JP7074461B2 - How and Devices to Reconstruct Display-Compatible HDR Images - Google Patents

Description

Patent Law Article 30, Paragraph 2 Applicable ETSI TS 103 433-1 V1.1.4 Stable Draft, Technical Specifications Dated May 22, 2017 High Performance Single Layer High Dynamic Range for Use in Consumer Electronic Devices (HDR) System; Part 1: Standard Dynamic Range (SDR) Compatible HDR System (SL-HDR1), page 41, section 7.2.3.1.9, page 41, section 7.2.3.2, Pages 43 and 44, Section 7.2.4, Annex E.I. 2 Page 117 (E.20), ETSI

Principles of the invention generally relate to image / video reconstruction from decoded image / video data. In particular, but not limited to, the technical field of the principles of the invention relates to the reconstruction of one image from another, taking into account the characteristics of the image, the reconstruction metadata, and the capabilities of the presentation display.

This section is intended to introduce the reader to various technical features that may be relevant to various aspects of the principles of the invention described and / or claimed below. This description is believed to be useful in providing the reader with background information that facilitates a deeper understanding of the various aspects of the principles of the invention. Therefore, it should be understood that the following statements should be read in this regard and not as an endorsement of the prior art.

In the following, the image data shall be used by the display and / or any other device to visualize and / or decode the image (or video), for example, with all information about the pixel value of the image (or video). Refers to one or more arrays of samples (pixel values) in a particular image / video format that specify all the information that can be made. The image is the first component of the shape of the first sample array, which usually represents the brightness (or Luma) of the image, and the second of the shapes of the other sample arrays, which usually represent the color (or chroma) of the image. And a third component. Alternatively, the same information can be equivalently represented by a set of arrays of color samples, such as a conventional three-color RGB representation.

The pixel value is represented by a vector of C values, where C is the number of components. Each value in the vector is represented by several bits that define the maximum dynamic range of the pixel values.

A standard dynamic range image (SDR image) is an image having a luminance value represented by a limited number of bits (usually 8 bits). This limited representation does not allow small signal variations to be rendered correctly, especially in the dark and bright range of brightness. In high dynamic range images (HDR images), the signal representation is extended to maintain high accuracy of the signal over its entire range. In HDR images, pixel values representing brightness levels are usually in floating point format (usually at least 10 per component), the most common format being the openEXR half-precision format (16 bits per RGB component, i.e. 48 bits per pixel). It is represented by a bit (ie float type or half-float type), or an integer usually having a long representation of at least 16 bits.

High Efficiency Video Coding (HEVC) Standards (ITU-TH.265, ITU Telecommunications Standardization Division (October 2014) Series H: audiovisual and multiple systems, infrastructure of audiovisual system The advent of coding, Recommendation ITU-TH.265) has made it possible to develop new video services with enhanced display experiences, such as the Ultra HD broadcast communication service. In addition to improving spatial resolution, Ultra HD can provide a wider color gamut (WCG) and a higher dynamic range (HDR) than the standard dynamic range (SDR) HD-TVs currently being deployed. Various solutions have been proposed for the representation and coding of HDR / WCG video (SMPTE 2014, "High Dynamic Range Electro-Optical Transfer Transformion of Masstering Reference of Mastering Reference Disprays", or SMPTE14, or SMPTE14. , Blinstein S, and Qu S, "Integrating HEVC Video Compression with a High Dynamic Range Video Pipeline," SMPTE Motion Image January 21, Vol. 21, Vol. 21, Vol.

SDR backward compatibility with decryption and rendering devices is an important feature in some video distribution systems, such as broadcast communication systems or multicasting systems.

Solutions based on the single layer encoding / decryption process may be backwards compatible, for example SDR compatibility, and can leverage existing legacy distribution networks and services.

Such a single-layer delivery solution allows for high quality HDR rendering on HDR-enabled mass consumer electronics (CE) devices, while high quality SDR rendering on SDR-enabled CE devices. Also provide.

Such a single-layer delivery solution can be used to reconstruct a coded signal, such as an SDR signal, and another signal, such as an HDR signal, from a decoded signal, such as an SDR signal. Generate relevant metadata (video frames or a few bytes per scene).

The metadata stores the parameter values used to reconstruct the signal and may be static or dynamic. Static metadata means metadata that remains the same for a video (set of images) and / or a program.

Static metadata is valid for the entire video content (scenes, movies, clips, ...) and may be independent of the content of the image. Static metadata may define, for example, the format, color space, and color gamut of an image. For example, SMPTE ST 2086: 2014, "Mastering Display Color Volume Metaltata Supporting High Luminance and Wide Color Gamut Images" is such kind of static metadata used in a production environment. The Mastering Display Color Volume (MDCV) SEI (Supplementary Extended Information) message is from H.M. 264 / AVC ("Advanced video coding for generic audiovisual service", SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS, Recommendation ITU-TH.264, ITU-T H.264, ITU, telecommunications standardization, ITU-T H.264, ITU, telecommunications standardization It is a distribution flavor of ST 2086.

Dynamic metadata is content dependent. That is, this metadata can change, for example, by image or by image group, depending on the content of the image / video. As an example, the SMPTE ST 2094: 2016 standard family of "Dynamic Metadata for Color Volume Transition" is dynamic metadata used in production environments. The SMPTE ST 2094-30 can be delivered along the HEVC coded video stream thanks to the Color Remapping Information (CRI) SEI message.

Other single-layer delivery solutions exist on the delivery network where display-fit dynamic metadata is delivered with legacy video signals. Solutions for these single-layer distributions are HDR10-bit image data (eg, Recommendation ITU-R BT. 2100-0, Image parameter values for high dynamic radiation). Image data in which the signal is represented as an HLG10 or PQ10 signal as specified in "production and international program exchange") and associated metadata can be generated from the input signal (usually 12 or 16 bits). For example, the HDR10 bit image data is encoded using the HEVC Main10 profile coding scheme to reconstruct the video signal from the decoded video signal and the associated metadata described above. The dynamic range of the reconstructed signal is adapted according to relevant metadata that may depend on the characteristics of the target display.

Published in August 2016, ETSI TS 103 433 V1.1.1 supports direct backward compatibility, i.e. leverages existing SDR distribution networks and services to leverage high quality SDRs on SDR CE devices. We are proposing a single-layer delivery solution that enables high quality HDR rendering on HDR-enabled CE devices, including rendering. Some elements of the specification are described in detail below in the description of FIG.

Display adaptation methods are proposed in this standard. This method aims to adapt the reconstructed HDR signal to a luminance level corresponding to the luminance capability of the display. For example, reconstructed HDR can be 1000 cd / m ² (nits), whereas the display used to render the image can only render up to 500 nits. One purpose of this display fit is to maximize the creative intent captured in the mapping between SDR and HDR. This display fit is re-used in tone mapping operations based on the ratio between the peak brightness of the original HDR and the peak brightness of the target SDR (fixed to 100 nits) to the maximum brightness of the presentation display. You are using the calculated metadata value. Since this display fit can be reduced to 100 nits, it is possible to provide an SDR signal that fits the SDR display. However, this prior art display adaptation method has not shown satisfactory results when used in displays with low peak brightness. First, some color shift occurs on a display with a low peak brightness, and second, on a display with a peak brightness of 100 nits, the SDR signal generated at the output of the post processor is the post processor. This is unacceptable as the post processor should act as a pass-through, unlike the input SDR image.

"Integrating HEVC Video Compression with a High Dynamic Range Video Pipeline" by Diaz R, Blinstein S, and Qu S, SMPTE Motion Image, Journ. 125, Issue 1, February 2016, pp. 14-21

Therefore, there needs to be a solution that addresses at least some of the problems of the prior art and reconstructs the HDR video to fit the display on which it will be rendered, especially those with low peak brightness. It turns out that it is said.

