JP2017050840A - Conversion method and conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conversion method and a conversion device that can perform a further improvement.SOLUTION: In a conversion method executed in a conversion device for converting the brightness of a picture whose brightness is defined by a first dynamic range to the brightness defined by a second dynamic range displayable by a display device, the second dynamic range has a smaller maximum value and is narrower than the first dynamic range, UI (User Interface) for determining a dynamic range of a picture to be displayed on the display device is displayed on the display device connected to a conversion device (S301), an input from a user to the UI displayed on the display device is accepted (S302), in accordance with the received input, a second dynamic range is determined (S 303), and the brightness of the picture is converted to the brightness defined by the determined second dynamic range (S306).SELECTED DRAWING: Figure 20

Description

  The present disclosure relates to a conversion method and a conversion apparatus related to video luminance.

  Conventionally, an image signal processing apparatus for improving a displayable luminance level has been disclosed (see, for example, Patent Document 1).

JP 2008-167418 A

  However, in the above patent document, further improvement is required.

  A conversion method according to an aspect of the present disclosure is performed in a conversion device that converts luminance of a video whose luminance is defined by a first dynamic range into luminance defined by a second dynamic range that can be displayed by the display device. The second dynamic range has a smaller maximum value and a narrow dynamic range than the first dynamic range, and the conversion method is connected to the conversion device. The display device displays a UI (User Interface) for determining the second dynamic range, accepts an input from the user for the UI displayed on the display device, and responds to the received input The second dynamic range is determined, and the brightness of the video is defined by the determined second dynamic range. Converting the luminance is.

  According to the said aspect, the further improvement is realizable.

It is a figure for demonstrating the evolution of a video technology. It is a figure for demonstrating the relationship between video production, a delivery system, and a display apparatus when introduce | transducing new video expression to a content. It is a figure for demonstrating the relationship between the master at the time of HDR introduction, a delivery system, and a display apparatus. It is a figure for demonstrating the SDR display process in SDRTV. It is a figure for demonstrating the SDR display process in SDRTV whose peak brightness | luminance is 300 nit. It is a figure for demonstrating conversion from HDR to SDR. It is a figure for demonstrating the case 1 in which only the HDR signal corresponding to HDR is stored in the HDR disc. It is a figure for demonstrating the case 2 in which the HDR signal corresponding to HDR and the SDR signal corresponding to SDR are stored in the HDR disc. It is a figure for demonstrating the conversion process from HDR to pseudo-HDR. It is a figure for demonstrating another example when only the HDR signal corresponding to HDR is stored in BD corresponding to HDR. It is a figure shown about the example of EOTF (Electro-Optical Transfer Function) corresponding to each of HDR and SDR. It is a figure shown about the example of reverse EOTF corresponding to each of HDR and SDR. It is explanatory drawing of the determination method of the code value of the luminance signal stored in a content, and the process which decompress | restores a luminance value from a code value at the time of reproduction | regeneration. It is a figure which shows an example of the display process which converts an HDR signal and performs HDR display within HDRTV. FIG. 11 is a diagram illustrating an example of display processing for performing HDR display using an HDR-compatible playback device and SDRTV. It is a figure which shows an example of the display process which performs HDR display with the reproducing | regenerating apparatus corresponding to HDR and SDRTV mutually connected via the standard interface. It is a block diagram which shows the structure of the converter of an embodiment, and a display apparatus. It is a flowchart which shows the conversion method and display method which are performed by the converter and display apparatus of embodiment. It is a figure for demonstrating 1st brightness | luminance conversion. It is a figure for demonstrating another example of 1st brightness | luminance conversion. It is a figure for demonstrating 2nd luminance conversion. It is a flowchart which shows the detailed process of a display setting. It is a figure for demonstrating 3rd luminance conversion. It is a figure for demonstrating the conversion process from HDR to pseudo-HDR. FIG. 3 is a diagram illustrating a configuration of an HDR-compatible device that performs pseudo-HDR conversion processing and displays user guidance for a user to set DPL in the HDR-compatible device. It is a figure which shows an example of the DPL setting method of the HDR corresponding | compatible apparatus which performs HDR-> pseudo HDR conversion process. 6 is a flowchart illustrating a conversion method by the conversion apparatus according to the second embodiment. It is a figure which shows an example of a message screen. It is a figure which shows an example of an image quality setting screen. It is a figure which shows an example of a dynamic range conversion adjustment screen. It is a figure which shows another example of a dynamic range conversion adjustment screen. It is a figure which shows another example of a dynamic range conversion adjustment screen. It is a figure for demonstrating the reproducing operation of a dual disc. It is a flowchart which shows the reproduction | regeneration operation | movement of a dual disc.

(Knowledge that became the basis of the present invention)
The inventor has found that the following problems occur with respect to the image signal processing apparatus described in the “Background Art” section.

  In the image signal processing device disclosed in Patent Document 1, linear luminance is calculated for each pixel based on the linear RGB value calculated from the pixels constituting the subject, and for each pixel based on the linear RGB value and the linear luminance. The corrected linear luminance and the corrected linear RGB value of the combined pixel obtained by synthesizing a plurality of pixels including the pixel are calculated, and the corrected linear luminance and the corrected linear RGB value are respectively gamma corrected to calculate the display luminance and the display RGB value. . As described above, in the image signal processing apparatus, the number of gradations that can be displayed is increased by correcting the linear luminance based on the corrected linear RGB values.

  However, in the luminance correction (conversion) of the image signal processing device disclosed in Patent Document 1, the luminance is corrected (converted) to the second luminance range reduced from the first luminance range. The brightness conversion method was not considered.

  Based on the above examination, the present inventor examined the following improvement measures in order to solve the above-mentioned problems.

  A conversion method according to an aspect of the present disclosure is performed in a conversion device that converts luminance of a video whose luminance is defined by a first dynamic range into luminance defined by a second dynamic range that can be displayed by the display device. The second dynamic range has a smaller maximum value and a narrow dynamic range than the first dynamic range, and the conversion method is connected to the conversion device. The display device displays a UI (User Interface) for determining the second dynamic range, accepts an input from the user for the UI displayed on the display device, and responds to the received input The second dynamic range is determined, and the brightness of the video is defined by the determined second dynamic range. Converting the luminance is.

  According to this, even if the numerical value indicating the second dynamic range that can be displayed by the display device is not directly input by the user, the input to the UI displayed on the display device is accepted, so that an appropriate value can be obtained according to the input. The second dynamic range can be easily determined. For this reason, it is possible to easily appropriately convert the luminance of the video defined by the first dynamic range into the luminance of the second dynamic range that can be displayed by the display device.

  Further, a sample image in which luminance is defined in the second dynamic range determined in the determination may be displayed on the display device.

  For this reason, the user can confirm whether the 2nd dynamic range determined according to the input with respect to UI is an appropriate dynamic range with respect to a display apparatus by seeing a sample image. For this reason, the user can intuitively determine the second dynamic range appropriate for the display device by performing input to the UI.

  In the display, a slider for determining the maximum value of the second dynamic range is displayed on the display device as the UI. In the reception, a value corresponding to the position of the slider knob is received from the user. May be accepted as input.

  For this reason, the user can easily adjust the second dynamic range.

  Each of the minimum value and the maximum value of the slider may be a predetermined fixed value.

  For this reason, the processing load can be reduced.

  The minimum value of the slider may be a predetermined fixed value, and the maximum value of the slider may be a value determined based on metadata relating to the luminance of the video.

  For this reason, the user can easily adjust the second dynamic range with high accuracy.

  The metadata may be peak luminance of the video.

  The metadata may be an average luminance of the video.

  Further, the conversion device is connected to the display device via HDMI (registered trademark), the first dynamic range is HDR (High Dynamic Range), and the conversion method further includes the display Information indicating whether or not the device can display a video corresponding to HDR is acquired, and if the acquired information indicates that the display device cannot display a video corresponding to HDR, the conversion is performed. A message may be displayed on the display device.

  Further, when the acquired information indicates that the display device cannot display an image corresponding to HDR, the UI may be displayed.

  For this reason, the user can easily adjust the second dynamic range.

  Note that these general comprehensive or specific modes may be realized by a recording medium such as a device, a system, an integrated circuit, a computer program, or a computer-readable CD-ROM, and the device, system, integrated circuit, computer. You may implement | achieve with arbitrary combinations of a program or a recording medium.

  Hereinafter, a display method and a display device according to an aspect of the present disclosure will be specifically described with reference to the accompanying drawings.

  Note that each of the embodiments described below shows a specific example of the present invention. Numerical values, shapes, materials, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment 1)
The present disclosure relates to an HDR (High Dynamic Range) signal, which is a high luminance signal having a high luminance range, and a TV or projector corresponding to an SDR (Standard Dynamic Range) signal, which is a normal luminance signal having a maximum luminance value of 100 nit. The present invention relates to an image conversion / playback method and apparatus for displaying on a display device such as a tablet or a smartphone.

