Improvements on depth-first handling of a processing chain

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures. A conversion is performed between the visual media data and a bitstream based on the list of candidate input pictures.

Description

Improvements On Depth-First Handling Of A Processing ChainCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority to and benefits of U.S. Provisional Patent Application No. 63 / 698,804, filed on September 25, 2024. All the aforementioned patent applications are hereby incorporated by reference in their entireties.TECHNICAL FIELD

[0002] This patent document relates to generation, storage, and consumption of digital audio video media information in a file format.BACKGROUND

[0003] Digital video accounts for the largest bandwidth used on the Internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video usage is likely to continue to grow.SUMMARY

[0004] A first aspect relates to a method for processing video data comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; and performing a conversion between the visual media data and a bitstream based on the list of candidate input pictures.

[0005] A second aspect relates to an apparatus for processing video data comprising: a processor; and a non- transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform any of the preceding aspects.

[0006] A third aspect relates to non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of the preceding aspects.

[0007] A fourth aspect relates to a non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures: and generating a bitstream based on the determining.

[0008] A fifth aspect relates to a method for storing bitstream of a video comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.

[0009] For the purpose of clarity, any one of the foregoing embodiments may be combined with any one or more of the other foregoing embodiments to create a new embodiment within the scope of the present disclosure.

[0010] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0012] FIG. 1 is a block diagram showing an example video processing system.

[0013] FIG. 2 is a block diagram of an example video processing apparatus.

[0014] FIG. 3 is a flowchart for an example method of video processing.

[0015] FIG. 4 is a block diagram that illustrates an example video coding system.

[0016] FIG. 5 is a block diagram that illustrates an example encoder.

[0017] FIG. 6 is a block diagram that illustrates an example decoder.

[0018] FIG. 7 is a schematic diagram of an example encoder.

[0019] FIG. 8 is a flowchart for another example method of video processing.DETAILED DESCRIPTION

[0020] It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and / or methods may be implemented using any number of techniques, whether currently known or yet to be developed. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0021] Section headings are used in the present document for ease of understanding and do not limit the applicability' of techniques and embodiments disclosed in each section only' to that section. Furthermore, H.266 terminology' is used in some description only for ease of understanding and not for limiting scope of the disclosed techniques. As such, the techniques described herein are applicable to other video codec protocols and designs also. In the present document, editing changes are shown to text by bold italics indicating cancelled text and bold indicating added text, with respect to the Versatile Video Coding (WC) specification and / or the SEI messages for coded video bitstreams (VSEI) standard.1. Initial discussion

[0022] This document is related to image / video coding technologies. Specifically, this disclosure is related to specifying a depth-first handling of a processing chain indicated by an SEI processing order (SPO) SEI message, with a processing-stage-based use of candidate input picture list. The ideas may' be applied individually or in various combinations, for video bitstreams coded by' any' codec, e.g., the WC standard and / or the versatile SEI messages for coded video bitstreams (VSEI) standard.2. Further discussion2.1 Video coding standards

[0023] Video coding standards have evolved primarily through the development of International Telecommunication Union (ITU) telecommunication standardization sector (ITU-T) and International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC) standards. The ITU-T produced H.261 and H.263, ISO / IEC produced motion picture experts group (MPEG)-1 and MPEG-4 Visual, and the two organizations jointly produced the H.262 / MPEG-2 Video and H.264 / MPEG-4 Advanced Video Coding (AVC) and H.265 / high efficiency video coding (HEVC) [1] standards. Since H.262, the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized. The Versatile Video Coding (WC) standard (ITU-T H.266 | ISO / IEC 23090-3) [2] and the associated Versatile Supplemental Enhancement Information for coded video bitstreams (VSEI) standard (ITU-T H.274 | ISO / IEC 23002-7) [3] are designed for use in a maximally broad range of applications, including both the simple uses such as television broadcast, video conferencing, or playback from storage media, and also more advanced use cases such as adaptive bit rate streaming, video region extraction, composition and merging of content from multiple coded video bitstreams, multiview video, scalable layered coding, and viewport-adaptive 360° immersive media.2.2 SEI messages in general and in WC

[0024] SEI messages assist in processes related to decoding, display or other purposes. However, SEI messages arc not required for constructing the luma or chroma samples by the decoding process. Conforming decoders arc not required to process this information for output order conformance. Some SEI messages are required for checking bitstream conformance and for output timing decoder conformance. Other SEI messages are not required for check bitstream conformance.

[0025] Annex D of WC specifies syntax and semantics for SEI message payloads for some SEI messages, and specifies the use of the SEI messages and video usability information (VUI) parameters for which the syntax and semantics are specified in ITU-T H.SEI | ISO / IEC 23002-7.2.3 The SEI processing order (SPO) SEI message

[0026] JVET-AI2006 [4] includes the specification of an SEI message named the SEI processing order (SPO) SEI message, for carrying information indicating the preferred processing order, as determined by the encoder (i.e., the content producer), for a group of ty pes of SEI messages that may be present in a coded video sequence (CVS).

[0027] An improved version of the specification of the SPO SEI message in JVET-AI2006 is as follows.8.30.1 SEI processing order SEI message8.30.1.1 SEI processing order SEI message syntax8.30.1.2 SEI processing order SEI message semantics

[0028] The SEI processing order (SPO) SEI message carries information indicating the preferred processing order, as determined by the encoder (i.e., the content producer), for a group of types of SEI messages that may be present in a CVS.

[0029] Use of this SEI message requires the definition of the following:- Two lists of payloadType values, SeiProcessingOrderSeiList and SpoProcessSeiList.

[0030] The semantics of the SPO SEI message uses the concept of types of SEI messages. SEI messages that have different payloadType values are considered different types of SEI messages. Additionally , different SEI messages that have the same pay loadType value but are differentiated by values of syntax elements in the SEI payload are considered different types of SEI messages. Such differentiation by values of syntax elements in the SEI payload is to be performed by comparing values sent using po_sei_prefix_data_bit[ i ][ j ] syntax elements (when present) or values sent as SEI messages within a processing order nesting SEI message (when present). For example, neural-network post-filter (NNPF) characteristics (NNPFC) SEI messages can be differentiated by having different nnpfe id values.

[0031] When the i-th SEI message seiA in any SPO SEI message has po_sei_wrapping_flag[ i ] and po_sei_prefix_flag[ i ] both equal to 0, there shall be no other SEI message seiB included in the same SPO SEI message or in a different SPO SEI message in the current CVS for which all of the following are true:- The value of po_sei_payload_type| i ] of seiB is the same as that for seiA.The value of po sei wrapping flag | i J of seiB is equal to 0.The value of po_sei_prefix_flag[ i ] of seiB is equal to 1.

[0032] When an SPO SEI message with a particular value of po id is present in any access unit of a CVS, an SPO SEI message with that particular value of po id shall be present in the first access unit of the CVS in decoding order. The number of SEI messages and the payloadTypc codes of the SEI messages indicated w ithin each SPO SEI message with the same value of po id persist in decoding order from the current access unit until the end of the CVS in output order.

[0033] The SPO SEI message can carry one or more SEI prefix indications of a particular payloadType. When present, each SEI prefix indication is a bit string that follows the SEI payload syntax of that value of payloadTypc and contains a number of complete syntax elements starting from the first syntax element in the SEI payload. These SEI prefix indications should provide sufficient information to determine the specific processing order for types of SEI messages having the same value of payloadType but a different preferred processing order.

[0034] po id contains an identifying number to identify the SPO SEI message.

[0035] A processing chain consists of a list of types of SEI messages identified by an SPO SEI message in the preferred processing order indicated in the SPO SEI message.

[0036] Each type of SEI message in the processing chain indicated by an SPO SEI message is identified by the syntax elements po sei payload type[ i ], po sei wrapping flag[ i ], po sei_processing order[ i ] and, when present, po_num_bits_in_prefix_indication_minusl [ i J and po_prefix_data_bit[ i J[ j J.

