Coding of video with inter-layer prediction based on multi-plane or multi-sphere images

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining to apply a multi-layer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video. A conversion is performed between the MPI based video or the MSI based video and a multi-layer bitstream including the MPI based video or the MSI based video based on the determination.

Description

Coding Of Video With Inter-Layer Prediction Based On Multi-Plane or Multi-Sphere ImagesCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the benefit of U.S. Patent Application No. 63 / 573,228 filed on April 2, 2024, which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure 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 multilayer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video; and performing a conversion between the MPI based video or the MSI based video and a multi-lay er bitstream including the MPI based video or the MSI based video based on the determination.

[0005] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the multi-layer 2D video codec comprises a multiview video coding (MVC) extension, an extension of multi view video coding with depth information (MVCD). an extension of multiview and depth video with enhanced non-base view coding (3D-AVC). a mulitview video high efficiency video coding (MV-HEVC) extension, a three-dimensional high efficiency video coding (3D-HEVC) extension, or a multi-layer capability in versatile video coding (WC).

[0006] Optionally , in any of the preceding aspects, another implementation of the aspect provides that for each set of multi-plane or multi-sphere images pertaining to a particular time instance for the MSI based video, each sphere image is projected into a projected 2D image using a projection method.

[0007] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the projection method comprises equirectangular projection (ERP) or the cubemap projection (CMP).

[0008] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the projected 2D image is referred to as an MSI layer.

[0009] Optionally , in any of the preceding aspects, another implementation of the aspect provides that for each set of multi-plane or multi-sphere images pertaining to a particular time instance for the MPI based video, a plane image is referred to as an MPI lay er.

[0010] Optionally, in any of the preceding aspects, another implementation of the aspect provides that for each set of multi-plane or multi-sphere images pertaining to a particular time instance for the MPI based video, each MPI layer or each MSI layer is encoded as a layer in a multi-layer bitstream of the multi-layer 2D video codec.

[0011] Optionally, in any of the preceding aspects, another implementation of the aspect provides that each MPI layer or each MSI layer is encoded using inter-layer prediction allowed by the the multi-layer 2D video codec.

[0012] Optionally, in any of the preceding aspects, another implementation of the aspect provides that frame packing is not applied.

[0013] Optionally, in any of the preceding aspects, another implementation of the aspect provides that depths of the MPI layers or MSI layers are encoded in an increasing order corresponding to an increasing order of layer identifiers of layers in the multi-layer bitstream of the multi-layer 2D video codec.

[0014] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a view id syntax element in a netw ork abstraction layer (NAL) unit header MVC extension for the MVC extension or the MVCD extension.

[0015] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a variable that represents a view order index of a view identified by a view identifier for the MVC extension or the MVCD extension.

[0016] Optionally’, in any of the preceding aspects, another implementation of the aspect provides that the variable is designated VOIdx, and wherein the view identifier is designated view id.

[0017] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the VOIdx is set equal to a value of i for which a syntax element view_id[i] included in a referred subset sequence parameter set (SPS) is equal to the view identifier.

[0018] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a syntax element in a network abstraction layer (NAL) unit header of the 3D-AVC extension for the MVC extension or the MVCD extension, and wherein the syntax element is designated view idx.

[0019] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a syntax element in a network abstraction layer (NAL) unit header for any extension of HEVC for the MVC extension or the MVCD extension, and wherein the syntax element is designated nuh layer id.

[0020] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a variable that represents a view order index for the MV-HEVC extension or the 3D-HEVC extension, wherein the variable is designated ViewOrderldxflld], and wherein lid is equal to a nuh layer id in a network abstraction layer (NAL) unit header.

[0021] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a syntax element in a network abstraction layer (NAL) unit header for the WC, and wherein the syntax element is designated nuh layer id.

[0022] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a layer identifier comprises a variable that represents a view identifier as specified in semantics of a scalability dimension information (SDI) supplemental enhancement information (SEI) message, wherein the variable is designated Viewld[i], and wherein i is an index of a view in a list of views in a current coded video sequence.

[0023] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the MPI based video or the MSI based video is decoded using the multi-layer 2D video codec, wherein the the multilayer 2D video codec comprises a multi view video coding (MVC) extension, an extension of multiview video coding with depth information (MVCD). an extension of multiview and depth video with enhanced non-base view coding (3D-AVC), a mulitview video high efficiency video coding (MV-HEVC) extension, a three-dimensional high efficiency video coding (3D-HEVC) extension, or a multi-layer capability in versatile video coding (WC).

[0024] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a coded picture in a layer is decoded using a standard decoding process, and wherein the standard decoding process comprises inter-layer prediction allowed by the the multi-layer 2D video codec.

[0025] Optionally, in any of the preceding aspects, another implementation of the aspect provides that each projected 2D image is converted into a spherical image by applying an inverse projection for the MSI based video.

[0026] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a multilayer MPI information (ML-MPI1) supplement enhancement information (SEI) message is included in the multilayer bitstream.

[0027] Optionally, in any of the preceding aspects, another implementation of the aspect provides that for each layer in the multi-layer bitstream of the the multi-layer 2D video codec, the ML-MPII SEI message comprises a value of a depth of the MPI layer coded in the MSI layer in the multi-layer bitstream.

[0028] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a number of the MPI layers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

[0029] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a multilayer MSI information (ML-MSII) supplement enhancement information (SEI) message is included in the multilayer bitstream.

[0030] Optionally, in any of the preceding aspects, another implementation of the aspect provides that for each layer in the multi-layer bitstream of the the multi-layer 2D video codec, the ML-MSII SEI message comprises a value of a depth of the MSI layer coded in the MSI layer in the multi-layer bitstream.

[0031] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the value represents a distance between a sphere of a spherical image in the MSI layer and an origin of the sphere.

[0032] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a number of the MSI layers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

[0033] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a projection type is used by an encoder to convert a spherical image to a 2D image, and wherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

[0034] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message comprises a covered area of a sphere surface.

[0035] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the covered area of the sphere surface comprises an upper half of the sphere.

[0036] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a rotation of the sphere is signaled in a sphere rotation SEI message, and wherein the rotation of the sphere comprises a yaw rotation, a pitch rotation, and a roll rotation.

[0037] Optionally, in any’ of the preceding aspects, another implementation of the aspect provides that a multilayer MPI information (ML-MPII) supplement enhancement information (SEI) message is extended to an extended ML-MPII SEI message configured to indicate whether inter-layer prediction is allowed or not allowed.

[0038] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a single syntax element is included in the extended ML-MPII SEI message to indicate whether the inter-layer prediction is allowed.

[0039] Optionally’, in any of the preceding aspects, another implementation of the aspect provides that when the extended ML-MPII SEI message indicates that the inter-layer prediction is allowed, for each layer in the multilayer bitstream of the the multi-layer 2D video codec, the extended ML-MPII SEI message comprises a value of a depth of the MPI lay er coded in the MSI lay er in the multi-layer bitstream.

