DISPLAY SYSTEM, DISPLAY METHOD, AND DISPLAY APPARATUS
`
`BACKGROUND
`
`1. Technical Field
`
`[0001]
`
`The present disclosure relates to a display system, a display method, and a display
`
`apparatus that convert and display luminance of a video.
`
`2. Description of the Related Art
`
`[0002]
`
`Conventionally, an image signal processing apparatus for improving a displayable
`
`luminance level
`
`is disclosed (for example,
`
`refer
`
`to Unexamined Japanese Patent
`
`Publication No. 2008-167418).
`
`SUMMARY
`
`The above-described conventional technology needs further improvement.
`
`[0003]
`
`[0004]
`
`20
`
`In one general aspect,
`
`the techniques disclosed here feature a display system
`
`including: a conversion apparatus; and a display apparatus, wherein the conversion
`
`apparatus includes: one or more memories, and circuitry which,
`
`in operation, performs:
`
`acquiring a first luminance signal indicating a first code value obtained by quantization of a
`
`luminance value of a video, the luminance of the video being included in a first luminance
`
`25
`
`range; converting the first code value into a second luminance value compatible with a
`
`second luminance range, a maximum value of
`
`the second luminance range being
`
`determined based on a luminance range of the display apparatus, the maximum value of
`
`the second luminance range being smaller than a maximum value of the first luminance
`
`range, and the maximum value of the second luminance range being larger than 100 nit;
`
`30
`
`determining a third luminance value associated with the second luminance value in
`
`advance, the third luminance value being compatible with a third luminance range with a
`
`maximum value of 100 nit; converting the second luminance value compatible with the
`1
`
`

`

`second luminance range into the third luminance value compatible with the third luminance
`
`range; determining a second code value by quantization of the determined third luminance
`
`value; converting the third luminance value compatible with the third luminance range into
`
`a third luminance signal
`
`indicating the second code value; and outputting the third
`
`luminance signal to the display apparatus, and wherein the display apparatus includes one
`
`or more memories, and circuitry which,
`
`in operation, performs: acquiring the third
`
`luminance signal and setting information indicating a display setting recommended to the
`
`display apparatus in display of the video; performing setting of the display setting of the
`
`display apparatus by using the acquired setting information; converting the second code
`
`value indicated by the acquired third luminance signal
`
`into the second luminance value
`
`compatible with the second luminance range by using the display setting of the display
`
`apparatus; and displaying the video on the display apparatus based on the second
`
`luminance value obtained by the third luminance conversion.
`
`[0005]
`
`It should be noted that these general or specific aspects may be implemented as a
`
`device, an integrated circuit, a computer program, a computer-readable recording medium
`
`such as a CD-ROM, or any selective combination of a device, an integrated circuit, a
`
`computer program, or a computer-readable recording medium.
`
`[0006]
`
`20
`
`The above-described aspect can achieve further improvement.
`
`[0007]
`
`Additional benefits and advantages of the disclosed embodiments will become
`
`apparent from the specification and drawings. The benefits and/or advantages may be
`
`individually obtained by the various embodiments and features of the specification and
`
`25
`
`drawings, which need not all be provided in order to obtain one or more of such benefits
`
`and/or advantages.
`
`[0008]
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`30
`
`FIG. 1
`
`is a diagram illustrating evolution of video techniques;
`
`FIG. 2 is a diagram illustrating a relationship among video production, delivery schemes,
`
`and display apparatus in introduction of new video representation into content;
`2
`
`