[0037] An SEI message type is not required to belong to any processing chain and may belong to any number of processing chains identified by SPO SEI messages with different po id values.

[0038] Each SEI message of an SEI message type identified within the SPO SEI message has the same persistence scope as if the SEI message was carried outside of the SPO SEI message and not identified within an SPO SEI message.

[0039] NOTE 1 - When an SEI message specifies a process and is not associated with a processing chain specified by any SPO SEI message, it is implicitly a processing chain by itself. Some standards, such as Rec. ITU-T H.266 1 1SO / 1EC 23090-3. have specified an implicit processing chain of a super-resolution NNPF followed by another NNPF. Implicitly specified processing chains are treated like processing chains specified by SPO SEI messages when selecting SEI messages to be applied.

[0040] NOTE 2 - Processing chains can be alternatives to each other, i.e., such that at most processing chain is chosen to be applied, or they can be complementary, i.e., such that more than one processing chain is chosen and applied separately, with each processing chain generating one output.

[0041] po for human viewing idc equal to 3 specifies that the intended optimal usage of the video resulting from the processing chain specified by this SPO SEI message includes for human viewing, po for human viewing idc equal to 2 specifies that that the video resulting from the processing chain specified by this SPO SEI message is suitable but not specifically optimized for human viewing, po for human viewing ide equal to 1 specifies that the video resulting from the processing chain specified by this SPO SEI message is unsuitable for human viewing, po for human viewing idc equal to 0 specifies that it is unknown if the video resulting from the processing chain specified by this SPO SEI message is suitable for human viewing.

[0042] po for machine analysis idc equal to 3 specifies that the intended optimal usage of the video resulting from the processing chain specified by this SPO SEI message includes machine analysis, po for machine analysis idc equal to 2 specifies that the video resulting from the processing chain specified by this SPO SEI message is suitable but not specifically optimized for machine analysis, po for machine analysis idc equal to 1 specifies that the video resulting from the processing chain specified by this SPO SEI message is unsuitable for machine analysis, po for machine analysis idc equal to 0 specifies that it is unknown if the video resulting from the processing chain specified by this SPO SEI message is suitable for machine analysis.

[0043] It is a requirement of bitstream conformance that the value of po for human viewing idc and po for machine analysis idc shall not be both equal to 1.

[0044] NOTE 3 - The values of po for human viewing idc and po for machine analysis idc are in force for the output of a processing chain instead of the respective syntax elements in an encoder optimization information (EOI) SEI message (eoi for human viewing idc and eoi for machine analysis idc) or a neural-network post-filter characteristics (NNPFC) SEI message (nnpfc for human viewing idc and mipfc for machine analysis idc), when the EOI or NNPFC SEI message is associated with the processing chain.

[0045] po_reserved_zero_4bits shall be equal to 0. Values greater than 0 for po_reserved_zero_4bits are reserved for future use by ITU-T | ISO / IEC and shall not be present in bitstreams conforming to this version of this Specification. Decoders conforming to this version of this Specification shall allow any value of po_reserved_zero_4bits in the range of 0 to 15, inclusive.

[0046] po_num_sei_messages_minus2 plus 2 indicates the number of types of SEI messages for which the preferred order of processing is indicated in the SPO SEI message. The variable PoNumProcStgs is set equal to po_num_sei_messages_minus2 + 2.

[0047] po breadth first flag equal to 1 specifies that the breadth-first handling of a processing chain specified in clause 8.30.3.2 shall be applied to determine the pictures that arc used for interpreting the semantics of the SEI messages applied as a part of the processing chain specified by this SPO SEI message, po breadth first flag equal to 0 specifies that the breadth-first handling of a processing chain specified in clause 8.30.3.2 or the depth-first handling of a processing chain specified in clause 8.30.3.3 shall be applied to detennine the pictures that are used for interpreting the semantics of the SEI messages applied as a part of the processing chain specified by this SPO SEI message.

[0048] NOTE 4 - When po breadth first flag is equal to 0, the processing chain can be performed for a picture without processing any SEI messages applying to subsequent picture units in output order.

[0049] po_sei_wrapping_flag[ i ] equal to 1 specifies that an SEI message that applies as the i-th SEI message type in the processing chain specified in this SPO SEI message, if present, is an SEI message that is included in a PON SEI message for which both of the following conditions are true:- pon_target_po_id[ j ] with any value of j is equal to po id.- There is a k-th loop entry in the processing order nesting SEI message such that the payloadType of the k-th nested SEI message is equal to po_sei_payload_type[ i ] and pon_processing_order[ k ] is equal to po_sei_processing_order[ i ].

[0050] po_sei_wrapping _flag[ i ] equal to 0 specifies that an SEI message that applies as the i-th SEI message type in the processing chain specified in this SPO SEI message, if present, is an SET message that is not included in a PON SEI message and for which both of the following conditions are true:- The payloadType of the SEI message is equal po_sei_payload_type[ i ].- po_sei_prefix_flag[ i ] is equal to 0, or when po_sei_prefix_flag[ i ] is equal to 1, the payload of the SEI message starts with the values of po_sei_prefix_data_bit[ i ][ j ].

[0051] NOTE 5 - po_sei_wrapping_flag[ i ] equal to 1 enables SEI messages to be carried within the processing order nesting SEI message to prevent such SEI messages from being incorrectly interpreted by decoders that do not process the SPO SEI message. Thus, po_sei_wrapping_flag[ i ] equal to 1 is intended to be used when po sei wrapping flag [ i ] equal to 0 can lead to unintended results being produced by such decoders.

[0052] po_sei_importance_flag[ i ] equal to 1 affects the derivation of PoSeiList, which is the list of SEI messages, PoSeiTypeList, which is the list SEI message type indices, and PoNumSeiMsgs, which is the number of SEI messages that a decoding system may process for a particular picture picA, as specified below.

[0053] po_sei_importance_flag[ i ] equal to 0 specifies that when the decoding system cannot interpret or does not support the functionality' indicated by the i-th SEI message type, it shall ignore all data associated with the loop variable value of i and exclude the i-th SEI message type from the processing chain performed by the decoding system.

[0054] po sei_processing degree flag[ i ] affects the derivation of PoSeiList, PoSeiTypeList, and PoNumSeiMsgs as specified below.

[0055] po_sei_payload_type[ i ] specifies the payloadType value of the i-th type of SEI message.

[0056] po_sei_prefix_flag[ i ] equal to 1 specifies that po_num_bits_in_prefix_indication_minusl [ i ] and some po_sci_prcfix_data_bit[ i ] [ j ] sy ntax elements arc present. po_sci_prcfix_flag[ i ] equal to 0 specifics that these sy ntax elements are not present.

[0057] The value of po_sei_payload_type[ i ] for each i in the range of 0 to po_num_sei_messages_minus2 + 1, inclusive, shall be equal to a value in SeiProcessingOrderSeiList.

[0058] When po_sei_payload_type[ i ] is equal to any value in SpoProcessSeiList, the i-th type of SEI message indicates a process.

[0059] spoPropertySeiList is set to consist of the pay loadType values included in SeiProcessingOrderSeiList excluding the paylaodTypc values included in SpoProcessSeiList. When po_sci_payload_typc[ i ] is equal to any’ value in spoPropertySeiList, the i-th type of SEI message indicates a property.

[0060] po_sei_processing_order[ i ] indicates the preferred order of processing of the i-th type of SEI message for which preferred processing order information is provided in the SPO SEI message. For any two different integer values of m and n. po sei processing order[ m ] less than po sei_processing order[ n ] indicates that the type of SEI message associated with index m should be processed before the type of SEI message associated with index n. and po_sei_processing_order[ m ] equal to po_sei_processing_order[ n ] indicates that there is no preferred order of processing between the types of SEI messages associated with indexes m and n (e.g., they can indicate different properties that are both applicable at that stage, or one can indicate a property and the other can indicate a process).

