Video coding and decoding of color components

Abstract

In an example encoding process, an input image is received in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components. A first image is formed comprising luma samples copied from the luma samples of the input image, and a second image is formed comprising luma samples copied from one or two of the chroma components of the input image. The first image is encoded as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream. In a decoding process, the primary picture is decoded into a first decoded picture, and the first auxiliary picture into a second decoded picture. An output image is formed in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

Description

Video Coding and Decoding of Color componentsTECHNICAL FIELD

[0001] Examples of embodiments herein relate generally to video encoding and decoding and, more specifically, relate to color components in encoding and decoding.BACKGROUND

[0002] Video encoding involves encoding images into data suitable for a bitstream, and video decoding involves decoding data from the bitstream into images that may be represented on a screen. The video is represented by pixels, the pixels that are captured or displayed have red (R), green (G), and blue (B) components, and individual pixels are represented through combinations of these components. For instance, “white” may be represented by high values for RGB, e.g., “255” for each of RGB in an 8-bit format; “black” may be represented by low values for RGB, e.g., “0” (zero) for each of RGB; and “pink” may be represented by (255,0,127) for RGB.

[0003] RGB is referred to as a “color space”, and there are multiple possible color spaces: RGB (red, green blue); HSV (hue, saturation, value); and YCbCr (luminance Y; blue chrominance Cb; red chrominance Cr). Luminance (Y), also referred to as “luma”: This component carries the brightness information, which represents the intensity of the image. Chrominance (Cb and Cr), also referred to as “chroma”, are responsible for carrying the color information of the image. There is also a green chrominance, Cg, but Cg can be calculated using the other three components, and only three components are typically used. In a digital video system, luminance is generally represented as an 8-bit or 10-bit value, with values ranging from 0 to 255 (8-bit) or 0 to 1023 (10-bit). Higher values indicate greater brightness, while lower values indicate lesser brightness.

[0004] A recent addition to these color spaces is YCoCg, which uses luma (Y), and two chroma values referred to as chrominance green (Cg) and chrominance orange (Co). Both YCbCr and YCgCo are also referred to as YUV. Components of Cb, Cr, Co, and Cg will be referred to herein as Cb, Cr, Co, or Cg color components or chroma components.

[0005] Chroma subsampling reduces the color information in a signal relative to luminance information. This reduces bandwidth and sample rate with limited impact on picture quality because chrominance components are less relevant to the human visual system than the luminance.

[0006] The 4:4:4 chroma format does not downsample the chrominance components. The 4:2:2 chroma format downsamples by a factor of 2 vertically and does not downsample horizontally. The 4:2:0 chroma format downsamples by a factor of 2 both vertically and horizontally, and samples colors out of half the pixels on the first row and ignores the second row of the sample completely.

[0007] The 4:2:0 and 4:2:2 chroma formats have been commonly used, but some use cases require the higher chroma fidelity provided with the 4:4:4 format. The reduction in video quality of 4:2:0 or 4:2:2 chroma format relative to 4:4:4 is more significant in graphics content than in camera-captured content.BRIEF SUMMARY

[0008] This section is intended to include examples and is not intended to be limiting.

[0009] In an example, a method is disclosed that includes receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0010] An additional example includes a computer program, comprising instructions for performing the method of the previous paragraph, when the computer program is run on an apparatus. The computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer-readable medium bearing the instructions embodied therein for use with the apparatus. Another example is the computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the apparatus.

[0011] An example of an apparatus includes one or more processors and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0012] An example of a computer program product includes a computer-readable storage medium bearing instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0013] In another example, an apparatus comprises means for: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0014] In an example, a method is disclosed that includes receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0015] An additional example includes a computer program, comprising instructions for performing the method of the previous paragraph, when the computer program is run on an apparatus. The computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer-readable medium bearing the instructions embodied therein for use with the apparatus. Another example is the computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the apparatus.

[0016] An example of an apparatus includes one or more processors and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0017] An example of a computer program product includes a computer-readable storage medium bearing instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0018] In another example, an apparatus comprises means for: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings use reference numerals, where the same reference numerals may be used to refer to like parts throughout, but parts having the same reference numeral can differ in operation and components. In the attached drawings:

[0020] FIG. 1 is a block diagram illustrating a system in accordance with an example;

[0021] FIG. 2 is a flowchart of an encoding process for encoding a video enabling use of an alternative chroma format in accordance with an example;

[0022] FIG. 3 is a flowchart of a decoding process for decoding a video that enables use of an alternative chroma format in accordance with an example;

[0023] FIG. 4 illustrates color components Cb and Cr in separate auxiliary picture layers with the packing flag equal to 0 (zero);

[0024] FIG. 5 illustrates color components Cb and Cr packed into a single auxiliary picture layer, with the packing flag equal to 1 (one), the horizontal packing flag equal to 1 (one), and the guard band size greater than 0 (zero);

[0025] FIG. 6 illustrates color components Cb and Cr packed into a single auxiliary picture layer, with the packing flag equal to 1 (one), the horizontal packing flag equal to 0 (zero), and the guard band size greater than 0 (zero); and

[0026] FIG. 7 is an example of a block diagram of an apparatus suitable for implementing any of the encoders or decoders described herein.DETAILED DESCRIPTION OF THE DRAWINGS

[0027] Abbreviations that may be found in the specification and / or the drawing figures are defined below, at the end of the detailed description section.

[0028] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the examples.

[0029] When more than one drawing reference numeral, word, or acronym is used within this description with 7”, and in general as used within this description, the 7 may be interpreted as “or”, “and”, or “both”. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or,” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0030] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0031] It is noted that capital and lowercase words or phrases are considered to be the same herein. For instance, the words Slice, slice, and SLICE are the same, as are the phrases Network Repository Function, network repository function, and NETWORK REPOSITORY FUNCTION.

[0032] Any flow diagram or signaling diagram herein is considered to be a logic flow diagram, and illustrates the operation of an exemplary method, results of execution of computer program instructions embodied on a computer readable memory, and / or functions performed by logic implemented in circuitry. For methods, flow diagrams, and signaling diagrams, the orders of method steps, blocks / operations in the flow, or signaling are not critical and instead are examples.

[0033] Technical context is now provided for technical areas related to the understanding of the examples. This is provided as brief overviews of possibly related technical areas.

[0034] Turning to color spaces and their use, the AVC (Advanced video coding), HEVC (High Efficiency Video Coding), and WC standards comprise profiles that support coding of 4:4:4 content, which may be in any of the following formats:

[0035] 1) Luma and two chroma (e.g., YCbCr or YCgCo), also known as YUV;

[0036] 2) Green, blue, and red (GBR, also known as RGB);

[0037] 3) Arrays representing other unspecified monochrome or tri-stimulus color samplings (for example, Y7X, also known as XY7).

[0038] In WC, the variables and terms associated with these arrays are referred to as luma (or L or Y) and chroma, where the two chroma arrays are referred to as Cb and Cr; regardless of the actual color representation method in use. The actual color representation method in use can be indicated in syntax that is specified in VUI (Video usability information) parameters as specified in Rec. ITU-T H.274 | ISO / IEC 23002-7, which are aligned with those specified in Rec. ITU-T H.273 | ISO / IEC 23091-2. Further information on the usage of these color representation indications is available in ITU T H-Suppl. 19 | ISO / IEC TR 23091-4.

[0039] In WC, the variables SubWidthC and SubHeightC are specified the table below, depending on the chroma format sampling structure, which is specified through sps_chroma_format_idc. The following table illustrates SubWidthC and SubHeightC values derived from sps_chroma_format_idc. This is referred to as Table 2.

[0040] The HEVC and WC standards support multilayer bitstreams, with layers identified by a layer ID (identification) value in the Network Abstraction Layer (NAL) unit header. A multilayer bitstream is a bitstream comprising multiple layers, which may be, but are not limited to, base and enhancement layers for scalable video coding or for auxiliary pictures. A multilayer bitstream may additionally or alternatively comprise independent layers that do not have inter-layer prediction relationship between each other and may represent different types of content.

[0041] A coded video sequence (CVS) of a multilayer bitstream includes a coded layer video sequence (CLVS) for each layer.

[0042] The definitions of picture unit (PU) and access unit (AU) in the VSEI (versatile supplemental enhancement information) specification are as follows:

[0043] picture unit (PU): A set of NAL units that comprise all VCL (Video coding layer) NAL units of a coded picture and their associated non-VCL NAL units; and

[0044] access unit (AU): A set of PUs that belong to different layers and comprise coded pictures associated with the same output time.