`

`FIG. 3 is a diagram illustrating a relationship among masters, delivery schemes, and
`
`display apparatusesin introducing HDR;
`
`FIG. 4A is a diagram illustrating SDR display processing within an SDR TV;
`
`FIG. 4B is a diagram illustrating the SDR display processing within the SDR TV with peak
`
`luminance of 300 nit:
`
`FIG. 5 is a diagram illustrating conversion from HDR to SDR;
`
`FIG. 6A is a diagram illustrating case 1 where an HDR disc stores only an HDR-enabled
`
`HDR signal.
`
`FIG. 6B is a diagram illustrating case 2 where an HDR disc stores an HDR-enabled HDR
`
`signal and an SDR-enabled SDR signal;
`
`FIG. 7 is a diagram illustrating conversion processing from HDR to pseudo HDR;
`
`FIG. 8A is a diagram illustrating an example of an electro-optical transfer function (EOTF)
`
`that supports each of HDR and SDR;
`
`FIG. 8B is a diagram illustrating an example of inverse EOTF that supports each of HDR
`
`and SDR:
`
`FIG. 9 is an illustrative diagram of a determination method of a code value of a luminance
`
`signal to be stored in content, and a process of restoring a luminance value from the code
`
`value during playback;
`
`FIG. 10A is a diagram illustrating one example of display processing to convert an HDR
`
`20
`
`signal and to perform HDR display within an HDR TV;
`
`FIG. 10B is a diagram illustrating one example of display processing to perform HDR
`
`display using an HDR-enabled playback apparatus and the SDR TV;
`
`FIG. 10C is a diagram illustrating one example of display processing to perform HDR
`
`display using the HDR-enabled playback apparatus and the SDR TV connected to each
`
`25
`
`other via a standardinterface;
`
`FIG. 11
`
`is a block diagram illustrating a configuration of a conversion apparatus and a
`
`display apparatus according to an exemplary embodiment;
`
`FIG. 12 is a flowchart
`
`illustrating a conversion method and a display method to be
`
`performed by the conversion apparatus and the display apparatus according to the
`
`30
`
`exemplary embodiment;
`
`FIG. 13A is a diagram illustrating first luminance conversion;
`
`FIG. 13B is a diagram illustrating another example of the first luminance conversion;
`3
`
`

`

`FIG. 14 is a diagram illustrating second luminance conversion;
`
`FIG. 15 is a flowchartillustrating detailed processing of display settings:
`
`FIG. 16 is a diagram illustrating third luminance conversion; and
`
`FIG. 17 is a diagram illustrating conversion processing from HDR to pseudo HDR.
`
`[0009]
`
`DETAILED DESCRIPTION
`
`(Underlying Knowledge Forming Basis of the Present Disclosure)
`
`The inventor of the present disclosure has found out that the following problem
`
`occurs regarding the image signal processing apparatus described in the column of
`
`"BACKGROUND ART".
`
`[0010]
`
`The image signal processing apparatus disclosed in Unexamined Japanese Patent
`
`Publication No. 2008-167418 calculates linear luminance for each pixel based on linear
`
`RGB values calculated from pixels that constitute a subject, calculates corrected linear
`
`luminance for each pixel and corrected linear RGB values of combined pixels obtained by
`
`combining a plurality of pixels that include the pixel based on the linear RGB values and
`
`the linear luminance, and then applies gamma correction to each of the corrected linear
`
`luminance and the corrected linear RGB values to calculate luminance for display and RGB
`
`20
`
`values for display. Thus, the image signal processing apparatus achieves increase in a
`
`number of displayable gradations by correcting the linear
`
`luminance based on the
`
`corrected linear RGB values.
`
`[0011]
`
`However, correction (conversion) of luminance in the image signal processing
`
`25
`
`apparatus and the like disclosed in Unexamined Japanese Patent Publication No.
`
`2008-167418 does not
`
`take into consideration a luminance conversion method for
`
`correcting (converting) luminance from a third luminance range to a second luminance
`
`range of which the luminance range is reduced.
`
`[0012]
`
`30
`
`In order to solve the above-described problem based on the above examination,
`
`the inventor of the present disclosure has examined the following improvement measure.
`
`