[1-1. background]
First, the transition of video technology will be described with reference to FIG. FIG. 1 is a diagram for explaining the evolution of video technology.

  Up to now, the main focus has been on the expansion of the number of display pixels, and so-called 2K, from 720 × 480 pixels of Standard Definition (SD) to 1920 × 1080 pixels of High Definition (HD). Video is prevalent.

  In recent years, introduction of so-called 4K video of Ultra High Definition (UHD) of 3840 × 1920 pixels or 4K of 4096 × 1920 pixels has been started with the aim of further improving the image quality of the video.

  In addition to increasing the resolution of images by introducing 4K, it is being studied to improve the image quality by expanding the dynamic range, expanding the color gamut, or adding or improving the frame rate.

  Among them, the dynamic range is the maximum brightness to express bright light such as specular reflection light that cannot be expressed by the current TV signal with more realistic brightness while maintaining the dark gradation in the conventional video. HDR (High Dynamic Range) has been attracting attention as a method corresponding to a luminance range whose value is expanded. Specifically, the method of the luminance range supported by conventional TV signals is called SDR (Standard Dynamic Range), and the maximum luminance value was 100 nits, whereas in HDR, the maximum is up to 1000 nits or more. It is assumed that the luminance value is enlarged. The standardization of HDR is ongoing in SMPTE (Society of Motion Picture & Television Engineers) and ITU-R (International Telecommunications Union Radiocommunications Sector).

  As a specific application destination of HDR, it is assumed that it is used in broadcasting, package media (Blu-ray (registered trademark) Disc, etc.), Internet distribution, and the like, like HD and UHD.

  In the following, in a video corresponding to HDR, the luminance of the video is composed of luminance values in the HDR luminance range, and a luminance signal obtained by quantizing the luminance value of the video is referred to as an HDR signal. . In a video corresponding to SDR, the luminance of the video is composed of luminance values in the luminance range of SDR, and a luminance signal obtained by quantizing the luminance value of the video is called an SDR signal.

[1-2. Relationship between master generation, distribution method, and display device]
FIG. 2 is a diagram for explaining the relationship between video production, a distribution method, and a display device when a new video expression is introduced into content.

  When introducing a new video expression (increase in the number of pixels, etc.) to improve the image quality of the video, as shown in FIG. 2, it is necessary to change the master for Home Entertainment on the video production side as shown in FIG. . Correspondingly, it is necessary to update (2) distribution methods such as broadcasting, communication, and package media, and (3) display devices such as TVs and projectors that display the video.

[1-3. Relationship between master, distribution method, and display device when introducing HDR]
In order for a user to enjoy content corresponding to a new video expression (for example, high-brightness video content (HDR content)) at home, it is necessary to newly introduce both an HDR compatible distribution method and an HDR compatible display device. . That is, in order to enjoy content corresponding to a new video expression at home, the user needs to prepare a distribution method and a display device corresponding to the new video expression. This should also be avoided when new video representations are introduced, such as SD video to HD video, HD video to 3D video, or HD video to UHD (4K) video. I could not.

  For this reason, it is expensive and is not easy to replace in terms of size, weight, etc., it is necessary to replace the TV, and the change to a new video expression depends on the spread of a display device (for example, TV) having a new function. Will do. Since neither the media side nor the content side can initially make a large investment, the spread of new video expressions often slows.

  Therefore, as shown in FIG. 3, in order to make full use of the HDR original video expression, as shown in FIG. It is expected that replacement for “HDRTV” will be required.

[1-4. SDRTV]
A TV (hereinafter referred to as “SDRTV”) that supports only video display corresponding to SDR (hereinafter referred to as “SDR display”) normally receives an input signal having a luminance value of up to 100 nits. For this reason, SDRTV is sufficient to represent the luminance value of the input signal if its display capability is 100 nits. However, SDRTV actually has a function of reproducing an image with an optimal luminance value in accordance with the viewing environment (dark room: cinema mode, bright room: dynamic mode, etc.), and the ability to express an image of 200 nits or more. There are many things that have. That is, such SDRTV can display video up to the maximum luminance (for example, 300 nits) of display capability by selecting a display mode according to the viewing environment.

  However, in the SDR input signal input to SDRTV, the luminance upper limit of the input signal is determined to be 100 nits. Therefore, as long as the SDR input interface is used as usual, a high-intensity video exceeding 100 nits that SDRTV has. It is difficult to use the reproduction capability for reproducing the HDR signal (see FIGS. 4A and 4B).

[1-5. HDR → SDR conversion]
High-brightness video content (hereinafter referred to as “HD-compatible broadcast”, “video distribution via communication network”, or “HD-compatible package media” (for example, HDR-compatible Blu-ray (registered trademark) Disc)). “HDR content” or “HDR video” is also recorded by SDRTV via an HDR-compatible playback device (for example, a communication STB (Set Top Box), Blu-ray (registered trademark) device, IPTV playback device). It is assumed that it will be output. When HDR content is played back with SDRTV, "HDR → SDR conversion" is implemented to convert HDR signals corresponding to HDR into SDR luminance range SDR signals with a maximum value of 100 nits so that images can be displayed correctly with SDRTV. To do. Thereby, SDRTV can display the SDR video obtained by converting from the HDR video using the converted SDR signal (see FIG. 5).

  However, even in this case, the user can use HDR compatible content (for example, Blu-ray (registered trademark) Disc, HDR IPTV content) and an HDR compatible playback device (for example, Blu-ray (registered trademark) device, HDR compatible IPTV playback device). ) Can be enjoyed only with SDR video expression (SDR expression). That is, even if HDR content and a playback device that supports HDR are prepared, if there is no HDR-compatible display device (for example, HDRTV) and only SDRTV is available, the video is displayed in HDR video representation (HDR representation). Cannot watch.

  Therefore, if the user cannot prepare HDRTV, even if he purchases HDR content or a transmission medium (playback apparatus), the value of HDR (that is, superiority to SDR due to high image quality of HDR) cannot be understood. Thus, since the user cannot understand the value of HDR without HDRTV, it can be said that the spread of HDR contents and HDR compatible distribution methods is determined according to the spread rate of HDRTV.

[1-6. Two methods for realizing HDR → SDR conversion]
An example of sending an HDR signal to the TV using Blu-ray (registered trademark) Disc (BD) will be described with reference to FIG. FIG. 6 is a diagram for explaining an example in which only an HDR signal corresponding to HDR is stored in an HDR-compatible BD.

  As shown in FIG. 6, in the case where an image obtained by reproducing a BD with a Blu-ray (registered trademark) device is displayed on HDRTV, even when an HDR-compatible BD (hereinafter referred to as “HDRBD”) is reproduced, Even when a compatible BD (hereinafter referred to as “SDRBD”) is reproduced, the Blu-ray (registered trademark) device outputs the luminance signal stored in the BD as it is to the HDRTV without conversion. Since HDRTV can display both HDR signals and SDR signals, it performs display processing according to the input luminance signal and displays HDR video or SDR video.

  On the other hand, when displaying an image that has been played back on a Blu-ray (registered trademark) device on SDRTV, when the HDRBD is played back, the Blu-ray (registered trademark) device converts the HDR signal into an SDR signal. The SDR signal obtained by the conversion process is output to SDRTV. When SDRBD is reproduced, the Blu-ray (registered trademark) device outputs the SDR signal stored in the BD to the SDRTV as it is without conversion. Thereby, SDRTV displays an SDR video.

  As described above, in the case of FIG. 6, even if an HDRBD and HDR-compatible Blu-ray (registered trademark) device is purchased, only SDR video can be enjoyed without HDRTV. Therefore, HDRTV is required for the user to view the HDR video, and it is expected that it will take time to spread the HDR-compatible Blu-ray (registered trademark) device or HDRBD.

[1-7. HDR → pseudo HDR conversion]
From the above, it can be said that in order to promote the spread of HDR, it is important to be able to promote the commercialization of HDR contents and distribution methods without waiting for the spread of HDRTV. For this purpose, if the HDR signal can be viewed with existing SDRTV as HDR video or pseudo HDR video closer to HDR video than SDR video, instead of SDR video, the user can view HDRTV. Even if you don't buy it, you can watch a higher quality video that is clearly different from the SDR video and is close to the HDR video. In other words, if the user can view the pseudo HDR video with SDRTV, the user can view the video with higher image quality than the SDR video only by preparing the HDR content and the HDR distribution device without preparing the HDRTV. . In short, enabling pseudo-HDR video to be viewed with SDRTV can be a user's motive for purchasing HDR content and HDR distribution equipment (see FIG. 7A).