The following is a brief overview of the principles of the invention so that a basic understanding of some of the features of the principles of the invention can be obtained. This overview is not an extensive overview of the principles of the invention. This overview is not intended to identify important or essential elements of the principles of the invention. The following outline is merely provided in brief form as a prelude to a more detailed description given below, with some features of the principles of the invention.

The principle of the present invention is a method and device for reconstructing image data representing the original image data from decoded image data and parameters obtained from a bit stream, the method in which the parameters are processed from the original image data and A device that includes desaturation of the Luma component, desaturation desaturation of the Luma component, and correction of the chroma component, these actions are the peak brightness of the presentation display attempting to display the reconstructed image, normal. Modulated according to the peak brightness of a standard dynamic range image and the value of a single degree of modulation mod that represents the original image data or the peak brightness of the mastering display used to grade the original image data. , Methods and devices, seek to eliminate at least one of the shortcomings of prior art.

Although the peak brightness feature is used herein, this principle is not limited to peak brightness and applies to any other value that characterizes the display, such as average brightness or center brightness.

In the first aspect, the present disclosure is a method of reconstructing image data (I ₃ ) representing the original image data (I ₁ ) from decoded image data (I ₂ ) and parameters obtained from a bit stream. The parameters are processed from the original image data (I ₁ ) and the reconstructed image is a method adapted to the characteristics of the presentation display, with two chroma components according to the reduced saturation Luma component and the reconstructed Luma component. A method comprising correcting two reconstructed chroma components, wherein the chroma correction includes brightness information data (D_PL) for a presentation display, brightness information data (SDR_PL) for a normal standard dynamic range image, And according to the value of a single degree of modulation mod representing the original image data (I ₁ ) or the brightness information data (C_PL) of the mastering display used to grade the original image data. The target is a method characterized by.

In the modified form of the first aspect, the value of the degree of modulation is

に従って計算され、ここで、Ｄ＿ＰＬは、プレゼンテーション・ディスプレイの輝度情報データであり、ＳＤＲ＿ＰＬは、通常の標準ダイナミック・レンジ画像の輝度情報データであり、Ｃ＿ＰＬは、元の画像データ（Ｉ_１）または元の画像データを等級付けするために使用されるマスタリング・ディスプレイの輝度情報データであり、ｉｎｖＰＱは、逆伝達関数である。

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of the normal standard dynamic range image, and C_PL is the original image data (I ₁ ) or the original. It is the brightness information data of the mastering display used for grading the image data of, and invPQ is an inverse transfer function.

In the second variant of the first aspect, this method reduces the saturation of the Luma component according to a parameter that adjusts the reduction of saturation, and reverse-maps the reduced saturation Luma component to reconstruct the Luma component. Further including obtaining and performing compression correction, the desaturation, inverse mapping, compression correction, and chroma correction are characterized by being in response to a single modulation modding value. .. In the modified form, the modulation degree value is

に従って計算され、ここで、Ｄ＿ＰＬは、プレゼンテーション・ディスプレイの輝度情報データであり、ＳＤＲ＿ＰＬは、通常の標準ダイナミック・レンジ画像の輝度情報データであり、Ｃ＿ＰＬは、元の画像データ（Ｉ_１）または元の画像データを等級付けするために使用されるマスタリング・ディスプレイの輝度情報データである。

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of the normal standard dynamic range image, and C_PL is the original image data (I ₁ ) or the original. It is the brightness information data of the mastering display used for grading the image data of.

In the modified embodiment of the first aspect, the value of SDR_PL is 100 nits.
Saturation reduction (120) operation
_y'1 = y'+ Max (0, a x mod x u'+ b x mod x v')
Further includes (31) to obtain the saturation reduction Luma component _y'1 according to, where a and b are two control parameters for adjusting the saturation reduction, y'is the Luma component and u. ', V'is a chroma component,
Inverse mapping (121)
γ = 2.0 + 0.4 × (1-mod)
Using a reference table constructed using a gamma function modulated by the degree of modulation according to
The color correction (122) operation uses the reference table lutCC, which defines the correction applied to the chroma component at a given luma component, and the reference table lutCC
lutCC (Y) = f (Y). (1 / Y)
Derived based on the saturation gain function sgf (), which has the effect of being modulated by the degree of modulation according to, where f (Y) = 1 / (R. (sgf (1 / Y) .mod + (1-mod)). / R), where R is a constant value equal to 2 and
The format is
γ = 2.0 + 0.4 × (1-mod)
Fits the gamma function modulated by the degree of modulation according to
The combined compression correction is to calculate the parameter T based on the parameters k0, k1, k2 obtained from the parameter set SP, where the parameter T is T = k0 × U'× V'+ k1 × U'× U'. According to + k2 × V'× V', it corresponds to the value of a single degree of modulation, and when the parameter T is smaller than 1, the coupling compression correction is S = √ (1-T), U = U'. , And V = V', and when the parameter T is greater than or equal to 1, the coupling compression correction is calculated according to S = 0, U = U'/ √T, and V = V'/ √T. And include.

In a second aspect, the disclosure is a device that reconstructs image data (I ₃ ) representing the original image data (I ₁ ) from decoded image data (I ₂ ) and parameters obtained from a bit stream. The parameters are processed from the original image data (I ₁ ) and the reconstructed image is a device adapted to the characteristics of the presentation display, with two chroma components according to the desaturation reduced Luma component and the reconstructed Luma component. A device that includes a processor configured to correct for and obtain two reconstructed chroma components, where the chroma correction is used for presentation display brightness information data, normal standard dynamic range image brightness information data, and It is characterized by depending on the value of a single degree of modulation mod representing the original image data (I ₁ ) or the brightness information data of the mastering display used to grade the original image data. , Target devices.

In the modified form of the second aspect, the value of the degree of modulation is

に従って計算され、ここで、Ｄ＿ＰＬは、プレゼンテーション・ディスプレイの輝度情報データであり、ＳＤＲ＿ＰＬは、通常の標準ダイナミック・レンジ画像の輝度情報データであり、Ｃ＿ＰＬは、元の画像データ（Ｉ_１）または元の画像データを等級付けするために使用されるマスタリング・ディスプレイの輝度情報データであり、ｉｎｖＰＱは、逆伝達関数である。

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of the normal standard dynamic range image, and C_PL is the original image data (I ₁ ) or the original. It is the brightness information data of the mastering display used for grading the image data of, and invPQ is an inverse transfer function.

In the second variant of the second aspect, the processor desaturates the Luma component according to the parameter that adjusts the desaturation, and reverse maps the desaturated Luma component to obtain the reconstructed Luma component. Further configured to perform compression correction,
Saturation reduction, demapping, compression correction, and chroma correction are characterized by being in response to a single modulation modding value.

In the modified embodiment of the second aspect, the value of the degree of modulation is

に従って計算され、ここで、Ｄ＿ＰＬは、プレゼンテーション・ディスプレイの輝度情報データであり、ＳＤＲ＿ＰＬは、通常の標準ダイナミック・レンジ画像の輝度情報データであり、Ｃ＿ＰＬは、元の画像データ（Ｉ_１）または元の画像データを等級付けするために使用されるマスタリング・ディスプレイの輝度情報データである。

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of the normal standard dynamic range image, and C_PL is the original image data (I ₁ ) or the original. It is the brightness information data of the mastering display used for grading the image data of.

In a third aspect, the present disclosure comprises a computer program product comprising program code instructions that perform the steps of the method according to any one of claims 1-8 when the program is run on a computer. set to target.

In a fourth aspect, the present disclosure is non-temporary processor readable with program code instructions that perform the steps of the method according to any one of claims 1-8 when the program is run on a computer. Target the medium.

The drawings show examples of the principles of the invention.