`

`[0013]
`
`A display system according to one aspect of the present disclosure is a display
`
`system including: a conversion apparatus; and a display apparatus, wherein the conversion
`
`apparatus includes: one or more memories, and circuitry which,
`
`in operation, performs:
`
`acquiring a first luminance signal indicating a first code value obtained by quantization of a
`
`luminance value of a video, the luminance of the video being included in a first luminance
`
`range; converting the first code value into a second luminance value compatible with a
`
`second luminance range, a maximum value of
`
`the second luminance range being
`
`determined based on a luminance range of the display apparatus, the maximum value of
`
`10
`
`the second luminance range being smaller than a maximum value of the first luminance
`
`range, and the maximum value of the second luminance range being larger than 100 nit;
`
`determining a third luminance value associated with the second luminance value in
`
`advance, the third luminance value being compatible with a third luminance range with a
`
`maximum value of 100 nit; converting the second luminance value compatible with the
`
`15
`
`second luminance range into the third luminance value compatible with the third luminance
`
`range; determining a second code value by quantization of the determined third luminance
`
`value; converting the third luminance value compatible with the third luminance range into
`
`a third luminance signal
`
`indicating the second code value; and outputting the third
`
`luminance signal to the display apparatus, and wherein the display apparatus includes one
`
`20
`
`or more memories, and circuitry which,
`
`in operation, performs: acquiring the third
`
`luminance signal and setting information indicating a display setting recommended to the
`
`display apparatus in display of the video; performing setting of the display setting of the
`
`display apparatus by using the acquired setting information; converting the second code
`
`value indicated by the acquired third luminance signal
`
`into the second luminance value
`
`25
`
`compatible with the second luminance range by using the display setting of the display
`
`apparatus; and displaying the video on the display apparatus based on the second
`
`luminance value obtained by the third luminance conversion.
`
`[0014]
`
`Since the display setting of the display apparatus is switched to the recommended
`
`30
`
`display setting and then luminance conversion is performed using the display setting, this
`
`allows the video to be displayed at the display setting suitable for the acquired HDR signal.
`
`[0015]
`
`

`

`In addition, a display method according to one aspect of the present disclosure Is a
`
`display method for displaying a video on the display apparatus of the above-described
`
`display system, the display method including: acquiring the third luminance signal and the
`
`setting information indicating the display setting recommendedto the display apparatus in
`
`display of the video; performing setting of the display setting of the display apparatus by
`
`using the acquired setting information; converting the second code value indicated by the
`
`acquired third luminance signal
`
`into the second luminance value compatible with the
`
`second luminance range by using the display setting of the display apparatus; and
`
`displaying the video on the display apparatus based on the second luminance value
`
`obtained by the converting the second code value.
`
`[0016]
`
`In addition, for example, the converting the second code value mayinclude: by
`
`using an electro-optical transfer function (EOTF) that associates the luminance value in the
`
`third luminance range with a plurality of second code values, determining the third
`
`luminance value associated with the second code value indicated by the acquired third
`
`luminance signal,
`
`the third luminance value being compatible with the third luminance
`
`range; determining the second luminance value associated with the third luminance value
`
`in advance,
`
`the second luminance value being compatible with the second luminance
`
`range; and performing third luminance conversion to convert the third luminance value
`
`20
`
`compatible with the third luminance range into the second luminance value compatible with
`
`the second luminance range.
`
`[0017]
`
`In addition, for example, performing setting of the display setting may include
`
`setting the EOTF that is set for the display apparatus as a recommended EOTF according
`
`25
`
`to the acquired setting information, and determining the third luminance value includes
`
`determining the third luminance value by using the recommended EOTF.
`
`[001 8]
`
`In addition, for example, performing setting of the display setting may include,
`
`when the EOTF that is set for the display apparatus cannot be switched, displaying a
`
`30
`
`message on the display apparatus for prompting a user to switch the EOTF that is set for
`
`the display apparatus to the recommended EOTF.
`
`