[0045] In HEVC, the Video Parameter Set (VPS) extension provides a mechanism to determine an auxiliary identifier for a layer in an auxiliary picture layer from the syntax elements describing that layer.

[0046] The value Auxld[ lid ] equal to 0 specifies the layer with nuhjayerjd equal to lid does not comprise auxiliary pictures. Auxld[ lid ] greater than 0 (zero) specifies the type of auxiliary pictures in layer with nuh_layer_id equal to lid as specified in a table provided in HEVC, as shown below. This is Table F.2 - Mapping of Auxld to the type of auxiliary pictures.

[0047] The VSEI standard includes a Scalability Dimension Information (SDI) supplemental enhancement information (SEI) message which enables signaling of an auxiliary picture type for individual layers, including alpha channels and depth maps, and to signal information about associated primary picture layers. The SDI SEI message includes a syntax element, sdi_aux_id[ i ], which assigns an auxiliary identifier to auxiliary pictures, as defined below.

[0048] sdi_aux_id[ i ] equal to 0 (zero) indicates that the i-th layer in the current CVS does not comprise auxiliary pictures. sdi_aux_id[ i ] greater than 0 indicates the type of auxiliary pictures in the i-th layer in the current CVS (coded video sequence) as specified in Table 15. When sdi_auxiliary_info_flag is equal to 0, the value of sdi_aux_id[ i ] is inferred to be equal to 0. The following is Table 15 - Mapping of sdi_aux_id[ i ] to the type of auxiliary pictures.

[0049] The Constituent Rectangles (CRs) SEI message in JVET-AJ2032 describes partitioning of a picture into constituent rectangles. The CR identifier numbering space associated with these constituent rectangles is limited to a single layer.

[0050] The CR SEI message provides several options for signaling the size and position of CRs, to allow flexibility for a variety of use cases, some of which may include large numbers of CRs in a picture. When all rectangles have the same size, their size and position can be efficiently signaled based upon a position in a grid of rectangles rows and rectangles columns.

[0051] Now that technical context has been described, issues with current techniques are described. Coding of content in 4:4:4 chroma format, whether RGB or YUV, is not supported by the most commonly deployed profiles of HEVC and WC, which instead support 4:2:0 chroma format. Some applications prefer a 4:4:4 chroma format, so that the color components are represented at full resolution, rather than downsampled to be coded using a 4:2:0 chroma format.

[0052] The prior approaches to enable formation of a 4:4:4 chroma format picture, from separately coded color components within a 4:2:0 or monochrome picture, each use an SEI message which supports coded pictures comprising a variety of content types in addition to the color components, such as alpha and depth. There is a complexity burden in implementing such SEI messages.

[0053] The examples herein address at least these issues. An overview is provided, then additional details are provided.

[0054] Referring to FIG. 1, this figure is a block diagram illustrating a system 100 in accordance with an example. The system 100 provides an overview of the operations that occur for the examples herein. In the example of FIG. 1, an encoding process 131 encodes input video 110-1 from the scene 15. The encoding process 131 is implemented in a transmitting apparatus 180-1, and the encoding processes uses a preprocessor 133 and an encoder 130. There is a capture of input video 110-1 at a viewpoint 10 of a scene 15, which includes a human being 20. The encoding process 131 produces a multilayer bitstream 101, which is received by the receiving apparatus 180-2. The receiving apparatus 180-2 implements a decoding process 141. The decoding process 141 operates on the multilayer bitstream 101, and forms the output video 110-2 (as a representation of the input video 110-1) for the scene 15-1, and the receiving apparatus 180-2 would present this, at some point, to the user, e.g., via a smartphone, television, or projector among many other options. The scene 15-1 has a viewpoint 10-1 and comprises representations of at least a human being 20-1. The encoder 130 and decoder 140 may be applied to multiple coding standards.

[0055] In terms of the examples herein, the encoding process 131 is assumed to have two parts, one of which is an encoder 130 that encodes in 4:2:0 or monochrome chroma format and outputs a multilayer bitstream. The examples here enable formation of a 4:4:4 chroma format target picture at the decoder when the encoder 135 encodes in 4:2:0 or monochrome chroma format. To enable this, a pre-processor 133, as a second part of the encoding process 131, processes input images of the input video 110-1 and forms first and second images (and possibly a third image), which are input to the encoder 130. The first image may be encoded as aprimary picture and the second image may be encoded as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream. The pre-processor 133 also may add message content (e.g., a parameter set, header, or information message) to help with enabling formation of a 4:4:4 chroma format target picture at the decoder 140. Examples of the message content that can be added are provided below.

[0056] At the decoder side, the decoder 140 has two parts, one of which is a decoder 140 that decodes in 4:2:0 or monochrome chroma format based on a multilayer bitstream 101. The decoding process 141 also includes, as a second part, a post-processor 145 that uses decoder output (from first and second images, and possibly a third image) to enable formation of a 4:4:4 chroma format target picture (e.g., based on the message content that also enables formation of a 4:4:4 chroma format target picture), which may be output as part of output video 110-1.

[0057] Turning to FIG. 2, this figure is a flowchart of an encoding process 131 for encoding a video enabling use of an alternative chroma format in accordance with an example. Operations 205, 210, and 215 are assumed to be performed by the pre-processor 133, and operation 220 is assumed to be performed by the encoder 130. In operation 205, input video is received (or accessed, such as from a memory) having input pictures in 4:4:4 chroma format, comprising samples for a luma component, and samples for two color components. A first image is formed comprising luma samples copied from the luma samples of the input image. This occurs in operation 210. In operation 215, a second image is formed comprising luma samples copied from one or two of the color components of the input image. In operation 220, the first image is encoded as a primary picture and the second image is encoded as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream. The first image may include color component samples formed by downsampling two color components of the input image. Alternatively, the first image may be formed to comprise color component samples set to a constant value.

[0058] It is noted that the terms “image” and “picture” are basically the same concepts, but video codecs typically use pictures not images. The term “image” in FIGS. 2 and 3 are used as a input image and the term “picture” is used for coded pictures.

[0059] FIG. 3 is a flowchart of a decoding process 141 for decoding a video that enables use of an alternative chroma format in accordance with an example. Operations 305, 310, and 315 are assumed to be performed by the decoder 140, and operation 320 is assumed to be performed by the post-processor 145. In operation 305, a multilayer bitstream is received (or accessed from a memory) including a primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format. In operation 310, the primary picture is decoded into a first decoded picture, and in operation 315, the first auxiliary picture is decoded into a second decoded picture. An output image is formed in operation 310 in a 4:4:4 chroma format using at least the luma samples from the first decoded picture and one or two color components from the second decoded picture.

[0060] As additional overview, a video bitstream may comprise an enhanced color format information message (as part of the message content), a primary picture layer luma component samples comprising the luma component samples of the input picture, and one or two auxiliary picture layers lumacomponent samples comprising Cb and Cr chroma / color components samples of the input picture, with the primary picture and auxiliary pictures coded in 4:2:0 or monochrome chroma format, to enable formation of a 4:4:4 chroma format target picture at the decoder. Two separate auxiliary pictures may be used for the Cb and the Cr color components, or a single auxiliary picture may comprise packed Cb and Cr color components, which may be referred to as packed Cb color components and Cr color components. As previously described, the terms “color component’ and “chroma component” are considered to be interchangeable for Cr and Cb and similar components.

[0061] The terms luma, Cb, and Cr color components can also be used to represent G, B, and R color components for the RGB color space, or other color spaces such as XY7.

[0062] Values may be defined herein for an auxiliary identifier (as part of message content) that is signaled in a parameter set or a scalability dimension information message, to identify an auxiliary picture coded in a video bitstream as comprising a Cb color component, a Cr color component, or packed Cb and Cr color components.

[0063] Message content such as information signaled in the parameter set or a scalability dimension information message may be used to determine the layer identifier signaled in a header of the data units, such as the NAL unit header, for the coded auxiliary picture for the Cb color component, a Cr color component, and / or packed the Cb and Cr color components, and the primary picture associated with those auxiliary pictures. The term Cb color component may also be referred to as Cb color component, and the term Cr color component may be referred to as Cr color component.