FIG. 6 is a high-level diagram illustrating an end-to-end workflow that supports delivery of content to a display with an improved display fit mechanism according to an embodiment of the principles of the invention. FIG. 6 illustrates an end-to-end workflow that supports content generation and delivery of HDR and SDR to CE displays with prior art solutions. It is a figure which shows the exemplary embodiment of the end-to-end workflow of FIG. 2 including the improved display conformance function by the embodiment of the principle of this invention. FIG. 6 illustrates an exemplary embodiment of the end-to-end workflow of FIG. 2, which includes an improved display conformance feature according to another embodiment of the principles of the invention. It is a figure which shows the perceptual transfer function. It is a figure which shows the example of the piecewise curve (piece-wise curve) used for mapping. It is a figure which shows the example of the curve used to transform a signal and return to a linear light region. It is a figure which shows the example of the architecture of the device by the embodiment of the principle of this invention.

Similar or same elements are indicated by the same reference number.

Hereinafter, the principle of the present invention will be described in more detail with reference to the accompanying drawings showing examples of the principle of the present invention. However, the principles of the invention can also be practiced in many alternative embodiments and should not be construed as being limited to the examples described herein. Therefore, although the principles of the present invention have room for various modifications and alternatives, specific examples of the principles of the present invention are shown in the drawings for illustration purposes and will be described in detail herein. However, there is no intention to limit the principle of the present invention to a specific embodiment, and conversely, the present disclosure is based on the spirit and scope of the principle of the present invention as defined by the claims. It should be understood that it covers the equivalent form and the alternative form.

The terminology used herein is merely to describe a particular embodiment and is not intended to limit the principles of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include more than one, unless the context explicitly indicates otherwise. Further, as used herein, the terms "prepared", "prepared", "contains", and / or "contains" are the mechanisms, integers, steps, actions, elements, and / described. Or that it specifies the existence of a component and that one or more other mechanisms, integers, steps, actions, elements, components, and / or groups thereof exist or are added. Does not exclude. Furthermore, when an element is described as "responsive" or "connected" to another element, that element may be directly responsive or connected to that other element. There may or may be intervening elements. In contrast, when one element is stated to be "directly responsive" or "directly connected" to another, there is no intervening element. As used herein, the term "and / or" includes any or all combinations of one or more of the items listed in connection, and the term "/". It may be abbreviated as.

Although terms such as first and second may be used herein to describe various elements, it will be appreciated that these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, the first element can be referred to as a second element, and similarly, the second element can be referred to as a first element without deviating from the teaching of the principle of the present invention.

Although some drawings include arrows on the communication path to indicate the main direction of communication, it should be understood that communication may occur in the opposite direction of the arrows shown.

Some embodiments will be described in connection with block diagrams and flow charts, in which each block performs a circuit element, module, or one or more designated logical functions. Represents a portion of code that contains one or more executable instructions. It should also be noted that in other embodiments, the functions described in these blocks may be performed in an order other than that described. For example, two blocks shown in succession may actually be executed at substantially the same time, or in reverse order, depending on the associated function.

When referred to herein as "according to an example" or "in an example," it is the particular mechanism, structure, or feature described in connection with that embodiment of the principles of the invention. It means that it may be included in at least one embodiment. The words "according to the Examples" or "in the Examples" can be found in various parts of the specification, but not all of them necessarily refer to the same Example and are separate practices. The examples or alternative embodiments are also not necessarily mutually exclusive.

The reference numbers found in the claims are for illustration purposes only and shall not have the effect of limiting the scope of the claims.

Although not explicitly stated, examples and variations of the present invention may be used in any combination or partial combination.

In the following, upper reference numerals such as (C1, C2, C3) indicate components of the first image, and lower reference numerals such as (c1, c2, c3) indicate the dynamics of the luminance of the first image. • Shows components of another image with a dynamic range of brightness lower than the range.

The dynamic range of the brightness of an image is the ratio of the maximum value to the minimum value of the brightness value of the image. Normally, the dynamic range of the brightness of the SDR image is 500 (100 cd / m2 for 0.2 cd / m2) and 10000 (1000 cd / m2 for 0.1 cd / m2) for the HDR image.

In the following, the primed sign is, for example,

など、大文字の符号である場合には、第１の画像のガンマ圧縮成分を示し、例えば（ｙ’、ｕ’、ｖ’）など、小文字の符号である場合には、第２の画像のガンマ圧縮成分を示す。

When it is an uppercase code, it indicates the gamma compression component of the first image, and when it is a lowercase code such as (y', u', v'), it indicates the gamma of the second image. Shows the compressed component.

Although the principles of the present invention will be described for image coding / decoding / reconstruction, the principles of the present invention are also extended to coding / decoding / reconstruction of image sequences (videos). This is because each image in the sequence is sequentially encoded / decoded / reconstructed as described below.

FIG. 1 is a high-level diagram showing an end-to-end workflow that supports content delivery to a display with an improved display fit mechanism according to an embodiment of the principles of the invention. Device A is configured to implement a method of encoding an image or video stream, device B is configured to implement a method of decoding an image or video stream as described below, and device C is configured to perform. It is configured to display the decrypted image or video stream. The two remote devices A and B communicate via a distribution network NET configured to provide at least an encoded image or video stream from device A to device B.

Device A configured to implement the encoding method is a mobile device, a communication device, a game device, a tablet (or tablet computer), a computer device such as a laptop, a still image camera, a video camera. , Encoding chips, still image servers, and video servers (eg, broadcast communication servers, video-on-demand servers, or web servers).

Device B configured to implement the decryption methods described herein belongs to a set that includes mobile devices, communication devices, gaming devices, computer devices, and set-top boxes.

Devices C configured to implement the display methods described herein include computer devices such as television sets (or televisions), tablets (or tablet computers), laptops, displays, and head mounts. -Belongs to a set including a display and a decoding chip.

According to an embodiment, the network is a broadcast communication network adapted to broadcast a still image or video image from device A to a plurality of decoding devices including device B. Networks based on DVB and ATSC are examples of such broadcast communications networks. According to another embodiment, the network is a broadband network adapted to deliver still or video images from device A to multiple decoding devices including device B. Internet-based networks, GSM® networks, or TV-over-IP networks are examples of such broadband networks.

In a preferred embodiment, the device B acquires the peak luminance capability of the device C and the peak luminance characteristics of the still or video image to be displayed. Device B then combines this peak luminance information into a single value. Hereinafter, this value is referred to as a modulation degree and is abbreviated as mod. This single value is used to modulate multiple parameters used during still or video image reconstruction to correct color shifts and color mismatches for prior art display fits. Therefore, this end-to-end workflow ensures that still or video images are optimally displayed depending on the capabilities of the display and the characteristics of the content.

In this preferred embodiment, the end-to-end workflow uses a broadcast communication server as device A, a set-top box as device B, television as device C, and DVB. Use a terrestrial broadcast network. In an alternative embodiment, device B and device C are combined into one device, for example a television with integrated set-top box decoding capabilities.

In an alternative embodiment, the distribution network NET is replaced with a physical packaging medium that stores the encoded image or video stream. Physical packaging media include not only optical packaging media such as Blu-ray® discs and UHD Blu-ray, but also memory-type packaging media.

FIG. 2 illustrates an end-to-end workflow that supports content generation and delivery of HDR and SDR to CE displays according to prior art solutions as defined in ETSI Recommendation TS103 403 V1.1.1. Is.

This workflow includes a solution for single-layer delivery with relevant metadata and reconstructs image I ₃ representing the original image data I ₁ from the decoded image data I ₂ and the parameter set SP. Examples of the use of the method are shown.

Basically, this single-layer delivery solution includes a coding part and a decoding part.

In the preprocessing portion, the original image I1 is output as _an output image in the preprocessing stage 20.

およびパラメータのセットＳＰに分解し、切替えステップ２４で、元の画像Ｉ_１または出力画像Ｉ_１２のいずれをビットストリームＢに符号化する（ステップ２３）かを決定する。

And the parameter set SP, and in the switching step 24, it is determined whether the original image I ₁ or the output image I ₁₂ is encoded in the bitstream B (step 23).

