​of the chromatic quantization parameter as a function of the luminance quantization parameter is shown. [Figure 2] An exemplary HDR Qpc table according to an embodiment of this disclosure is shown. [Figure 3] An exemplary Qpc table according to an embodiment of this disclosure is shown. [Figure 4A] An example Qpc table for HDR PQ content types is shown. [Figure 4B] An example Qpc table for HDR Hybrid-Long Gamma (HLG) content types is shown. [Figure 5A] An example of SDR Qpc mapping function-based Luma quantization parameters is shown (continues in Figure 5B). [Figure 5B] An exemplary SDR Qpc mapping function-based Luma quantization parameter is shown (continued from Figure 5A). [Modes for carrying out the invention]

[0017] <Definition> Throughout this document, technical terms used in relation to video coding and decoding are defined in accordance with Versatile Video Coding (Draft 5), document JVET-N1001-v3, Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3, and ISO / IEC JTC 1 / SC 29 / WG 11, 14th meeting: Geneva, CH, 19-27, March 2019.

[0018] <Explanation> <1. Derivation of Chroma PQ based on user-defined Qpc table> In accordance with embodiments of this disclosure, the chroma QP of HDR content may be determined using a user-defined Qpc table. Figure 2 shows Table (200), which represents an exemplary HDR Qpc table according to embodiments of this disclosure. Table (200) serves essentially the same purpose for HDR content as the default SDR Qpc table specified in current VVCs serves for SDR content. Those skilled in the art will understand that the disclosed approach based on a user-defined Qpc table for HDR content unifies codec design for all SDR and HDR signal types and leads to more flexible and efficient QP control for future codec development.

[0019] According to one embodiment of the present disclosure, the HDR Qpc table described may be directly signaled with high-level syntax such as video parameter sets (VPS), signal parameter sets (SPS), PPS, adaptation parameter sets (APS), slice headers, and SEI messages. To reduce signaling overhead, and according to other embodiments of the present disclosure, the default Qpc table may be used as a normative table in the standard specification or as a non-normative example in the standard specification.

[0020] Referring to Figure 2, a new syntax element chroma_qp_table_idc may be added to the SPS. If the value of chroma_qp_table_idc is equal to 0, it refers to the original SDR Qpc table in the VVC specification text (see table (100) in Figure 1). If the value of chroma_qp_table_idc is equal to 1, it refers to table (200) in Figure 2. According to one embodiment of this disclosure, the variable chroma_qp_table_idc is an index of the Qpc to the array as a function of qPi when ChromaArrayType is equal to 1. The value of chroma_qp_table_idc may be in the range of 0 or greater and 1 or less.

[0021] According to further embodiments of the present disclosure, one Qpc table may be signaled and shared by both Cb and Cr, or two separate tables designed for Cb and Cr, respectively, may be signaled. To reduce signaling overhead, each Qpc table may be coded differentially, approximated by a piecewise linear function, coded run-length encoding, coded by Lempel-Ziv-Welch (LZW) or a similar algorithm, or coded by a mixture of the above techniques.

[0022] The above-described Qpc table may be used for HDR content using HLG or PQ transfer characteristics. Referring to Figures 1 and 2, it can be seen that some Qpc values ​​can be directly derived from the tables (100, 200) and other Qpc tables designed for content types such as HLG by being equal to or subtracting a constant value from qPi. To conserve encoded bits, the range of table elements that need to be signaled in the bitstream can be specified by the start and end indices [startID, endID].

[0023] The following describes various methods for signaling chromatic QP values ​​in accordance with the teachings of this disclosure. Throughout this disclosure, the term "delta Qp," also represented as "dQp," is used to describe the difference between two consecutive QP values.

[0024] <Method 1a> In this method, the difference between two adjacent Qpc entries in [startID,endID] is coded: dQpc[i]=Qpc[i]-Qpc[i-1] (1)

[0025] In general, the SDR and HDR Qpc tables provided in this disclosure may contain only dQp values ​​of 0 and 1. Delta QP values ​​can be directly signaled. Alternatively, a codeword can be composed of multiple Delta QP values. For example, the Delta QP values ​​of pairs of Cb and Cr with the same index value may be combined. Another example is that for Cb, two consecutive index value Delta QP values ​​can be combined, and similarly for Cr. Optionally, a sequence of codewords constructed from combinations of Delta QP values ​​can be further compressed using methods such as Huffman coding or other lossless compression algorithms. For Delta Qpc values ​​other than 0 and 1, the maximum Delta value can be specified in the syntax. In some cases, startID and endID may be constrained to be even or odd values ​​to reduce the number of bits that need to be signaled.