[0040] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a number of the MPI layers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

[0041] Optionally, in any of the preceding aspects, another implementation of the aspect provides that when the extended ML-MPII SEI message indicates that the inter-layer prediction is not allowed, the extended ML-MPII SEI message comprises all information in the ML-MPII SEI message.

[0042] Optionally, in any’ of the preceding aspects, another implementation of the aspect provides that a multilayer MSI information (ML-MSII) supplement enhancement information (SEI) message is configured to specify whether inter-layer prediction is allowed or not allowed.

[0043] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a single syntax element is included in the ML-MSII SEI message to indicate whether the inter-layer prediction is allowed.

[0044] Optionally, in any of the preceding aspects, another implementation of the aspect provides that when the extended ML-MPII SEI message indicates that the inter-layer prediction is allowed, for each layer in the multilayer bitstream of the the multi-lay er 2D video codec, the ML-MSII SEI message comprises a value of a depth of the MSI lay er coded in the MSI lay er in the multi-layer bitstream.

[0045] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the value represents a distance betw een a sphere of a spherical image in the MSI layer and an origin of the sphere.

[0046] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a number of the MSI lay ers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

[0047] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a projection type is used by an encoder to convert a spherical image to a 2D image, and wherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

[0048] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes a covered area of a sphere surface.

[0049] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the covered area of the sphere surface comprises an upper half of the sphere.

[0050] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a rotation of the sphere is signaled in a sphere rotation SEI message, and wherein the rotation of the sphere comprises a y aw rotation, a pitch rotation, and a roll rotation.

[0051] Optionally, in any of the preceding aspects, another implementation of the aspect provides that when the ML-MSII SEI message indicates that the inter-layer prediction is not alloyved, the extended ML-MSII SEI message comprises a number of sphere images pertaining to each time instance.

[0052] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes a value of a depth of each sphere image.

[0053] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the value represents a distance between a sphere of a spherical image in the MSI layer and an origin of the sphere.

[0054] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes a projection type used by an encoder to convert a spherical image to a 2D image, and yvherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

[0055] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes a covered area of a sphere surface.

[0056] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the covered area of the sphere surface comprises an upper half of the sphere.

[0057] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes a rotation of the sphere, and w herein the rotation of the sphere comprises a yayv rotation, a pitch rotation, and a roll rotation.

[0058] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message includes an indication of how projected 2D images of the sphere images pertaining to each time instance are frame packed.

[0059] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message indicates whether the MSI layers are temporarily interleaved.

[0060] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message indicates whether the MSI layers are frame packed in a side-by-side maimer or in a top-to- bottom maimer when the MSI layers are not temporarily interleaved.

[0061] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the ML-MSII SEI message indicates a number of the MSI layers that are spatially packet in height.

[0062] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the conversion includes encoding the visual media data into the bitstream.

[0063] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the conversion includes decoding the visual media data from the bitstream.

[0064] 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 the method of any of the disclosed aspects.

[0065] A third aspect relates to 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 the disclosed aspects.

[0066] 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 multi-layer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video; and generating a multi-layer bitstream including the MPI based video or the MSI based video based on the determination.

[0067] A fifth aspect relates to a method for storing bitstream of a video comprising: determining to apply a multi-layer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video; and generating a multi-layer bitstream including the MPI based video or the MSI based video based on the determination; and storing the multi-layer bitstream in a non-transitory computer-readable recording medium, asdf

[0068] A sixth aspect relates to a method, apparatus, or system described in the present disclosure.

[0069] 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.

[0070] 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

[0071] 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.

[0072] FIG. 1 is a block diagram showing an example video processing system.

[0073] FIG. 2 is a block diagram of an example video processing apparatus.

[0074] FIG. 3 is a flowchart for an example method of video processing.

[0075] FIG. 4 is a block diagram that illustrates an example video coding system.

[0076] FIG. 5 is a block diagram that illustrates an example encoder.

[0077] FIG. 6 is a block diagram that illustrates an example decoder.

[0078] FIG. 7 is a schematic diagram of an example encoder.DETAILED DESCRIPTION

[0079] 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.

[0080] Section headings are used in the present disclosure 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 disclosure, 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 supplemental enhancement information (SEI) messages for coded video bitstreams (VSEI) standard.1. Initial discussion

[0081] This disclosure is related to image / video coding technologies. Specifically, this disclosure is related to video with inter-layer prediction based on multi-plane images (MPI) or multi-sphere images (MSI). The ideas may be applied individually or in various combinations, for video bitstreams coded by any codec, e.g., the WC standard, the high efficiency' video coding (HEVC) standard, the advanced video coding (AVC) standard, and / or the versatile SEI messages for coded video bitstreams (VSEI) standard.2. Further discussion2.1 Video coding standards

[0082] 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)-l and MPEG-4 Visual, and the two organizations jointly produced the H.262 / MPEG-2 Video, 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 J 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, HEVC, and AVC

[0083] SEI messages assist in processes related to decoding, display or other purposes. However, SEI messages are not required for constructing the luma or chroma samples by the decoding process. Conforming decoders are 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.

[0084] The syntax and semantics for SEI message payloads are specified in Annex D (of WC, HEVC, and AVC) and in ITU-T H.274 | ISO / IEC 23002-7.

[0085] In WC, HEVC, and AVC, an SEI message includes some syntax elements before the SEI payload and the SEI payload. For simplicity, the syntax elements before the SEI payload in an SEI message are referred to as SEI message header (SMH). One or more SEI messages are contained in an SEI network abstraction layer (NAL) unit. Each NAL unit includes a NAL unit header followed by the raw byte sequence payload (RBSP) syntax for the particular type of NAL unit.

[0086] In WC and HEVC, two NAL unit types are specified for SEI NAL units, one for prefix SEI NAL units, and one for suffix SEI NAL units. The NAL unit types in WC for prefix and suffix SEI NAL units are the values 23 and 24 (of nal unit type), respectively, and named PREFIX SEI NUT and SUFFIX SEI NUT, respectively. The NAL unit types in HEVC for prefix and suffix SEI NAL units are the values 39 and 40 (of nal unit type), respectively, and also named PREFIX SEI NUT and SUFFIX SEI NUT, respectively.

[0087] In AVC, there is only one NAL unit type specified for SEI NAL units. The NAL unit in WC for SEI NAL units is the value 6 (of nal unit type), not named.

[0088] The SEI RBSP syntax and semantics are as follows (same for WC, HEVC, and AVC):

[0089] Supplemental enhancement information (SEI) contains information that is not necessary to decode the samples of coded pictures from video coding layer (VCL) NAL units. An SEI RBSP contains one or more SEI messages.

[0090] The general SEI message syntax and semantics in WC are as follows (technically the same but editorially slightly differently in HEVC and AVC):

[0091] Each SEI message consists of the variables specifying the type payloadType and size payloadSize of the SEI message payload. SEI message payloads are specified in Annex D. The derived SEI message payload size payloadSize is specified in bytes and shall be equal to the number of RBSP bytes in the SEI message payload.