[0061] For i greater than 0, po_sei_processing_order[ i ] shall be greater than or equal to po_sei_processing_order[ i - 1 ].

[0062] Let seiMsgA be an SEI message that applies as the i-th SEI message type in the processing chain specified in this SPO SEI message, persists for a particular picture picA, and is associated with po_sci_proccssing_ordcr[ i ] equal to poValA.

[0063] Let seiMsgSet be a set of of SEI messages that consists of each SEI message for which all of the following conditions are true:The SEI message applies as the k-th SEI message type in the processing chain specified in this SPO SEI message with any value of k less than i.The SEI message persists for picA.- po_sei_processing_order[ k ] is less than poValA.- The payloadType value of the SEI message is among the values included in SpoProcessSeiList.

[0064] The pictures to which the semantics of seiMsgA apply' are specified as follows:- If seiMsgSet is non-empty’, the semantics of seiMsgA apply to all the pictures generated by the process implied by’ the SEI message that has the greatest value of po_sei_processing_order[ k ] among the SEI messages in seiMsgSet.- Otherwise, the semantics of seiMsgA apply to picA.

[0065] NOTE 6 - When an NNPF process outputs more than one NNPF-generated picture, the semantics of an SEI message that follows the NNPF in the processing order apply to all these NNPF-generated pictures.

[0066] po_num_bits_in_prefix_indication_minus 1 [ i ] and po_sei_prefix_data_bit[ i ] [ j ] , when present, have the same semantics as the num_bits_in_prefix_indication_minusl [ i ] and sei_prefix_data_bit[ i ][ j ] syntax elements of the SEI prefix indication SEI message, with prefix_sei_payload_ty pe replaced by po_sei_payload_ty pe[ i ].

[0067] When more than one SPO SEI message with a particular value of po id is present in a CVS. the values of po_num_sei_messages_minus2 and, for each value of i, the values of po_sei_wrapping_flag[ i ], po_sei_prelix_flag[ i ], po_sei_importance_flag[ i ]. po_sei_payload_type[ i ], po_sei_processing_order[ i ] shall be the same as in the other SPO SEI messages in the CVS with the same value of po id.

[0068] po_byte_alignment_bit_equal_to_one shall be equal to 1.

[0069] The lists PoProcStgldx, indicating the processing stage indices of the SEI message types in the processing chain, and PoSeiTypeldx, indicating the SEI message ty pe indices of the processing stages in the processing chain, are derived as follows:- For each of the SEI message types of in the processing chain, the following applies in a non-decreasing order of the corresponding po_sei_processing_order[ i ] values, with j being set equal to 0 initially:PoProcStgldxf i ] = jPoSeiTypeIdx[ j ] = i (xx)Where PoProcStgIdx[ i ] indicates the processing stage index of the i-th SEI message type in the processing chain, and PoSeiTypeIdx[ j ] indicates the SEI message type index of the j -th processing stage in the processing chain.

[0070] For a picture, the list PoSeiList, indicting the list of SEI messages, associated with SEI message types in the processing chain indicated by the SPO SEI message, that may be applied to the picture, the list PoSciTypcList. indicating the SEI message type indices of the SEI messages that may be applied to the picture, and the variable PoNumSeiMsgs, indicating the number of SEI messages that may be applied to the picture, are derived as follows:- PoSeiList is initially empty, and j and PoNumSeiMsgs are both initially set equal to 0.- The following applies in the same non-decreasing order of po_sei_processing_order[ i ] values as above for deriving the lists PoProcStgldx and PoSeiTypeldx for all values of i in the range of 0 to po_num_sei_messages_minus2 + 1, inclusive, unless terminated earlier as specified below:- When an SEI message seiA associated with the i-th SEI message type persists for picA, the following applies:- If the decoding system can interpret and supports the functionality indicated by seiA. seiA is added at the end of PoSeiList, PoSeiTypeList[ j ] is set equal to i, PoNumSeiMsgs is set equal to PoNumSeiMsgs + 1, and j is set equal to j + 1.- Otherwise, if po_sei_importance_flag[ i J is equal to 1 and po_sci_proccssing_dcgrcc_llag| i J is equal to 0, the derivation of PoSeiList, PoSciTypcList. and PoNumSeiMsgs are terminated.- Otherwise, if po_sei_importance_flag[ i ] is equal to 1 and po_sei_processing_degree_flag[ i ] is equal to 1, the processing chain specified by this SPO SEI message should not be performed for picA, PoSeiList is set to be empty, PoNumSeiMsgs is set equal to 0, and the derivation of PoSeiList, PoSciTypcList. and PoNumSeiMsgs are terminated.2.4 WC SEI payloadType values

[0071] In the semantics of the SPO SEI message, two lists are used, SeiProcessingOrderSeiList and SpoProcessSeiList, which are defined in JVET-AI2005 [5] as follows: SeiProcessingOrderSeiList is set to consist of the SEI payloadType values 3, 4, 5, 19. 137, 142. 144, 147, 148, 149, 150, 153, 155, 165, 177, 210, and 211, and SpoProcessSeiList is set to consist of the payloadType values 19, 142, 155. 210, and 211.

[0072] These SEI payloadType values are all included in the following syntax table in JVET-AI2005, which defines SEI pay loadType values for all SEI messages that may be used in a WC bitstream:2.5 Handling of a processing chain

[0073] As can be seen from the semantics of the SPO SEI message, a processing chain consists of a list of types of SEI messages identified by an SPO SEI message in the preferred processing order indicated in the SPO SEI message.

[0074] An improved version of the specification for handling of a processing chain specified in JVET-AI2006 is as follows.

[0075] In clause 3, add the following definitions (adjust the subclause numbering when adding):3.1 corresponding picture: For a particular picture picA, the corresponding picture in a picture list is the picture in the picture list that is either picA itself or a processed version of picA generated when the process implied by an SEI message is applied.NOTE - The particular picture picA could be a picture that is not in the picture list, in which case the corresponding picture in the picture list is a processed version of picA. When picA is in the picture list, it's corresponding picture in the picture list is itself.3.2 inserted picture: A picture that was interpolated or extrapolated when the process implied by an SEI message (e.g., an NNPF activation (NNPFA) SEI message activating an NNPF with PictureRateUpsamplingFlag or TemporalExtrapolationFlag equal to 1) is applied.3.3 associated inserted picture: For a particular picture picA. an associated inserted picture in a picture list is a picture picB in the picture list that is the corresponding picture of an inserted picture generated when applying the process implied by an SEI message to a corresponding picture of picA.

[0076] NOTE - The particular picture picA could be a picture that is not in the picture list.8.30.2 Handling of a processing chain8.30.2.1 General

[0077] Processing chains are alternatives to each other, i.e., at most one processing chain can be chosen to be applied by a decoding system at one time.

[0078] A special NNPF cascading case is defined as the case when such two NNPFs are both activated for a picture: the two post processing filters (PPFs) are both NNPFs. one of the two NNPFs has nnpfc purpose equal to 4 and the other has multiple input pictures, and neither of the two NNPFs is associated with an SPO SEI message. In thiscase, the tw o NNPFs are implicitly considered as belonging to one processing chain, and the NNPF with nnpfc_purpose equal to 4 is applied first.

[0079] Except for the special NNPF cascading case, each processing chain containing multiple SEI message types is indicated by an SPO SEI message with a particular value of po id. Except for the special NNPF cascading case, any SEI message for which the payloadTypc is present in SpoProcessSeiList but is not indicated by an SPO SEI message is in its own processing chain.

[0080] The PoSeiList for a corresponding picture of picA or for an associated inserted picture of picA is derived to be the same as the PoSeiList derived for picA.