[0026] The following description of further embodiments will focus on the differences from the previously described embodiments. Therefore, features common to both embodiments will be omitted in the following description, and unless otherwise requested in the following description, the features of the previously described embodiments should be considered to be implemented, or at least implementable, in the further embodiments.

[0027] <Method 1b> In this method, the difference values ​​between each pair of {qPi,Qpc} in [startID,endID] may be encoded as follows: dQp[i]=qPi[i]-Qpc[i] (2) The delta-QP value between qPi and Qpc may be in the range of 0 to 18. This suggests that method 1a may be more suitable for encoding than method 1b.

[0028] <Method 1c> This method is based on fitting the Qpc mapping curve from qPi via a piecewise linear function defined as follows:

number

number

[0029] <Method 1d> In this method, run-length coding may be used to encode the dQpc[i] value defined by equation (1). For example, referring to table (100) in Figure 1, the delta Qp value is derived as a sequence of 0s and 1s. The delta value (0 or 1) may be coded along with the count of the resulting value. Figure 3 shows table (300), which is an exemplary description of a Qpc table based on this method.

[0030] According to one embodiment of the present disclosure, a default Qpc table may be predefined for each of the different signal types, such as SDR, PQ, and HLG content. Figures 4A and 4B show tables (400A and 400B) representing exemplary Qpc tables for HDR PQ and HLG content, respectively. If no user-defined Qpc table exists, the encoder and decoder may apply a default Qpc table instead. Embodiments of the present disclosure may assume that no user-defined Qpc is signaled. This approach has the advantage of saving more bits.

[0031] The following table corresponds to Method 1a above and shows an exemplary syntax for the raw byte sequence payload (RBSB) of the SPS and tile group header, where syntax elements following the teachings of this disclosure are written in italics, in contrast to other existing syntax elements. A detailed explanation of the various syntax elements follows. The default QPc table can be specified in the SPS by signaling a default QPc table type index. If no default table is provided, a predefined Qpc table may be sent in the SPS along with the delta QP value between two adjacent table elements. One or more alternative QPc tables for use in the slice may be signaled in the PPS to override the Qpc table in the SPS.

[0032] [Table 1-1]

[0033] [Table 1-2]

[0034] [Table 1-3]

[0035] Setting sps_default_qpc_table_flag to 1 means that the default chromatic quantization parameter table will be used, and therefore you do not need to send a Qpc table. Instead, an index indicating which default Qpc table to use will be signaled. Setting sps_default_qpc_table_flag to 0 indicates that no default Qpc table is defined and it must be sent with SPS.

[0036] `default_qpc_table_type_idx` indicates which default Qpc table to use when `sps_default_qpc_table_flag` is 1. `default_qpc_table_type_idx` is 0 and `pps_slice_qpc_table_present_flag` is 0, indicating the use of one or more default SDR Qpc tables. `default_qpc_table_type_idx` is 1 and `pps_slice_qpc_table_present_flag` is 0, indicating the use of one or more HDR PQ Qpc tables. `default_qpc_table_type_idx` is 2 and `pps_slice_qpc_table_present_flag` is 0, indicating the use of one or more default HLG Qpc tables. `default_qpc_table_type_idx` is 3, meaning it is reserved for future use.

[0037] If sps_separate_qpc_table_enable_flag is 1, it specifies that Cb and Cr should use separate Qpc tables. sps_cr_qp_delta[i] and sps_cr_qp_gap_idx are defined and signaled in SPS, while slice_cr_qp_delta[i] and slice_cr_qp_gap_idx are defined in the slice header. If sps_separate_qpc_table_enable_flag is 0, it specifies that Cb and Cr should use the same Qpc table.

[0038] sps_qpc_table_start_index_div2 specifies the starting index when signaling delta QP values ​​in a Qpc table element. It is defined as an even number between 0 and 63. For table elements with an index less than sps_qpc_table_start_index_div2*2, Qpc is set to the same value as qPi.