`

`[0019]
`
`In addition, for example, performing setting of the display setting may include
`
`setting a display parameterthat is set for the display apparatus as a recommendeddisplay
`
`parameter according to the acquired setting information.
`
`[0020]
`
`In addition, for example, performing setting of the display setting may include,
`
`when the display parameter that
`
`is set for the display apparatus cannot be switched,
`
`displaying a message on the display apparatus for prompting a user to switch the display
`
`parameter that is set for the display apparatus to the recommendeddisplay parameter.
`
`10
`
`[0021]
`
`In addition,
`
`for example,
`
`the performing the third luminance conversion may
`
`include: by using luminance-related information according to a display parameter indicating
`
`the display setting of the display apparatus, determining a luminance value associated with
`
`the third luminance value in advance as the second luminance value; and switching
`
`15
`
`luminance conversion processing according to the display parameter.
`
`[0022]
`
`In addition,
`
`for example,
`
`the performing the third luminance conversion may
`
`include: when the display parameter is a normal mode, performing luminance conversion to
`
`convert the second luminance value into a direct proportion value in direct proportion to the
`
`20
`
`third luminance value; and when the display parameter is a dynamic mode in which a
`
`high-luminance pixel becomes brighter and a low-luminance pixel becomes darker than
`
`pixels in the normal mode, performing luminance conversion to convert
`
`the second
`
`luminance value of the low-luminance pixel
`
`into a value lower than the direct proportion
`
`value in direct proportion to the third luminance value, and to convert the second luminance
`
`25
`
`value of the high-luminance pixel
`
`into a value higher than the direct proportion value in
`
`direct proportion to the third luminance value.
`
`[0023]
`
`In addition, for example, performing setting of the display setting may include,
`
`when the acquired setting information indicates that an acquired luminance signal is the
`
`30
`
`third luminance signal converted using the second luminance range, switching a brightness
`
`setting of the display apparatus to a setting of brightest display.
`
`

`

`[0024]
`
`In addition, a display method according to one aspect of the present disclosure Is a
`
`display methodfor displaying a video on a display apparatus, the display method including:
`
`converting a first code value obtained by quantization of a luminance value of the videointo
`
`a second luminance value compatible with a second luminance range, the luminance value
`
`of the video being included in a first luminance range, a maximum value of the second
`
`luminance range being determined based on a luminance range of the display apparatus,
`
`the maximum value of the second luminance range being smaller than a maximum value of
`
`the first luminance range, and the maximum value of the second luminance range being
`
`10
`
`larger than 100 nit; converting the second luminance value into a third luminance value
`
`compatible with a third luminance range with a maximum value of 100 nit; acquiring, by the
`
`display apparatus, a third luminance signal
`
`indicating a second code value obtained by
`
`quantization of the third luminance value; acquiring setting information indicating a display
`
`setting recommendedto the display apparatus in display of the video; performing setting of
`
`15
`
`the display setting of the display apparatus by using the acquired setting information;
`
`converting the second code value indicated by the acquired third luminance signal into the
`
`second luminance value compatible with the second luminance range by using the set
`
`display setting; and displaying the video on the display apparatus based on the second
`
`luminance value obtained by the converting the second code value.
`
`20
`
`[0025]
`
`In addition, for example, converting the second code value mayinclude: by using
`
`an electro-optical transfer function (EOTF) that associates the luminance valuein the third
`
`luminance range with a plurality of second code values, determining the third luminance
`
`value associated with the second code value indicated by the acquired third luminance
`
`25
`
`signal,
`
`the third luminance value being compatible with the third luminance range;
`
`determining the second luminance value associated with the third luminance value in
`
`advance, the second luminance value being compatible with the second luminance range;
`
`and performing third luminance conversion to convert the third luminance value compatible
`
`with the third luminance range into the second luminance value compatible with the second
`
`30
`
`luminance range.
`
`[0026]
`
`In addition, for example, performing setting of the display setting may include
`8
`
`