[0064] An enhanced color format information message (e.g., as message content) may be defined herein that includes a packing flag syntax element signaled to indicate whether two color components are packed into a single coded picture. When that flag is set, an additional horizontal packing flag syntax element indicates whether the two color components are packed horizontally or vertically.

[0065] In an embodiment, the enhanced color format information message may also comprises a guard band syntax element to signal a guard band size, which is used with the packing flag and horizontal packing flag to determine the location of the Cr color components in the coded picture.

[0066] In an embodiment, the decoded auxiliary pictures and syntax elements indicated in the enhanced color format information message are used to form a 4:4:4 target picture from the luma component of the decoded primary picture, and the Cb and Cr color components comprised in the one or two auxiliary pictures.

[0067] In an embodiment, video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the target picture from the syntax elements comprised in the auxiliary picture for the Cb color components or packed Cb and Cr color components.

[0068] In an embodiment, a constraint is placed on a video bitstream that enhanced color format is associated with an auxiliary picture layer, for each access unit comprising a coded primary picture. If the packing flag is set, the access unit should also comprise a coded auxiliary picture for packed Cb and Cr colorcomponents. Otherwise, the access unit should also comprise a coded auxiliary picture for the Cb color components and a coded auxiliary picture for the Or color components.

[0069] Now that an overview has been provided, more details are provided. The invention proposes an enhanced color format information (ECFI) SEI message, which is simplified as compared to current ECFI SEI messages, carried in a video bitstream which also comprises a primary picture comprising a luma component and auxiliary pictures comprising Cb and Cr color components, with the primary picture and auxiliary pictures coded in 4:2:0 or monochrome chroma format, to enable formation of a 4:4:4 chroma format target picture at the decoder / receiver. A supplemental enhancement information (SEI) message is defined as the follows: a syntax structure that provides a particular type of information that assists in processes related to decoding, display or other purposes but is not needed by the decoding process in order to determine the values of the samples in decoded pictures.

[0070] Cb and Cr color components are either carried as two separate auxiliary picture layers or the Cb and Cr color components are packed into a single auxiliary picture layer, as indicated by a packing flag syntax element in the ECFI message.

[0071] When the packing flag indicates that the Cb and Cr color components are packed into a single auxiliary picture layer, a horizontal packing flag is also signaled, which indicates whether Cb and Cr are packed horizontally as left / right or vertically as top / bottom.

[0072] In an embodiment, the Cb color component plane is placed in the top left corner in the auxiliary picture, and the Cr color plane is placed on the right or bottom of the auxiliary picture, depending on the horizontal packing flag value. If the horizontal packing flag is set, the Cr color plane is placed on the right. If the horizontal packing flag is not set, the Cr color plane is placed on the bottom.

[0073] A guard band size syntax element may be signaled, which indicates a distance between the positions of the Cb and Cr color planes in the packed auxiliary picture. Use of a guard band can avoid compression artifacts at the boundaries of the Cb and Cr regions that may be present in the absence of a guard band. The guard band signaled is applied to either horizontal or vertical packing, depending on the value of the horizontal packing flag.

[0074] In an embodiment, when horizontal packing is in use, an encoder selects the guard band size in a manner that the left border of the Cr color component plane aligns with a border of a coding structure, such as a coding tree unit boundary, a tile boundary, a slice boundary, and / or a subpicture boundary.

[0075] In an embodiment, when vertical packing is in use, an encoder selects the guard band size in a manner that the top border of the Cr color component plane aligns with a border of a coding structure, such as a coding tree unit boundary, a tile boundary, a slice boundary, and / or a subpicture boundary.

[0076] An encoder may include and / or code any content within the guard band, such as a smooth transition between boundary sample values of Cb and Cr color component planes, a constant sample value, or sample value(s) that can be coded efficiently, for example matching intra prediction blocks.

[0077] FIG. 4 shows an illustration of Cb and Cr in separate auxiliary picture layers. That is, this figure illustrates color components Cb and Cr in separate auxiliary picture layers with the packing flag equal to 0 (zero).

[0078] FIG. 5 shows an illustration of Cb and Cr packed into a single auxiliary picture layer, with horizontal packing and a guard band size greater than 0. More specifically, FIG. 5 illustrates color components Cb and Cr packed into a single auxiliary picture layer, with the packing flag equal to 1 (one), the horizontal packing flag equal to 1 (one), and the guard band size greater than 0 (zero).

[0079] FIG. 6 shows an illustration of Cb and Cr packed into a single auxiliary picture layer, with vertical packing and a guard band size greater than 0. That is, FIG. 6 illustrates color components Cb and Cr packed into a single auxiliary picture layer, with the packing flag equal to 1 (one), the horizontal packing flag equal to 0 (zero), and the guard band size greater than 0 (zero).

[0080] If the packing flag is not set, the auxiliary pictures comprising the Cb and Cr color components are restricted to have the same cropped picture dimensions as the primary picture.

[0081] If the packing flag is set, the size of the auxiliary picture comprising Cb and Cr color components is restricted so that the Cb and Cr color planes have the same dimensions as the cropped decoded primary picture. The restricted auxiliary picture dimensions are determined by the size of the cropped decoded primary picture and the guard band size and the value of the horizontal packing flag, as shown in the restriction below.

[0082] If ecf i_hor_packi ng_flag is equal to 1 , it is a suggestion of bitstream conformance that CroppedPicWidth [ CbCrLayerld ] should be equal to 2 * PrimaryPicWidth + ecfi_guard_band_size and CroppedPicHeight[ CbCrLayerld ] should be equal to PrimaryPicHeight. It is noted that “hor” means “horizontal”.

[0083] Otherwise (ecfi_hor_packing_flag equal to 0), it is a suggestion of bitstream conformance that CroppedPicWidth[ CbCrLayerld ] should be equal to PrimaryPicWidth and CroppedPicHeight[ CbCrLayerld ] should be equal to 2 * PrimaryPicHeight + ecfi_guard_band_size.

[0084] If the packing flag is set, the ECFI SEI message is associated with the auxiliary picture layer comprising the packed Cb and Cr color components.

[0085] In an embodiment, when the packing flag is not set, the ECFI SEI message is associated with the auxiliary picture layer comprising the Cb color component.

[0086] In an embodiment, a restriction is placed that the auxiliary picture layer comprising the Cb color component must have a lower value of layer ID than the layer comprising the Cr color component.

[0087] In an embodiment, video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, for the target picture is determined from the syntax elements comprised in the auxiliary picture for the Cb color components or packed Cb and Cr color components.

[0088] Auxiliary picture layers in a video bitstream have an auxiliary identifier value for each layer, which is determined by the data unit header for the layer, such as a NAL unit header in HEVC or WC, aswell as the information in a parameter set or information message, such as a video parameter set or the scalability dimension information SEI message.

[0089] One or more values may be defined for an auxiliary identifier signaled in the video parameter set or a scalability dimension information SEI message, or other parameter set or information message, to identify an auxiliary picture providing one or two chroma color component planes for the 4:4:4 chroma format.

[0090] In an embodiment, three new values are defined for an auxiliary identifier signaled in the video parameter set or a scalability dimension information SEI message, or other parameter set or information message, to identify an auxiliary picture coded in a video bitstream as Cb color components, Cr color components, or packed Cb and Cr color components. The auxiliary identifiers can be named as AUX_CB, AUX_CR, and AUX_CB_CR, respectively. The Table below shows a mapping of Auxld values including the new identifier values, which are for columns 3, 4, 5, and 6.

[0091] Use of an auxiliary identifier value allows media aware network elements and decoders to easily determine which NAL units comprise Cb and / or Cr color components. This enables sub-bitstream extraction, where NAL units for particular auxiliary layers to be discarded from the bitstream if they are not needed.

[0092] Information in the video parameter set or a scalability dimension information SEI message is used to determine the primary picture layer associated with an auxiliary layer or layers. In an alternate embodiment, the layer identifier values for each auxiliary picture layer and the primary picture layer are explicitly signaled.

[0093] The primary picture comprises the luma color component, and is coded in either YUV 4:2:0 or monochrome chroma format. A YUV 4:2:0 primary picture may optionally comprise the Cb and Cr color components, which are at a reduced resolution because of the chroma format.