[0039] sps_qpc_table_end_index_div2 specifies the end index before signaling the delta QP value in the Qpc table element. It is defined as an even number between 0 and 63. For table elements with an index greater than sps_qpc_table_end_index_div2*2, sps_cb_qp_delta[i] and sps_cr_qp_delta[i] are set to 1. sps_cb_qp_delta[i] specifies the delta value between spsQpcb[i] and spsQpcb[i-1] in sps_cb_qp_delta[0] to construct the quantization parameter table for Cb defined in SPS. The i-th entry in the quantization parameter table for Cb in SPS is derived as follows: spsQpcb[i]=sps_cb_qp_delta[i]+spsQpcb[i-1]

[0040] sps_cr_qp_delta[i] specifies the delta values ​​of spsQpcr[i] and spsQpcr[i-1] around sps_cr_qp_delta[0] to construct the quantization parameter table for Cr defined in SPS. The i-th entry in the quantization parameter table for Cr in SPS is derived as follows: spsQpcr[i]=sps_cr_qp_delta[i]+spsQpcr[i-1]

[0041] If pps_slice_qpc_table_present_flag is 1, it specifies that quantization parameter tables for the Cb and Cr components of the current slice exist and are defined in the slice header. If pps_slice_qpc_table_present_flag is 0, it specifies that quantization parameter tables for the Cb and Cr components of the current slice do not exist in the slice header, and that the default quantization parameter tables are applied to Cb and Cr.

[0042] slice_cb_qp_delta[i] specifies the delta value between sliceQpcb[i] and sliceQpcb[i-1] by slice_cb_qp_delta[0] in order to construct the slice quantization parameter table for Cb. The i-th entry of the slice Qpc table for the Cb component is derived as follows: sliceQpcb[i]=slice_cb_qp_delta[i]+sliceQpcb[i-1]

[0043] slice_cr_qp_delta[i] is defined when sps_separate_qpc_table_enable_flag is 1, and specifies the delta value between sliceQpcr[i] and sliceQpcr[i-1] as slice_cr_qp_delta[0] for constructing the slice quantization parameter table for Cr. The i-th entry in the slice Qpc table for the Cr component is derived as follows: sliceQpcr[i]=slice_cr_qp_delta[i]+sliceQpcr[i-1]

[0044] <2. Derive Chroma QP independently from Luma QP> According to further embodiments of the present disclosure, the luma QP and chroma QP can be signaled independently. Such an approach has the advantage of eliminating the dependency of the chroma QP on the luma QP. The derivation of the chroma QP according to embodiments of the present disclosure will be described in detail below.

[0045] The initial values ​​of the chromatic quantization parameters for slices SliceQpCb and SliceQpCr can be derived as follows: SliceQpCb=26+init_qp_minus26+slice_cb_qp_delta (3) SliceQpCr=26+init_qp_minus26+slice_cr_qp_delta (4) If the current quantization group is the first quantization group of a slice or brick, then qP Cb_PREV and qP Cr_PREV These are set to SliceQpCb and SliceQpCr respectively. Otherwise, qP Cb_PREV and qP Cr_PREV This is set to be equal to the chroma quantization parameter Qpc of the last chroma coding unit of the previous quantization group in the decoding order.

[0046] qP Cb_PRED and qP Cr_PRED is the predicted chroma quantization parameter for the current coding unit. qP is the first quantization group in the CTB row within the brick if the top coding unit is available. Cb_PRED and qP Cr_PRED Set it to the Qpc of the top-level CU, otherwise, qP Cb_PRED =(qP Cb_A +qP Cb_B +1)>>1 (5) qP Cr_PRED =(qPCr_A +qP Cr_B +1)>>1 (6) Here, qP Cb_A and qP Cr_A If the left-side coding block is not the first coding block in the left-side quantization group, or if the left-side coding block is not available, then qP Cb_PREV and qP Cr_PREV If set to and the top coding block is not the first coding block in the top quantization group, or if the top coding block is unavailable, then qP Cb_B and qP Cr_B is qP Cb_PREV and qP Cr_PREV It will be set to this.