[0081] A decoding system may choose and apply a processing chain according to the following ordered steps:1) The bitstream is decoded and a processing chain is chosen, and the list PoCdoPicList is set to be the list of the cropped decoded output pictures in output order resulted from decoding the bitstream.2) The list CandlnputPicList is set to be identical to PoCdoPicList.NOTE 1 - The list CandlnputPicList may be updated during the next step.3) If the chosen processing chain is indicated by an SPO SEI message and po breadth first flag in the SPO SEI message is equal to 1, the breadth-first handling of a processing chain is invoked. Otherwise, either the depth-first handling of a processing chain or the breadth-first handling of a processing chain is invoked.- When applying an NNPF to a picture during the invocation of a process for handling of a processing chain, the following applies:- The filtered and / or interpolated pictures are generated by the NNPF by applying the NNPF process specified in the semantics of the NNPFC SEI message, in a patch-wise manner, to the current picture.- The order of the pictures generated by the NNPF by applying the NNPF process being stored into the output tensor of the NNPF is in output order.4) The list PoOutputPicList is set to be identical to CandlnputPicList.

[0082] NOTE 2 - The list PoOutputPicList contains the final output of the processing chain.8.30.2.2 Breadth-first handling of a processing chain

[0083] For each SEI message types, with SEI message type index i, of the chosen processing chain, the following applies in increasing order of the corresponding processing stage index PoProcStgldxf i ] values:- The following applies for each picture picA in CandlnputPicList in output order, when an SEI message associated with the i-th SEI message type is present in PoSeiList of picA:- When PoProcStgIdx[ i ] is greater than 0, the following exceptions apply for the interpretation of the SEI message:The interface variables for purposes of interpretation of the SEI message are derived from picA instead of the syntax elements indicating properties for the respective cropped decoded picture.The semantics of the SEI message, or the semantics of the SEI message and, when the SEI message is an NNPFA SEI message, the associated NNPFC SEI message, apply to pictures in CandlnputPicList instead of cropped decoded pictures.When the i-th SEI message type is present in SpoProcessingList, the process implied by the SEI message is performed and the list CandlnputPicList is updated by replacing pictures with the corresponding processed pictures, if any, resulting from the process and inserting the other pictures, if any, resulting from the process into CandlnputPicList so that the output order is obeyed.8.30.2.3 Depth-first handling of a processing chain

[0084] The following is repeatedly applied, in output order, for each picture picA in CandlnputPicList:- The following applies for each SEI message with SEI message index seildx in PoSeiList of picA in increasing order of list indexes for PoSeiList:- When PoProcStgldxf PoSeiTypeList[ seildx ] ] is greater than 0, the following exceptions apply for the interpretation of the SEI message:The interface variables for purposes of interpretation of the SEI message are derived from the pictures in CandlnputPicList instead of the syntax elements indicating properties for the respective cropped decoded pictures.- The semantics of the SEI message, or of the SEI message and, when the SEI message is an NNPFASEI message, the associated NNPFC SEI message, apply to pictures in CandlnputPicList instead of cropped decoded pictures.- The process implied by the SEI message is invoked repeatedly, in output order, for picA and each of the pictures in CandlnputPicList that is picA or an associated inserted picture of picA. After each invocation of the process, the list CandlnputPicList is updated by replacing pictures with the corresponding processed pictures, if any’, resulting from the process and inserting the other pictures, if any, resulting from the process into CandlnputPicList so that the output order is obeyed.3. Technical problems solved by disclosed technical solutions

[0085] An example design of the depth-first handling of a processing chain have the following problems:

[0086] First, the list CandlnputPicList is used to contain candidate input pictures for the process implied by an SEI message of any processing stage, and the list CandlnputPicList is updated after each invocation of a process implied by7an SEI message. Consequently , for a cropped decoded output (CDO) picture that is not the first CDO picture in output order among all CDO pictures, during the invocation of the process implied by an SEI message of processing stage 0, an input picture may' be an output picture of the process implied by an SEI message of processing stage greater than 0. That is problematic.

[0087] Second, regardless of whether the SEI payloadType value of the seildx-th SEI message in PoSeiList of a picture picA in CandlnputPicListf 0 ] is present in SpoProcessSeiList, the process implied by the SEI message is invoked. However, the process should only be invocated when the SEI payloadType value of the SEI message is present in SpoProcessSeiList.4. A listing of solutions and embodiments

[0088] To solve the above-described problems, methods as summarized below are disclosed. The aspects should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these examples can be applied individually or combined in any manner.1 ) In one example, for depth-first handling of a processing chain, a processing-stage-based use of candidate input picture list is specified. a. In one example, for depth-first handling of a processing chain, each processing stage has its own candidate input picture list. i. In one example, for the first processing stage (i.e., processing stage 0), the candidate input list contains cropped decoded output pictures. ii. In one example, for the i-th processing stage, where i is greater than 0, the candidate input list contains pictures outputted by the previous processing stage.2) In one example, an array of candidate input picture lists, e.g., named CandlnputPicListf i ] for i ranging from 0 to PoNumProcStgs - 1, inclusive, is specified, which contains input pictures for the i-th processing stage. a. Furthermore, additionally, the list CandlnputPicListf PoNumProcStgs ] is specified, for temporally storing the final output of the chosen processing chain.3) In one example, it is specified that, for each i in the range of 0 to PoNumProcStgs. inclusive, the list CandlnputPicListf i ] is initialized to be identical to PoCdoPicList, which contains the list of the cropped decoded output pictures in output order resulted from decoding the bitstream.4) In one example, it is specified that, for depth-first handling of a processing chain, only when the SEI payloadT pc value of the seildx-th SEI message in PoSeiList of a picture picA in CandlnputPicListf 0 ] is present in SpoProcessSeiList, the process implied by the SEI message is invoked repeatedly, in output order, for picA and each of the pictures in CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] ] that is picA or an associated inserted picture of picA.5) In one example, it is specified that, for depth-first handling of a processing chain, after each invocation of the process implied by the seildx-th SEI message in PoSeiList of a picture picA in CandlnputPicListf 0 ], each list CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] +j ] with j in the range of 1 to PoNumProcStgs - PoProcStgldxf PoSeiTypeListf seildx ] ], inclusive, is updated by replacing pictures with the corresponding processed pictures, if any, resulting from the process and inserting the other pictures, if any, resulting from the process into CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] + j ] so that the output order is obeyed.5. Embodiments

[0089] Below are some example embodiments for some of the aspects summarized above in Section 4. Added or modified texts are shown enclosed in { { }}.5.1 First embodimentIn clause 3, add the following definitions (adjust the subclause numbering when adding):3.4 corresponding picture: For a particular picture picA, the corresponding picture in a picture list is the picture in the picture list that is either picA itself or a processed version of picA generated when the process implied by an SEI message is applied.

[0090] NOTE - The particular picture picA could be a picture that is not in the picture list, in which case the corresponding picture in the picture list is a processed version of picA. When picA is in the picture list, it's corresponding picture in the picture list is itself.3.5 inserted picture: A picture that was interpolated or extrapolated when the process implied by an SEI message (e.g., an NNPFA SEI message activating an NNPF with PictureRateUpsamplingFlag or TemporalExtrapolationFlag equal to 1) is applied.3.6 associated inserted picture: For a particular picture picA, an associated inserted picture in a picture list is a picture picB in the picture list that is the corresponding picture of an inserted picture generated when applying the process implied by an SEI message to a corresponding picture of picA.

[0091] NOTE - The particular picture picA could be a picture that is not in the picture list.8.30.2 Handling of a processing chain8.30.2.1 General

[0092] Processing chains are alternatives to each other, i.e., at most one processing chain can be chosen to be applied by a decoding system at one time.

[0093] A special NNPF cascading case is defined as the case when such two NNPFs are both activated for a picture: the two PPFs are both NNPFs, one of the two NNPFs has impfc_purpose equal to 4 and the other has multiple input pictures, and neither of the two NNPFs is associated with an SPO SEI message. In this case, the two NNPFs are implicitly considered as belonging to one processing chain, and the NNPF with nnpfc_purpose equal to 4 is applied first.