[0092] NOTE - The NAL unit by te sequence containing the SEI message might include one or more emulation prevention by tes (represented by emulation_prevention_three_byte syntax elements). Since the paydoad size of an SEI message is specified in RBSP bytes, the quantity of emulation prevention bytes is not included in the size pay loadSize of an SEI pay load.

[0093] payload typc bytc is a byte of the pax load type of an SEI message.

[0094] payload size byte is a byte of the payload size of an SEI message.2.3 Multiplane image (MPI) and MPI information (MPII) SEI message

[0095] Multiplane image (MPI) is a way of representing a scene for visual synthesis, which consists of a set of parallel red green blue alpha (RGBA) layers, each containing color and transparency information. By blending these layers together, multiplane image can simulate complex appearance effects, eliminate depth errors, and synthesize soft edges. Multiplane image can also be rendered efficiently on graphics hardware, unlike neural radiance fields that require heavy computation.

[0096] JVET-AE0066 (publicly available herein: https: / / www.jvet- experts.org / doc_end_user / current_document.php?id=13014) and JVET-AF0167 (publicly available herein: https: / / www.jvet-experts.org / doc_end_user / current_document.php7idM3425) propose a method to signal multiplane image information (MPII) in SEI message. The MPII SEI message conveys information that can be used byra decoder to reconstruct an MPI picture from a decoded output picture containing packed MPI texture and opacity layers. The MPII SEI message supports different packing arrangements of texture and opacity layers including side-by-side, top-and-bottom, and temporal interleaving. The MPII SEI message can also convey depth information of each MPI layer.

[0097] An example syntax and sematics of the MPII SEI message as documented in J VET-AF2032 (publicly available herein: https: / / www.jvet-experts.org / doc_end_user / current_document.php7idM3592) are as follows.

[0098] The multiplane image information (MPII) SEI message specifies the multiplane image (MPI) scene representation information that may be used for view synthesis.

[0099] When an MPII SEI message is present in any access unit (AU) of a coded layer video sequence (CLVS), an MPII SEI message shall be present in the first AU of the CLVS and persists for all subsequent pictures of the current layer in output order until one or more of the following conditions are true:- A new CLVS of the current layer begins.The bitstream ends.- A picture in the current layer in an AU associated with an MPII SEI message is output that follows the current picture in output order.

[0100] NOTE 1 - This SEI message can work together with the multiview acquisition information SEI message for view synthesis. The multiview acquisition information SEI message specifies the intrinsic and extrinsic parameters for current camera view. When multiple views are available, the reconstructed novel views can be rendered from multiplane images of nearby views.

[0101] Use of this SEI message requires the definition of the following variables:- Cropped decoded output picture width and height in units of luma samples, denoted herein by CroppedWidth and CroppedHeight, respectively.A chroma format indicator, denoted herein by ChromaFormatldc, as described in subclause 7.3.A cropped decoded picture array decPicCurrO[ c!dx ][ x ][ y ], with cldx = 0.. (ChromaFormatldc = = 0 ) ? 0 : 2, x = 0..( cldx = = 0 ) ? CroppedWidth : CroppedWidth / SubWidthC - 1, y = O..( cldx = = 0 ) ? CroppedHeight : CroppedHeight / SubHeightC - 1.In output order a temporally following cropped decoded picture array decPicCurrl [ cldx ][ x ][ y ], with cldx = 0.. (ChromaFormatldc = = 0 ) ? 0 : 2, x = 0..( cldx = = 0 ) ? CroppedWidth : CroppedWidth / SubWidthC - 1, y = 0..( cldx = = 0 ) ? CroppedHeight : CroppedHeight / SubHeightC - 1.

[0102] The variables SubWidthC and SubHeightC are derived from ChromaFormatldc as specified by Table 2.

[0103] mpii num layers minusl plus 1 specifies the number of texture and opacity layers for the MPI representation.

[0104] mpii lay er depth equal distance flag equal to 1 indicates that equal distance is used to generate MPI layers and depth parameter for each layer Z[ i ] can be derive using nearest depth value ZNear and farthest depth value ZFar.

[0105] The depth value for i-th MPI layer, Z[ i ], is derived as follows:Z[ i ] = i * ( ZFar - Znear ) (mpi num layers minusl ) + ZNear (xx)

[0106] mpii layer depth equal distance flag equal to 0 indicates that the depth information for each layer follows next in the SEI message.

[0107] The variables in the x column of Table xx are derived from the respective variables in the s, e, n and v columns of Table xx as follows:- If the value of e is in the range of 0 to 127, exclusive, x is set equal to t -I )’ * 2, e 1 1* ( I + n — 2V).- Otherwise (e is equal to 0), x is set equal to ( -l)s* 2 '30 + v’ * n.

[0108] NOTE 2 - The above specification is similar to that found in IEC 60559: 1989.Table xx - Association between depth parameter variables and syntax elements

[0109] NOTE 3 - In some applications, disparity is used instead of depth (the disparity value D and depth value Z relationship is D = 1 : Z). Corresponding to Equation (xx), the disparity value for the i-th MPI layer is D[ i ] = i * ( DFar - Dnear ) (mpi num layers minusl ) + DNear.

[0110] mpii texture opacity interleave flag equal to 1 indicates decoded output pictures correspond to temporally interleaved texture and opacity constituent pictures in output order as illustrated in Figure XX. mpii texture opacity interleave flag equal to 0 indicates decoded output pictures correspond to spatially packed texture and opacity constituent pictures as illustrated in Figures XX and XX.[OHl] mpii texture opacity arrangement flag equal to 0 indicates decoded output pictures represent texture and opacity’ constituent pictures in a top-bottom packing arrangement as illustrated in Figure XX. mpii texture opacity arrangement flag equal to 1 indicates decoded output pictures represent texture and opacity’ constituent pictures in a side-by-side packing arrangement as illustrated in Figure XX.

[0112] For each specified picture packing arrangement scheme, there are two constituent pictures that are referred to as picture 0 and picture 1. When mpii texture opacity interleave flag is equal to 0. the constituent picture associated with the upper-left sample of the decoded picture is considered to be constituent picture 0 and the other constituent picture is considered to be constituent picture 1. When mpii texture opacity interleave flag is equal to 1, the first decoded picture in the current CLVS is constituent picture 0 and the next decoded picture in output order is constituent picture 1 and the display time of the constituent picture 0 should be delayed to coincide with the display time of constituent picture 1. The two constituent pictures form the spatially' packed texture and opacity’ picture of a MPI, with picture 0 being associated with the spatially packed texture picture and picture 1 being associated with the spatially’ packed opacity’ picture.

[0113] mpii_picture_nmn_layers_in_height_minusl plus 1 specifies the number of spatially packed layers in height for picture 0 and picture 1. The variable hLayers is set equal to mpii_picture_num_layers_in_height_minusl + 1 and the variable wLayers is set equal to(mpii num layers minusl + 1) / hLayers.