[0047] The variables QpCb and QpCr for each coding unit can be derived as follows:

number

number

[0048] Chroma quantization parameter Qp' Cb and Qp' Cr This is derived as follows: Qp′Cb=QpCb+QpBdOffsetC (9) Qp′Cr=QpCr+QpBdOffsetC (10) The current quantization parameters of the coding unit, their predictions, and the difference values ​​between CuCbQpDeltaVal and CuCrQpDeltaVal can be specified in the transform unit layer. There are several methods for coding the delta QP value.

[0049] The following describes exemplary methods as taught in this disclosure. The difference between the QP of each color component (e.g., luma, chroma Cb, and chroma Cr) and its predicted value is abbreviated as dPQ' to distinguish it from dPQ, which represents the difference between consecutive QPs in the context of the Qpc table, as described above.

[0050] <Method 2a> In this method, the dQP of the three color components, luma, chroma Cb, and chroma Cr, is encoded, represented by the variables CuQpDeltaVal, CuCbQpDeltaVal, and CuCrQpDeltaVal, respectively.

[0051] The following description of further embodiments will focus on the differences between them and the embodiments described above. Therefore, features common to both embodiments will be omitted from the following description, and it should be assumed that features of the previously described embodiments will be implemented, or at least can be implemented, in the further embodiments unless otherwise required by the following description.

[0052] <Method 2b> In this method, the dQP' of the luma component CuQpDeltaVal is encoded. Furthermore, the difference between the dQp' of each chroma component and the luma dQp' is encoded as follows: CbdQpDeltaVal=CuCbQpDeltaVal-CuQpDeltaVal (11) CrdQpDeltaVal=CuCrQpDeltaVal-CuQpDeltaVal (12)

[0053] <Method 2c> In this method, the element CrCbdQpDeltaVal is defined as follows: CrCbdQpDeltaVal=CuCrQpDeltaVal-CuCbQpDeltaVal (13) Encoded, where the elements CuCrQpDeltaVal and CuCbQpDeltaVal have the same definitions as in the case of method 2c described above.

[0054] <Method 2d> In this method, the element CrCbdQpDeltaVal is defined as follows: CrCbdQpDeltaVal=CuCrQpDeltaVal-CuCbQpDeltaVal Encoded, where the elements CuCrQpDeltaVal and CuCbQpDeltaVal have the same definitions as in the case of method 2c described above.

[0055] <Method 2e> In this method, the difference values ​​from ChromaQP and LumaQP are defined as follows: dQp′Cb=Qp′Y-Qp′Cb (14) dQp′Cr = Qp′Y - Qp′Cr (15) The data is encoded. The signaling in Method 2e is the same as in Method 2a, as it does not require signaling slice_cb_qp_delta and slice_cr_qp_delta (see below) in the slice header.

[0056] The following table shows exemplary syntax for a raw-byte sequence payload (RBSB) for SPS and tile group headers, corresponding to method 2a above, and the syntax elements taught in this disclosure are shown in italics, in contrast to other existing syntax elements. A detailed description of the various syntactic elements follows.

[0057] [Table 2-1]

[0058] [Table 2-2]

[0059] [Table 2-3]

[0060] [Table 2-4]

[0061] [Table 2-5]

[0062] The methods and systems described herein may be implemented in hardware, software, firmware, or any combination thereof. Features described as blocks, modules, or components may be implemented together (e.g., in a logic device such as an integrated logic device) or separately (e.g., as separate connected logic devices). The software portion of the method of the disclosure may comprise a computer-readable medium having instructions that, when executed, perform at least partially the method described. The computer-readable medium may include, for example, random-access memory (RAM) and / or read-only memory (ROM). The instructions may be executed by a processor (e.g., a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable logic array (FPGA), a graphics processing unit (GPU), or a general-purpose GPU).

[0063] Numerous embodiments of this disclosure have been described. Nevertheless, it will be understood that various modifications can be made without departing from the intent and scope of this disclosure. Therefore, other embodiments are within the scope of the claims.

[0064] The above examples are provided to those skilled in the art as a complete disclosure and explanation of how embodiments of the present disclosure can be created and used, and are not intended to limit the scope of what the inventors consider to be such disclosures.