[0094] A target picture in 4:4:4 chroma format can be formed using information signaled in the ECFI SEI message that identifies the location the Cb and Cr color components in the coded pictures. The luma color component of the target picture is taken from the primary picture. If the packing flag is set, the Cb color component is taken from the auxiliary picture with an auxiliary identifier of AUX_CB, otherwise the Cb colorcomponent is taken from the top left location in the auxiliary picture with an auxiliary identifier of AUX_CB_CR. If the packing flag is set, the Cr color component is taken from the auxiliary picture with an auxiliary identifier of AUX_CR, otherwise it is taken from a determined location in the auxiliary picture with an auxiliary identifier of AUX_CB_CR, based on the value of the horizontal packing flag. If the horizontal packing flag is set, the Cr color component location is the right side of the picture, with a horizontal offset determined by the guard band size. If the horizontal packing flag is not set, the Cr color component location is the bottom portion of the picture, with a vertical offset determined by the guard band size.

[0095] In an embodiment, a video bitstream may comprise multiple views or scalable layers, each with auxiliary picture layers comprising Cb and Cr color components. A 4:4:4 target picture can be formed for each view or scalable layer.

[0096] In an embodiment, a single new auxiliary identifier value is defined for use in the auxiliary picture layers. The determination of whether the auxiliary picture comprises the Cb, Cr, or packed Cb and Cr color components is determined using the syntax elements signaled in the ECFI SEI message. When Cb and Cr are carried in separate auxiliary picture layers, the layer with the lower ID value is determined to comprise a predefined color component plane, such as the Cb color component.

[0097] In an embodiment, AUX_CB and AUX_CR values are defined for an auxiliary identifier signaled in the video parameter set or a scalability dimension information SEI message as described above. An encoder signals the auxiliary identifiers AUX_CB and AUX_CR for, but does not include an ECFI SEI message in, auxiliary layers comprising Cb or Cr color components, respectively. Likewise, in an embodiment, a decoder decodes the auxiliary identifiers AUX_CB and AUX_CR for layers and determines that these auxiliary layers comprise Cb or Cr color components, respectively, for 4:4:4 target pictures.

[0098] In an embodiment, an AUX_CB_CR value are defined for an auxiliary identifier signaled in the video parameter set or a scalability dimension information SEI message as described above. An encoder signals the auxiliary identifiers AUX_CB_CR for, but does not include an ECFI SEI message in, an auxiliary layers comprising packed Cb or Cr color components.

[0099] Likewise, in an embodiment, a decoder decodes the auxiliary identifiers AUX_CB_CR for a layer and determines that this auxiliary layer comprises packed Cb or Cr color components for 4:4:4 target pictures. The decoder determines a value of horPacking Flag, which indicates horizontal packing (when equal to 1) or vertical packing (when equal to 0), as follows:

[0100] 1) When CroppedPicHeight[ CbCrLayerld ] is equal to PrimaryPicHeight, horPackingFlag is set equal to 1 ;

[0101] 2) When CroppedPicWidth[ CbCrLayerld ] is PrimaryPicWidth, horPackingFlag is set equal to 0.

[0102] In an additional embodiment, the decoder determines a value of guardBandSize, which indicates the guard band size, as follows:

[0103] 1) If howPackingFlag is equal to 1, guardBandSize is set equal to CroppedPicWidth[ CbCrLayerld ] ? ( 2 * PrimaryPicWidth );

[0104] 2) Otherwise (horPackingFlag is equal to 0), guardBandSize is set equal to CroppedPicHeight[ CbCrLayerld ] ? ( 2 * PrimaryPicHeight).

[0105] Possible syntax is described now. The syntax of the enhanced color format information SEI message may be as follows.

[0106] Proposed semantics are now described. This part describes Enhanced color format information SEI message semantics.

[0107] The enhanced color format information (ECFI) SEI message indicates that one or two auxiliary pictures comprise Cb and Cr color planes used with an associated primary picture to form a 4:4:4 target picture.

[0108] Use of this SEI message includes the definition of the following variables:

[0109] 1) A layer identifier of auxiliary layer carrying the Cb color plane to form a 4:4:4 target picture, denoted herein by CbLayerld.

[0110] 2) A layer identifier of the primary picture of the auxiliary layer associated with the ECFI SEI message, denoted herein by PrimaryLayerld.

[0111] 3) A layer identifier of auxiliary layer carrying the Cr color plane to form a 4:4:4 target picture, denoted herein by CrLayerld.

[0112] 4) For each value of lid among PrimaryLayerld, CbLayerld, and CrLayerld, use of this SEI message requires the definition of the following variables:

[0113] 4a) A picture width and picture height in units of luma samples of the cropped decoded picture, denoted herein by CroppedPicWidth[ lid ] and CroppedPicHeight[ lid ], respectively.

[0114] 5) A bit depth for the luma sample array of the input pictures, denoted herein by BitDepthY.

[0115] 6) A chroma format indicator, denoted herein by ChromaFormatldc, as described below.

[0116] When an ECFI SEI message is present in any PU of a CLVS, an ECFI SEI message should be present for the first PU of the CLVS in decoding order. All ECFI SEI messages that apply to the same CLVS should have the same content.

[0117] PrimaryPicWidth and PrimaryPicHeight are set equal to the value of CroppedPicWidth[ PrimaryLayerld ] and CroppedPicHeight[ PrimaryLayerld ], respectively.

[0118] The variables SubWidthC and SubHeightC are derived from ChromaFormatldc as specified by Table 2.

[0119] ecfi_packing_flag equal to 1 indicates that the picture associated with the ECFI SEI message comprises packed regions comprising Cb and Cr color planes. ecfi_packing_flag equal to 0 indicates that the picture associated with the ECFI SEI message comprises a Cb color plane.

[0120] If ecfi_packing_flag equal to 1, the following applies:

[0121] 1) CbCrLayerld is set equal to CbLayerld.

[0122] 2) CbLayerld should be equal to CrLayer Id.

[0123] 3) It is a suggestion of bitstream conformance that if an access unit in the CVS comprises a picture with layer identifier equal to PrimaryLayerld, a picture should be present with layer identifier equal to CbCrLayerld.

[0124] Otherwise (ecfi_packing_flag equal to 0), the following applies:

[0125] 1) CbLayerld should be less than CrLayerld.

[0126] 2) It is a suggestion of bitstream conformance that if an access unit in the CVS comprises a picture with layer identifier equal to PrimaryLayerld, a picture should be present with layer identifier equal to CbLayerld and a picture should be present be present with layer identifier equal to CrLayerld.

[0127] ecfi_hor_packing_flag, when present, equal to 1 indicates that the Cb color component is located on the left side of the picture and the Cr component is located on the right side of the picture. ecfi_hor_packi ng_flag equal to 0 indicates that the Cb component is located on the top of the picture and the Cr component is on the bottom of the picture.

[0128] ecfi_guard_band_size, when present, specifies the size of the guard band between the packed color components in luma samples.

[0129] It is a suggestion of bitstream conformance that ecfi_guard_band_size % (ecfi_hor_packing_flag ? SubWidthC : SubWidthH ) should be equal 0. It is noted that this uses a conditional operator, which takes three operands and follows the “syntax: condition ? expressionl : expression2”. If the condition evaluates to true, expressionl is executed; otherwise, expression2 is executed. The “%” is a modulo operator.

[0130] If ecfi_packing_flag equal to 0, it is a suggestion of bitstream conformance that CroppedPicWidth[ CbLayerld ] should be equal to PrimaryPicWidth, CroppedPicHeight[ CbCrLayerld ] should be equal to Pri maryPic Height, it is a suggestion of bitstream conformance that CroppedPicWidth[ CrLayerld ] should be equal to PrimaryPicWidth, and CroppedPicHeight[ CrLayerld ]should be equal to PrimaryPicHeight..

[0131] Otherwise (ecfi_packing_flag equal to 1), the following applies:

[0132] 1) If ecfi_hor_packing_flag equal to 1, it is a suggestion of bitstream conformance that CroppedPicWidth [ CbCrLayerld ] should be equal to 2 * PrimaryPicWidth + ecfi_guard_band_size and CroppedPicHeight[ CbCrLayerld ]should be equal to PrimaryPicHeight.

[0133] 2) Otherwise (ecfi_hor_packing_flag equal to 1 ), it is a suggestion of bitstream conformance that CroppedPicWidth[ CbCrLayerld ] should be equal to PrimaryPicWidth and CroppedPicHeight[ CbCrLayerld ] should be equal to 2 * Pri mary PicHeight + ecfi_guard_band_size.