  Instead of converting the HDR signal into an SDR video signal and displaying the SDR video on SDRTV, it is necessary to do the following to display the pseudo HDR video on SDRTV. That is, as shown in FIG. 7B, when the HDR content is played back in the configuration in which the SDRTV is connected to the HDR distribution system, the video having the maximum value of SDRTV 100 nit so that the video of the HDR content can be correctly displayed by the SDRTV. Using the signal input, a pseudo-HDR signal for displaying a video having a maximum display capability of SDRTV, for example, 200 nits or more is generated. Then, it is necessary to realize “HDR → pseudo HDR conversion processing” that enables the generated pseudo HDR signal to be sent to SDRTV. In this way, by sending the pseudo HDR signal obtained by performing “HDR → pseudo HDR conversion processing” to SDRTV, it is possible to provide SDRTV users with a higher quality picture close to that of HDR video, and the spread of HDR Can be promoted. FIG. 7B is a diagram for describing another example in which only HDR signals corresponding to HDR are stored in an HDR-compatible BD.

[1-8. About EOTF]
Here, EOTF will be described with reference to FIGS. 8A and 8B.

  FIG. 8A is a diagram illustrating an example of EOTF (Electro-Optical Transfer Function) corresponding to each of HDR and SDR.

  EOTF is generally called a gamma curve, shows the correspondence between code values and luminance values, and converts code values into luminance values. That is, EOTF is relationship information indicating a correspondence relationship between a plurality of code values and luminance values.

  FIG. 8B is a diagram illustrating an example of inverse EOTF corresponding to each of HDR and SDR.

  The inverse EOTF indicates the correspondence between the luminance value and the code value. In contrast to the EOTF, the luminance value is quantized and converted into a code value. That is, inverse EOTF is relationship information indicating a correspondence relationship between a luminance value and a plurality of code values. For example, when the luminance value of a video corresponding to HDR is expressed by a code value of a 10-bit gradation, the luminance values in the HDR luminance range up to 10,000 nit are quantized to 1024 values from 0 to 1023. Mapped to the integer value of. That is, by performing the quantization based on the inverse EOTF, the luminance value in the luminance range up to 10,000 nits (the luminance value of the video corresponding to HDR) is converted into an HDR signal that is a 10-bit code value. In an EOTF corresponding to HDR (hereinafter referred to as “HDR EOTF”) or an inverse EOTF corresponding to HDR (hereinafter referred to as “HDR inverse EOTF”), an EOTF corresponding to SDR (hereinafter referred to as “SDR EOTF”). ) Or an inverse EOTF corresponding to SDR (hereinafter referred to as “inverse EOTF of SDR”). For example, in FIG. 11A and FIG. The value (peak luminance) is 10,000 nits. That is, the HDR luminance range includes the entire SDR luminance range, and the HDR peak luminance is larger than the SDR peak luminance. The HDR luminance range is a luminance range obtained by expanding the maximum value from 100 nit, which is the maximum value of the SDR luminance range, to 10,000 nit.

  For example, HDR EOTF and HDR inverse EOTF are SMPTE 2084 standardized by the American Film and Television Engineers Association (SMPTE) as an example.

[1-9. How to use EOTF]
FIG. 9 is an explanatory diagram of a method for determining the code value of the luminance signal stored in the content and the process of restoring the luminance value from the code value during reproduction.

  The luminance signal indicating the luminance in this example is an HDR signal corresponding to HDR. The image after grading is quantized by the inverse EOTF of HDR, and the code value corresponding to the luminance value of the image is determined. Image coding or the like is performed based on this code value, and a video stream is generated. At the time of reproduction, the decoding result of the stream is converted into a linear signal by inverse quantization based on HDR EOTF, and the luminance value for each pixel is restored. Hereinafter, quantization using the inverse EOTF of HDR is referred to as “inverse HDR EOTF conversion”. Inverse quantization using HDR EOTF is referred to as “HDR EOTF conversion”. Similarly, quantization using inverse SDR EOTF is referred to as “inverse SDR EOTF conversion”. Inverse quantization using SDR EOTF is referred to as “SDR EOTF conversion”.

[1-10. Necessity of pseudo HDR]
Next, the necessity of pseudo HDR will be described with reference to FIGS. 10A to 10C.

  FIG. 10A is a diagram illustrating an example of display processing in which HDR display is performed by converting an HDR signal in HDRTV.

  As shown in FIG. 10A, when displaying an HDR video, even if the display device is HDRTV, the maximum value of the HDR luminance range (peak luminance (HPL (HDR Peak Luminance): example 1500 nit)) is displayed as it is. May not be possible. In this case, the linear signal after the inverse quantization using the HDR EOTF is adjusted to the maximum value of the luminance range of the display device (peak luminance (DPL (Display Peak Iluminance): example 750 nit)). Perform brightness conversion. Then, by inputting the video signal obtained by performing the luminance conversion to the display device, it is possible to display the HDR video that matches the maximum luminance range which is the limit of the display device.

  FIG. 10B is a diagram illustrating an example of display processing for performing HDR display using an HDR-compatible playback device and SDRTV.

  As shown in FIG. 10B, when displaying an HDR video, if the display device is SDRTV, the maximum value of the luminance range of the SDRTV to be displayed (peak luminance (DPL: 300 nits)) exceeds 100 nits. , “HDR to pseudo HDR conversion processing” in the HDR-compatible playback device (Blu-ray (registered trademark) device) in FIG. 10B, “HDR EOTF conversion” and SDRTV luminance range If “luminance conversion” using the maximum value of DPL (eg 300 nit) is performed, and the signal obtained by performing “luminance conversion” can be directly input to the “display device” of SDRTV, The same effect as HDRTV can be realized.

  However, since SDRTV has no means for directly inputting such a signal from the outside, it cannot be realized.

  FIG. 10C is a diagram illustrating an example of a display process for performing HDR display using an HDR-compatible playback device and SDRTV connected to each other via a standard interface.

  As shown in FIG. 10C, it is usually necessary to input a signal that can obtain the effect of FIG. 10B to SDRTV using an input interface (such as HDMI (registered trademark)) provided in SDRTV. In SDRTV, a signal input via an input interface passes through “SDR EOTF conversion”, “brightness conversion for each mode”, and “display device” in order, and an image that matches the maximum luminance range of the display device. Is displayed. For this reason, in HDR-compatible Blu-ray (registered trademark) equipment, a signal (pseudo-mode) that can cancel “SDR EOTF conversion” and “brightness conversion for each mode” that passes immediately after the input interface in SDRTV. HDR signal) is generated. In other words, within the HDR-compatible Blu-ray (registered trademark) device, immediately after “HDR EOTF conversion” and “luminance conversion” using SDRTV peak luminance (DPL), “inverse luminance conversion for each mode” And “inverse SDR EOTF conversion”, the same effect as when the signal immediately after “luminance conversion” is input to the “display device” (broken arrow in FIG. 10C) is realized in a pseudo manner.

[1-11. Conversion device and display device]
FIG. 11 is a block diagram illustrating configurations of the conversion device and the display device according to the embodiment. FIG. 12 is a flowchart illustrating a conversion method and a display method performed by the conversion device and the display device according to the embodiment.

  As illustrated in FIG. 11, the conversion apparatus 100 includes an HDR EOTF conversion unit 101, a luminance conversion unit 102, an inverse luminance conversion unit 103, and an inverse SDR EOTF conversion unit 104. The display device 200 includes a display setting unit 201, an SDR EOTF conversion unit 202, a luminance conversion unit 203, and a display unit 204.

  Detailed description of each component of the conversion device 100 and the display device 200 will be given in the description of the conversion method and the display method.

  Hereinafter, the HDR luminance range (0 to HPL [nit]) is referred to as a “first luminance range”. The luminance range (0 to DPL [nit]) of the display is indicated as “second luminance range”. The SDR luminance range (0 to 100 [nit]) is referred to as a “third luminance range”. The first luminance range is also referred to as “first dynamic range”, and the second luminance range is also referred to as “second dynamic range”. That is, the second dynamic range is a narrow dynamic range having a maximum value smaller than that of the first dynamic range.

[1-12. Conversion method and display method]
A conversion method performed by the conversion apparatus 100 will be described with reference to FIG. The conversion method includes steps S101 to S104 described below.

  First, the HDR EOTF conversion unit 101 of the conversion apparatus 100 acquires an HDR video that has been subjected to inverse HDR EOTF conversion. The HDR EOTF conversion unit 101 of the conversion device 100 performs HDR EOTF conversion on the HDR signal of the acquired HDR video (S101). As a result, the HDR EOTF converter 101 converts the acquired HDR signal into a linear signal indicating a luminance value. HDR EOTF is, for example, SMPTE 2084.

  Next, the luminance conversion unit 102 of the conversion device 100 performs first luminance conversion that converts the linear signal converted by the HDR EOTF conversion unit 101 using display characteristic information and content luminance information (S102). . In the first luminance conversion, the luminance value corresponding to the HDR luminance range which is the first luminance range (hereinafter referred to as “HDR luminance value”) is used as the luminance value corresponding to the luminance range of the display which is the second luminance range. (Hereinafter referred to as “display luminance value”). Details will be described later.