[0114] Let variable fWidth and fHeight specify the width and height of picture 0 and picture 1 , respectively, and are derived as follows:- If mpii texture opacity interleave flag is equal to 1, the following applies: fWidth = CroppedWidth fHeight = CroppedHeight- Otherwise (mpii texture opacity interleave flag is equal to 0)- If mpii texture opacify arrangement flag is equal to 0, the following applies:IWidth = CroppedWidth , fHeight = CroppedHeight / 2Otherwise (mpii texture opacity arrangement flag is equal to 1). the following applies: fWidth = CroppedWidth / 2 , fHeight = CroppedHeightLet variable eWidth = fWidth / subWidthC and variable cHeight = fHeight / subHeightC.Let array pictured [ cldx J[ x J[ y J specify samples in picture 0 and array picture 1 [ cldx J[ x J[ y J specify samples in picture 1, with cldx = 0..(ChromaFormatIdc = = 0 ) ? 0 : 2, x = O..( cldx = = 0 ) ? fWidth: eWidth - 1, y = O..( cldx = = 0 ) ? fHeight : cHeight - 1 and are derived as follows:- If mpii texture opacity interleave flag is equal to 1, the following applies: pictured [ cldx ][ x ][ y ] = decPicCurrd[ cldx ][ x ][ y ] picturel[ cldx ][ x ][ y ] = decPicCurrl [ cldx ][ x ][y ]- Otherwise (mpii texture opacity interleave flag is equal to d)- Let variable cW = ( cldx = = d )? fWidth : eWidth- Let variable cH = ( cldx = = )? fHeight : cHeight- If mpii texture opacity arrangement flag is equal to d, the following applies: picture | cldx ] [ x ] [ y ] = decPicCurrd[ cldx ] [ x ] [ y ] picturel[ cldx ][ x ][ y ] = decPicCurrd[ cldx ][ x ][ y + cH ]Otherwise (mpii texture opacity arrangement flag is equal to 1). the following applies: pictured[ cldx ] [ x ] [ y ] = decPicCurrd[ cldx ] [ x ] [ y ] picturel[ cldx J[ x J[ y J = decPicCurrd[ cldx J[ x + cW J[ y JLet variable layerWidth and layerHeight specify the width and height for decoded MPI layer, respectively. The variables are derived as follows: layerWidth = fWidth / wLayers layerHeight = fHeight / hLayersThe reconstruction of MPI process is described as follows:The outputs of this process are:- a 4D MPI texture layer array recTextureLayer[ i ][ cldx ][ w ][ h ] with i = d..mpii_num_layers_minusl, cldx = d..(ChromaFonnatIdc = = 0 ) ? d : 2, w = d..( cldx = = ) ? layerWidth : layerWidth / SubWidthC - 1, and h = d..( cldx = = d ) ? layerHeight : layerHeight / SubHeightC - 1.- a 3D MPI opacity layer array recOpacityLayer[ i ][ w ][ h ] with i = d..mpii_num_layers_minusl,x = 0.. layerWidth - 1, and y = 0.. layerHeight - 1.The array recTextureLayer and array recOpacityLayer are derived as follows: for( i = 0; i <= mpii num layers minusl ; i++ ) { k = i % wLayers m = ( i - k ) / hLayers for( cldx = 0; cldx < ChromaFormatldc = = 0 ) ? 1 : 3; cldx++ ) for( h = 0; h < ( cldx = = 0 ) ? layerHeight : layerHeight / SubHeightC ; h++ ) for( w = 0; w < ( cldx = = 0 ) ? layerWidth : layerWidth / SubWidthC ; w++ ) { u = k * ( cldx = = 0 ) ? layerWidth : layerWidth / SubWidthC + w v = m * ( cldx = = 0 ) ? layerHeight : layerHeight / SubHeightC + h recTextureLa er[ i ][ cldx ][ w ][ h ] = pictured [ cldx ][ u ][ v ] } for( h = 0; h < layerHeight; h++ ) for( w = 0; w < layerWidth; w++ ) recOpacityLayer[ i ][ w ][ h ] = picture 1

[0000] [ k * layerWidth + w ][ m * layerHeight + h ] }2.4 Multi-sphere image (MSI) based video

[0115] Multi-sphere image (MSI) is basically multiple image spheres inside each other as opposed to the case of MPI that is multiple image planes on top of each other, both used for image composition. One work on MSI improvement can be foimd in the paper by T. Habtegebrial, C. Gava, M. Rogge, D. Stricker, and Varun Jampani, "SOMSI: Spherical novel view synthesis with soft occlusion multi-sphere images," Proceedings of the IEEE / CVF Conference on Computer Vision and Pattern Recognition (CVPR), 2022. pp. 15725-15734.

[0116] One way of coding an MSI based video is to encode it using a 2D video codec such as AVC, HEVC, or VVC as follows. For each set of multi-sphere images pertaining to a particular time instance, first each sphere image is projected using a projection method, e.g., the equirectangular projection (ERP) or the cubemap projection (CMP), into a projected 2D image (also referred to as an MSI layer), then the projected 2D images of the sphere images are frame-packed, similarly as the multiple image planes in the case of MPI are frame-packed as indicated by the MPII SEI message, using one of the three frame-packing modes: side-by-side, top-bottom, or temporal- interleaved. At the decoder side, first a coded picture is decoded using the standard decoding process, then the decoded picture is de-packed, similarly as in the MPI case as specified by the semantics of the MPII SEI message, into multiple projected 2D images, and finally each projected 2D image is converted into a sphere image by apply ing the inverse projection. For signalling, an MSI information (MSII) SEI message can be specified to consist of the following pieces information: a) the number of sphere images pertaining to each time instance; b) the depth of each sphere image, i.e., the distance between the sphere and the origin of the sphere, c) the projection type, e g., ERP or CMP, used to convert a sphere image to a 2D image at the encoder side, and d) how the projected 2Dimages of the sphere images pertaining to each time instance are frame-packed, similarly as in the MPII SEI message, including whether the MSI layers are temporally interleaved, and if not, whether they are frame-packed in the side-by-side or top-bottom manner, and the number of spatially packed MSI layers in height.3. Technical problems solved by disclosed technical solutions

[0117] An example design for coding and signalling of MPI or MSI based video does not allow for efficient inter-layer prediction, including prediction between different MPI or MSI layers.4. A listing of solutions and embodiments