In step 23, image I ₂ can be encoded with any legacy video codec, and bitstream B is transported within the existing legacy distribution network and has associated associated metadata (set of parameters SP). ) Is carried on a specific channel or embedded in the bitstream B.

In the modified form, the bitstream B with the attached metadata is stored on a storage medium such as a Blu-ray disc or a set-top box disc.

In a variant, the associated metadata attached is either transported on another particular channel or stored on a separate storage medium.

Preferably, the coded video is H.I. 265 / HEVC Codec (ITU-TH.265, ITU Telecommunication Standardization Division (October 2014) Series H: audiovisual and multidimedia systems, infrastructure of audiovistic H.265), or H. 264 / AVC (“Advanced video coding for generic audiovisual Services”, Series H: AUDIOVISUMAL AND MULTIMEDIA SYSTEMS, Recommendation ITU-TH.264, ITU-TH.264, ITU-T H.264, ITU Telecommunications Standardization Division, etc.

When the information data ID is encoded in step 23 the original image I ₁ (possibly represented by a component (C1, U', V') or Y'CbCr4: 2: 0PQ10 or HLG10 video signal). If determined, this original image I ₁ can be encoded with the HEVC Main 10 profile.

If the information data ID determines that the output image I ₁₂ is encoded in step 23, then the output image I ₁₂ can be represented as a Y'CbCr 4: 2: 0 gamma transfer characteristic (standard dynamic range) signal. , Main10 profile or any HEVC profile such as Main profile.

The information data ID can also be carried as related metadata (step 23). Decoded image in the post-processing part

を、ビットストリームＢから得（ステップ１１）、パラメータのセットＳＰを、図１で説明したように得（ステップ１０）、前処理ステージ２０の機能を逆にしたものである後処理ステージ１２で、復号画像

Was obtained from the bitstream B (step 11), the parameter set SP was obtained as described with reference to FIG. 1 (step 10), and in the post-processing stage 12, which is the reverse of the functions of the pre-processing stage 20. Decrypted image

およびパラメータのセットＳＰから画像Ｉ_３を再構成する。

And the image _I3 is reconstructed from the parameter set SP.

This single-layer delivery solution may also include optional format conformance steps 21, 22, 25, 26.

For example, in step 21 (arbitrary selection), the format of the original image I ₁ can be adapted to the specific format (C1, U', V') of the input of the preprocessing stage 20 and step 22 (arbitrary selection). ), The format of the output image I ₁₂ (c, u', v') can also be adapted to a particular output format before encoding. Decrypted image in step 25

のフォーマットを後処理ステージ１２の入力の特定のフォーマットに適合させることができ、ステップ２６で、画像Ｉ_３を目標の装置（例えばセット・トップ・ボックス、接続されているＴＶ、ＨＤＲ／ＳＤＲ対応型ＣＥデバイス、Ｂｌｕ－ｒａｙディスク・プレイヤ）の少なくとも１つの特徴に適合させ、且つ／あるいは復号画像

The format of the image I3 can be adapted to the specific format of the input of the post-processing stage 12, and in step 26, the image _I3 is converted to a target device (eg, set-top box, connected TV, HDR / SDR compatible type). A CE device, a Blu-ray disc player) and / or a decoded image adapted to at least one feature.

と画像Ｉ_３または元の画像Ｉ_１とが異なる色空間および／または色域で表現されているときには、逆色域マッピングを使用することができる。

And when the image I ₃ or the original image I ₁ is represented in a different color space and / or color gamut, reverse color gamut mapping can be used.

The above format matching steps (21, 22, 25, 26) may include color space conversion and / or color gamut mapping. RGB / YUV conversion, RGB / YUV or YUV / RGB conversion, BT. 709 / BT. 2020 or BT. 2020 / BT. Normal format conforming processes such as 709, chroma component downsampling or upsampling can be used. Note that the well-known YUV color space also refers to the well-known VCbCr of the prior art. ETSI Recommendation TS103 433 V1.1.1 Release 2016-8 provides an example of a format conformance process and reverse color gamut mapping (Annex D).

The input format matching step 21 may include adapting the bit depth of the original image I ₁ to a specific bit depth, for example 10 bits, by applying a transfer function to the original image I ₁ . For example, the PQ or HLG transfer function can be used (Recommendation ITU-R BT. 2100-0).

More specifically, the pretreatment stage 20 includes steps 200-202.

In step 200, the first component C1 of the original image I ₁ is c ₁ = TM (C1).
By mapping with, the first component c1 of the output image I ₁₂ is obtained. Here, TM is a mapping function. The mapping function TM can reduce or increase the dynamic range of the luminance of the original image I ₁ , and its inverse function can increase or decrease the dynamic range of the luminance of the image.

In step 201, the second and third components U', V'of the original image I ₁ are corrected according to the first component c ₁ , so that the second and third components u of the output image I ₁₂ are u. Derive', v'.

Chroma component correction can be maintained in control by adjusting the mapping parameters. Therefore, the color saturation and hue are also in the controlled state.

According to the embodiment of step 201, the second and third components U'and V'are divided by a scaling function β ₀ (c ₁ ) having a value determined by the first component c ₁ .

Mathematically, the second and third components u', v'are

で与えられる。

Given in.

Optionally, in step 202, the _first component c1 can be adjusted as follows to further control perceptual saturation.
c = c ₁ -max (0, a.u'+ b.v')
Here, a and b are two parameters of the parameter set SP.

By this step 202, the brightness of the output image I ₁₂ can be controlled to ensure the matching of the perceived color between the color of the output image I ₁₂ and the color of the original image I ₁ .

The set of parameters SP can include parameters relating to the mapping function TM or its inverse function ITM, the scaling function β ₀ (c ₁ ). These parameters are associated with dynamic metadata and are carried in a bitstream, such as bitstream B. The parameters a and b can also be included in the bitstream and carried.

More specifically, in the post-processing portion, in step 10, the parameter set SP is obtained.

According to the embodiment of step 10, the set of parameters SP is carried by static / dynamic metadata obtained from a particular channel or from a bitstream such as bitstream B, or in some cases to a storage medium. It will be remembered.

In step 11, the decoded image I ₂ is obtained by decoding the bitstream B, which makes the decoded image I ₂ available on the SDR or HDR capable CE display.

More specifically, the post-processing stage 12 includes steps 120-122.

In the optional step 120, the first component c of the decoded image I ₂ can be adjusted as follows.
c ₁ = c + max (0, a.u'+ b.v')
Here, a and b are two parameters of the parameter set SP.

In step 121, the first component C1 of the image I ₃ is obtained by back-mapping the first component c ₁ as follows.
C ₁ = ITM (c ₁ )

In step 122, the second and third components u', v'of the decoded image I ₂ are back-corrected according to the first component c ₁ to make the second and third components U'of the image I ₃ . , V'is derived.

According to the embodiment of step 122, the second and third components u'and v'are multiplied by a scaling function β ₀ (c ₁ ) having a value determined by the first component c ₁ .

Mathematically, the second and third components U', V are:

で与えられる。

Given in.

The end-to-end workflow of FIG. 2 further provides the display conformance feature specified in annex E of ETSI TS103 433 V1.1.1. This feature uses recalculated metadata values based on the ratio between the original HDR peak brightness, the target SDR peak brightness fixed at 100 cd / m2, and the maximum brightness of the presentation display. This display adaptation is done only in step 121. This display fit did not give satisfactory results, as mentioned in the Background Techniques section.

According to a first exemplary embodiment of the method of FIG. 2, further comprising the improved display fit function shown in the pre-processed portion of FIG. 3, the first component C1 of the original image I1 is the _first component C1.