  From the above, the HDR EOTF converter 101 functions as an acquisition unit that acquires the HDR signal as the first luminance signal indicating the code value obtained by quantizing the luminance value of the video. The HDR EOTF conversion unit 101 and the luminance conversion unit 102 determine the code value indicated by the HDR signal acquired by the acquisition unit based on the luminance range of the display (display device 200). It functions as a conversion unit that converts a display luminance value corresponding to the luminance range of the display that is a maximum value (DPL) that is smaller than the value (HPL) and larger than 100 nits.

  More specifically, the HDR EOTF conversion unit 101 uses the acquired HDR signal and the HDR EOTF in step S101 to determine the HDR code value as the first code value indicated by the acquired HDR signal. An HDR luminance value associated with the HDR code value in the HDR EOTF is determined. The HDR signal is obtained by quantizing the luminance value of the video (content) using the HDR inverse EOTF that associates the luminance value in the HDR luminance range with a plurality of HDR code values. The code value of HDR is shown.

  In step S102, the luminance conversion unit 102 determines a display luminance value corresponding to the luminance range of the display, which is associated with the HDR luminance value in advance in the HDR luminance value determined in step S101. The first luminance conversion is performed to convert the HDR luminance value corresponding to the luminance range of the display into the display luminance value corresponding to the luminance range of the display.

  Further, the conversion device 100 includes content luminance information including at least one of a maximum luminance value (CPL: Content Peak Luminance) and an average luminance value (CAL: Content Average Luminance) of video (content) before step S102. Is acquired as information relating to the HDR signal. CPL (first maximum luminance value) is, for example, the maximum value among luminance values for a plurality of images constituting an HDR video. CAL is an average luminance value that is an average of luminance values for a plurality of images constituting an HDR video, for example.

  Moreover, the conversion apparatus 100 has acquired the display characteristic information of the display apparatus 200 from the display apparatus 200 before step S102. The display characteristic information refers to the maximum value (DPL) of luminance that can be displayed on the display device 200, the display mode of the display device 200 (see later), the input / output characteristics (EOTF corresponding to the display device), and the like. This is information indicating display characteristics.

  In addition, the conversion apparatus 100 may transmit recommended display setting information (see below, also referred to as “setting information”) to the display apparatus 200.

  Next, the reverse luminance conversion unit 103 of the conversion device 100 performs reverse luminance conversion according to the display mode of the display device 200. Accordingly, the inverse luminance conversion unit 103 performs the second luminance conversion for converting the luminance value corresponding to the luminance range of the display that is the second luminance range into the luminance value corresponding to the luminance range of the SDR that is the third luminance range. Perform (S103). Details will be described later. That is, the inverse luminance conversion unit 103 uses the display luminance value obtained in step S102 as the third luminance value corresponding to the luminance range of SDR, which is associated with the display luminance value in advance and has a maximum value of 100 nits. Luminance value corresponding to SDR (hereinafter referred to as “SDR luminance value”) The luminance value of SDR is determined, and the display luminance value corresponding to the luminance range of the display is changed to the luminance value of SDR corresponding to the luminance range of SDR. A second luminance conversion for conversion is performed.

  Then, the inverse SDR EOTF converter 104 of the conversion apparatus 100 performs pseudo SDR EOTF conversion to generate a pseudo HDR video (S104). That is, the inverse SDR EOTF converter 104 performs inverse dynamic EOTF (Electro-Optical) of SDR (Standard Dynamic Range), which is third relational information that associates a luminance value in the HDR luminance range with a plurality of third code values. The determined SDR brightness value is quantized using Transfer Function), the third code value obtained by the quantization is determined, and the SDR brightness value corresponding to the SDR brightness range is indicated as the third code value. A pseudo HDR signal is generated by converting the SDR signal as the third luminance signal. The third code value is a code value corresponding to SDR, and is hereinafter referred to as “SDR code value”. That is, the SDR signal is obtained by quantizing the luminance value of the video using the SDR inverse EOTF that associates the luminance value in the luminance range of the SDR and a plurality of SDR code values. Expressed as a code value. Then, conversion device 100 outputs the pseudo HDR signal (SDR signal) generated in step S104 to display device 200.

  The conversion apparatus 100 generates the SDR luminance value corresponding to the pseudo HDR by performing the first luminance conversion and the second luminance conversion on the HDR luminance value obtained by dequantizing the HDR signal. Then, the SDR luminance value is quantized using the SDR EOTF to generate an SDR signal corresponding to the pseudo HDR. The luminance value of SDR is a numerical value in the luminance range of 0 to 100 nit corresponding to SDR. However, since the conversion is performed based on the luminance range of the display, HDR EOTF and SDR are performed on the HDR luminance value. This is a numerical value different from the luminance value in the luminance range of 0 to 100 nit corresponding to the SDR obtained by performing the luminance conversion using the EOTF.

  Next, a display method performed by the display device 200 will be described with reference to FIG. The display method includes steps S105 to S108 described below.

  First, the display setting unit 201 of the display device 200 sets the display setting of the display device 200 using the setting information acquired from the conversion device 100 (S105). Here, the display device 200 is an SDRTV. The setting information is information indicating display settings recommended for the display device, and information indicating how to perform pseudo-HDR video EOTF and display at which setting a beautiful video can be displayed (that is, Information for switching the display setting of the display device 200 to the optimal display setting). The setting information includes, for example, a gamma curve characteristic at the time of output in the display device, a display mode such as a living mode (normal mode) and a dynamic mode, a numerical value of backlight (brightness), and the like. Further, a message that prompts the user to change the display setting of the display device 200 by a manual operation may be displayed on the display device 200 (hereinafter also referred to as “SDR display”). Details will be described later.

  In addition, the display apparatus 200 acquires SDR signal (pseudo HDR signal) and the setting information which shows the display setting recommended with respect to the display apparatus 200 in the case of a video display before step S105.

  The display device 200 may acquire the SDR signal (pseudo HDR signal) before step S106 or after step S105.

  Next, the SDR EOTF converter 202 of the display device 200 performs SDR EOTF conversion on the acquired pseudo-HDR signal (S106). That is, the SDR EOTF converter 202 performs inverse quantization on the SDR signal (pseudo HDR signal) using the SDR EOTF. Accordingly, the SDR EOTF converter 202 converts the SDR code value indicated by the SDR signal into an SDR luminance value.

  Then, the luminance conversion unit 203 of the display device 200 performs luminance conversion according to the display mode set in the display device 200. Thereby, the luminance conversion unit 203 converts the SDR luminance value corresponding to the SDR luminance range (0 to 100 [nit]) into the display luminance value corresponding to the display luminance range (0 to DPL [nit]). The third luminance conversion is performed (S107). Details will be described later.

  From the above, the display device 200 uses the setting information acquired in step S105 to obtain the third code value indicated by the acquired SDR signal (pseudo HDR signal) in step S106 and step S107. 0 to DPL [nit]).

  More specifically, in the conversion from the SDR signal (pseudo HDR signal) to the display luminance value, in step S106, using the EOTF that associates the luminance value in the luminance range of the SDR with a plurality of third code values. Then, for the SDR code value indicated by the acquired SDR signal, the SDR luminance value related to the SDR code value by the SDR EOTF is determined.

  In the conversion to the display brightness value, in step S107, the display brightness value corresponding to the brightness range of the display, which is related in advance to the determined brightness value of the SDR, is determined, and the SDR value corresponding to the SDR brightness range is determined. A third luminance conversion is performed for converting the luminance value into a display luminance value corresponding to the luminance range of the display.

  Finally, the display unit 204 of the display device 200 displays the pseudo HDR video on the display device 200 based on the converted display luminance value (S108).

[1-13. First luminance conversion]
Next, details of the first luminance conversion (HPL → DPL) in step S102 will be described with reference to FIG. 13A. FIG. 13A is a diagram for describing an example of the first luminance conversion.

  The luminance conversion unit 102 of the conversion device 100 performs first luminance conversion that converts the linear signal (HDR luminance value) obtained in step S101 using display characteristic information and content luminance information of the HDR video. . In the first luminance conversion, the HDR luminance value (input luminance value) is converted into a display luminance value (output luminance value) that does not exceed the display peak luminance (DPL). That is, the first luminance conversion converts the luminance of the HDR video into luminance defined by the second dynamic range.

  The DPL is determined using the maximum brightness and display mode of the SDR display, which is display characteristic information. The display mode is, for example, mode information such as a theater mode that is displayed dark on the SDR display and a dynamic mode that is displayed brightly. For example, when the display mode is a mode in which the maximum brightness of the SDR display is 1,500 nits and the display mode is a brightness that is 50% of the maximum brightness, the DPL is 750 nits. Here, DPL (second maximum luminance value) is the maximum luminance value that can be displayed in the display mode in which the SDR display is currently set. That is, in the first luminance conversion, DPL as the second maximum luminance value is determined using display characteristic information that is information indicating display characteristics of the SDR display.