[0118] 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, an MPI or MSI based video is encoded using a multi-layer 2D video codec such as the multiview video coding (MVC) extension, the extension of multiview video coding with depth information (MVCD), or the extension of multiview and depth video with enhanced non-base view coding (3D-AVC) of the AVC standard, the MV-HEVC or 3D-HEVC extension of the HEVC standard, or the multi-layer capability of the WC standard, as follows: a. For each set of multi-plane or multi-sphere images pertaining to a particular time instance, the following steps are applied: i. In case of MSI, each sphere image is first projected using a projection method, e.g., the equirectangular projection (ERP) or the cubemap projection (CMP), into a projected 2D image (also referred to as an MSI layer). ii. A plane image in the case of MPI is referred to as an MPI layer. iii. Each MPI or MSI layer is encoded as a layer in a multi-layer bitstream of the multi-layer 2D video codec, possibly using inter-layer prediction allowed by the the multi-layer 2D video codec. Frame packing is not applied.1. Preferably, the MPI or MSI layers are encoded such a way that the depths of the MPI or MSI layers are in increasing order of the increasing order of the layer identifiers of the layers in the multi-layer bitstream of the multi-layer 2D video codec. a. In one example, in the context of the MVC or MVCD extension of AVC, the layer identifier is the view id syntax clement in the NAL unit header MVC extension. i. In one example, alternatively, in the context of the MVC or MVCD extension of AVC, the layer identifier is the variable VOIdx. which represents the view order index of the viewidentified by view id and is set equal to the value of i for which the syntax element view idf i ] included in the referred subset sequence parameter set is equal to view id. b. In one example, in the context of the 3D-AVC extension of AVC, the layer identifier is the view idx syntax element in the NAL unit header 3D- AVC extension. c. In one example, in the context of any extension of HEVC, the layer identifier is the nuh laycr id syntax element in the NAL unit header. i. In one example, alternatively, in the context of the MV-HEVC or 3D-HEVC extension of HEVC. the layer identifier is the variable ViewOrderIdx[ lid ], where lid is equal to the nuh layer id in the NAL unit header. d. In one example, in the context of WC, the layer identifier is the nuh layer id syntax element in the NAL unit header. i. In one example, alternatively, in the context of W C. the layer identifier is the variable Viewidf i ] as specified in the semantics of the scalability dimension information (SDI) SEI message specified in the VSEI / H.274 standard, where i is the index of a view in the list of the views in the current coded video sequence. ) In one example, an MPI or MSI based video encoded as above is decoded using a multi-layer 2D video codec such as the MVC, MVCD, or 3D- AVC extension of the AVC standard, the MV-HEVC or 3D-HEVC extension of the HEVC standard, or the multi-layer capability of the WC standard, by applying the following steps: a. A coded picture in a layer is decoded using the standard decoding process, possibly using interlayer prediction allowed by the the multi-layer 2D video codec. b. In the case of MSI, each projected 2D image is converted into a sphere image by applying the inverse projection. ) In one example, a multi-layer MPI information (ML-MPII) SEI message to be included in a bitstream of a multi-layer 2D video codec is specified, consisting of the following pieces of information: a. For each layer in the bitstream of the multi-layer 2D video codec, the value of the depth of the MPI layer coded in that layer in the bitstream of the multi-layer 2D video codec. Note that the number of MPI layers is derived to be equal to the number of layers in the bitstream of the multilayer 2D video codec. ) In one example, a multi-layer MSI information (ML-MSII) SEI message to be included in a bitstream of a multi-layer 2D video codec is specified, consisting of the following pieces of information:a. For each layer in the bitstream of the multi-layer 2D video codec, the value of the depth of the MSI layer coded in that layer in the bitstream of the multi-layer 2D video codec, i.e., the distance between the sphere of a sphere image in the MSI layer and the origin of the sphere. Note that the number of MSI layers is derived to be equal to the number of layers in the bitstream of the multilayer 2D video codec. b. The projection type, e.g., ERP or CMP, used to convert a sphere image to a 2D image at the encoder side. c. The covered area of the sphere surface, e.g., the upper half of the sphere surface. d. The rotation of the sphere, including the yaw rotation, the pitch rotation, and the roll rotation, similarly as signalled by the sphere rotation SEI message in the VSEI / H.274 standard. ) In one example, the MPII SEI message may be extended to allow both cases of with or without inter-layer prediction allowed, as follows: a. In one example, one syntax element may be signalled to indicate whether inter-layer prediction is allowed. b. In one example, when it is indicated that inter-layer prediction is allowed, the extended MPII SEI message additionally contains, for each layer in the bitstream of the multi-layer 2D video codec, the value of the depth of the MPI layer coded in that layer in the bitstream of the multi-layer 2D video codec. Note that the number of MPI layers is derived to be equal to the number of layers in the bitstream of the multi-layer 2D video codec. c. In one example, when it is indicated that inter-layer prediction is disallowed, the extended MPII SEI message additionally contains all information as in the current MPII SEI message. ) In one example, an MSII SEI message may be specified to allow both cases of with or without inter-layer prediction allowed, as follows: a. In one example, one syntax element may be signalled to indicate whether inter-layer prediction is allowed. b. In one example, when it is indicated that inter-layer prediction is allowed, the MSII SEI message additionally contains, the following pieces of information: i. For each layer in the bitstream of the multi-layer 2D video codec, the value of the depth of the MSI layer coded in that layer in the bitstream of the multi-layer 2D video codec, i.e., the distance betw een the sphere of a sphere image in the MSI layer and the origin of the sphere. Note that the number of MSI layers is derived to be equal to the number of layers in the bitstream of the multi-layer 2D video codec. ii. The projection type, e.g., ERP or CMP, used to convert a sphere image to a 2D image at the encoder side. iii. The covered area of the sphere surface, e.g., the upper half of the sphere surface.iv. The rotation of the sphere, including the yaw rotation, the pitch rotation, and the roll rotation, similarly as signalled by the sphere rotation SEI message in the VSEI / H.274 standard. c. In one example, when it is indicated that inter-layer prediction is disallowed, the MSII SEI message additionally contains the following pieces of information: i. The number of sphere images pertaining to each time instance ii. The depth of each sphere image, i.e., the distance between the sphere and the origin of the sphere. iii. The projection type, e.g., ERP or CMP, used to convert a sphere image to a 2D image at the encoder side. iv. The covered area of the sphere surface, e.g., the upper half of the sphere surface. v. The rotation of the sphere, including the yaw rotation, the pitch rotation, and the roll rotation, similarly as signalled by the sphere rotation SEI message in the VSEI / H.274 standard. vi. How the projected 2D images of the sphere images pertaining to each time instance are frame-packed, similarly as in the MPII SEI message, including1. Whether the MSI layers are temporally interleaved.2. If the MSI layers are not temporally interleaved, whether they are frame-packed in the side-by-side or top-bottom manner.3. The number of spatially packed MSI layers in height.5. 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.

[0119] 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 wireless fidelity (Wi-Fi) or cellular interfaces.

[0120] The system 4000 may include a coding component 4004 that may implement the various coding or encoding methods described in the present disclosure. 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 thevideo. The coding techniques are therefore sometimes called video compression or video transcoding techniques. The output of the coding component 4004 may be either 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.

[0121] 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 technology attachment (SATA), peripheral component interconnect (PCI), integrated drive electronics (IDE) interface, and the like. The teclmiques described in the present disclosure 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.

[0122] 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 disclosure. 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 teclmiques described in the present disclosure. In some embodiments, the video processing circuitry 4106 may be at least partly included in the processor 4102, e.g., a graphics co-processor.