によって元の画像Ｉ_１のＲＧＢ成分から得られる線形光輝度成分Ｌであり、第２および第３の成分Ｕ’、Ｖ’は、以下のように平方根（ＢＴ．７０９ＯＥＴＦに近い）を用いる擬似ガンマ化を元の画像Ｉ_１のＲＧＢ成分に適用することによって導出される。

Is a linear luminance component L obtained from the RGB component of the original image I ₁ , and the second and third components U'and V'are pseudogamma using a square root (close to BT.709OETF) as follows. It is derived by applying the conversion to the RGB component of the original image _I1 .

In step 200, the first component y ₁ of the output image I ₁₂ is obtained by mapping the linear light luminance component L as follows.
y ₁ = TM (L)

In step 201, the second and third components u'and _v'of the output image I ₁₂ are derived by correcting the second and third components U'and V'according to the first component y1. do.

In the post-processing portion, in step 13, the peak luminance (D_PL) parameter of the presentation display is obtained from the display device displaying the output image. Obtain the peak luminance (C_PL) parameters for content or mastering from the decoded image or from the set of parameters SP. These parameters are combined with the peak luminance (SDR_PL) of the SDR presentation display, which typically corresponds to 100 nits, to obtain the modulation modding used in the reconstruction process.

In step 120, the first component of the decoded image I ₂ can be adjusted according to the degree of modulation modding to achieve improved display fit. Linear modulation can be used as follows.
y ₁ = y + max (0, a.mod.u'+ b.mod.v')

Other types of modulation can also be used, for example gamma modulation.

In step 121, the linear light luminance component L of the image I ₃ is obtained by inversely mapping the first component c ₁ as follows.
L = ITM (y ₁ )

In step 122, the second and third components u', v'of the output image I ₂ are back-corrected according to the first component y ₁ , so that the second and third components U'of the image I ₃ are used. , V'is derived.

According to the embodiment of step 122, the second and third components u'and v'are multiplied by a scaling function β ₀ (y ₁ ) having a value determined by the first component y ₁ .

Mathematically, the two first and second components U', V'are

で与えられる。

Given in.

In step 12, the scaling function β ₀ (.) (So-called lutCC) is reconstructed (derived) from the obtained color correction parameters (for further details, recommendation ETSI TS103 433 V1.1.1, clause 7.2). See 3.3.2).

As specified in Clause 6.2.6 of TS103 433 V1.1.1, the derivation of lutCC is encoded in the HDR resolution process and is included in the parameter set SP, the saturation gain function corresponding to the color correction. sgf (1 / L) is used. This derivation is performed as follows.
lutCC (Y) = f (Y). (1 / Y), f (Y) = 1 / (R.sgf (1 / Y))
Here, R is a constant value equal to 2.

Updated f function f (Y) = 1 / (R. (sgf (1 / Y) .mod + (1-mod) / R) to achieve improved display fit
To adjust this lutCC derivation according to the modding degree modding, the resulting modulation value is equal to 1 when D_PL = SDR_PL (display is SDR) and D_PL = C_PL (content-fitted display). At some point, the resulting modulation value is invariant, and when SDR_PL <D_PL <C_PL, it is between 1 and its invariant value, so that adaptation may be required.

In step 12, the inverse mapping function ITM (so-called lutMapY) is reconstructed (derived) from the resulting mapping parameters (for further details, see Recommendation ETSI TS103 433 V1.1.1, Clause 7.2.3. See 1).

The derivation of lutMapY includes a "gamma application function". To achieve improved display fit, the gamma function is modulated by the degree of modulation as follows.
γ = 2.0 + 0.4. (1-mod)

As a result, the obtained gamma modulation value is
When the peak brightness (D_PL) of the presentation display is 100 nits (SDR_PL), it is equal to 2.4.
Equal to 2.0 when the peak brightness of the presentation display (D_PL) = the peak brightness of the content or mastering (C_PL).
When SDR_PL <D_PL <C_PL, it is guaranteed to be modulated between 2.4 and 2.0.

In step 122, the combined compression correction is performed. First, the parameter T,
T = k0 x U'x V'+ k1 x U'x U'+ k2 x V'x V'
Calculate as follows.

Then, depending on the value of T, the parameters S, U, and V are calculated as follows.
In the case of (T <1), S = √ (1-T), U = U', V = V'
In other cases, S = 0, U = U'/ √T, V = V'/ √T

The first case corresponds to the normal case. The second case is not possible in principle, but it can also occur due to quantization and compression.

To achieve improved display fit, the parameters k0, k1 and k2 are modulated by the degree of modulation and the value of T is T = k0 x mod x U'x V'+ k1 x mod x U'x U'+ k2. × mod × V'× V'
To be.

Finally, step 26 includes gamma correction. To achieve improved display fit, modify the gamma function as follows:
γ = 2.0 + 0.4. (1-mod)

The resulting gamma of this modulation is 2.4 on the SDR display, 2.0 when the peak brightness of the presentation display is the same as the peak brightness of the content, and 2.0 and 2 otherwise. .. Fits between 4.

According to a second exemplary embodiment of the method of FIG. 2 shown in the pre-processed portion of FIG. 4, further comprising an improved display conformance feature, the first component C1 of the original image I1 is the _first component C1.

によって元の画像Ｉ_１のガンマ圧縮ＲＧＢ成分から得られる成分Ｙ’であり、第２および第３の成分Ｕ’、Ｖ’は、以下のように、元の画像Ｉ_１のＲＧＢ成分にガンマ化を適用することによって得られる。

Is a component Y'obtained from the gamma-compressed RGB component of the original image I ₁ , and the second and third components U'and V'are gammaized to the RGB component of the original image I ₁ as follows. Obtained by applying.

ここで、γは、好ましくは２．４に等しいガンマ因子とすることができる。

Here, γ can be a gamma factor preferably equal to 2.4.

It should be noted that the component Y', which is a non-linear signal, is different from the linear light luminance component L.

In step 200, the _first component y'1 of the output image I ₁₂ is obtained by mapping the above component Y'as follows.
_y'1 = TM (Y')

In step 121, the reconstructed component is obtained by inversely mapping the _first component y'1 as follows.

を得る。

To get.

ここで、ＩＴＭは、マッピング関数ＴＭの逆関数である。

Here, ITM is an inverse function of the mapping function TM.

Therefore, the reconstituted component

の値は、成分Ｙ’の値のダイナミック・レンジに属する。

The value of belongs to the dynamic range of the value of component Y'.

In step 201, the first component y'1 and the reconstituted component

に従って第１および第２の成分Ｕ’、Ｖ’を補正することによって、出力画像Ｉ_１２の第２および第３の成分ｕ’、ｖ’を導出する。

By correcting the first and second components U'and V'according to the above, the second and third components u'and v'of the output image I ₁₂ are derived.

This step 201 makes it possible to control the colors of the output image I ₁₂ and ensure that they match the colors of the original image I ₁ .

Chroma component correction can be maintained in control by adjusting the mapping (reverse mapping) parameters. Therefore, the color saturation and hue are also in the controlled state. Such control is usually not possible when using nonparametric perceptual transfer functions.

According to the embodiment of step 201, the second and third components u'and v'are the components.

に対する再構成成分

Reconstruction component for

の比によって決まる値を有するスケーリング関数β_０（ｙ’_１）で割る。ここで、Ωは、元の画像Ｉ_１の原色によって決まる定数値（例えばＢＴ．２０２０では１．３に等しい）である。

Divide by the scaling function β ₀ ( _y'1 ), which has a value determined by the ratio of. Here, Ω is a constant value determined by the primary colors of the original image I ₁ (for example, equal to 1.3 in BT.2020).

On the decoding side, in step 13, the peak luminance (D_PL) parameter of the presentation display is obtained from the display device displaying the output image. The peak luminance (C_PL) parameter for content or mastering is obtained from the decoded image or from the set of parameters SP. These parameters are combined with the peak luminance (SDR_PL) of the SDR presentation display, which typically corresponds to 100 nits, to give the modding modding used in the reconstruction process as defined below.