`

`setting the EOTF that is set for the display apparatus as a recommended EOTF according
`
`to the acquired setting information, and determining the third luminance value includes
`
`determining the third luminance value by using the recommended EOTF.
`
`[0027]
`
`In addition, for example, the performing setting of the display setting may include
`
`setting a display parameterthat is set for the display apparatus as a recommendeddisplay
`
`parameter according to the acquired setting information.
`
`[0028]
`
`In addition,
`
`for example,
`
`the performing the third luminance conversion may
`
`10
`
`include: by using luminance-related information according to a display parameter indicating
`
`the display setting of the display apparatus, determining a luminance value associated with
`
`the third luminance value in advance as the second luminance value; and switching
`
`luminance conversion processing according to the display parameter.
`
`[0029]
`
`15
`
`In addition,
`
`for example,
`
`the performing the third luminance conversion may
`
`include: when the display parameter is a normal mode, performing luminance conversion to
`
`convert the second luminance value into a direct proportion value in direct proportion to the
`
`third luminance value; and when the display parameter is a dynamic mode in which a
`
`high-luminance pixel becomes brighter and a low-luminance pixel becomes darker than
`
`20
`
`pixels in the normal mode, performing luminance conversion to convert
`
`the second
`
`luminance value of the low-luminance pixel
`
`into a value lower than the direct proportion
`
`value in direct proportion to the third luminance value, and to convert the second luminance
`
`value of the high-luminance pixel
`
`into a value higher than the direct proportion value in
`
`direct proportion to the third luminance value.
`
`25
`
`[0030]
`
`It should be noted that these general or specific aspects may be implemented as a
`
`device, an integrated circuit, a computer program, a computer-readable recording medium
`
`such as a CD-ROM, or any selective combination of a device, an integrated circuit, a
`
`computer program, or a computer-readable recording medium.
`
`30
`
`[0031]
`
`The display method and the display apparatus according to one aspect of the
`
`present disclosure will be specifically described below with reference to the accompanying
`9
`
`

`

`drawings.
`
`[0032]
`
`Exemplary embodiments described below indicate one specific example of the
`
`present disclosure. Numerical values, shapes, materials, dispositions and connection
`
`forms of the components, steps, order of the steps, and the like that are indicated in the
`
`following exemplary embodiments are one example, and do notintend to limit the present
`
`disclosure.
`
`Also,
`
`among the components described in
`
`the following exemplary
`
`embodiments, components that are not described in an independent claim which
`
`represents the highest concept are described as optional components.
`
`[0033]
`
`EXEMPLARY EMBODIMENT
`
`The present disclosure relates to an image conversion-playback method and
`
`apparatus for displaying a high dynamic range (HDR) signal, which is a high-luminance
`
`signal with a high luminance range, in a display apparatus, such as a TV, projector, tablet,
`
`and smart phone, the display apparatus supporting a standard dynamic range (SDR) signal,
`
`which is a normal luminance signal having a luminance range with a maximum luminance
`
`value of 100 nit.
`
`[0034]
`
`[1-1. Background]
`
`20
`
`First, transition of video techniques will be described with reference to FIG 1.
`
`FIG
`
`1
`
`is a diagram illustrating evolution of the video techniques.
`
`[0035]
`
`Until now, high definition of video has focused on increase in a number of display
`
`pixels. So-called 2K video is widely used, from 720 x 480-pixel Standard Definition (SD)
`
`25
`
`video to 1920 x 1080-pixel High Definition (HD) video.
`
`[0036]
`
`In recent years,
`
`introduction of so-called 4K video has started with a view toward
`
`higher definition of video,
`
`including 3840 x 1920-pixel Ultra High Definition (UHD) video
`
`and 4096 x 1920-pixel 4K video.
`
`30
`
`[0037]
`
`In addition to high resolution of video through introduction of 4K, consideration is
`
`10
`
`