[0123] FIG. 3 is a flowchart for an example method 4200 of video processing. The method 4200 determines to apply a multi-layer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multisphere images (MSI) based video at step 4202. A conversion is performed between the MPI based video or the MSI based video and a multi-layer bitstream including the MPI based video or the MSI based video based on the determination at step 4204. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof.

[0124] 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 programproduct 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.

[0125] 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.

[0126] 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 from video 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.

[0127] 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.

[0128] 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.

[0129] 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 techniques described in this disclosure.

[0130] 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 unit4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy encoding unit 4414.

[0131] 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.

[0132] 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.

[0133] Partition unit 4401 may partition a picture into one or more video blocks. Video encoder 4400 and video decoder 4500 may support various video block sizes.

[0134] 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 (CUP) mode in which the prediction is based on an 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.

[0135] 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.

[0136] 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.

[0137] 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 betw een 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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 indicates a 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.

[0142] As discussed above, video encoder 4400 may predictively signal the motion vector. Two examples of predictive signaling teclmiques that may be implemented by video encoder 4400 include advanced motion vector prediction (AMVP) and merge mode signaling.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] Inverse quantization unit 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.

[0149] After reconstruction unit 4412 reconstructs the video block, the loop filtering operation may be performed to reduce video blocking artifacts in the video block.

[0150] 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.

[0151] FIG. 6 is a block diagram illustrating an example of video decoder 4500 which may be video decoder 4324 in the sy stem 4300 illustrated in FIG. 4. The video decoder 4500 may be configured to perform any or all of the teclmiques 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 video decoder 4500. In some examples, a processor may be configured to perform any or all of the teclmiques described in this disclosure.

[0152] 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.

[0153] 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 motioninformation. Motion compensation unit 4502 may. for example, determine such information by performing the AMVP and merge mode.

[0154] 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 syntax elements.

[0155] 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.

[0156] 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.

[0157] 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., dequantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies an inverse transform.

[0158] 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 display7device.

[0159] FIG. 7 is a schematic diagram of an example encoder 4600. The encoder 4600 is suitable for implementing the techniques 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 SAG 4604 and the ALF 4606 utilize the original samples of the current picture to reduce the mean square errors between 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.

[0160] 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 blocksfrom 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 SAG 4604, and the ALF 4606 for filtering prior to those images being stored in the reference picture buffer 4612.

[0161] A listing of solutions preferred by some examples is provided next.

[0162] The following solutions show examples of techniques discussed herein.

[0163] 1. A method for processing media data comprising: determining to perform a conversion on multiplane images (MPI) based video or multi-sphere images (MSI) based video via a multi-layer two-dimensional (2D) video codec, wherein each MPI layer or MSI layer is coded as a layer in a multi-layer bitstream of the multi-layer 2D video codec with inter-layer prediction allowed; and performing the conversion between a visual media data and the multi-layer bitstream based on the multi-layer 2D video codec.

[0164] 2. The method of solution 1, wherein frame packing is not applied.

[0165] 3. The method of any of solutions 1 -2, wherein the multi-layer 2D video codec is a multiview video coding (MVC) extension, an extension of multiview video coding with depth information (MVCD), an extension of multiview and depth video with enhanced non-base view coding, mulitview video high efficiency video coding (MV-HEVC) extension, three-dimensional high efficiency video coding (3D-HEVC) extension, or the multi-layer versatile video coding (WC).

[0166] 4. The method of any of solutions 1-3, wherein for each set of multi-plane or multi-sphere images pertaining to a particular time instance in MSI video, each sphere image is projected into a projected 2D image acting as an MSI layer by using equirectangular projection (ERP) or the cubemap projection (CMP).

[0167] 5. The method of any of solutions 1-4, wherein a plane image is referred to as an MPI layer.

[0168] 6. The method of any of solutions 1-5, wherein depths of the MPI layers or MSI layers are in increasing order of the increasing order of the layer identifiers of the layers in the multi-layer bitstream of the multilayer 2D video codec.

[0169] 7. The method of any of solutions 1-6, wherein the MVC extension or MVCD extension of AVC is used and the layer identifier is the view id syntax element in the network abstraction layer (NAL) unit header MVC extension, or wherein the MVC extension or MVCD extension of AVC is used and the layer identifier is a variable VOIdx, which represents the view order index of the view identified by view id and is set equal to the value of i for which the syntax element view idf i ] included in the referred subset sequence parameter set is equal to view id, or wherein the 3D-AVC extension of AVC is used and the layer identifier is the view idx syntax element in the NAL unit header 3D-AVC extension, or wherein HEVC is used and the layer identifier is the nuli layer id syntaxelement in the NAL unit header, or wherein the MV-HEVC extension or the 3D-HEVC extension of HEVC is used and the layer identifier is the variable ViewOrderIdx[ lid ], where lid is equal to the nuh layer id in the NAL unit header, or wherein WC is used and the layer identifier is the nuh layer id syntax element in the NAL unit header, or wherein WC is used and the layer identifier is a variable Viewld[ i ] in a scalability dimension information (SDI) supplemental enhacement information (SEI) message, where i is the index of a view in the list of the views in the current coded video sequence.

[0170] 8. The method of any of solutions 1-7, wherein a coded picture in a layer is decoded using using inter-layer prediction allowed by the the multi-layer 2D video codec, and wherein in the case of MSI, each projected 2D image is converted into a sphere image by applying the inverse projection.

[0171] 9. The method of any of solutions 1-8. wherein a multi-layer MPI information (ML-MPII) SEI message is included in the multi-layer bitstream, wherein the ML-MPII SEI message comprises a value of a depth of an MPI layer coded each layer in the multilayer bitstream, and wherein the number of MPI layers is equal to the number of layers in the multilayer bitstream.

[0172] 10. The method of any of solutions 1-9, wherein a multi-layer MSI information (ML-MSII) SEI message is included in the multi-layer bitstream, wherein the ML-MSII SEI message comprises a value of a depth of each MSI layer in the multilayer bitstream, a projection type used to convert a sphere image to a 2D image, a covered area of a sphere surface, and a rotation of the sphere.

[0173] 11. The method of any of solutions 1-10, wherein the depth of the MSI layer is the distance between a sphere of a sphere image in the MSI layer and an origin of the sphere where the number of MSI layers is equal to the number of layers in the multi-layer bitstream, or wherein the rotation of the sphere includes a yaw rotation, a pitch rotation, and a roll rotation.

[0174] 12. The method of any of solutions 1-11, wherein the MPII SEI message is extended such that one syntax element is signalled to indicate whether inter-layer prediction is allowed, or wherein when inter-layer prediction is allowed, the extended MPII SEI message additionally contains a value of a depth of each MPI layer coded in the multi-layer bitstream where the number of MPI layers is equal to the number of layers in the multilayer bitstream, or wherein when inter-layer prediction is disallowed, the extended MPII SEI message additionally contains further MPI information.