[0134] 3) The variables CrMinHor, CrMinVer, CrMaxHor, and CrMaxVer are derived as follows:

[0135] if (ecfi_hor_packing_flag) {

[0136] CrMinHor = PrimaryPicWidth + ecfi_guard_band_size

[0137] CrMaxHor = 2*PrimaryPicWidth + ecfi_guard_band_size - 1

[0138] CrMinVer = 0

[0139] CrMaxVer = PrimaryPicHeight - 1

[0140] } else {

[0141] CrMinHor = 0

[0142] CrMaxHor = PrimaryPicWidth - 1

[0143] CrMinVer = PrimaryPicHeight + ecfi_guard_band_size

[0144] CrMaxVer = 2*PrimaryPicHeight + ecfi_guard_band_size - 1

[0145] }

[0146] A target picture is generated with width PrimaryPicWidth, height PrimaryPicHeight, SubWidthC equal to 1, SubHeightC equal to 1, Chroma Formatl de equal to 3, and bit depth BitDepthY.

[0147] Video usability information, including color_primaries, transfer_characteristics, and matrix_coefficients, if present in the layer with layer identifier equal to CbLayerld, applies to the target picture.

[0148] The luma samples of the target picture are set equal to the luma samples of the layer with nuh_layer_id equal to PrimaryPicLayerld.

[0149] If ecfi_packing_flag equal to 0,

[0150] 1) The Cb samples are set equal to the luma samples of the layer with layer identifier equal to CbLayerld,

[0151] 2) The Cr samples are set equal to the luma samples of the layer with layer identifier equal to CrLayerld

[0152] Otherwise

[0153] 1) The Cb samples are set equal to the luma samples in the rectangular region bounded by (0, 0) to (PrimaryPicWidth - 1 , PrimaryPicHeight - 1 ), inclusive, of the layer with layer identifier equal to CbCrLayerld;

[0154] 2) The Cr samples are set equal to the luma samples in the rectangular region bounded by (CrMinHor, CrMinVer) to (CrMaxHor, CrMaxVer), inclusive, of the layer with layer identifier equal to CbCrLayerld.

[0155] This section concerns the VSEI Scalability Dimension Information (SDI) SEI message. The following is Table 15 - Mapping of sdi_aux_id[ i ] to the type of auxiliary pictures.

[0156] The following is Table 4 - Persistence scope of SEI messages (informative):

[0157] This section concerns WC. The following is a possible section for use in WC.

[0158] D.X.X Use of the enhanced color format information SEI message in WC

[0159] It is a suggestion of bitstream conformance that when a CLVS comprises an enhanced color format information (ECFI) SEI message, a scalability dimension information (SDI) SEI message should precede the ECFI SEI message in the CVS.

[0160] When present, the ECFI SEI message should be associated with a layer having a layer index I Idx such that sdi_aux_id[ 11 dx ] is equal to AUX_CB, or AUX_CB_CR.

[0161] When sdi_aux_id[ lldx ] is not equal to AUX_CB or AUX_CB_CR, the lldx-th layer in the CVS should not be associated with a ECFI SEI message.

[0162] For purposes of interpretation of the enhanced color format information SEI message, the following variables are specified:

[0163] 1) CbLayerld is set equal to the value of nuhjayerjd with which the ECFI SEI message is associated and cbLIdx is set to a value such that sdi Jayer Jd[ cbLIdx ] is equal to CbLayerld.

[0164] 2) PrimaryLayerld is set equal to sdi Jayer Jd[ sdi_associated_primaryjayerjdx[ cbLIdx ]

[0000] ].

[0165] 3) If sdi_auxjd[ cbLIdx ] is equal to AUX_CB_CR, CrLayerld is set equal to CbLayerld. Otherwise, CrLayerld is set equal to sdi JayerJd[ crLIdx ] for the value of CrLdx such that sdi_auxjd[ crLIdx ] is equal to AUX_CR and sdi Jayer_id[ sdi_associated_primaryjayerjdx[ crLIdx ]

[0000] ] is equal to PrimaryLayerld.

[0166] 4) For each value of lid among PrimaryLayerld, CbLayerld, and CrLayerld, the following variables are specified from the syntax elements and variables applying to the layer with nuh_layer_id equal to lid:

[0167] a) CroppedWidth[ lid ] is set equal to the value of pps_pic_width JnJuma_samples ? SubWidthC * ( pps_conf_winjeft_offset + pps_conf_win_right_offset ) for currPic.

[0168] b) CroppedHeight[ lid ] is set equal to the value of pps_pic_height_in_luma_samples ? SubHeightC * ( pps_conf_win_top_offset + pps_conf_win_bottom_offset ) for currPic.

[0169] 5) BitDepth Y is set equal to BitDepth for the layer with nuhjayerjd equal to PrimaryLayerld.

[0170] 6) ChromaFormatldc is set equal to sps_chroma_format_idc for the layer with nuh_layer_id equal to PrimaryLayerld.

[0171] The values of BitDepth and sps_chroma_formatjdc should be the same for the layers with nuhjayerjd equal to any of PrimaryLayerld, CbLayerld, and CrLayerld.

[0172] HEVC

[0173] D.X.X Use of the enhanced color format information SEI message in HEVC

[0174] It is a suggestion of bitstream conformance that when a CLVS comprises an enhanced color format information (ECFI) SEI message, vps_extension_flag should be equal to 1.

[0175] When a CLVS comprises an enhanced color format information (ECFI) SEI message, it is a suggestion of bitstream conformance that when an auxiliary picture with Auxld[ lid ] equal to AUX_CB, AUX_CR, or AUX_CB_CR is present in an access unit, a primary picture associated with the auxiliary picture is present in the same access unit, having Auxld[ nuhLayerldB ] equal to 0 such that Scalabilityld[ LayerldxlnVps[ lid ] ][j ] is equal to Scalabilityld[ LayerldxlnVps[ nuhLayerldB ] ][j ] for all values of j in the range of 0 to 2, inclusive, and 4 to 15, inclusive.

[0176] When present, the ECFI SEI message should be associated with a layer having nuh_layer_id lid such that Audi d[ lid ] is equal to AUX_CB or AUX_CB_CR.

[0177] When Aud ld[ lid ] is not equal to AUX_CB or AUX_CB_CR, the layer with nuhjayerjd equal to lid in the CVS should not be associated with a ECFI SEI message.

[0178] For purposes of interpretation of the enhanced color format information SEI message, the following variables are specified:

[0179] 1) PrimaryLayerld is set equal to nuhLayerldB.

[0180] 2) CbLayerld is set equal to the value of nuhjayerjd with which the ECFI SEI message is associated.

[0181] 3) If Auxld[ CbLayerld ] is equal to AUX_CB_CR, CrLayerld is set equal to CbLayerld. Otherwise, CrLayerld is set to a value such that Auxl d[ CrLayerld ] is equal to AUX_CR and Scalability ld[ LayerldxlnVps[ CrLayerld ] ][j ] is equal to Scalabilityld[ LayerldxlnVps[ nuhLayerldB ] ][j ] for all values of j in the range of 0 to 2, inclusive, and 4 to 15, inclusive.

[0182] 4) For each value of lid among PrimaryLayerld, CbLayerld, and CrLayerld, the following variables are specified from the syntax elements and variables applying to the layer with nuh_layer_id equal to lid:

[0183] a) CroppedPicWidth[ lid ] is set equal to pic_widthjnjuma_samples ? SubWidthC * ( conf_winjeft_offset + conf_win_right_offset ).

[0184] b) CroppedPicHeight[ lid ] is set equal to and pic_heightjn_luma_samples? SubHeightC * ( conf_win_top_offset + conf_win_bottom_offset ).

[0185] 5) BitDepth Y is set equal to BitDepth Y for the layer with nuhjayerjd equal to PrimaryLayerld

[0186] 6) ChromaFormatldc is set equal to chromajormatjdc for the layer with nuh_layer_id equal to PrimaryLayerld.

[0187] The values of BitDepth and sps_chroma_formatjdc should be the same for the layers with nuhjayerjd equal to any of PrimaryLayerld, CbLayerld, and CrLayerld.