`

`given to high definition of video through extension of a dynamic range, enlargement of a
`
`color gamut, and addition or improvementof a frame rate.
`
`[0038]
`
`Among those improvements, regarding the dynamic range, HDR (High Dynamic
`
`Range) attracts attention as a scheme that supports a luminance range with an extended
`
`maximum luminance value for representing bright light including specular reflection light
`
`that cannot be represented by current TV signals with brightness more similar to actual
`
`brightness while maintaining dark area gradation in conventional video.
`
`Specifically, while
`
`a scheme of the luminance range supported by conventional TV signals is referred to as
`
`SDR (Standard Dynamic Range) with the maximum luminance value of 100 nit, HDR is
`
`assumed to extend the maximum luminance value to 1,000 nit or more. Standardization
`
`of HDR is under way in organizations such as SMPTE (Society of Motion Picture &
`
`Television
`
`Engineers)
`
`and
`
`ITU-R
`
`(International
`
`Telecommunications
`
`Union
`
`Radiocommunications Sector).
`
`[0039]
`
`Assumed specific application of HDR includes broadcast, package media (such as
`
`Blu-ray (registered trademark) disc), and Internet delivery, similarly to HD and UHD.
`
`[0040]
`
`Hereinafter, in an HDR-enabled video, luminance of the video includes a luminance
`
`20
`
`value within the luminance range of HDR.
`
`A luminance signal obtained through
`
`quantization of the luminance value of the video is referred to as an HDR signal.
`
`In an
`
`SDR-enabled video,
`
`luminance of
`
`the video includes a luminance value within the
`
`luminance range of SDR.
`
`A luminance signal obtained through quantization of the
`
`luminance value of the video is referred to as an SDR signal.
`
`25
`
`[0041]
`
`[1-2. Relationship among master generation, delivery schemes, and display apparatuses]
`
`FIG. 2 is a diagram illustrating a relationship among video production, delivery
`
`schemes, and display apparatus in introduction of new video representation into content.
`
`[0042]
`
`30
`
`When new video representation (increase in a number of pixels or the like)
`
`is
`
`introduced for high definition of video, as illustrated in FIG. 2,
`
`it is necessary to (1) change
`
`a master for home entertainment use on a video production side. Accordingly,
`11
`
`it is also
`
`

`

`necessary to (2) renew the delivery schemes, such as broadcast, communication, and
`
`package media, and to (3) renew the display apparatus that displays the video, such as a
`
`TV, projector, and the like.
`
`[0043]
`
`[1-3. Relationship among masters, delivery schemes,
`
`and display apparatuses
`
`in
`
`introducing HDR]
`
`In order that a user enjoys at home content that supports new video representation
`
`(for example, high-luminance video content
`
`(HDR content)),
`
`it
`
`is necessary to newly
`
`introduce both an HDR-enabled delivery scheme and an HDR-enabled display apparatus.
`
`That is,
`
`in order to enjoy at home the content that supports the new video representation,
`
`the user needs to prepare the delivery scheme and the display apparatus that support the
`
`new video representation. This is also unavoidable when new video representation is
`
`introduced, such as when video representation is changed from SD videos to HD videos,
`
`from HD videos to three-dimensional
`
`(3D) videos, and from HD videos to ultra high
`
`definition (UHD, 4K) videos.
`
`[0044]
`
`For this reason, change to the new video representation, which needs replacement
`
`purchase of a TV which is expensive and does not allow easy replacementin terms ofsize,
`
`weight, etc., will be dependent on wider use of the display apparatus having new functions
`
`20
`
`(for example, a TV). Since a medium side and content side are also unable to make large
`
`investment at first,
`
`the new video representation comes into wide use slowly in many
`
`cases.
`
`[0045]
`
`Therefore, as illustrated in FIG 3,
`
`regarding HDR as well,
`
`it
`
`is expected that
`
`25
`
`replacement purchase of a TV (hereinafter referred to as "HDR TV")
`
`that supports
`
`HDR-enabled video display (hereinafter referred to as "HDR display") is required in order to
`
`take full advantage of original video representation of HDR.
`
`[0046]
`
`[1-4. SDR TV]
`
`30
`
`A TV (hereinafter referred to as "SDR TV")
`
`that supports only display of an
`
`SDR-enabled video (hereinafter referred to as "SDR display") normally receives an input
`
`signal with a luminance value of up to 100 nit. Accordingly, the SDR TV with display
`12
`
`