[0175] 13. The method of any of solutions 1-12, wherein a MSI information (MSII) SEI message is included in the multi-layer bitstream, or wherein a syntax element is signalled to indicate whether mtcr-laycr prediction is allowed, or wherein the MSII SEI message comprises a value of a depth of each MSI layer in the multilayer bitstream, a projection type used to convert a sphere image to a 2D image, a covered area of a sphere surface, and a rotation of the sphere.

[0176] 14. The method of any of solutions 1-13, w herein w hen inter-layer prediction is disallowed, the MSIISEI message additionally contains a number of sphere images pertaining to each time instance, a depth of each sphere image, a projection type used to convert a sphere image to a 2D image, a covered area of a sphere surface,a rotation of the sphere, and indications of how projected 2D images of the sphere images pertaining to each time instance are frame-packed including an indication of whether the MSI layers are temporally interleaved, an indication of whether they are frame-packed in the side-by-side or top-bottom manner when the MSI layers are not temporally interleaved, and a number of spatially packed MSI layers in height.

[0177] 15. The method of any of solutions 1-14, wherein the conversion includes encoding the visual media data into the multi-layer bitstream.

[0178] 16. The method of any of solutions 1-15, wherein the conversion includes decoding the visual media data from the multi-layer bitstream.

[0179] 17. 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 1-16.

[0180] 18. 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 1-16.

[0181] 19. 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 perform a conversion on multi-plane images (MPI) based video or multi-sphere images (MSI) based video via a multi-layer two-dimensional (2D) video codec, wherein each MPI layer or MSI layer is coded as a layer in a multilayer bitstream of the multi-layer 2D video codec with inter-layer prediction allowed: and generating a bitstream based on the determining.

[0182] 20. A method for storing bitstream of a video comprising: determining to perform a conversion on multi-plane images (MPI) based video or multi-sphere images (MSI) based video via a multi-layer two-dimensional (2D) video codec, wherein each MPI layer or MSI layer is coded as a layer in a multi-layer bitstream of the multilayer 2D video codec with inter-layer prediction allowed; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.

[0183] 21. A method, apparatus, or system described in the present disclosure.

[0184] 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 know ledge of presence and absence of syntax elements according to the format rule to produce decoded video.

[0185] In the present disclosure, 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 orspread 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.

[0186] The disclosed and other solutions, examples, embodiments, modules and the functional operations described in this disclosure can be implemented in digital electronic circuitry , or in computer software, firmware, or hardware, including the structures disclosed in this disclosure 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 artificially generated signal, e.g., a machinegenerated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

[0187] 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 intercomrected by a communication network.

[0188] The processes and logic flows described in this disclosure 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.. a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0189] 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. Generali}', 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 optical disks. 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.

[0190] While the present disclosure 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 the present disclosure 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.

[0191] 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 sy stem components in the embodiments described in the present disclosure should not be understood as requiring such separation in all embodiments.

[0192] 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 the present disclosure.

[0193] 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 the 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 otherwise stated.

[0194] 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.

[0195] 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 show n 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 multi-layer two-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video; and performing a conversion between the MPI based video or the MSI based video and a multi-layer bitstream including the MPI based video or the MSI based video based on the determination.

2. The method of claim 1, wherein the multi-layer 2D video codec comprises a multiview video coding (MVC) extension, an extension of multiview video coding with depth information (MVCD), an extension of multiview and depth video with enhanced non-base view coding (3D-AVC), a mulitview video high efficiency video coding (MV-HEVC) extension, a three-dimensional high efficiency video coding (3D-HEVC) extension, or a multi-layer capability in versatile video coding (WC).

3. The method of any of claims 1 -2, wherein for each set of multi-plane or multi-sphere images pertaining to a particular time instance for the MSI based video, each sphere image is projected into a projected 2D image using a projection method.

4. The method of claim 3, wherein the projection method comprises equirectangular projection (ERP) or the cubemap projection (CMP).

5. The method of any of claims 3-4, wherein the projected 2D image is referred to as an MSI layer.

6. The method of claim 1, wherein for each set of multi-plane or multi-sphere images pertaining to a particular time instance for the MPI based video, a plane image is referred to as an MPI layer.

7. The method of claim 1, wherein for each set of multi -plane or multi-sphere images pertaining to a particular time instance for the MPI based video, each MPI layer or each MSI layer is encoded as a layer in a multilayer bitstream of the multi-layer 2D video codec.

8. The method of claim 7, wherein each MPI layer or each MSI layer is encoded using inter-layer prediction allowed by the the multi-layer 2D video codec.

9. The methof of any of claims 7-8, wherein frame packing is not applied.

10. The method of any of claims 3-9, wherein depths of the MPI layers or MSI layers are encoded in an increasing order corresponding to an increasing order of layer identifiers of layers in the multi-layer bitstream of the multi-layer 2D video codec.

11. The method of claim 10, wherein a lay er identifier comprises a view id syntax element in a network abstraction layer (NAL) unit header MVC extension for the MVC extension or the MVCD extension.

12. The method of claim 10, wherein a layer identifier comprises a variable that represents a view order index of a view identified by a view identifier for the MVC extension or the MVCD extension.

13. The method of claim 12, wherein the variable is designated VOIdx, and wherein the view identifier is designated view id.

14. The method of claim 13, wherein the VOIdx is set equal to a value of i for which a syntax element view_id[i] included in a referred subset sequence parameter set (SPS) is equal to the view identifier.

15. The method of claim 10, wherein a layer identifier comprises a syntax element in a network abstraction lay er (NAL) unit header of the 3D-AVC extension for the MVC extension or the MVCD extension, and wherein the syntax element is designated view idx.

16. The method of claim 10, wherein a lay er identifier comprises a sy ntax element in a netw ork abstraction layer (NAL) unit header for any extension of HEVC for the MVC extension or the MVCD extension, and wherein the syntax element is designated nuh layer id.

17. The method of claim 10, wherein a layer identifier comprises a variable that represents a view order index for the MV-HEVC extension or the 3D-HEVC extension, wherein the variable is designated ViewOrderIdx[lId], and wherein lid is equal to a nuh layer id in a network abstraction layer (NAL) unit header.

18. The method of claim 10, wherein a layer identifier comprises a syntax element in a netw ork abstraction layer (NAL) unit header for the WC, and wherein the syntax element is designated nuh layer id.

19. The method of claim 10, wherein a layer identifier comprises a variable that represents a view identifier as specified in semantics of a scalability dimension information (SDI) supplemental enhancement information (SEI) message, wherein the variable is designated Viewld[i], and wherein i is an index of a view in a list of view s in a current coded video sequence.

20. The method of claim 1. wherein the MPI based video or the MSI based video is decoded using the multilayer 2D video codec, wherein the the multi-layer 2D video codec comprises a multiview video coding (MVC) extension, an extension of multiview video coding with depth information (MVCD), an extension of multiview and depth video with enhanced non-base view coding (3D-AVC), a mulitview video high efficiency video coding (MV- HEVC) extension, a three-dimensional high efficiency video coding (3D-HEVC) extension, or a multi-layer capability in versatile video coding (WC).