  In the first luminance conversion, CAL and CPL in the content luminance information are used, luminance values below the CAL are the same before and after the conversion, and the luminance value is changed only for luminance values near the CPL. To do. That is, as shown in FIG. 13A, in the first luminance conversion, when the HDR luminance value is CAL or less, the HDR luminance value is not converted, and the HDR luminance value is determined as the display luminance value. When the HDR luminance value is equal to or higher than CPL, the DPL as the second maximum luminance value is determined as the display luminance value.

  In the first luminance conversion, the peak luminance (CPL) of the HDR video in the luminance information is used, and when the HDR luminance value is CPL, DPL is determined as the display luminance value.

  In the first luminance conversion, as shown in FIG. 13B, the linear signal (HDR luminance value) obtained in step S101 may be converted so as to be clipped to a value not exceeding DPL. By performing such luminance conversion, the processing in the conversion device 100 can be simplified, and the device can be reduced, the power consumption can be reduced, and the processing speed can be increased. FIG. 13B is a diagram for describing another example of the first luminance conversion.

[1-14. Second luminance conversion]
Next, details of the second luminance conversion (DPL → 100 [nit]) in step S103 will be described with reference to FIG. FIG. 14 is a diagram for describing the second luminance conversion.

  The reverse luminance conversion unit 103 of the conversion device 100 performs reverse luminance conversion corresponding to the display mode on the display luminance value in the display luminance range (0 to DPL [nit]) converted by the first luminance conversion in step S102. Apply. In the reverse luminance conversion, when the luminance conversion processing (step S107) corresponding to the display mode by the SDR display is performed, the display luminance value of the display luminance range (0 to DPL [nit]) after the processing of step S102 is acquired. This is a process for making it possible. That is, the second luminance conversion is an inverse luminance conversion of the third luminance conversion.

  With the above processing, the second luminance conversion is performed by converting the display luminance value (input luminance value) of the display luminance range which is the second luminance range into the SDR luminance value (output luminance) of the SDR luminance range which is the third luminance range. Value).

  In the second luminance conversion, the conversion formula is switched depending on the display mode of the SDR display. For example, when the display mode of the SDR display is the normal mode, the luminance is converted to a directly proportional value that is directly proportional to the display luminance value. In the second luminance conversion, when the display mode of the SDR display is a dynamic mode in which a high luminance pixel is brighter and a low luminance pixel is darker than in the normal mode, the inverse function is used to obtain the low luminance pixel. The luminance value of the SDR is converted to a value higher than the direct proportional value that is directly proportional to the display luminance value, and the luminance value of the SDR of the high luminance pixel is converted to a value lower than the direct proportional value that is directly proportional to the display luminance value. That is, in the second luminance conversion, the display luminance value determined in step S102 is related to the display luminance value using luminance relationship information corresponding to the display characteristic information that is information indicating the display characteristic of the SDR display. The brightness value is determined as the brightness value of the SDR, and the brightness conversion process is switched according to the display characteristic information. Here, the luminance-related information according to the display characteristic information includes, for example, a display luminance value (input luminance value) determined for each display parameter (display mode) of the SDR display as shown in FIG. This is information relating brightness values (output brightness values).

[1-15. Display settings]
Next, details of the display setting in step S105 will be described with reference to FIG. FIG. 15 is a flowchart showing detailed processing for display setting.

  The display setting unit 201 of the SDR display performs the following steps S201 to S208 in step S105.

  First, the display setting unit 201 uses the setting information to determine whether the EOTF set for the SDR display (EOF for SDR display) matches the EOTF assumed when the pseudo HDR video (SDR signal) is generated. Determine (S201).

  If the display setting unit 201 determines that the EOTF set in the SDR display is different from the EOTF indicated by the setting information (EOTF matching the pseudo HDR video) (Yes in S201), the display setting unit 201 sets the EOTF for the SDR display in the system. It is determined whether switching is possible on the side (S202).

  If the display setting unit 201 determines that switching is possible, the setting information is used to switch the SDR display EOTF to an appropriate EOTF (S203).

  From step S201 to step S203, in the display setting setting (S105), the EOTF set in the SDR display is set to the recommended EOTF corresponding to the acquired setting information. Accordingly, in step S106 performed after step S105, the luminance value of SDR can be determined using the recommended EOTF.

  If it is determined that switching is not possible on the system side (No in S202), a message prompting the user to change the EOTF manually is displayed on the screen (S204). For example, a message “Please set the display gamma to 2.4” is displayed on the screen. That is, if the EOTF set for the SDR display cannot be switched in the display setting setting (S105), the display setting unit 201 switches the EOTF set for the SDR display (EOF for SDR display) to the recommended EOTF. A message for prompting the user to do so is displayed on the SDR display.

  Next, the pseudo-HDR video (SDR signal) is displayed on the SDR display, but it is determined whether the display parameters of the SDR display match the setting information using the setting information before display (S205).

  If the display setting unit 201 determines that the display parameter set in the SDR display is different from the setting information (Yes in S205), the display setting unit 201 determines whether the display parameter of the SDR display can be switched (S206). .

  When the display setting unit 201 determines that the display parameter of the SDR display can be switched (Yes in S206), the display setting unit 201 switches the display parameter of the SDR display according to the setting information (S207).

  From step S204 to step S207, in the display setting setting (S105), the display parameter set in the SDR display is set to the recommended display parameter corresponding to the acquired setting information.

  If it is determined that switching is not possible on the system side (No in S206), a message prompting the user to change the display parameters set in the SDR display by manual operation is displayed on the screen (S208). For example, a message “Please set the display mode to dynamic mode and maximize the backlight” is displayed on the screen. That is, in the setting (S105), when the display parameter set in the SDR display cannot be switched, a message for prompting the user to switch the display parameter set in the SDR display to the recommended display parameter is displayed. To display.

[1-16. Third luminance conversion]
Next, details of the third luminance conversion (100 → DPL [nit]) in step S107 will be described with reference to FIG. FIG. 16 is a diagram for describing the third luminance conversion.

  The luminance conversion unit 203 of the display device 200 converts the SDR luminance value in the SDR luminance range (0 to 100 [nit]) into (0 to DPL [nit]) according to the display mode set in step S105. . This processing is performed so as to be an inverse function of inverse luminance conversion for each mode in S103.

  In the third luminance conversion, the conversion formula is switched depending on the display mode of the SDR display. For example, when the display mode of the SDR display is the normal mode (that is, when the set display parameter is a parameter corresponding to the normal mode), the display luminance value is converted into a direct proportional value that is directly proportional to the luminance value of the SDR. . In the third luminance conversion, when the display mode of the SDR display is the dynamic mode in which the high luminance pixel is brighter and the low luminance pixel is darker than the normal mode, the display luminance value of the low luminance pixel is SDR. The luminance value of the display luminance value of the high luminance pixel is converted to a value that is higher than the directly proportional value that is directly proportional to the luminance value of the SDR, to a value lower than the directly proportional value that is directly proportional to the luminance value. That is, in the third luminance conversion, for the luminance value of the SDR determined in step S106, luminance related in advance to the luminance value of the SDR using luminance relationship information corresponding to the display parameter indicating the display setting of the SDR display. The value is determined as the display luminance value, and the luminance conversion processing is switched according to the display parameter. Here, the brightness-related information according to the display parameter is, for example, as shown in FIG. 16, the SDR brightness value (input brightness value) determined for each display parameter (display mode) of the SDR display, and the display brightness. This is information that relates values (output luminance values).

[1-17. Effect]
A normal SDRTV has an input signal of 100 nits, but has an ability to express an image of 200 nits or more according to the viewing environment (dark room: cinema mode, bright room: dynamic mode, etc.). However, since the upper limit of luminance of the input signal to SDRTV was determined to be 100 nits, it was not possible to directly use that capability.

  When displaying HDR video in SDRTV, using the fact that the peak brightness of SDRTV to be displayed exceeds 100 nits (usually 200 nits or more), the HDR video is not converted to SDR video of 100 nits or less, but luminance exceeding 100 nits. “HDR → pseudo HDR conversion processing” is performed so as to maintain the gradation of the range to some extent. For this reason, it can be displayed on SDRTV as a pseudo HDR video close to the original HDR.

  When this “HDR → pseudo HDR conversion processing” technology is applied to Blu-ray (registered trademark), as shown in FIG. 17, only the HDR signal is stored in the HDR disk, and Blu-ray (registered trademark) equipment is stored. When the SDRTV is connected to the Blu-ray (registered trademark), the Blu-ray (registered trademark) device performs “HDR → pseudo HDR conversion processing”, converts the HDR signal into a pseudo HDR signal, and sends the pseudo HDR signal to the SDRTV. Thereby, SDRTV can display a video having a pseudo HDR effect by converting the received pseudo HDR signal into a luminance value. In this way, even if there is no HDR-compatible TV, if HDR-compatible BD and HDR-compatible Blu-ray (registered trademark) equipment are prepared, pseudo HDR video with higher image quality than SDR video can be obtained even with SDRTV. Can be displayed.