In step 120, the first component of the decoded image I ₂ can be adjusted according to the degree of modulation modding to achieve improved display fit. Linear modulation can be used as follows.
y ₁ = y + max (0, a.mod.u'+ b.mod.v')

Other types of modulation can also be used, for example gamma modulation.

In the post-processing portion, in step 121, the component Y'of the image I ₃ is obtained by back-mapping the _first component y'1 as follows.

In step 122, the second and _third components u', v'of the decoded image I ₂ are reverse-corrected according to the _first component y'1 and the component Y'. The components U'and V'of 3 are derived.

According to the embodiment of step 122, the second and third components u'and v'are multiplied by the scaling function β ₀ ( _y'1 ).

Mathematically, the two first and second components U', V'are

で与えられる。

Given in.

The mapping function TM of FIGS. 2, 3 and 4 converts the components of the original image I ₁ into the components of the output image I ₁₂ thereby reducing (or increasing) the dynamic range of their luminance values. Based on a perceptual transfer function with the purpose of doing. Therefore, the value of the component of the output image I ₁₂ belongs to a dynamic range that is lower (or larger) than the value of the component of the original image I ₁ .

The above perceptual transfer function uses a limited set of control parameters.

FIG. 5a is a diagram showing a perceptual transfer function that can be used to map the luminance component, but a similar perceptual transfer function for mapping the Luma component can be used.

The mapping is controlled by the peak luminance parameter of the mastering display (equal to 5000 cd / m ² in FIG. 5a). Apply content-dependent signal elongation between black and white levels for better control of black and white levels. Then, as shown in FIG. 5b, the conversion signal is mapped using a piecewise curve composed of three parts. The lower section and the upper section are linear, and their steepness is determined by the shadowGain parameter and the highlightGain parameter, respectively. The intermediate section is a parabola that forms a smooth bridge between the two linear sections. The width of the crossover is determined by the midToneWidthAdjFactor parameter.

All parameters that control the mapping can be carried as metadata using, for example, the SEI message specified in JCTVC-W0133 as carrying SMPTE ST2094-20 metadata.

FIG. 5c is a diagram showing an example of the inverse of the perceptual transmission function TM (FIG. 5a), based on how the perceptual optimal video signal is based on the maximum brightness of the target legacy display, eg 100 cd / m ² . It shows whether it can be converted back to the linear optical region.

In step 10 (FIG. 1), the parameter set SP is acquired and the decoded image is obtained.

から画像Ｉ_３を再構成する。

Image I ₃ is reconstructed from.

These parameters can be obtained from metadata obtained from a bitstream, such as bitstream B.

Recommendation ETSI TS103 433 V1.1.1, Clause 6, 2016-08 provides an example of the syntax of this metadata.

The syntax of Recommendation ETSI TS103 433 v1.1.1 was written to reconstruct HDR video from SDR video, but this syntax can be any decoded image.

からの任意の画像Ｉ_３の再構成に拡張することができる。

Can be extended to the reconstruction of any image I ₃ from.

The post-processing (step 12) acts on the inverse mapping function ITM and the scaling function β ₀ (.) Derived from the dynamic metadata. This is because they are determined by the _first component c1.

According to Recommendation ETSI TS103 433 V1.1.1, the above dynamic metadata can be carried according to either so-called parameter-type mode or table-type mode.

Parameterized mode can be useful in delivery workflows whose main purpose is to provide a direct SDR backwards compatible service with very low additional payload or bandwidth specifications for carrying dynamic metadata. be. Tableed modes can be useful in workflows with low-end terminals, or when higher levels of adaptation are needed to properly represent both HDR and HDR streams.

In parameterized mode, the conveyed dynamic metadata is the luminance mapping parameter representing the inverse function ITM, ie tmInputSignalBlackLevelOffset,
tmInputSignalWhiteLevelOffset,
shadowGain,
highlightGain,
midToneWidthAdjFactor,
tmAutoFineTuning parameters.

In addition, the other dynamic metadata carried is the color correction parameters (saturationGainNumVal, saturationGainX (i), and saturationGainY (i)) used to define the function β ₀ (.) (ETSI Recommendation ETSI). TS 103 433 V1.1.1, Clauses 6.3.5 and 6.3.6).

Note that the parameters a and b can be carried / hidden, respectively, in the saturationGain function parameters as described above.

These dynamic metadata provide HEVC color volume reconstruction information (CVRI) user data registration SEI messages with syntax based on the SMPTE ST 2094-20 specification (Recommendation ETSI TS 103 433 V1.1.1 Annex A.3). Can be used and transported.

A typical dynamic metadata payload is about 25 bytes per scene.

At step 101, the CVRI SEI message is parsed to obtain mapping and color correction parameters.

In step 12, the inverse mapping function ITM (so-called lutMapY) is reconstructed (derived) from the resulting mapping parameters (for further details, see Recommendation ETSI TS103 433 V1.1.1, Clause 7.2.3. See 1).

In step 12, the scaling function β ₀ (.) (So-called lutCC) is also reconstructed (derived) from the obtained color correction parameters (for further details, recommendation ETSI TS103 433 V1.1.1, Clause 7.2. See 3.3.2).

The derivation of lutCC uses the function sgf (1 / L) corresponding to the color correction included in the parameter set SP, which is encoded by the HDR resolution process. This derivation is performed as follows.
lutCC (Y) = f (Y). (1 / Y), f (Y) = 1 / (R.sgf (1 / Y))

Updated f function f (Y) = 1 / (R. (sgf (1 / Y) .mod + (1-mod) / R) to achieve improved display fit:
To adjust this lutCC derivation according to the modding degree modding, the resulting modulation value is equal to 1 when D_PL = SDR_PL (display is SDR) and D_PL = C_PL (content-fitted display). In some cases, the resulting modulation value is invariant, otherwise it can be between 1 and its invariant value.

In table mode, the dynamic data carried is the pivot point of the piecewise curve representing the inverse mapping function ITM. For example, the dynamic metadata is luminanceMappingNumVal, which indicates the number of pivot points, luminanceMappingX , which indicates the x value of the pivot point, and luminanceMappingY, which indicates the y value of the pivot point (for further details, Recommendation ETSI TS 103 433 V1.1. 1. See Articles 6.2.7 and 6.3.7).

In addition, the other dynamic metadata carried can be the pivot point of a linear curve for each section representing the scaling function β ₀ (.). For example, the dynamic metadata is colorCorrectionNumVal, which indicates the number of pivot points, colorCorrectionX, which indicates the x value of the pivot point, and colorCorrectionY, which indicates the y value of the pivot point (for further details, recommendation ETSI TS 103 433 V1.1. 1. See Articles 6.2.8 and 6.3.8).

These dynamic metadata use HEVC color remapping information (CRI) SEI messages with syntax based on the SMPTE ST 2094-30 specification (Recommendation ETSI TS 103 433 V1.1.1, Annex A.4). Can be transported.

A typical payload is about 160 bytes per scene.

In step 102, the CRI (color remapping information) SEI message (specified in the HEVC / H.265 version published in December 2016) is parsed and a segmentally linear curve representing the inverse mapping function ITM. The pivot point of, and the pivot point of the linear curve for each section representing the scaling function β ₀ (.), And the chroma / luma injection parameters a and b are obtained.

In step 12, the inverse mapping function ITM is derived from the function of the pivot points for the linear curve for each section representing the inverse mapping function ITM (for further details, recommendation ETSI TS103 433 V1.1.1, Clause 7.2. See 3.3).

In step 12, the scaling function β ₀ (.) Is also derived from the function of the pivot points for the divisional linear curve representing the scaling function β ₀ (.) (For more details, see Recommendation ETSI TS103 433 V1.1.1. , See clause 7.2.3.4).

Note that static metadata that is also used in the post-processing stage can be carried by SEI messages. For example, the choice between parameter-type mode and table-type mode is made by the information (TSI) user data registration SEI message (payloadMode) specified in Recommendation ETSI TS103 433 V1.1.1 (Clause A.2.2). Can be transported. Static metadata, such as primary colors or the maximum display luminance of the mastering display, is carried by the Mastering Display Color Volume (MDCV) SEI message as defined in AVC, HEVC.