[0094] Except for the special NNPF cascading case, each processing chain containing multiple SEI message types is indicated by an SPO SEI message with a particular value of po id. Except for the special NNPF cascading case, any SEI message for which the payloadType is present in SpoProcessSeiList but is not indicated by an SPO SEI message is in its own processing chain.

[0095] The PoSeiList for a corresponding picture of picA or for an associated inserted picture of picA is derived to be the same as the PoSeiList derived for picA.

[0096] A decoding system may choose and apply a processing chain according to the following ordered steps:1 ) The bitstream is decoded and a processing chain is chosen, and the list PoCdoPicList is set to be the list of the cropped decoded output pictures in output order resulted from decoding the bitstream.2) {{For each i in the range of 0 to PoNumProcStgs, inclusive, the list CandlnputPicListf i ] is set to be identical to PoCdoPicList. } }{{NOTE 1 - The lists CandInputPicList[ i ] for i in the range of 1 to PoNumProcStgs, inclusive, may be updated during the next step. The list CandInputPicList[ PoNumProcStgs ] is for temporally storing the final output of the chosen processing chain.}}3) If the chosen processing chain is indicated by an SPO SEI message and po breadth first flag in the SPO SEI message is equal to 1, the breadth-first handling of a processing chain is invoked. Otherwise, either the depth-first handling of a processing chain or the breadth-first handling of a processing chain is invoked.- When applying an NNPF to a picture during the invocation of a process for handling of a processing chain, the following applies:- The filtered and / or interpolated pictures are generated by the NNPF by applying the NNPF process specified in the semantics of the NNPFC SEI message, in a patch-wise manner, to the current picture.- The order of the pictures generated by the NNPF by applying the NNPF process being stored into the output tensor of the NNPF is in output order.4) The list PoOutputPicList is set to be identical to CandlnputPicList.NOTE 2 - The list PoOutputPicList contains the final output of the processing chain.8.30.2.2 Breadth-first handling of a processing chain

[0097] For each SEI message types, with SEI message type index i. of the chosen processing chain, the following applies in increasing order of the corresponding processing stage index PoProcStgIdx[ i ] values:The following applies for each picture picA in {{CandlnputPicListf PoProcStgldxf i ] ]} } in output order, when an SEI message associated with the i-th SEI message type is present in PoSeiList of picA:- When PoProcStgldxf i ] is greater than 0, the following exceptions apply for the interpretation of the SEI message:- The interface variables for purposes of interpretation of the SEI message are derived from picA instead of the syntax elements indicating properties for the respective cropped decoded picture.- The semantics of the SEI message, or the semantics of the SEI message and, when the SEI message is an NNPFA SEI message, the associated NNPFC SEI message, apply to pictures in {{CandlnputPicListf PoProcStgldxf i ] ]}} instead of cropped decoded pictures.- When the i-th SEI message type is present in SpoProcessingList, the process implied by the SEI message is performed and {{each list CandlnputPicListf PoProcStgldxf i ] +j ] with j in the range of 1 to PoNumProcStgs - PoProcStgldxf i ], inclusive,} } is updated by replacing pictures with the corresponding processed pictures, if any, resulting from the process and inserting the other pictures, if any, resulting from the process into {{CandlnputPicListf PoProcStgldxf i ] + j ]}} so that the output order is obeyed.8.30.2.3 Depth-first handling of a processing chain

[0098] The following is repeatedly applied, in output order, for each picture picA in {{CandlnputPicListf 0 ]} }: - The following applies for each SEI message with SEI message index seildx in PoSeiList of picA in increasing order of list indexes for PoSeiList:- When PoProcStgldxf PoSeiTypcList| seildx ] ] is greater than 0, the following exceptions apply for the interpretation of the SEI message:- The interface variables for purposes of interpretation of the SEI message arc derived from the pictures in {{CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] ]}} instead of the syntax elements indicating properties for the respective cropped decoded pictures.- The semantics of the SEI message, or of the SEI message and, when the SEI message is an NNPFA SEI message, the associated NNPFC SEI message, apply to pictures in{{CandhrputPicList[ PoProcStgldx} PoSeiTypeList[ seildx J J J} } instead of cropped decoded pictures.{{When the SEI payloadType value of the SEI message is present in SpoProcessSeiList,} } the process implied by the SEI message is invoked repeatedly, in output order, for picA and each of the pictures in {{CandInputPicList[ PoProcStgIdx[ PoSeiTypeListf seildx ] ] ]}} that is picA or an associated inserted picture of picA. After each invocation of the process, {{each list CandlnputPicListf PoProcStgIdx[ PoSeiTypeListf seildx ] ] +j ] with j in the range of 1 to PoNumProcStgs - PoProcStgldxf PoSeiTypcList| seildx ] ], inclusive,} } is updated by replacing pictures with the corresponding processed pictures, if any. resulting from the process and inserting the other pictures, if any, resulting from the process into {{CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] + j ]}} so that the output order is obeyed.6. References[1] ITU-T and ISO / IEC, ‘‘High efficiency video coding". Rec. ITU-T H.265 | ISO / IEC 23008-2 (in force edition).[2] ITU-T and ISO / IEC, “Versatile Video Coding". Rec. ITU-T H.266 | ISO / IEC 23090-3.[3] ITU-T and ISO / IEC, “Versatile Supplemental Enhancement Information Messages for Coded Video Bitstreams”, Rec. ITU-T Rec. H.274 | ISO / IEC 23002-7.[4] J. Boyce, J. Chen, S. Deshpande, M. M. Hannuksela, S. McCarthy, G. J. Sullivan, H. Tan, and Y.-K. Wang (editors), JVET-AI2006, “Additional SEI messages for VSEI version 4 (Draft 3)”.[5] G. J. Sullivan, B. Bross, M. M. Hannuksela, and Y.-K. Wang (editors), JVET-AI2005, “Additions and corrections for WC version 4 (Draft 9)”.

[0099] FIG. 1 is a block diagram showing an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of the system 4000. The system 4000 may include input 4002 for receiving video content. The video content may be received in a raw or uncompressed format, e.g., 8 or 10 bit multi-component pixel values, or may be in a compressed or encoded format. The input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interface include wired interfaces such as Ethernet, passive optical network (PON), etc. and wireless interfaces such as Wi-Fi or cellular interfaces.

[0100] The system 4000 may include a coding component 4004 that may implement the various coding or encoding methods described in the present document. The coding component 4004 may reduce the average bitrate of video from the input 4002 to the output of the coding component 4004 to produce a coded representation of the video. The coding techniques are therefore sometimes called video compression or video transcoding techniques. The output of the coding component 4004 may be cither stored, or transmitted via a communication connected, as represented by the component 4006. The stored or communicated bitstream (or coded) representation of the video received at the input 4002 may be used by a component 4008 for generating pixel values or displayable video that is sent to a display interface 4010. The process of generating user- viewable video from the bitstream representation is sometimes called video decompression. Furthermore, while certain video processing operations are referred to as “coding” operations or tools,it will be appreciated that the coding tools or operations are used at an encoder and corresponding decoding tools or operations that reverse the results of the coding will be performed by a decoder.

[0101] Examples of a peripheral bus interface or a display interface may include universal serial bus (USB) or high definition multimedia interface (HDMI) or Displayport, and so on. Examples of storage interfaces include serial advanced technology7attachment (SATA), peripheral component interconnect (PCI), integrated drive electronics (IDE) interface, and the like. The techniques described in the present document may be embodied in various electronic devices such as mobile phones, laptops, smartphones or other devices that are capable of performing digital data processing and / or video display.