  Therefore, although it is considered that an HDR compatible TV is necessary to view the HDR video, the pseudo HDR video that can realize the HDR effect can be viewed with the existing SDRTV. Thereby, the spread of HDR-compatible Blu-ray (registered trademark) can be expected.

  An HDR signal sent by broadcasting, package media such as Blu-ray (registered trademark), or Internet delivery such as OTT is converted into a pseudo HDR signal by performing HDR-pseudo HDR conversion processing. As a result, it is possible to display the HDR signal as a pseudo HDR video with the existing SDRTV.

(Embodiment 2)
In the conversion device 100 according to the first embodiment, the display characteristic information of the display device 200 is acquired from the display device 200, and the first luminance conversion is performed based on the display peak luminance (DPL) of the display device 200 obtained from the display characteristic information. However, it is not limited to this. That is, the conversion apparatus does not need to acquire DPL from the display apparatus 200, for example, may acquire DPL of the display apparatus 200 by a user's input.

  Next, a second embodiment will be described.

  In general, the user does not know the concept of HDR, how an HDR signal looks on a non-HDR compatible TV (SDRTV), and how a pseudo HDR signal looks on a non-HDR compatible TV (SDRTV). Have difficulty. That is, it is difficult to determine whether a user is an SDR video or an HDR video by viewing the video displayed on the TV.

  In addition, the type of non-HDR compatible TV owned by the user varies depending on the user, and the performance (maximum luminance, etc.) also varies. There is a high possibility that the user does not grasp the type of non-HDR compatible TV and its performance. Further, some non-HDR compatible TVs do not hold information indicating the maximum luminance that can be displayed by the non-HDR compatible TV, or do not have means for transmitting the information to the HDR compatible player.

  In such a situation, the user needs to appropriately set the DPL of the display device in order to perform appropriate pseudo-HDR conversion in the HDR-compatible Blu-ray (registered trademark) device or HDR distribution device. That is, in the present embodiment, a conversion method in the case of causing a non-HDR compatible TV to output a pseudo HDR signal obtained by performing pseudo HDR conversion of an HDR signal to a Blu-ray (registered trademark) device or an HDR distribution device. explain. The conversion method includes a simple setting method for causing a Blu-ray (registered trademark) device or an HDR distribution device to perform an appropriate pseudo-HDR conversion according to the display capability of the output destination non-HDR compatible TV.

  Next, a conversion device and a conversion method according to Embodiment 2 will be described.

[2-1. Configuration of conversion device]
FIG. 18 is a diagram illustrating a configuration of an HDR-compatible device that performs pseudo-HDR conversion processing and displays user guidance for the user to set DPL in the HDR-compatible device.

  As illustrated in FIG. 18, the conversion device 110 includes a UI display unit 111, an input reception unit 112, a determination unit 113, and a conversion unit 114. Each of the UI display unit 111, the input reception unit 112, the determination unit 113, and the conversion unit 114 is realized by, for example, a microcomputer, a processor, or a dedicated circuit. That is, each processing unit constituting the conversion device 110 may be realized by software or hardware.

  The UI display unit 111 causes a display device connected to the conversion device 110 to display a UI for determining a dynamic range of an image to be displayed on the display device. Specifically, the UI display unit 111 outputs UI data for displaying the UI on the display device to the display device via, for example, HDMI (registered trademark).

  The input receiving unit 112 receives an input from the user with respect to the UI displayed on the display device. Specifically, the input receiving unit 112 receives, for example, an input signal transmitted from a remote controller when a remote controller (not shown) is operated by a user via an infrared communication interface. A mobile terminal such as a smartphone or a tablet terminal may be used instead of the remote control.

  The determination unit 113 determines a second dynamic range that has a smaller maximum value and a narrow dynamic range than the first dynamic range, according to the input received by the input reception unit 112.

  The conversion unit 114 converts the luminance of the video into luminance defined by the determined second dynamic range.

  Note that the HDR-compatible device having the conversion device 110 is connected to a non-HDR compatible TV such as UHDTV or HDTV via HDMI (registered trademark). When the HDR compatible device detects the start of the HDR → pseudo HDR conversion process in the conversion device 110, “The disc is an HDR compatible disc. Since your TV is a non-HDR compatible TV, it is not an HDR video but an Ultra HD Blu. -Ray (registered trademark) device may play back the video that has been subjected to the HDR → pseudo HDR conversion process. Please make settings for the conversion process. " That is, the conversion device 110 acquires information indicating whether or not the TV (display device) can display a video corresponding to HDR, and the acquired information indicates that the TV cannot display a video corresponding to HDR. In this case, a message for performing the HDR → pseudo HDR conversion process may be displayed on the TV.

  Next, the DPL setting process performed before the HDR → pseudo HDR conversion process is described with reference to FIG.

  FIG. 19 is a diagram illustrating an example of a DPL setting method for an HDR-compatible device that executes HDR → pseudo HDR conversion processing.

  Even when the user does not know the DPL value of the non-HDR compatible TV, the user can recognize the brightness and resolution of the non-HDR compatible TV on which the pseudo HDR signal is displayed. Therefore, if the user can adjust the DPL used for the HDR → pseudo HDR conversion process while watching the sample image displayed on the non-HDR compatible TV, the chart picture or the HDR video is appropriately displayed based on the DPL value. Value can be set. For this purpose, for example, an HDR-compatible device having the conversion device 110 may display a UI for determining a DPL value on a non-HDR compatible TV together with a sample image. That is, the UI display unit 111 of the conversion apparatus 110 may display a sample image whose luminance is defined in the second dynamic range determined by the determination unit 113 on the non-HDR compatible TV.

  Note that the UI display unit 111 of the conversion device 110 may display a UI when the information acquired from the TV indicates that the TV is not capable of displaying a video corresponding to HDR. That is, in this case, the display unit 111 of the conversion device 110 may automatically transition to a UI display screen. For this reason, the user can adjust the second dynamic range, and can cause the conversion apparatus to appropriately convert the dynamic range.

  Here, the UI is, for example, a slider for determining DPL which is the maximum value of the second dynamic range in the conversion device 110. A value corresponding to the position of the slider knob is accepted as an input value from the user. For this reason, the user can easily adjust the maximum value of the second dynamic range.

  For this reason, the sample image in which the brightness is defined in the second dynamic range determined according to the position of the slider knob is displayed on the non-HDR compatible TV. The sample image is, for example, an image showing a chart for adjusting luminance, an image having a wide range of luminance distribution in the content, or the like.

  The minimum value of the slider is a predetermined fixed value, for example, 200 nit. That is, when the slider knob is positioned at the leftmost position of the slider, DPL is set to 200 nit, for example.

  The maximum value of the slider is a predetermined fixed value, for example, 700 nit. That is, when the slider knob is positioned on the rightmost side of the slider, DPL is set to 700 nit, for example. Thus, since the minimum value and the maximum value of the slider are fixed values, the processing load can be reduced.

  The maximum value of the slider may be a value determined based on metadata related to the brightness of the HDR content video. That is, when the slider knob is positioned on the rightmost side of the slider, the DPL is set to a value determined based on, for example, metadata relating to the luminance of the video. Here, the metadata relating to the luminance of the video may be, for example, MaxCLL (Maximum Content Light Level) or MaxFALL (Maximum Frame-Average Light Level). Thus, since the maximum value of the slider is determined using MaxCLL or MaxFALL, the second dynamic range can be adjusted with high accuracy.

  MaxCLL is a value indicating the maximum luminance of a pixel in all frames in the content. That is, MaxCLL is the peak luminance of the video. MaxFALL is a value indicating the maximum value of the average luminance in the frame in all frames in the content. That is, MaxFALL is the average luminance of the video.

[2-2. Operation]
Next, operation | movement of the converter 110 is demonstrated using FIG.

  FIG. 20 is a flowchart illustrating a conversion method by the conversion apparatus according to the second embodiment.

  The UI display unit 111 of the conversion device 110 displays a UI for determining the maximum value (DPL) of the second dynamic range on the TV (S301). As described above, the timing for displaying the UI may be when the conversion apparatus 110 determines that the content to be reproduced is HDR content and the connected TV is a non-HDR compatible TV.

  At this time, a message screen 120 as shown in FIG. 21 is displayed on the non-HDR compatible TV, and the user performs an operation to display a UI according to the message screen 120 displayed on the non-HDR compatible TV. It may be time. FIG. 21 is a diagram illustrating an example of a message screen.

  On the message screen 120, for example, an image quality setting button 121 and a cancel button 122 are displayed together with a message. If the image quality setting button 121 is selected and determined by the user, the screen transitions to the next image quality setting screen 130. If the cancel button 122 is selected and determined by the user, the reproduction processing of the HDR compatible disc is stopped, and the home screen (not shown) is returned.