21. The method of claim 20, wherein a coded picture in a layer is decoded using a standard decoding process, and wherein the standard decoding process comprises inter-layer prediction allowed by the the multi-layer 2D video codec.

22. The method of claim 20, wherein each projected 2D image is converted into a spherical image by applying an inverse projection for the MSI based video.

23. The method of claim 1, wherein a multi-layer MPI information (ML-MPII) supplement enhancement information (SEI) message is included in the multi-layer bitstream.

24. The method of claim 23, wherein for each layer in the multi-layer bitstream of the the multi-layer 2D video codec, the ML-MPII SEI message comprises a value of a depth of the MPI layer coded in the MSI layer in the multi-layer bitstream.

25. The method of claim 24, wherein a number of the MPI lay ers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

26. The method of claim 1, wherein a multi-layer MSI information (ML-MSII) supplement enhancement information (SEI) message is included in the multi-layer bitstream. l. The method of claim 26, wherein for each layer in the multi-layer bitstream of the the multi-layer 2D video codec, the ML-MSII SEI message comprises a value of a depth of the MSI layer coded in the MSI layer in the multi-layer bitstream.

28. The method of claim 27, wherein the value represents a distance between a sphere of a spherical image in the MSI layer and an origin of the sphere.

29. The method of any of claims 27-28, wherein a number of the MSI layers is derived to be equal to a number of layers in the multi -layer bitstream of the multi-layer 2D video codec.

30. The method of any of claims 27-29. wherein a projection type is used by an encoder to convert a spherical image to a 2D image, and wherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

31. The method of any of claims 27-30, wherein the ML-MSII SEI message comprises a covered area of a sphere surface.

32. The method of claim 31, wherein the covered area of the sphere surface comprises an upper half of the sphere.

33. The method of claim 32, wherein a rotation of the sphere is signaled in a sphere rotation SEI message, and wherein the rotation of the sphere comprises a yaw rotation, a pitch rotation, and a roll rotation.

34. The method of claim 1, wherein a multi-layer MPI information (ML-MPII) supplement enhancement information (SEI) message is extended to an extended ML-MPII SEI message configured to indicate whether interlayer prediction is allowed or not allowed.

35. The method of claim 34, wherein a single syntax element is included in the extended ML-MPII SEI message to indicate whether the inter-lax er prediction is allowed.

36. The method of any of claims 34-35, wherein when the extended ML-MPII SEI message indicates that the inter-layer prediction is allowed, for each lay er in the multi-layer bitstream of the the multi-layer 2D video codec, the extended ML-MPII SEI message comprises a value of a depth of the MPI layer coded in the MSI layer in the multi-layer bitstream.

37. The method of claim 36, wherein a number of the MPI layers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

38. The method of claim 34, wherein when the extended ML-MPII SEI message indicates that the inter-layer prediction is not allowed, the extended ML-MPII SEI message comprises all information in the ML-MPII SEI message.

39. The method of claim 1, wherein a multi-layer MSI information (ML-MSII) supplement enhancement information (SEI) message is configured to specify whether inter-layer prediction is allowed or not allowed.

40. The method of claim 39. wherein a single syntax element is included in the ML-MSII SEI message to indicate whether the inter-layer prediction is allowed.

41. The method of claim 40, wherein when the extended ML-MPII SEI message indicates that the inter-layer prediction is allowed, for each lax er in the multi-layer bitstream of the the multi-layer 2D video codec, the ML- MSII SEI message comprises a value of a depth of the MSI layer coded in the MSI layer in the multi-layer bitstream.

42. The method of claim 41, wherein the value represents a distance betw een a sphere of a spherical image in the MSI layer and an origin of the sphere.

43. The method of any of claims 41-42, wherein a number of the MSI layers is derived to be equal to a number of layers in the multi-layer bitstream of the multi-layer 2D video codec.

44. The method of any of claims 41-43, wherein a projection type is used by an encoder to convert a spherical image to a 2D image, and wherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

45. The method of claim 44, wherein the ML-MSII SEI message includes a covered area of a sphere surface.

46. The method of claim 45, w herein the covered area of the sphere surface comprises an upper half of the sphere.

47. The method of claim 46, wherein a rotation of the sphere is signaled in a sphere rotation SEI message, and wherein the rotation of the sphere comprises a yaw rotation, a pitch rotation, and a roll rotation.

48. The method of claim 39, wherein when the ML-MSII SEI message indicates that the inter-layer prediction is not allowed, the extended ML-MSII SEI message comprises a number of sphere images pertaining to each time instance.

49. The method of claim 48, wherein the ML-MSII SEI message includes a value of a depth of each sphere image.

50. The method of claim 49, wherein the value represents a distance between a sphere of a spherical image in the MSI layer and an origin of the sphere.

51. The method of any of claims 48-50. wherein the ML-MSII SEI message includes a projection type used by an encoder to convert a spherical image to a 2D image, and wherein the projection type comprises equirectangular projection (ERP) or the cubemap projection (CMP).

52. The method of any of claims 48-51, wherein the ML-MSII SEI message includes a covered area of a sphere surface.

53. The method of claim 52, wherein the covered area of the sphere surface comprises an upper half of the sphere.

54. The method of any of claims 48-53, wherein the ML-MSII SEI message includes a rotation of the sphere, and wherein the rotation of the sphere comprises a yaw rotation, a pitch rotation, and a roll rotation.

55. The method of any of claims 48-54, wherein the ML-MSII SEI message includes an indication of how projected 2D images of the sphere images pertaining to each time instance are frame packed.

56. The method of claim 55, wherein the ML-MSII SEI message indicates whether the MSI layers are temporarily interleaved.

57. The method of claim 56, w herein the ML-MSII SEI message indicates whether the MSI layers are frame packed in a side-by-side maimer or in a top-to-bottom manner when the MSI layers are not temporarily interleaved.

58. The method of any of claims 56-57, wherein the ML-MSII SEI message indicates a number of the MSI layers that are spatially packet in height.

59. The method of any of claims 1-58, wherein the conversion includes encoding the visual media data into the bitstream.

60. The method of any of claims 1-58, wherein the conversion includes decoding the visual media data from the bitstream.

61. 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 1-60.

62. 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 1-60.

63. 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 multi-layer two-dimensional (2D) video codec to a multi-planc images (MPI) based video or a multi-sphere images (MSI) based video; and generating a multi-layer bitstream including the MPI based video or the MSI based video based on the determination.

64. A method for storing bitstream of a video comprising: determining to apply a multi-layer tw o-dimensional (2D) video codec to a multi-plane images (MPI) based video or a multi-sphere images (MSI) based video; and generating a multi-layer bitstream including the MPI based video or the MSI based video based on the determination; and storing the multi-layer bitstream in a non-transitory computer-readable recording medium.

65. A method, apparatus, or system described in the present disclosure.

Images