`

`capability of 100 nit is sufficient for representing the luminance value of the input signal.
`
`However, many of the SDR TVsactually have a function of playing a video with an optimal
`
`luminance value adapted to viewing environments (dark room: cinema mode, bright room:
`
`dynamic mode, etc.), and have capability of video representation of 200 nit or more. That
`
`is, such an SDR TV can display a video with up to maximum luminance of display
`
`capability (for example, 300 nit) by selecting a display mode according to the viewing
`
`environment.
`
`[0047]
`
`However, since a luminance upper limit of the SDR-scheme input signal that is
`
`input into the SDR TV is determined as 100 nit, as long as a conventional SDR-scheme
`
`input interface is used,
`
`it is difficult to use high-luminance video playback capability of the
`
`SDR TV exceeding 100 nit for playback of the HDR signal (refer to FIG. 4A and FIG. 4B).
`
`[0048]
`
`[1-5. HDR to SDR conversion]
`
`It is assumed that high-luminance video content (hereinafter referred to as "HDR
`
`content" or "HDR video")
`
`is output from the SDR TV via an HDR-enabled playback
`
`apparatus (for example, communication set top box (STB), Blu-ray device, IPTV playback
`
`apparatus), the high-luminance video content being delivered by delivery schemes such as
`
`HDR-enabled broadcast, video delivery via communication networks, or HDR-enabled
`
`20
`
`package media (for example, HDR-enabled Blu-ray disc). When the SDR TV plays the
`
`HDR content, "HDR to SDR conversion" is implemented for converting the HDR-enabled
`
`HDR signal into the SDR signal in the SDR luminance range with a maximum value of 100
`
`nit such that the SDR TV can display the video correctly. This allows the SDR TV to
`
`display the SDR video obtained by conversion from the HDR video by using the converted
`
`25
`
`SDR signal (refer to FIG. 5).
`
`[0049]
`
`However, even in this case, although the user has purchased the HDR-enabled
`
`content
`
`(for example, Blu-ray disc, HDR IPTV content) and HDR-enabled playback
`
`apparatus (for example, Blu-ray device, HDR-enabled IPTV playback apparatus), the user
`
`30
`
`can enjoy a video only in SDR video representation (SDR representation) on the SDR TV.
`
`That is, even if the HDR content and HDR-enabled playback apparatus are prepared, when
`
`there is no HDR-enabled display apparatus (for example, HDR TV) and there is only the
`13
`
`