[0102] FIG. 2 is a block diagram of an example video processing apparatus 4100. The apparatus 4100 may be used to implement one or more of the methods described herein. The apparatus 4100 may be embodied in a smartphone, tablet, computer, Internet of Things (loT) receiver, and so on. The apparatus 4100 may include one or more processors 4102, one or more memories 4104 and video processing circuitry 4106. The processor(s) 4102 may' be configured to implement one or more methods described in the present document. The memory (memories) 4104 may be used for storing data and code used for implementing the methods and techniques described herein. The video processing circuitry 4106 may be used to implement, in hardware circuitry, some techniques described in the present document. In some embodiments, the video processing circuitry 4106 may be at least partly included in the processor 4102, e.g., a graphics co-processor.

[0103] FIG. 3 is a flowchart for an example method 4200 of video processing. The method 4200 determines for depth-first handling of a processing chain, a processing-stage-based use of candidate input picture list is specified at step 4202. A conversion between a visual media data and a bitstream is perfomed based on the candidate input picture list at step 4204. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof.

[0104] It should be noted that the method 4200 can be implemented in an apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In such a case, the instructions upon execution by the processor, cause the processor to perform the method 4200. Further, the method 4200 can be performed by a non-transitory computer readable medium comprising a computer program product for use by a video coding device. The computer program product comprises computer executable instructions stored on the non-transitory computer readable medium such that when executed by' a processor cause the video coding device to perform the method 4200.

[0105] FIG. 4 is a block diagram that illustrates an example video coding system 4300 that may utilize the techniques of this disclosure. The video coding system 4300 may include a source device 4310 and a destination device 4320. Source device 4310 generates encoded video data which may be referred to as a video encoding device. Destination device 4320 may decode the encoded video data generated by source device 4310 which may be referred to as a video decoding device.

[0106] Source device 4310 may include a video source 4312, a video encoder 4314, and an input / output (I / O) interface 4316. Video source 4312 may include a source such as a video capture device, an interface to receive video data from a video content provider, and / or a computer graphics system for generating video data, or a combination of such sources. The video data may comprise one or more pictures. Video encoder 4314 encodes the video data fromvideo source 4312 to generate a bitstream. The bitstream may include a sequence of bits that form a coded representation of the video data. The bitstream may include coded pictures and associated data. The coded picture is a coded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. I / O interface 4316 may include a modulator / demodulator (modem) and / or a transmitter. The encoded video data may be transmitted directly to destination device 4320 via I / O interface 4316 through network 4330. The encoded video data may also be stored onto a storage medium / server 4340 for access by destination device 4320.

[0107] Destination device 4320 may include an I / O interface 4326, a video decoder 4324, and a display device 4322. I / O interface 4326 may include a receiver and / or a modem. I / O interface 4326 may acquire encoded video data from the source device 4310 or the storage medium / server 4340. Video decoder 4324 may decode the encoded video data. Display device 4322 may display the decoded video data to a user. Display device 4322 may be integrated with the destination device 4320. or may be external to destination device 4320, which can be configured to interface with an external display device.

[0108] Video encoder 4314 and video decoder 4324 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (WC) standard and other current and / or further standards.

[0109] FIG. 5 is a block diagram illustrating an example of video encoder 4400, which may be video encoder 4314 in the system 4300 illustrated in FIG. 4. Video encoder 4400 may be configured to perform any or all of the techniques of this disclosure. The video encoder 4400 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of video encoder 4400. In some examples, a processor may be configured to perform any or all of the teclmiques described in this disclosure.

[0110] The functional components of video encoder 4400 may include a partition unit 4401, a prediction unit 4402 which may include a mode select unit 4403, a motion estimation unit 4404, a motion compensation unit 4405, an intra prediction unit 4406, a residual generation unit 4407, a transform processing unit 4408, a quantization unit 4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy encoding unit 4414.

[0111] In other examples, video encoder 4400 may include more, fewer, or different functional components. In an example, prediction unit 4402 may include an intra block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode in which at least one reference picture is a picture where the current video block is located.

[0112] Furthermore, some components, such as motion estimation unit 4404 and motion compensation unit 4405 may be highly integrated, but are represented in the example of video encoder 4400 separately for purposes of explanation.

[0113] Partition unit 4401 may partition a picture into one or more video blocks. Video encoder 4400 and video decoder 4500 may7support various video block sizes.

[0114] Mode select unit 4403 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra or inter coded block to a residual generation unit 4407 to generate residual block data and to a reconstruction unit 4412 to reconstruct the encoded block for use as a reference picture. In some examples, mode select unit 4403 may select a combination of intra and inter prediction (CIIP) mode in which the prediction is based onan inter prediction signal and an intra prediction signal. Mode select unit 4403 may also select a resolution for a motion vector (e.g., a sub-pixel or integer pixel precision) for the block in the case of inter prediction.

[0115] To perform inter prediction on a current video block, motion estimation unit 4404 may generate motion information for the current video block by comparing one or more reference frames from buffer 4413 to the current video block. Motion compensation unit 4405 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from buffer 4413 other than the picture associated with the current video block.

[0116] Motion estimation unit 4404 and motion compensation unit 4405 may perform different operations for a current video block, for example, depending on whether the current video block is in an I slice, a P slice, or a B slice.

[0117] In some examples, motion estimation unit 4404 may perform uni-directional prediction for the current video block, and motion estimation unit 4404 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. Motion estimation unit 4404 may then generate a reference index that indicates the reference picture in list 0 or list 1 that contains the reference video block and a motion vector that indicates a spatial displacement between the current video block and the reference video block. Motion estimation unit 4404 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current block based on the reference video block indicated by the motion information of the current video block.

[0118] In other examples, motion estimation unit 4404 may perform bi-directional prediction for the current video block, motion estimation unit 4404 may search the reference pictures in list 0 for a reference video block for the current video block and may also search the reference pictures in list 1 for another reference video block for the current video block. Motion estimation unit 4404 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors that indicate spatial displacements between the reference video blocks and the current video block. Motion estimation unit 4404 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current video block based on the reference video blocks indicated by the motion information of the current video block.

[0119] In some examples, motion estimation unit 4404 may output a full set of motion information for decoding processing of a decoder. In some examples, motion estimation unit 4404 may not output a full set of motion information for the current video. Rather, motion estimation unit 4404 may signal the motion information of the current video block with reference to the motion information of another video block. For example, motion estimation unit 4404 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

[0120] In one example, motion estimation unit 4404 may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder 4500 that the current video block has the same motion information as another video block.

[0121] In another example, motion estimation unit 4404 may identify, in a syntax structure associated with the current video block, another video block and a motion vector difference (MVD). The motion vector difference indicatesa difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 4500 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0122] As discussed above, video encoder 4400 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 4400 include advanced motion vector prediction (AMVP) and merge mode signaling.

[0123] Intra prediction unit 4406 may perform intra prediction on the current video block. When intra prediction unit 4406 performs intra prediction on the current video block, intra prediction unit 4406 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a predicted video block and various syntax elements.

[0124] Residual generation unit 4407 may generate residual data for the current video block by subtracting the predicted video block(s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks that correspond to different sample components of the samples in the current video block.

[0125] In other examples, there may be no residual data for the current video block for the current video block, for example in a skip mode, and residual generation unit 4407 may not perform the subtracting operation.

[0126] Transform processing unit 4408 may generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to a residual video block associated with the current video block.

[0127] After transform processing unit 4408 generates a transform coefficient video block associated with the current video block, quantization unit 4409 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values associated with the current video block.

[0128] Inverse quantization imit 4410 and inverse transform unit 4411 may apply inverse quantization and inverse transforms to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. Reconstruction unit 4412 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 4402 to produce a reconstructed video block associated with the current block for storage in the buffer 4413.

[0129] After reconstruction unit 4412 reconstructs the video block, the loop filtering operation may be performed to reduce video blocking artifacts in the video block.

[0130] Entropy encoding unit 4414 may receive data from other functional components of the video encoder 4400. When entropy encoding unit 4414 receives the data, entropy’ encoding unit 4414 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data.