[0188] This part concerns mapping of Auxld to the type of auxiliary pictures. The following table is Table F.2 - Mapping of Auxld to the type of auxiliary pictures:

[0189] Turning to FIG. 7, this figure is an example of a block diagram of an apparatus 180 suitable for implementing any of the encoders or decoders described herein. The apparatus 180 includes circuitry comprising one or more processors 720, one or more memories 725, one or more transceivers 730, one or more network (N / W) interface(s) (l / F(s)) 755 and user interface (Ul) circuitry and elements 757, interconnected through one or more buses 727. Depending on implementation, some apparatus may not have all of the circuitry. For example, an apparatus 180 might not have Ul circuitry and elements 757. An apparatus may have additional circuitry, not described here. FIG. 7 is presented merely as an example.

[0190] Each of the one or more transceivers 730 includes a receiver, Rx, 732 and a transmitter, Tx, 733. The one or more buses 727 may be address, data, and / or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 730 are connected to one or more antennas 705, and may communicate using wireless link 711, which could implement any number of wireless communication interfaces such as Wi-Fi, cellular, or satellite.

[0191] The one or more memories 725 include computer program code 723. The apparatus 180 includes a program 740, comprising one of or both parts 740-1 and / or 740-2. The program 740 may implement the encoder 130 and pre-processor 133, a decoder 140 and post-processor 145, or a codec (130 / 133 +140 / 145), which implements both the encoding process 131 and decoding process 141. The program itself may be implemented in a number of ways. The program 740 may be implemented in circuitry as program 740-1 , such as being implemented as part of the one or more processors 720, and comprises instructions implemented in circuitry. The program 740-1 may be implemented also as an integrated circuit or through other circuitry such as a programmable gate array. In another example, the program 740 may be implemented as program 740-2, which is implemented as computer program code (having corresponding instructions) 723 and is executed by the one or more processors 720. For instance, the one or more memories 725 store instructions that, when executed by the one or more processors 720, cause the apparatus 180 to perform one or more of the operations as described herein.

[0192] The network interface(s) (N / W l / F(s)) 755 are wired interfaces communicating using link(s) 756, which could be fiber optic or other wired interfaces. The apparatus 180 could include only wireless transceiver(s) 730, only N / W l / Fs 755, or both wireless transceiver(s) 730 and N / W l / Fs 755.

[0193] The apparatus 180 may or may not include Ul circuitry and elements 757. These could include a display such as a touchscreen, speakers, or interface elements such as for headsets. For instance, an apparatus 180 of a smartphone would typically include at least a touchscreen and speakers. The Ul circuitry and elements 757 may also include circuity to communicate with external Ul elements (not shown) such as displays, keyboards, mice, headsets, and the like.

[0194] The one or more memories 725 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductorbased memory devices, flash memory, firmware, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processor(s) 720 may be of any type suitable to the local technical environment, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processor(s) 720 control the apparatus 180 to perform the operations as described herein. The processor(s) 720 may execute instructions, including microcode, but are not implemented solely in software.

[0195] The following are additional examples.

[0196] Example 1. A method comprising: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0197] Example 2. The method according to example 1, wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

[0198] Example 3. The method according to example 1 , wherein the first image is formed to comprise chroma component samples set to a constant value.

[0199] Example 4. The method according to any of examples 1 to 3, further comprising: signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0200] Example 5. The method according to any of examples 1 to 3, further comprising signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0201] Example 6. The method according to example 1, wherein: the second image comprises Cb color components of the input image; and the method further comprises: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

[0202] Example 7. The method according to example 6, further comprising: in a parameter set, header, or information message, performing the following: signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0203] Example 8. The method according to example 1, where the second image comprises packed Cb and Cr color components.

[0204] Example 9. The method according to example 8, further comprising: in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0205] Example 10. The method according to example 8, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

[0206] Example 11. The method according to example 8 or 9, wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0207] Example 12. The method according to any of examples 1 to 11 , further comprising: forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

[0208] Example 13. The method according to example 12, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flag indicates that themultilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0209] Example 14. The method according to example 13, wherein forming the color format information message further comprises: when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0210] Example 15. The method according to example 12, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

[0211] Example 16. The method according to example 11, further comprising signaling in the information message an indication of a size of the guard band.

[0212] Example 17. A method comprising: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0213] Example 18. The method according to example 17, wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

[0214] Example 19. The method according to any of examples 17 to 18, further comprising: receiving signaling in a parameter set, header, or information message an auxiliary identifier associated with first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0215] Example 20. The method according to any of examples 17 to 18, further comprising receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0216] Example 21. The method according to example 17, wherein: the second decoded picture comprises Cb color components of an input image; and the method further comprises: decoding a second auxiliary picture into a third decoded picture comprising a Cr color components of the input image.

[0217] Example 22. The method according to example 21, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures,where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

[0218] Example 23. The method according to example 21, further comprising: in a parameter set, header, or information message, receiving the following: signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0219] Example 24. The method according to example 17, where the first auxiliary picture comprises packed Cb and Cr color components.

[0220] Example 25. The method according to example 24, further comprising: in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0221] Example 26. The method according to example 24, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

[0222] Example 27. The method according to example 24 or 25, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0223] Example 28. The method according to any of examples 17 to 27, wherein the means are further configured for: receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

[0224] Example 29. The method according to example 28, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0225] Example 30. The method according to example 29, wherein forming the color format information message further comprises: when the packing flag is equal to the first value, there is additional signaling of a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0226] Example 31. The method according to example 28, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color component or packed Cb and Cr color components.

[0227] Example 32. The method according to example 27, wherein the means are further configured for receiving signaling in the information message of an indication of a size of the guard band.

[0228] Example 33. An apparatus comprising means for: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0229] Example 34. The apparatus according to example 33, wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

[0230] Example 35. The apparatus according to example 33, wherein the first image is formed to comprise chroma component samples set to a constant value.

[0231] Example 36. The apparatus according to any of examples 33 to 35, wherein the means are further configured for: signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0232] Example 37. The apparatus according to any of examples 33 to 35, wherein the means are further configured for signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0233] Example 38. The apparatus according to example 33, wherein: the second image comprises Cb color components of the input image; and the means are further configured for: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

[0234] Example 39. The apparatus according to example 38, wherein the means are further configured for: in a parameter set, header, or information message, performing the following: signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0235] Example 40. The apparatus according to example 33, where the second image comprises packed Cb and Cr color components.

[0236] Example 41. The apparatus according to example 40, wherein the means are further configured for: in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0237] Example 42. The apparatus according to example 40, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

[0238] Example 43. The apparatus according to example 40 or 41 , wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0239] Example 44. The apparatus according to any of examples 33 to 43, wherein the means are further configured for: forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

[0240] Example 45. The apparatus according to example 44, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0241] Example 46. The apparatus according to example 45, wherein forming the color format information message further comprises: when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0242] Example 47. The apparatus according to example 44, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

[0243] Example 48. The apparatus according to example 43, wherein the means are further configured for signaling in the information message an indication of a size of the guard band.

[0244] Example 49. An apparatus comprising means for: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0245] Example 50. The apparatus according to example 49, wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

[0246] Example 51. The apparatus according to any of examples 49 to 50, wherein the means are further configured for: receiving signaling in a parameter set, header, or information message an auxiliaryidentifier associated with first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0247] Example 52. The apparatus according to any of examples 49 to 50, wherein the means are further configured for receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0248] Example 53. The apparatus according to example 49, wherein: the second decoded picture comprises Cb color components of an input image; and the means are further configured for: decoding a second auxiliary picture into a third decoded picture comprising a Cr color components of the input image.

[0249] Example 54. The apparatus according to example 53, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures, where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

[0250] Example 55. The apparatus according to example 53, wherein the means are further configured for: in a parameter set, header, or information message, receiving the following: signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0251] Example 56. The apparatus according to example 49, where the first auxiliary picture comprises packed Cb and Cr color components.

[0252] Example 57. The apparatus according to example 56, wherein the means are further configured for: in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0253] Example 58. The apparatus according to example 56, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

[0254] Example 59. The apparatus according to example 56 or 57, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0255] Example 60. The apparatus according to any of examples 49 to 59, wherein the means are further configured for: receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

[0256] Example 61. The apparatus according to example 60, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flagindicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0257] Example 62. The apparatus according to example 61 , wherein forming the color format information message further comprises: when the packing flag is equal to the first value, there is additional signaling of a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0258] Example 63. The apparatus according to example 60, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color component or packed Cb and Cr color components.

[0259] Example 64. The apparatus according to example 59, wherein the means are further configured for receiving signaling in the information message of an indication of a size of the guard band.