According to the embodiment of step 103, the information data ID is explicitly signal-communicated by the syntactic elements in the bitstream and is therefore obtained by parsing the bitstream.

For example, the above syntax elements are part of the SEI message.

According to embodiments, the information data IDs identify what processing was applied to the original image _I1 to process the parameter set SP.

According to this embodiment, the information data ID can then be used to infer how the parameters are used to reconstruct the image I ₃ (step 12).

For example, when equal to 1, the information data ID has a parameter set SP obtained by applying the preprocessing stage (step 20) to the original HDR image I ₁ , and the decoded image I ₂ is an SDR image. Indicates that.

When equal to 2, the information data ID has parameters obtained by applying the preprocessing stage (step 20) to the HDR10 bit image (input in step 20), the decoded image.

がＨＤＲ１０画像であること、およびマッピング関数ＴＭがＰＱ伝達関数であることを示す。

Indicates that is an HDR10 image and that the mapping function TM is a PQ transfer function.

When equal to 3, the information data ID has parameters obtained by applying the preprocessing stage (step 20) to the HDR10 image (input in step 20), the decoded image.

がＨＬＧ１０画像であること、およびマッピング関数ＴＭが元の画像Ｉ_１に対するＨＬＧ伝達関数であることを示す。

Indicates that is an HLG10 image and that the mapping function TM is _an HLG transfer function for the original image I1.

According to another embodiment where the information data ID is equal to 2, the modulation degree value is

であり、ここで、ｉｎｖＰＱ（Ｃ）は、ＳＴ－２０８４の数式５．１および５．２によって指定されるＰＱ ＥＯＴＦの逆関数である。この実施形態では、圧縮補正は、修正したパラメータｋ０＝ｋ１＝ｋ２＝０を使用し、飽和度低下は、修正したパラメータａ＝ｂ＝０を使用する。

Here, invPQ (C) is the inverse function of PQ EOTF specified by the formulas 5.1 and 5.2 of ST-2084. In this embodiment, the compression correction uses the modified parameter k0 = k1 = k2 = 0, and the saturation reduction uses the modified parameter a = b = 0.

According to another embodiment where the information data ID is equal to 3, the modulation degree value is

であり、ここで、ｉｎｖＨＬＧ（Ｃ）は、勧告ＩＴＵ－Ｔ Ｈ．２６５ ｖ４（２０１７年３月）の§Ｅ．３．１、表Ｅ－４、ｐ．３７８に、または等価にＡＲＩＢ ＳＴＤ－Ｂ６７に規定されるＨＬＧ ＥＯＴＦの逆関数である。この実施形態では、圧縮補正は、修正したパラメータｋ０＝ｋ１＝ｋ２＝０を使用し、飽和度低下は、修正したパラメータａ＝ｂ＝０を使用する。

And here, invHLG (C) is the recommendation ITU-T H. et al. §E. Of 265 v4 (March 2017). 3.1, Table E-4, p. It is the inverse function of HLG EOTF specified in ARIB STD-B67 in 378 or equivalently. In this embodiment, the compression correction uses the modified parameter k0 = k1 = k2 = 0, and the saturation reduction uses the modified parameter a = b = 0.

According to the embodiment of step 103, the information data ID is implicitly signal-communicated.

For example, the syntax element transfer-chartactics present in the VUI of HEVC (annex E) or AVC (annex E) usually identifies the transfer function (mapping function TM) used. Since different single-layer delivery solutions use different transfer functions (PQ, HLG, ...), the syntax element transfer-perceptualistics can be used to implicitly identify the recovery mode used.

The information data ID can also be implicitly signaled by a service defined at a higher level transport or system layer.

According to another embodiment, the peak luminance value and color space of image I ₃ can be obtained by syntactic analysis of the MDCV SEI message carried by the bit stream, and the information data ID is the peak luminance value and color. It can be inferred from the specific combination of spaces (primary colors).

In FIGS. 1 to 4, modules are functional units, and these functional units may or may not be related to distinguishable physical units. For example, these modules, or parts thereof, may be combined into a single component or circuit, or these modules, or parts thereof, may provide the functionality of a piece of software. In contrast, some modules may consist of multiple separate physical entities. Devices conforming to the principles of the invention are pure hardware, such as using dedicated hardware such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field Programmable Gate Arrays) or VLSIs (Very Large Scale Integration Circuits). It is implemented using some integrated electronic components that are implemented using hardware or embedded in a device, or a combination of hardware and software components.

FIG. 6 is a diagram illustrating an exemplary architecture of a device 60 that can be configured to implement the methods described in connection with FIGS. 1 to 4.

Device 60 includes the following elements linked by data and address bus 61:
For example, a microprocessor 62 (or CPU), which is a DSP (ie, a digital signal processor).
ROM (ie, read-only memory) 63.
RAM (ie, random access memory) 64.
An I / O interface 65 that receives data to be transmitted from an application.
And battery 66.

According to the embodiment, the battery 66 is outside the device. In each of the memories referred to herein, the word "register" as used herein corresponds to a small area (several bits) or a very large area (eg, the entire program, or a large amount of received or decoded data). there is a possibility. ROM 63 includes at least programs and parameters. The ROM 63 can store algorithms and instructions that execute the techniques according to the principles of the invention. When turned on, the CPU 62 uploads a program to the RAM 64 and executes the corresponding instruction.

The RAM 64 contains a program uploaded and executed by the CPU 62 after the device 60 is turned on in a register, input data in the register, and intermediate data in various states of the method in the register to execute the method. The other variables of are included in the register.

The embodiments described herein can be implemented, for example, as a method or process, device, software program, data stream, or signal. Even if only described in the context of a single embodiment embodiment (eg, only as a method or device), embodiments of the features described therein are performed in other embodiments (eg, programs). You can also do it. The device can be implemented, for example, with the appropriate hardware, software, and firmware. The method can be implemented in a device such as, for example, a processor, where the processor refers to processing devices in general, such as, for example, computers, microprocessors, integrated circuits, or programmable logic devices. Processors also include communication devices such as computers, mobile phones, personal digital assistants (“PDAs”), and other devices that facilitate the communication of information between end users.

According to the embodiment, the input video or the original image of the input video is obtained from the source. For example, the source is
Local memory (63 or 64), such as video memory or RAM (ie, random access memory), flash memory, ROM (ie, read-only memory), hard disk, etc.
For example, a storage interface (65) such as a large-capacity storage device, RAM, flash memory, ROM, optical disk, magnetic support, etc.
Communication interfaces (65), such as wired interfaces (eg, bus interface, wide area network interface, local area network interface) or wireless interface (such as IEEE802.11 interface, or Bluetooth® interface), as well as images. Intake circuits (eg, CCDs (ie, charge-binding elements), or CMOS (ie, sensors such as complementary metal oxide semiconductors)).
Belongs to a set containing.

According to the embodiment, a bitstream carrying metadata is sent to the destination. As an example, one or both of these bitstreams are stored in local or remote memory, such as video memory or RAM (64), hard disk. In the variant, at least one of the bitstreams is transmitted to a storage interface (65), such as a mass storage device, flash memory, ROM, optical disk, or magnetic support, and / or, for example point-to-point. It is transmitted via a communication interface (65) such as a link, a communication bus, a point-to-multipoint link, or an interface to a broadcast communication network.

According to another embodiment, the bitstream carrying the metadata is obtained from the source. For example, the bitstream is read from local memory such as video memory (64), RAM (64), ROM (63), flash memory (63), or hard disk (63). In a variant, the bitstream is received from a storage interface (65), such as a mass storage device, RAM, ROM, flash memory, optical disk, or magnetic support, and / or, for example, a point-to-point link. Received from a communication interface (65), such as a bus, point-to-multipoint link, or interface to a broadcast communication network.