[0131] FIG. 6 is a block diagram illustrating an example of video decoder 4500 which may be video decoder 4324 in the system 4300 illustrated in FIG. 4. The video decoder 4500 may be configured to perform any or all of the techniques of this disclosure. In the example shown, the video decoder 4500 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the videodecoder 4500. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

[0132] In the example shown, video decoder 4500 includes an entropy decoding unit 4501, a motion compensation unit 4502, an intra prediction unit 4503, an inverse quantization unit 4504, an inverse transformation unit 4505, a reconstruction unit 4506, and a buffer 4507. Video decoder 4500 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 4400.

[0133] Entropy decoding unit 4501 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data). Entropy decoding unit 4501 may decode the entropy coded video data, and from the entropy decoded video data, motion compensation unit 4502 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. Motion compensation unit 4502 may, for example, determine such information by performing the AMVP and merge mode.

[0134] Motion compensation unit 4502 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used with sub-pixel precision may be included in the sy ntax elements.

[0135] Motion compensation unit 4502 may use interpolation filters as used by video encoder 4400 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. Motion compensation unit 4502 may determine the interpolation filters used by video encoder 4400 according to received syntax information and use the interpolation filters to produce predictive blocks.

[0136] Motion compensation unit 4502 may use some of the syntax information to determine sizes of blocks used to encode frame(s) and / or slice(s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter coded block, and other information to decode the encoded video sequence.

[0137] Intra prediction unit 4503 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. Inverse quantization unit 4504 inverse quantizes, i.e., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies an inverse transform.

[0138] Reconstruction unit 4506 may sum the residual blocks with the corresponding prediction blocks generated by motion compensation unit 4502 or intra prediction unit 4503 to form decoded blocks. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in buffer 4507, which provides reference blocks for subsequent motion compensation / intra prediction and also produces decoded video for presentation on a display device.

[0139] FIG. 7 is a schematic diagram of an example encoder 4600. The encoder 4600 is suitable for implementing the teclmiques of WC. The encoder 4600 includes three in-loop filters, namely a deblocking filter (DF) 4602, a sample adaptive offset (SAG) 4604, and an adaptive loop filter (ALF) 4606. Unlike the DF 4602, which uses predefined filters, the SAO 4604 and the ALF 4606 utilize the original samples of the current picture to reduce the mean square errorsbetween the original samples and the reconstructed samples by adding an offset and by applying a finite impulse response (FIR) filter, respectively, with coded side information signaling the offsets and filter coefficients. The ALF 4606 is located at the last processing stage of each picture and can be regarded as a tool trying to catch and fix artifacts created by the previous stages.

[0140] The encoder 4600 further includes an intra prediction component 4608 and a motion estimation / compensation (ME / MC) component 4610 configured to receive input video. The intra prediction component 4608 is configured to perform intra prediction, while the ME / MC component 4610 is configured to utilize reference pictures obtained from a reference picture buffer 4612 to perform inter prediction. Residual blocks from inter prediction or intra prediction are fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are fed into an entropy coding component 4618. The entropy coding component 4618 entropy codes the prediction results and the quantized transform coefficients and transmits the same toward a video decoder (not shown). Quantization components output from the quantization component 4616 may be fed into an inverse quantization (IQ) components 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. The REC component 4624 is able to output images to the DF 4602, the SAO 4604, and the ALF 4606 for filtering prior to those images being stored in the reference picture buffer 4612.

[0141] FIG. 8 is a flowchart for another example method 4700 of video processing. The method 4700 determines to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures at step 4702. A conversion between the visual media data and a bitstream based on the list of candidate input pictures at step 4704. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof.

[0142] It should be noted that the method 4700 can be implemented in an apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In such a case, the instructions upon execution by the processor, cause the processor to perform the method 4700. Further, the method 4700 can be performed by a non-transitory computer readable medium comprising a computer program product for use by a video coding device. The computer program product comprises computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method 4700.

[0143] A listing of solutions preferred by some examples is provided next.

[0144] The following solutions show examples of techniques discussed herein.

[0145] 1. A method for processing media data comprising: determining for depth-first handling of a processing chain, a processing-stage-based use of candidate input picture list is specified; and performing a conversion between a visual media data and a bitstream based on the candidate input picture list.

[0146] 2. The method of solution 1, wherein for depth-first handling of a processing chain, each processing stage has its own candidate input picture list.

[0147] 3. The method of any of solutions 1-2, wherein for a first processing stage, denoted as processing stage0, the candidate input list contains cropped decoded output pictures.

[0148] 4. The method of any of solutions 1-3, wherein for an i-th processing stage, where i is greater than 0, the candidate input list contains pictures outputted by a previous processing stage.

[0149] 5. The method of any of solutions 1-4, wherein an array of candidate input picture lists, denoted as candidate input picture list i (CandInputPicList[ i )] for i ranging from 0 to processing order number of processing stages (PoNumProcStgs) - 1, inclusive, contains input pictures for an i-th processing stage.

[0150] 6. The method of any of solutions 1-5. wherein a list CandInputPicList[ PoNumProcStgs ] is employed for temporally storing a final output of a chosen processing chain.

[0151] 7. The method of any of solutions 1-6, wherein for each i in the range of 0 to PoNumProcStgs, inclusive, the list CandInputPicList[ i ] is initialized to be identical to processing order cropped decoded output picture list (PoCdoPicList), which contains a list of the cropped decoded output pictures in output order resulting from decoding the bitstream.

[0152] 8. The method of any of solutions 1-7, wherein for depth-first handling of a processing chain, only when a supplemental enhancement information (SEI) pay load type (payloadType) value of the SEI index (seildx)-th SEI message in picture order SEI list (PoSeiList) of a picture picA in CandlnputPicListf 0 ] is present in SEI processing order (SPO) process SEI list (SpoProcessSeiList), the process implied by the SEI message is invoked repeatedly, in output order, for a picture (picA) and each of the pictures in CandlnputPicListf processing order processing state index (PoProcStgIdx)[ processing order SEI type list (PoSeiTypeList)[ seildx ] ] ] that is picA or an associated inserted picture of picA.

[0153] 9. The method of any of solutions 1-8, wherein for depth-first handling of a processing chain, after each invocation of the process implied by the seildx-th SEI message in PoSeiList of a picture picA in CandlnputPicListf 0 ], each list CandlnputPicListf PoProcStgldxf PoSciTypeList| seildx ] ] +j ] with j in the range of 1 to PoNumProcStgs - PoProcStgldxf PoSeiTypeListf seildx ] ], inclusive, is updated by replacing pictures with the corresponding processed pictures, if any, resulting from the process and inserting the other pictures, if any, resulting from the process into CandlnputPicListf PoProcStgldxf PoSeiTypeListf seildx ] ] +j ] so that the output order is obeyed.

[0154] 10. The method of any of solutions 1-9. wherein the conversion includes encoding the visual media data into the bitstream.

[0155] 1 1. The method of any of solutions 1 -9, wherein the conversion includes decoding the visual media data from the bitstream.

[0156] 12. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform the method of any of solutions 1-11.

[0157] 13. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non- transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of solutions 1-11.

[0158] 14. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining for depth-first handling of a processing chain, a processing-stage-based use of candidate input picture list is specified; and generating a bitstream based on the determining.

[0159] 15. A method for storing bitstream of a video comprising: determining for depth-first handling of a processing chain, a processing-stage-based use of candidate input picture list is specified; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.

[0160] 16. A method, apparatus, or system described in the present document.

[0161] The following solutions show further examples of techniques discussed herein.

[0162] 1. A method for processing media data comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; and performing a conversion between the visual media data and a bitstream based on the list of candidate input pictures.

[0163] 2. The method of solution 1, wherein the list of candidate input pictures includes cropped decoded pictures in output order.

[0164] 3. The method of any of solutions 1 -2, wherein for an i-th processing stage, where i is greater than 0, the list of candidate input pictures contains pictures output by a previous processing stage.