  The conversion device 110 transitions to an image quality setting screen 130 as shown in FIG. 22, for example, when the “image quality setting” button 121 on the message screen 120 is selected and determined by an input to the user's remote control or the like. FIG. 22 is a diagram illustrating an example of the image quality setting screen.

  On the image quality setting screen 130, a dynamic range conversion adjustment button 131 for transitioning to a conversion adjustment screen 140 on which a UI for setting DPL is displayed. That is, the image quality setting screen 130 is a setting menu of the conversion device 110, and is an example of a guide screen to a menu for setting DPL. In addition, the image quality setting screen 130 may include buttons for transitioning to a screen for performing resolution adjustment, noise reduction, and brightness / color adjustment, and buttons for returning the image quality setting to the standard. Good.

  When the dynamic range conversion adjustment button 131 is selected and determined on the image quality setting screen 130, the conversion device 110 transitions to a dynamic range conversion adjustment screen 140 as shown in FIG. FIG. 23 is a diagram illustrating an example of a dynamic range conversion adjustment screen.

  On the dynamic range conversion adjustment screen 140, the slider 141 as a UI for setting the maximum value (DPL) of the second dynamic range, the message 142 explaining the dynamic range conversion adjustment, and the slider 141 are moved. A message 143 for explaining the effect of the time, a sample image 144, an enter button 145, and an undo button 146 are displayed. Thus, the UI is displayed on the TV by displaying the dynamic range conversion adjustment screen 140. That is, the dynamic range conversion adjustment screen 140 is a setting menu for the conversion device 110 and is a menu screen for setting DPL. In the example of FIG. 23, the dynamic range conversion adjustment screen 140 causes the user to set an appropriate DPL value by comparing brightening with a dynamic range feeling.

  Further, instead of the dynamic range conversion adjustment screen 140 shown in FIG. 23, a dynamic range conversion adjustment screen 150 shown in FIG. 24 may be displayed. FIG. 24 is a diagram illustrating another example of the dynamic range conversion adjustment screen.

  Instead of the message 143 of the dynamic range conversion adjustment screen 140, the dynamic range conversion adjustment screen 150 displays a message 151 that prompts the user to confirm whether the brightness setting of the non-HDR compatible TV is an appropriate setting. In general, if the display device is in an appropriate display mode and is not set to be set to output the maximum luminance, the image after pseudo HDR conversion does not function properly. For this reason, displaying the message 151 can prompt the user to check whether the brightness setting of the display device is an appropriate setting.

  Returning to FIG. 20, the input receiving unit 112 of the conversion apparatus 110 receives input from the user via the remote controller or the like (S302). The determination unit 113 of the conversion device 110 determines the second dynamic range according to the input received by the input reception unit 112 (S303). The conversion apparatus 110 changes the luminance of the sample image 144 to the luminance defined by the determined second dynamic range (S304).

  As shown in FIGS. 23 and 24, the slider 141 is an example of the above-described UI, and is a UI for changing the maximum value of the second dynamic range according to the position of the knob. The sample image 144 is an image in which, for example, 11 levels of luminance gradation are expressed. The brightness of the sample image 144 is adjusted according to the position of the knob of the slider 141. Therefore, the user can set an appropriate DPL according to the position of the knob by moving the knob of the slider 141 so that all gradations can be distinguished.

  Further, instead of the dynamic range conversion adjustment screens 140 and 150 shown in FIGS. 23 and 24, a dynamic range conversion adjustment screen 160 shown in FIG. 25 may be displayed. FIG. 25 is a diagram illustrating another example of the dynamic range conversion adjustment screen.

  The dynamic range conversion adjustment screen 160 has a luminance distribution in a wide range in the content, instead of the sample image 144 that is an image in which gradation levels of eleven levels of brightness are expressed in the dynamic range conversion adjustment screens 140 and 150. A sample image 161 as an image is displayed.

  The conversion apparatus 110 determines whether or not the determination button 145 is selected and determined (S305). If the determination button 145 is selected and determined (Yes in S305), the luminance of the content to be reproduced is converted to the luminance defined by the second dynamic range having the determined DPL value as the maximum value, Output to a non-HDR compatible TV (S306). If the determination button 145 is selected and not determined (No in S305), the process returns to step S302.

  As shown in FIG. 23, the enter button 145 is a button for determining the DPL value adjusted by the slider 141. If the enter button 145 is selected and determined, the value is changed to the DPL value adjusted by the slider 141. Is done. The undo button 146 is a button for returning to the DPL value that was set before adjustment by the slider 141. If the undo button 146 is selected and determined, before the adjustment by the slider 141, Return to the DPL value that was set to.

  Note that the determination button 145 and the undo button 146 are not necessarily displayed, and the DPL value may be determined at a position where the knob of the slider 141 is moved. That is, in this case, when the adjustment by the slider 141 is finished and the home screen is returned, it is assumed that the DPL value is changed according to the position where the knob of the slider 141 is moved, and this value is set to the maximum value. The second dynamic range may be determined.

[2-3. Effect]
In general, the user often does not know the maximum luminance (DPL) of the TV he owns, and unless the maximum luminance (DPL) is set in the HDR compatible device, the HDR compatible device appropriately performs pseudo-HDR conversion. Can not do. The conversion device 110 guides the user to adjust visual effects such as whether the sample image is bright or dark as a whole and whether there is a sense of resolution as a whole while allowing the user to visually recognize the sample image. That is, the user determines that the user is preferable while viewing the visual effect reflected in the displayed sample image, instead of directly inputting the DPL value of the non-HDR compatible TV to the conversion device 110. By specifying the position of the slider knob, the conversion device 110 can set the DPL value corresponding to the position of the slider knob.

  As a result, the user does not need to directly input a numerical value such as 700 nit, 500 nit, 350 nit, or 200 nit as the DPL value, and the visual effect that the user has determined is appropriate by visually recognizing the visual effect reflected in the sample image. The degree can be specified, and the DPL value suitable for the HDR → pseudo HDR conversion process can be determined indirectly and intuitively.

  That is, according to the method of the present disclosure, the user can indirectly determine the value of DPL by adjusting the position of the knob of the slider 141 to a position that is appropriate in appearance rather than a numerical value. The pseudo HDR conversion can be performed by the conversion device 110.

  That is, even if a numerical value indicating the second dynamic range that can be displayed by the display device is not directly input by the user, an input to the UI displayed on the display device is accepted, and an appropriate second value is determined according to the input. The dynamic range can be easily determined. For this reason, it is possible to easily appropriately convert the luminance of the video defined by the first dynamic range into the luminance of the second dynamic range that can be displayed by the display device.

  In addition, a sample image whose luminance is defined in the second dynamic range determined in the determination is displayed on the display device. For this reason, the user can confirm whether the 2nd dynamic range determined according to the input with respect to UI is an appropriate dynamic range with respect to a display apparatus by seeing a sample image. For this reason, the user can intuitively determine the second dynamic range appropriate for the display device by performing input to the UI.

(Other embodiments)
As described above, the embodiments have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated in the said embodiment and it can also be set as a new embodiment.

  Thus, other embodiments will be exemplified below.

  The HDR video is, for example, a video in a Blu-ray (registered trademark) Disc, a DVD, a moving image distribution site on the Internet, broadcast, or HDD.

  The conversion device 100 (HDR → pseudo HDR conversion processing unit) may exist inside a disk player, a disk recorder, a set top box, a television, a personal computer, or a smartphone. The conversion device 100 may exist inside a server device in the Internet.

  The display device 200 (SDR display unit) is, for example, a television, a personal computer, or a smartphone.

  The display characteristic information acquired by the conversion apparatus 100 may be acquired from the display apparatus 200 via an HDMI (registered trademark) cable or a LAN cable using HDMI (registered trademark) or another communication protocol. The display characteristic information acquired by the conversion apparatus 100 may acquire display characteristic information included in the model information of the display apparatus 200 via the Internet. Alternatively, the user may perform a manual operation to set display characteristic information in the conversion device 100. Further, the display characteristic information of the conversion apparatus 100 may be acquired immediately before the pseudo HDR video generation (steps S101 to S104), or may be at the time of initial setting of the device or at the time of display connection. For example, the display characteristic information may be acquired immediately before the conversion to the display luminance value, or may be performed at the timing when the conversion device 100 is first connected to the display device 200 with an HDMI (registered trademark) cable.

  Further, the HDR video CPL and CAL may be one for each content, or may exist for each scene. That is, in the conversion method, the luminance information corresponding to each of the plurality of scenes of the video, and for each scene, the first maximum luminance value that is the maximum value among the luminance values for the plurality of images constituting the scene. And luminance information (CPL, CAL) including at least one of average luminance values that are averages of luminance values for a plurality of images constituting the scene, and in the first luminance conversion, for each of the plurality of scenes, The display brightness value may be determined according to the brightness information corresponding to the scene.

  Also, CPL and CAL may be included in the same medium (Blu-ray (registered trademark) Disc, DVD, etc.) as the HDR video, or separated from the HDR video, for example, obtained by the conversion device 100 from the Internet. You may get it from the place. That is, luminance information including at least one of CPL and CAL may be acquired as video meta information or may be acquired via a network.