[0065] Modifications of the modes described above for performing the methods and systems disclosed herein, which are obvious to those skilled in the art, are intended to be within the scope of the following claims. All patents and publications referenced herein represent the level of the art to which this disclosure relates. All references cited herein are incorporated by reference to the same extent as each reference is incorporated by reference in its entirety.

[0066] Naturally, this disclosure is not limited to any particular method or system, and any particular method or system can be modified. Furthermore, the terms used herein are intended solely to describe and not to limit any particular embodiment. As used herein and in the appended claims, the singular forms “a,” “an,” and “the” refer to multiple subjects unless the content explicitly indicates otherwise. The term “plurality” refers to two or more subjects unless the content explicitly indicates otherwise. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art relating to this disclosure.

Claims

1. A non-temporary computer-readable recording medium for decoding an encoded image contained in an encoded bitstream, The recording medium includes computer instructions, When the aforementioned computer instruction is executed by the processor, the processor will: The system receives an encoded bitstream containing one or more encoded images, each containing a luma component, a first chroma component, and a second chroma component. To determine a first chroma quantization parameter (QP) table for the first chroma component and a second chroma quantization parameter (QP) table for the second chroma component, syntax parameters are extracted from the encoded bitstream. Based on the first chroma QP table and the second chroma QP table, one or more encoded images are decoded. The syntax parameter includes a value obtained by subtracting 26 from the starting chroma QP value of the table, and one or more offset parameters for determining the mapping from the chroma QP value to the corresponding chroma QP value using a piecewise linear representation. Given a chroma quantization value qP[i] for i greater than the termination index value, the chroma quantization value Qpc[i] is determined as qP[i] - offset, where offset represents a fixed value. A non-temporary computer-readable recording medium.

2. The one or more offset parameters include the delta QP chromatic parameter dQpc[i] = Qpc[i] - Qpc[i-1], where i represents the index and Qpc[i-1] and Qpc[i] represent consecutive chromatic QP values. A non-temporary computer-readable recording medium according to claim 1.

3. A non-temporary computer-readable recording medium for generating an encoded video bitstream, The recording medium includes computer instructions, When the aforementioned computer instruction is executed by the processor, the processor will: The system receives a sequence of images in which each image includes a luma component, a first chroma component, and a second chroma component. To generate an encoded video bitstream, the sequence of images is encoded using lumina quantization parameter (QP) values ​​and chroma QP values. The decoder encodes signal parameters in the encoded video bitstream in order to determine a first chroma QP table for the first chroma component and a second chroma QP table for the second chroma component. The signal parameter includes a value obtained by subtracting 26 from the starting chroma QP value of the table, and one or more offset parameters for determining the mapping from the chroma QP value to the corresponding chroma QP value using a piecewise linear representation. Given a chroma quantization value qP[i] for i greater than the termination index value, the chroma quantization value Qpc[i] is determined as qP[i] - offset, where offset represents a fixed value. A non-temporary computer-readable recording medium.

4. The one or more offset parameters include the delta QP chromatic parameter dQpc[i] = Qpc[i] - Qpc[i-1], where i represents the index and Qpc[i-1] and Qpc[i] represent consecutive chromatic QP values. The non-temporary computer-readable recording medium according to claim 3.

5. A non-temporary computer-readable recording medium for transmitting an encoded video bitstream, The recording medium includes computer instructions, When the computer instruction is executed by the processor, it causes the processor to generate and transmit the bitstream. The processor generates the bitstream, The system receives a sequence of images, each containing a luma component, a first chroma component, and a second chroma component. To generate an encoded video bitstream, the sequence of images is encoded using the luma quantization parameter (QP) value and the chroma QP value. The decoder encodes signal parameters in the encoded video bitstream in order to determine a first chroma QP table for the first chroma component and a second chroma QP table for the second chroma component. The signal parameter includes a value obtained by subtracting 26 from the starting chroma QP value of the table, and one or more offset parameters for determining the mapping from the chroma QP value to the corresponding chroma QP value using a piecewise linear representation. Given a chroma quantization value qP[i] for i greater than the termination index value, the chroma quantization value Qpc[i] is determined as qP[i] - offset, where offset represents a fixed value. A non-temporary computer-readable recording medium.

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