[0165] 4. The method method of any of solutions 1-3, wherein the list of candidate input pictures is denoted asCandInputPicList[ i ] and contains input pictures for all values of i in a range of zero to a processing order number of processing stages (PoNumProcStgs) minus one.

[0166] 5. The method of any of solutions 1 -4, wherein CandInputPicList[PoNumProcStgs] stores a final output of the processing chain.

[0167] 6. The method of any’ of solutions 1-5, wherein a processing order cropped decoded output picture list(PoCdoPicList) contains a list of cropped decoded pictures in output order resulting from decoding the bitstream.

[0168] 7. The method of any of solutions 1-6, wherein CandInputPicList[i] contains pictures from PoCdoPicList for values of i up to PoNumProcStgs.

[0169] 8. The method of any of solutions 1-7, wherein the processing chain is applied to CandInputPicList[i] according to depth-first handling.

[0170] 9. The method of any of solutions 1-8, wherein when an supplemental enhancement information (SEI) payload type (payloadType) value of an i-th SEI message type is present in a SEI processing order (SPO) process SEI list (SpoProcessSeiList), a process implied by’ the SEI message is performed.

[0171] 10. The method of any of solutions 1-9, wherein each list CandInputPicList[PoProcStgIdx[ i ] + j ], wherePoProcStgldx is a processing order stage index, with j in the range of 1 to PoNumProcStgs - PoProcStgldxf i ], inclusive, is updated by replacing pictures with corresponding processed pictures, if any, resulting from the process and inserting other pictures, if any, resulting from the process into CandInputPicList[ PoProcStgldxf i ] + j ] so that an output order is obeyed.

[0172] 11. The method of any of solutions 1-10, wherein a process implied by an SEI message is invoked repeatedly, in output order, for each of the pictures in CandInputPicList[ PoProcStgIdx[ PoSeiTypeList[ seildx ] ] ], where PoSeiTypcList is a processing order SEI type list and seildx is a SEI index, that is a corresponding picture of a particular picture (picA) or an associated inserted picture of picA.

[0173] 12. The method of any of solutions 1-11, wherein interface variables for purposes of interpretation of anSEI message are derived from pictures in CandInputPicList[ PoProcStgldxf PoSeiTypeList[ seildx ] ] ].

[0174] 13. The method of any of solutions 1-12, wherein the conversion includes encoding the visual media data into the bitstream.

[0175] 14. The method of any of solutions 1 -12, wherein the conversion includes decoding the visual media data from the bitstream.

[0176] 15. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform the method of any of solutions 1-14.

[0177] 16. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non- transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of solutions 1-14.

[0178] 17. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by7a method performed by7a video processing apparatus, wherein the method comprises: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; and generating a bitstream based on the determining.

[0179] 18. A method for storing bitstream of a video comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.

[0180] In the solutions described herein, an encoder may conform to the format rule by producing a coded representation according to the format rule. In the solutions described herein, a decoder may use the format rule to parse syntax elements in the coded representation with the knowledge of presence and absence of syntax elements according to the format rule to produce decoded video.

[0181] In the present document, the term ‘‘video processing’" may refer to video encoding, video decoding, video compression or video decompression. For example, video compression algorithms may be applied during conversion from pixel representation of a video to a corresponding bitstream representation or vice versa. The bitstream representation of a current video block may, for example, correspond to bits that are either co-located or spread in different places within the bitstream, as is defined by the syntax. For example, a macroblock may be encoded in terms of transformed and coded error residual values and also using bits in headers and other fields in the bitstream. Furthermore, during conversion, a decoder may parse a bitstream with the knowledge that some fields may be present,or absent, based on the determination, as is described in the above solutions. Similarly, an encoder may determine that certain syntax fields are or are not to be included and generate the coded representation accordingly by including or excluding the syntax fields from the coded representation.

[0182] The disclosed and other solutions, examples, embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine- readable propagated signal, or a combination of one or more them. The term ‘‘data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificial!}' generated signal, e g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

[0183] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g.. one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g.. files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0184] The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0185] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e g., magnetic, magneto optical disks, or opticaldisks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and compact disc read-only memory' (CD ROM) and Digital versatile disc-read only memory (DVD-ROM) disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry'.

[0186] While this patent document contains many specifics, these should not be construed as limitations on the scope of any subject matter or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular techniques. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0187] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

[0188] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.

[0189] A first component is directly coupled to a second component when there are no intervening components, except for a line, a trace, or another medium between the first component and the second component. The first component is indirectly coupled to the second component when there are intervening components other than a line, a trace, or another medium between the first component and die second component. The term “coupled” and its variants include both directly coupled and indirectly coupled. The use of the term “about” means a range including ±10% of the subsequent number unless otherw ise stated.

[0190] While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

[0191] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled may’be directly connected or may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

Claims

CLAIMSWhat is claimed is:

1. A method for processing media data comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures: and performing a conversion between the visual media data and a bitstream based on the list of candidate input pictures.

2. The method of claim 1, wherein the list of candidate input pictures includes cropped decoded pictures in output order.

3. The method of any of claims 1-2. wherein for an i-th processing stage, where i is greater than 0, the list of candidate input pictures contains pictures output by a previous processing stage.

4. The method method of any of claims 1-3, wherein the list of candidate input pictures is denoted as CandInputPicList[ i ] and contains input pictures for all values of i in a range of zero to a processing order number of processing stages (PoNumProcStgs) minus one.

5. The method of any of claims 1-4, wherein CandInputPicList[PoNumProcStgs] stores a final output of the processing chain.

6. The method of any of claims 1-5, wherein a processing order cropped decoded output picture list (PoCdoPicList) contains a list of cropped decoded pictures in output order resulting from decoding the bitstream.

7. The method of any of claims 1-6, wherein CandInputPicList[i] contains pictures from PoCdoPicList for values of i up to PoNumProcStgs.

8. The method of any of claims 1-7. wherein the processing chain is applied to CandInputPicList[i] according to depth-first handling.

9. The method of any of claims 1-8, wherein when an supplemental enhancement information (SEI) payload type (payloadType) value of an i-th SEI message ty pe is present in a SEI processing order (SPO) process SEI list (SpoProcessSeiList), a process implied by' the SEI message is performed.

10. The method of any of claims 1-9, wherein each list CandInputPicList[PoProcStgIdx[ i ] + j ], where PoProcStgldx is a processing order stage index, with j in the range of 1 to PoNumProcStgs - PoProcStgIdx[ i ], inclusive, is updated by replacing pictures with corresponding processed pictures, if any, resulting from the processand inserting other pictures, if any, resulting from the process into CandlnputPicList[ PoProcStgIdx[ i J + j J so that an output order is obeyed.11 . The method of any of claims 1 -10, wherein a process implied by an SEI message is invoked repeatedly, in output order, for each of the pictures in CandInputPicList[ PoProcStgIdx[ PoSeiTypeList[ seildx ] ] ], where PoSeiTypeList is a processing order SEI t pe list and seildx is a SEI index, that is a corresponding picture of a particular picture (picA) or an associated inserted picture of picA.

12. The method of any of claims 1-11, wherein interface variables for purposes of interpretation of an SEI message are derived from pictures in CandInputPicList[ PoProcStgIdx[ PoSeiTypeList[ seildx ] ] ].

13. The method of any of claims 1-12, wherein the conversion includes encoding the visual media data into the bitstream.

14. The method of any of claims 1-12, wherein the conversion includes decoding the visual media data from the bitstream.

15. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by’ the processor, cause the processor to perform the method of any of claims 1-14.

16. A non-transitory computer readable medium comprising a computer program product for use by’ a video coding device, the computer program product comprising computer executable instructions stored on the non- transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of claims 1-14.

17. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; and generating a bitstream based on the determining.

18. A method for storing bitstream of a video comprising: determining to apply a processing chain to visual media data, wherein the processing chain comprises a plurality of processing stages, and wherein each processing stage is applied to a list of candidate input pictures; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.

Images