`

`SDR TV,
`
`the user cannot view the video in HDR video representation (HDR
`
`representation).
`
`[0050]
`
`Therefore,
`
`if the user cannot prepare the HDR TV, even if the user purchases the
`
`HDR content or transmission media (playback apparatus), the user does not understand
`
`values of HDR (that is, superiority of high definition HDR over SDR). Thus, since the user
`
`does not understand the values of HDR without the HDR TV, wide use of the HDR content
`
`or HDR-enabled delivery scheme is decided depending on a speed at which HDR TVs
`
`come into wide use.
`
`[0051]
`
`[1-6. Two schemesof implementing HDR to SDR conversion]
`
`When the HDR signal is sent to a TV by using a Blu-ray disc (BD), the following
`
`two cases can be assumedasillustrated in FIG 6A and FIG 6B.
`
`FIG6A is a diagram
`
`illustrating case 1 where an HDR-enabled BD stores only an HDR-enabled HDR signal.
`
`FIG. 6B is a diagram illustrating case 2 where an HDR-enabled BD stores an HDR-enabled
`
`HDR signal and an SDR-enabled SDR signal.
`
`[0052]
`
`Asillustrated in FIG. 6A,
`
`in case 1 where the HDR TV displays a video obtained by
`
`the Blu-ray device playing a BD, the Blu-ray device outputs a luminance signal stored in
`
`20
`
`the BD to the HDR TV asit is without conversion, regardless of whether the Blu-ray device
`
`plays the HDR-enabled BD (hereinafter referred to as "HDR BD") or SDR-enabled BD
`
`(hereinafter referred to as "SDR BD"). Then, the HDR TV, which can perform display
`
`processing of both the HDR signal and the SDR signal, performs display processing in
`
`accordance with the input luminancesignal, and displays the HDR video or SDR video.
`
`25
`
`[0053]
`
`On the other hand,
`
`in case 1 where the SDR TV displays a video obtained by the
`
`Blu-ray device playing a BD, when the HDR BD is played, the Blu-ray device performs
`
`conversion processing to convert the HDR signal into the SDR signal, and then outputs the
`
`SDR signal obtained by the conversion processing to the SDR TV. Meanwhile, when the
`
`30
`
`SDR BD is played, the Blu-ray device outputs the SDR signal stored in the BD asit is to
`
`the SDR TV without conversion. Accordingly, the SDR TV displays the SDR video.
`
`14
`
`

`

`[0054]
`
`In addition, as illustrated in FIG. 6B, case 2 where the HDR TVdisplays the video
`
`obtained by the Blu-ray device playing the BD is similar to case 1.
`
`[0055]
`
`On the other hand,
`
`in case 2 where the SDR TV displays a video obtained by the
`
`Blu-ray device playing the BD, the Blu-ray device outputs the SDR signal stored in the BD
`
`as it is to the SDR TV without conversion, regardless of whether the Blu-ray device plays
`
`the HDR BD or the SDR BD.
`
`[0056]
`
`In both case 1 and case 2, even if the user purchases the HDR BD and the
`
`HDR-enabled Blu-ray device, the user can enjoy only the SDR video without the HDR TV.
`
`Therefore, the user needs the HDR TV in order to view the HDR video, and it is estimated
`
`that wide use of HDR-enabled Blu-ray device or HDR BD takestime.
`
`[0057]
`
`[1-7. HDR to pseudo HDR conversion]
`
`Accordingly,
`
`in order to accelerate wide use of HDR, it may be said to be important
`
`that commercialization of HDR content and delivery scheme can be promoted without
`
`waiting for wide use of the HDR TV.
`
`Forthis purpose, if it is possible to enable viewing of
`
`the HDR signal on the existing SDR TV, not as the SDR video but as the HDR video or
`
`20
`
`pseudo HDR video that is more similar to the HDR video than to the SDR video, the user
`
`can view the higher definition video similar to the HDR video apparently different from the
`
`SDR video, without purchasing the HDR TV.
`
`Thatis, if the user can view the pseudo HDR
`
`video on the SDR TV, only by preparing the HDR content and HDR delivery device, the
`
`user can view the video with higher definition than that of the SDR video without preparing
`
`25
`
`the HDR TV.
`
`In short, enabling viewing of the pseudo HDR video on the SDR TV can
`
`become motivation of the user to purchase the HDR content or HDR delivery device (refer
`
`to FIG7).
`
`[0058]
`
`In order to implement display of the pseudo HDR video on the SDR TYV,it is
`
`30
`
`necessary to implement "HDR to pseudo HDR conversion processing" that makes it
`
`possible to generate the pseudo HDR signal for displaying the video with maximum
`
`luminance of display capability of the SDR TV, for example, the video of