According to the embodiment, the device 60 configured to carry out the method described above is
Mobile device,
Communication device,
Game device,
Tablet (or tablet computer),
Laptop,
Still image camera,
Video camera,
Coding / decoding chip,
TV set,
Set-top box,
display,
Still image servers, and video servers (eg, broadcast communication servers, video-on-demand servers, or web servers).
Belongs to a set containing.

The various processes and mechanisms described herein can be implemented in a variety of different devices or applications. Examples of such devices are encoders, decoders, postprocessors that process the output of the decoder, preprocessors that provide inputs to the encoder, video coders, video decoders, video codecs, web servers, set top boxes. , Laptops, personal computers, mobile phones, PDA, and any other device or other communication device that processes images or videos. It will be clear that this device may be mobile or installed in a mobile vehicle.

Further, the method can be carried out by instructions executed by the processor, and such instructions (and / or data values generated by the execution) can be stored in a computer-readable storage medium. A computer-readable storage medium takes the form of a computer-readable program product having computer-readable program code implemented on one or more computer-readable media running on a computer. be able to. The computer-readable storage medium used herein is considered to be a non-temporary storage medium having a unique ability to store information and a unique ability to provide the retrieval of information. Computer-readable storage media are, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or devices, or any suitable combination thereof. Can be. Below are more specific examples of computer-readable storage media to which the principles of the invention can be applied, but these are merely exemplary and exhaustive, as will be readily appreciated by those skilled in the art. Please understand that it is not a list. Specific examples are portable computer disksets, hard disks, read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM). ), Optical storage device, magnetic storage device, or any suitable combination of the above.

Instructions can form an application program that is tangibly implemented on a processor-readable medium.

Instructions can be included, for example, in hardware, firmware, software, or a combination thereof. Instructions can be seen, for example, in the operating system, separate applications, or a combination of the two. A processor can therefore have the characteristics of both a device, for example, a device configured to perform a process and a device including a processor readable medium (such as a storage device) having instructions to execute the process. In addition, processor-readable media can store data values generated by the implementation in addition to or in place of the instructions.

It will be apparent to those skilled in the art that the practice may produce various signals formatted to carry, for example, information that can be stored or transmitted. This information may include, for example, instructions for performing the method, or data generated by one of the described embodiments. For example, the signal carries the rules for writing or reading the syntax of the embodiments described in the principles of the invention as data, or the actual syntax written in the examples described in the principles of the invention. The value can be formatted to be carried as data. Such signals can be formatted, for example, as electromagnetic waves (eg, spectral portions of radio frequencies) or as baseband signals. Formatting may include, for example, encoding a data stream and modulating a carrier wave with the encoded data stream. The information carried by the signal can be, for example, analog information or digital information. The signal can be transmitted over a variety of different known wired or wireless links. The signal can be stored on a processor readable medium.

Some embodiments have been described. However, it will be understood that various modifications can be made. For example, elements of different embodiments may be combined, supplemented, modified, or removed to give rise to other embodiments. Further, the disclosed structures and processes can be substituted with other structures and processes, and the resulting embodiments perform at least substantially the same functions as the disclosed embodiments, at least substantially in the same manner. Those skilled in the art will then understand that at least substantially the same result will be achieved. Therefore, the other embodiments described above are contemplated in the present application.

Claims (14)

It is a method of reconstructing the image data (I3) representing the original image data (I1) from the decoded image data (I2) and the parameters obtained from the bit stream (101), wherein the parameters are the original image data (I). Processed from I1), the reconstructed image is a method that fits the characteristics of the presentation display.
A method comprising correcting two chroma components according to a reduced saturation Luma component and a reconstituted Luma component to obtain two reconstituted Chroma components (122).
Chroma correction (120),
Luminance information data (D_PL) of the presentation display,
Luminance information data (SDR_PL) of a normal standard dynamic range image, and luminance information data (C_PL) of a mastering display used to grade the original image data (I1) or the original image data.
A method, characterized in that it corresponds to a single modulation modding value representing. To reduce the saturation of the Luma component according to the parameters for adjusting the reduction of saturation (120),
Inverse mapping (121) of the saturated Luma component to obtain a reconstructed Luma component,
Further including performing compression corrections,
Claimed, wherein the saturation reduction (120), the inverse mapping (22), the compression correction, and the chroma correction (120) correspond to the value of the single modulation modding. Item 1. The method according to Item 1. The value of the degree of modulation is

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of a normal standard dynamic range image, and C_PL is the original image data (I1) or The method of claim 2 , which is the brightness information data of the mastering display used to grade the original image data. The method according to any one of claims 1 to 3 , wherein the value of SDR_PL is 100 nits. The saturation reduction (120) operation
y'1 = y'+ Max (0, a x mod x u'+ b x mod x v')
Further includes (31) to obtain the saturation reduction Luma component y'1 according to the above, where a and b are two control parameters for adjusting the saturation reduction, and y'is the Luma component. The method according to any one of claims 1 to 4 , wherein u'and v'are the chroma components. The reverse mapping (121)
γ = 2.0 + 0.4 × (1-mod)
The method of claim 2 , wherein the reference table is constructed using a gamma function modulated by the degree of modulation according to. The color correction (122) operation uses a reference table lutCC that defines the correction applied to the chroma component at a given luma component, said reference table lutCC.
lutCC (Y) = f (Y) · (1 / Y)
Derived based on the saturation gain function sgf (), which has the effect of being modulated by the degree of modulation according to, where f (Y) = 1 / (R · (sgf (1 / Y) · mod + (1-mod)). / R), the method according to any one of claims 1 to 6 , wherein R is a constant value equal to 2. The format is
γ = 2.0 + 0.4 × (1-mod)
The method according to any one of claims 1 to 7 , wherein the gamma function modulated according to the degree of modulation is adapted. Combined compression correction,
The parameter T is calculated based on the parameters k0, k1 and k2 obtained from the parameter set SP.
T = k0 x U'x V'+ k1 x U'x U'+ k2 x V'x V'
According to the value of the single degree of modulation according to
When the parameter T is less than 1, the combined compression correction is S = √ (1-T), U = U', and V = V'.
To calculate according to
When the parameter T is 1 or more, the combined compression correction is applied to S = 0, U = U'/ √T, and V = V'/ √T.
The method of any one of claims 1-8 , comprising calculating according to. A device that reconstructs image data (I3) representing the original image data (I1) from decoded image data (I2) and parameters obtained from the bit stream (101), wherein the parameters are the original image data (I). Processed from I1), the reconstructed image is a device that fits the characteristics of the presentation display.
A device comprising a processor configured to correct two chroma components according to a reduced saturation Luma component and a reconstructed Luma component to obtain two reconstructed Chroma components (122).
Chroma correction (120),
Luminance information data (D_PL) of the presentation display,
Luminance information data (SDR_PL) of a normal standard dynamic range image, and luminance information data (C_PL) of a mastering display used to grade the original image data (I1) or the original image data.
A device, characterized in that it corresponds to a single modulation modding value representing. The processor
The Luma component is reduced in saturation according to the parameters that adjust for the reduction in saturation (120).
The saturated Luma component was reverse-mapped (121) to obtain a reconstructed Luma component.
Further configured to perform compression correction,
Claimed, wherein the saturation reduction (120), the inverse mapping (22), the compression correction, and the chroma correction (120) correspond to the value of the single modulation modding. Item 10. The device according to item 10. The value of the degree of modulation is

Where D_PL is the brightness information data of the presentation display, SDR_PL is the brightness information data of a normal standard dynamic range image, and C_PL is the original image data (I1) or 11. The device of claim 11 , which is the brightness information data of the mastering display used to grade the original image data. A computer program comprising program code instructions that perform the steps of the method according to any one of claims 1-9 when executed on a computer . A non-temporary processor readable medium having program code instructions that perform the steps of the method according to any one of claims 1-9 when executed on a computer.

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