[0260] Example 65. An apparatus comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components; forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the chroma components of the input image; and encoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

[0261] Example 66. The apparatus according to example 65, wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

[0262] Example 67. The apparatus according to example 65, wherein the first image is formed to comprise chroma component samples set to a constant value.

[0263] Example 68. The apparatus according to any of examples 65 to 67, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0264] Example 69. The apparatus according to any of examples 65 to 67, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier ofthe layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0265] Example 70. The apparatus according to example 65, wherein: the second image comprises Cb color components of the input image; and the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

[0266] Example 71. The apparatus according to example 70, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: in a parameter set, header, or information message, performing the following: signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0267] Example 72. The apparatus according to example 65, where the second image comprises packed Cb and Cr color components.

[0268] Example 73. The apparatus according to example 72, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0269] Example 74. The apparatus according to example 72, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

[0270] Example 75. The apparatus according to example 72 or 73, wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0271] Example 76. The apparatus according to any of examples 65 to 75, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

[0272] Example 77. The apparatus according to example 76, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0273] Example 78. The apparatus according to example 77, wherein forming the color format information message further comprises: when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0274] Example 79. The apparatus according to example 76, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

[0275] Example 80. The apparatus according to example 75, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform signaling in the information message an indication of a size of the guard band.

[0276] Example 81. An apparatus comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture; decoding the first auxiliary picture into a second decoded picture; and forming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

[0277] Example 82. The apparatus according to example 81 , wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

[0278] Example 83. The apparatus according to any of examples 81 to 82, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving signaling in a parameter set, header, or information message an auxiliary identifier associated with first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

[0279] Example 84. The apparatus according to any of examples 81 to 82, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

[0280] Example 85. The apparatus according to example 81 , wherein: the second decoded picture comprises Cb color components of an input image; and the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:decoding a second auxiliary picture into a third decoded picture comprising a Cr color components of the input image.

[0281] Example 86. The apparatus according to example 85, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures, where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

[0282] Example 87. The apparatus according to example 85, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: in a parameter set, header, or information message, receiving the following: signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; and signaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

[0283] Example 88. The apparatus according to example 81 , where the first auxiliary picture comprises packed Cb and Cr color components.

[0284] Example 89. The apparatus according to example 88, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

[0285] Example 90. The apparatus according to example 88, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

[0286] Example 91. The apparatus according to example 88 or 89, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

[0287] Example 92. The apparatus according to any of examples 81 to 91 , wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

[0288] Example 93. The apparatus according to example 92, wherein the color format information message further comprises: signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

[0289] Example 94. The apparatus according to example 93, wherein forming the color format information message further comprises: when the packing flag is equal to the first value, there is additionalsignaling of a horizontal packing flag, wherein a first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

[0290] Example 95. The apparatus according to example 92, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color component or packed Cb and Cr color components.

[0291] Example 96. The apparatus according to example 91, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform receiving signaling in the information message of an indication of a size of the guard band.

[0292] Example 97. A computer program, comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the methods of any of examples 1 to 32.

[0293] Example 98. The computer program according to example 97, wherein the computer program is a computer program product comprising a computer-readable medium bearing the instructions embodied therein for use with the apparatus.

[0294] Example 99. The computer program according to example 97, wherein the computer program is directly loadable into an internal memory of the apparatus.

[0295] As used in this application, the term “circuitry” may refer to one or more or all of the following:

[0296] (a) hardware-only circuit implementations (such as implementations in analog, digital, and / or quantum circuitry) and

[0297] (b) combinations of hardware circuits and software such as (as applicable): (i) a combination of analog, digital, and / or quantum hardware ci rcuit(s) with software / firmware and (ii) any or all portions of hardware processor(s) (including digital and / or quantum processor(s)) with software, and memory(ies) that work together to cause an apparatus, such as a mobile device, computing device, or server, to perform various functions) and

[0298] (c) any or all portions of hardware circuit(s), such as microprocessor(s), processor(s) and / or quantum processors, that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0299] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0300] In an example embodiment, software (e.g., application logic, an instruction set) as used herein is maintained on any one of various conventional computer-readable media. In the context of this document, a “computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in FIG.7. A computer-readable medium may comprise a computer-readable storage medium (e.g., memories 725 or other device) that may be any media or means that can contain, store, and / or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable storage medium does not comprise propagating signals, and therefore may be considered to be non-transitory. The term “non-transitory”, as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM, random access memory, versus ROM, read-only memory).

[0301] If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.

[0302] Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and / or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[0303] It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

[0304] The following abbreviations that may be found in the specification and / or the drawing figures are defined as follows:

[0305] AU access unit

[0306] AVC Advanced video coding

[0307] CR Constituent Rectangle

[0308] CTU coding tree unit

[0309] CLVS coded layer video sequence

[0310] CVS coded video sequence

[0311] CU coding unit

[0312] ECFI enhanced color format information

[0313] ECM Enhanced Compression Model

[0314] HDMI high definition multimedia interface

[0315] HEVC High Efficiency Video Coding

[0316] ID identification

[0317] JVET Joint video experts team

[0318] NAL Network Abstraction Layer

[0319] PU picture unit

[0320] SDI Scalability Dimension Information

[0321] SEI supplemental enhancement information

[0322] VCL Video coding layer

[0323] VPS Video Parameter Set

[0324] VSEI versatile supplemental enhancement information

[0325] VUI video usability information

[0326] WC versatile video coding

Claims

What is claimed is:

1. A method comprising:receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components;forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the two chroma components of the input image; andencoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

2. The method according to claim 1 , wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

3. The method according to claim 1 , wherein the first image is formed to comprise chroma component samples set to a constant value.

4. The method according to any of claims 1 to 3, further comprising:signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

5. The method according to any of claims 1 to 3, further comprising signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

6. The method according to claim 1 , wherein:the second image comprises Cb color components of the input image; andthe method further comprises: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

7. The method according to claim 6, further comprising:in a parameter set, header, or information message, performing the following:signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

8. The method according to claim 1 , where the second image comprises packed Cb and Cr color components.

9. The method according to claim 8, further comprising:in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

10. The method according to claim 8, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

11. The method according to claim 8 or 9, wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

12. The method according to any of claims 1 to 11, further comprising:forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

13. The method according to claim 12, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising the Cb color components and a second auxiliary picture comprising Cr color components.

14. The method according to claim 13, wherein forming the color format information message further comprises:when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

15. The method according to claim 12, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

16. The method according to claim 11 , further comprising signaling in the information message an indication of a size of the guard band.

17. A method comprising:receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and a first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture;decoding the first auxiliary picture into a second decoded picture; andforming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

18. The method according to claim 17, wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

19. The method according to any of claims 17 to 18, further comprising:receiving signaling in a parameter set, header, or information message an auxiliary identifier associated with a first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

20. The method according to any of claims 17 to 18, further comprising receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayerbitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

21. The method according to claim 17, wherein:the second decoded picture comprises Cb color components of an input image; andthe method further comprises: decoding a second auxiliary picture into a third decoded picture comprising Cr color components of the input image.

22. The method according to claim 21, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures, where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

23. The method according to claim 21, further comprising:in a parameter set, header, or information message, receiving the following:signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

24. The method according to claim 17, where the first auxiliary picture comprises packed Cb and Cr color components.

25. The method according to claim 24, further comprising:in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

26. The method according to claim 24, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

27. The method according to claim 24 or 25, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

28. The method according to any of claims 17 to 27, wherein the means are further configured for: receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

29. The method according to claim 28, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

30. The method according to claim 29, wherein forming the color format information message further comprises:when the packing flag is equal to the first value, there is additional signaling of a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

31. The method according to claim 28, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or the packed Cb and Cr color components.

32. The method according to claim 27 further comprising receiving signaling in the information message of an indication of a size of the guard band.

33. An apparatus comprising means for:receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components;forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the two chroma components of the input image; andencoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

34. The apparatus according to claim 33, wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

35. The apparatus according to claim 33, wherein the first image is formed to comprise chroma component samples set to a constant value.

36. The apparatus according to any of claims 33 to 35, wherein the means are further configured for: signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

37. The apparatus according to any of claims 33 to 35, wherein the means are further configured for signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

38. The apparatus according to claim 33, wherein:the second image comprises Cb color components of the input image; andthe means are further configured for: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

39. The apparatus according to claim 38, wherein the means are further configured for:in a parameter set, header, or information message, performing the following:signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

40. The apparatus according to claim 33, where the second image comprises packed Cb and Cr color components.

41. The apparatus according to claim 40, wherein the means are further configured for:in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

42. The apparatus according to claim 40, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

43. The apparatus according to claim 40 or 41 , wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

44. The apparatus according to any of claims 33 to 43, wherein the means are further configured for: forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

45. The apparatus according to claim 44, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

46. The apparatus according to claim 45, wherein forming the color format information message further comprises:when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

47. The apparatus according to claim 44, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

48. The apparatus according to claim 43, wherein the means are further configured for signaling in the information message an indication of a size of the guard band.

49. An apparatus comprising means for:receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture;decoding the first auxiliary picture into a second decoded picture; andforming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

50. The apparatus according to claim 49, wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

51. The apparatus according to any of claims 49 to 50, wherein the means are further configured for: receiving signaling in a parameter set, header, or information message an auxiliary identifier associated with first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

52. The apparatus according to any of claims 49 to 50, wherein the means are further configured for receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

53. The apparatus according to claim 49, wherein:the second decoded picture comprises Cb color components of an input image; andthe means are further configured for: decoding a second auxiliary picture into a third decoded picture comprising a Cr color components of the input image.

54. The apparatus according to claim 53, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures, where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

55. The apparatus according to claim 53, wherein the means are further configured for:in a parameter set, header, or information message, receiving the following:signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

56. The apparatus according to claim 49, where the first auxiliary picture comprises packed Cb and Cr color components.

57. The apparatus according to claim 56, wherein the means are further configured for:in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

58. The apparatus according to claim 56, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

59. The apparatus according to claim 56 or 57, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

60. The apparatus according to any of claims 49 to 59, wherein the means are further configured for: receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

61. The apparatus according to claim 60, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

62. The apparatus according to claim 61 , wherein forming the color format information message further comprises:when the packing flag is equal to the first value, there is additional signaling of a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

63. The apparatus according to claim 60, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or the packed Cb and Cr color components.

64. The apparatus according to claim 59, wherein the means are further configured for receiving signaling in the information message of an indication of a size of the guard band.

65. An apparatus comprising:one or more processors; andone or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform:receiving an input image in a 4:4:4 chroma format, comprising samples for a luma component, and samples for two chroma components;forming a first image comprising luma samples copied from the luma samples of the input image; forming a second image comprising luma samples copied from one or two of the two chroma components of the input image; andencoding the first image as a primary picture and the second image as a first auxiliary picture coded in 4:2:0 or monochrome chroma format in a multilayer bitstream.

66. The apparatus according to claim 65, wherein the first image comprises chroma component samples formed by downsampling two chroma components of the input image.

67. The apparatus according to claim 65, wherein the first image is formed to comprise chroma component samples set to a constant value.

68. The apparatus according to any of claims 65 to 67, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:signaling in a parameter set, header, or information message an auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

69. The apparatus according to any of claims 65 to 67, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform signaling, in a parameter set, header, or information message, an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

70. The apparatus according to claim 65, wherein:the second image comprises Cb color components of the input image; andthe one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: forming a third image comprising Cr color components of the input image, and encoding the third image as a second auxiliary picture in the multilayer bitstream.

71. The apparatus according to claim 70, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:in a parameter set, header, or information message, performing the following:signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

72. The apparatus according to claim 65, where the second image comprises packed Cb and Cr color components.

73. The apparatus according to claim 72, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:in a parameter set, header, or information message, signaling a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

74. The apparatus according to claim 72, wherein the packed Cb and Cr color components in the second image are packed either horizontally or vertically.

75. The apparatus according to claim 72 or 73, wherein the second image comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

76. The apparatus according to any of claims 65 to 75, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:forming a color format information message that comprises information to enable formation of a 4:4:4 chroma format target picture from the primary picture and one or more auxiliary pictures.

77. The apparatus according to claim 76, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises the first auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both the first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

78. The apparatus according to claim 77, wherein forming the color format information message further comprises:when the packing flag is equal to the first value, additionally signaling a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

79. The apparatus according to claim 76, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or packed Cb and Cr color components.

80. The apparatus according to claim 75, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform signaling in the information message an indication of a size of the guard band.

81. An apparatus comprising:one or more processors; andone or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform:receiving a multilayer bitstream including a primary picture and a first auxiliary picture, the primary picture and first auxiliary picture coded in 4:2:0 or monochrome chroma format; decoding the primary picture into a first decoded picture;decoding the first auxiliary picture into a second decoded picture; andforming an output image in 4:4:4 chroma format using at least luma samples from the first decoded picture and one or two chroma components from the second decoded picture.

82. The apparatus according to claim 81 , wherein the first decoded picture comprises chroma component samples formed by downsampling two chroma components of an input image.

83. The apparatus according to any of claims 81 to 82, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:receiving signaling in a parameter set, header, or information message an auxiliary identifier associated with first auxiliary picture that identifies the first auxiliary picture as comprising any of Cb color components, Cr color components, or packed Cb and Cr color components.

84. The apparatus according to any of claims 81 to 82, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform receiving signaling, in a parameter set, header, or information message, of an indication of a layer identifier of a layer of the multilayer bitstream comprising the primary picture, an indication of a layer identifier of a layer of the multilayer bitstream comprising the first auxiliary picture, or both the layer identifier of the layer of the multilayer bitstream comprising the primary picture and the indication of the layer identifier of the layer of the multilayer bitstream comprising the first auxiliary picture.

85. The apparatus according to claim 81 , wherein:the second decoded picture comprises Cb color components of an input image; andthe one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform: decoding a second auxiliary picture into a third decoded picture comprising a Cr color components of the input image.

86. The apparatus according to claim 85, wherein forming the output image comprises forming the output image in 4:4:4 chroma format using the first, second, and third decoded pictures, where the luma samples come from the first decoded picture, the Cb color components come from the second decoded picture, and the Cr color components come from the third decoded picture.

87. The apparatus according to claim 85, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:in a parameter set, header, or information message, receiving the following:signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the Cb color components; andsignaling of a second auxiliary identifier associated with the second auxiliary picture that identifies the second auxiliary picture as comprising the Cr color components.

88. The apparatus according to claim 81 , where the first auxiliary picture comprises packed Cb and Cr color components.

89. The apparatus according to claim 88, wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:in a parameter set, header, or information message, receiving signaling of a first auxiliary identifier associated with the first auxiliary picture that identifies the first auxiliary picture as comprising the packed Cb and Cr color components.

90. The apparatus according to claim 88, wherein the packed Cb and Cr color components in the first auxiliary picture are packed either horizontally or vertically.

91. The apparatus according to claim 88 or 89, wherein the first auxiliary picture comprises packed Cb and Cr color components which are packed either horizontally or vertically with a guard band between the Cb color components and Cr color components.

92. The apparatus according to any of claims 81 to 91 , wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform:receiving a color format information message that comprises information to enable formation of the output image in 4:4:4 chroma format from the primary picture and one or more auxiliary pictures.

93. The apparatus according to claim 92, wherein the color format information message further comprises:signaling of a packing flag, where a first value of the packing flag indicates that the multilayer bitstream comprises a second auxiliary picture comprising packed Cb and Cr color components or a second value of the packing flag indicates that the multilayer bitstream comprises both a first auxiliary picture comprising Cb color components and a second auxiliary picture comprising Cr color components.

94. The apparatus according to claim 93, wherein forming the color format information message further comprises:when the packing flag is equal to the first value, there is additional signaling of a horizontal packing flag, wherein the first value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed horizontally or a second value of the horizontal packing flag indicates that the Cb color components and Cr color components are packed vertically.

95. The apparatus according to claim 92, wherein video usability information (VUI), including any of color primaries, transfer characteristics, matrix coefficients, and full range flag, is determined for the 4:4:4 chroma format target picture from syntax elements comprised in the one or more auxiliary pictures for the Cb color components or the packed Cb and Cr color components.

96. The apparatus according to claim 91 , wherein the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform receiving signaling in the information message of an indication of a size of the guard band.

97. A computer program, comprising instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the methods of any of claims 1 to 32.

98. The computer program according to claim 97, wherein the computer program is a computer program product comprising a computer-readable medium bearing the instructions embodied therein for use with the apparatus.

99. The computer program according to claim 97, wherein the computer program is directly loadable into an internal memory of the apparatus.

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