  In the first luminance conversion (HPL → DPL) of the conversion device 100, a fixed value may be used without using CPL, CAL, and display peak luminance (DPL). Further, the fixed value may be changed from the outside. In addition, CPL, CAL, and DPL may be switched in several types. For example, DPL may be set to only three types of 200 nit, 400 nit, and 800 nit, and the value closest to the display characteristic information is used. You may make it do.

  Further, the HDR EOTF may not be SMPTE 2084, and other types of HDR EOTF may be used. Further, the maximum luminance (HPL) of the HDR video may not be 10,000 nits, for example, 4,000 nits or 1,000 nits.

  Further, the bit width of the code value may be 16, 14, 12, 10, 8 bits, for example.

  The inverse SDR EOTF conversion is determined from the display characteristic information, but a fixed conversion function (which can be changed from the outside) may be used. Inverse SDR EOTF conversion is performed in, for example, Rec. ITU-R BT. A function defined in 1886 may be used. Also, the types of inverse SDR EOTF conversion may be limited to several types, and the one closest to the input / output characteristics of the display device 200 may be selected and used.

  The display mode may be a fixed mode and may not be included in the display characteristic information.

  Moreover, the conversion apparatus 100 does not need to transmit setting information, and it is good also as a fixed display setting in the display apparatus 200, and does not need to change a display setting. In this case, the display setting unit 201 is not necessary. The setting information may be flag information indicating whether the image is a pseudo HDR video. For example, in the case of a pseudo HDR video, the setting information may be changed to a setting that displays the brightest image. That is, in the display setting setting (S105), when the acquired setting information indicates that the signal indicates a pseudo-HDR image converted using DPL, the brightness setting of the display device 200 is set to display the brightest. You may switch to.

  From the HDR-compatible device side, the backlight maximum luminance for displaying the DPL value of TV, 100 nit for SDR, and the maximum luminance value for pseudo-HDR depending on the type of content to be reproduced (HDR or SDR) It is also possible to set the TV appropriately depending on the content type by sending the setting using the HDMI (registered trademark) CEC command.

  Moreover, the 1st brightness | luminance conversion (HPL-> DPL) of the converter 100 converts, for example with the following formula.

  Here, L represents a luminance value normalized to 0 to 1, and S1, S2, a, b, and M are values set based on CAL, CPL, and DPL. In is a natural logarithm. V is a luminance value after conversion normalized to 0 to 1. As shown in FIG. 13A, when CAL is set to 300 nit, CPL is set to 2,000 nit, DPL is set to 750 nit, and conversion is not performed up to CAL + 50 nit, and conversion is performed for 350 nit or more, each value is, for example, It becomes a value like this.

S1 = 350/10000
S2 = 2000/10000
M = 750/10000
a = 0.023
b = S1−a * ln (S1) = 0.112105

  That is, in the first luminance conversion, when the SDR luminance value is between the average luminance value (CAL) and the first maximum luminance value (CPL), the natural logarithm is used to correspond to the HDR luminance value. Determine the display brightness value.

  By converting HDR video using information such as content peak brightness and content average brightness of the HDR video, the conversion formula can be changed according to the content, and conversion can be performed so as to keep the HDR gradation as much as possible. It becomes. In addition, adverse effects such as being too dark and too bright can be suppressed. Specifically, the gradation is kept as much as possible by mapping the content peak luminance of the HDR video to the display peak luminance. In addition, the overall brightness is prevented from changing by not changing the pixel values below the average luminance.

  Also, by converting the HDR video using the peak brightness value and display mode of the SDR display, the conversion formula can be changed according to the display environment of the SDR display, and there is a sense of HDR according to the performance of the SDR display. Video (pseudo HDR video) can be displayed with the same gradation and brightness as the original HDR video. Specifically, the display peak brightness is determined according to the maximum brightness of the SDR display and the display mode, and the HDR video is converted so as not to exceed the peak brightness value. The display is performed with almost no gradation reduction, and the brightness that cannot be displayed is reduced to the displayable brightness.

  As described above, brightness information that cannot be displayed can be reduced, and display can be performed in a form close to the original HDR video without reducing the gradation of displayable brightness. For example, for a display with a peak luminance of 1,000 nits, the overall brightness is maintained by converting to a pseudo HDR video with a peak luminance of 1,000 nits, and the luminance value changes depending on the display mode of the display. For this reason, the luminance conversion formula is changed according to the display mode of the display. If the pseudo-HDR image allows a luminance larger than the peak luminance of the display, the high luminance may be replaced with the peak luminance on the display side, and in that case, it is darker than the original HDR video. Become. On the contrary, if the luminance lower than the peak luminance of the display is converted as the maximum luminance, the small luminance is replaced with the peak luminance on the display side, and the whole image becomes brighter than the original HDR video. Moreover, since it is smaller than the peak luminance on the display side, the performance relating to the gradation of the display is not used at the maximum.

  On the display side, the pseudo HDR video can be displayed better by switching the display setting using the setting information. For example, when the brightness is set to dark, high brightness display cannot be performed, so that the HDR feeling is impaired. In that case, by changing the display setting or displaying a message prompting the user to change the display setting, the display performance can be maximized and a high gradation video can be displayed.

  In content such as Blu-ray (registered trademark), video signals and graphics signals such as captions and menus are multiplexed as independent data. At the time of reproduction, each is decoded individually, and the decoded result is synthesized and displayed. Specifically, subtitles and menu planes are superimposed on the video plane.

  Here, even if the video signal is HDR, graphics signals such as subtitles and menus may be SDR. In the HPL → DPL conversion of the video signal, the following two conversions (a) and (b) are possible.

(A) When performing HPL-> DPL conversion after graphics synthesis Convert graphics EOTF from SDR EOTF to HDR EOTF. 2. The graphics after EOTF conversion are combined with the video.
3. HPL → DPL conversion is performed on the synthesis result.

(B) When performing HPL → DPL conversion before graphics synthesis Convert graphics EOTF from SDR EOTF to HDR EOTF. 2. Perform HPL → DPL conversion on video.
3. The graphics after the EOTF conversion and the video after the DPL conversion are synthesized.

  In the case of (b), the order of 1 and 2 may be switched.

  In both methods (a) and (b), the graphics peak luminance is 100 nits. However, for example, when the DPL is high luminance such as 1000 nits, the graphics luminance remains 100 nits. In some cases, the luminance of graphics is lowered with respect to the video after the HPL → DPL conversion. In particular, adverse effects such as darkening of subtitles superimposed on video are assumed. Therefore, the luminance of graphics may be converted according to the value of DPL. For example, the luminance of the caption may be preliminarily defined as what percentage of the DPL value is set, and may be converted based on the set value. Graphics other than subtitles such as menus can be processed similarly.

  In the above, the reproducing operation of the HDR disc storing only the HDR signal has been described.

  Next, the multiplexed data stored in the dual disk in which both the HDR signal and the SDR signal shown in Case 2 in FIG. 6B are described with reference to FIG. FIG. 18 is a diagram for explaining multiplexed data stored in a dual disk.

  In the dual disc, as shown in FIG. 26, the HDR signal and the SDR signal are stored as different multiplexed streams. For example, in an optical disc such as Blu-ray (registered trademark), data of a plurality of media such as video, audio, subtitles, and graphics is formed as one multiplexed stream by an MPEG-2 TS-based multiplexing method called M2TS. Stored. These multiplexed streams are referred to from reproduction control metadata such as a playlist, and are reproduced by the player analyzing the metadata at the time of reproduction, or individual languages stored in the multiplexed stream. Select the data. This example shows a case where playlists for HDR and SDR are individually stored, and each playlist refers to an HDR signal or an SDR signal. Further, identification information indicating that both the HDR signal and the SDR signal are stored may be separately indicated.

  Although it is possible to multiplex both HDR signals and SDR signals in the same multiplexed stream, multiplexing is performed so as to satisfy a buffer model such as T-STD (System Target Decoder) defined in MPEG-2 TS. In particular, it is difficult to multiplex two videos having a high bit rate within a predetermined data read rate range. For this reason, it is desirable to separate multiplexed streams.

  Data such as audio, subtitles, or graphics needs to be stored for each multiplexed stream, and the amount of data increases compared to the case of multiplexing to one. However, the increase in the amount of data can reduce the amount of video data by using a video encoding method with a high compression rate. For example, by changing MPEG-4 AVC used in the conventional Blu-ray (registered trademark) to HEVC (High Efficiency Video Coding), the compression ratio can be improved by 1.6 to 2 times. Also, the dual disk is stored in a combination of 2K HDR and SDR, such as a combination of 4K SDR and 2K HDR, or 2K, or a combination of 2K and 4K. It is also possible to allow only combinations that fit within the capacity of the optical disk by prohibiting storing two.

  FIG. 27 is a flowchart showing a dual disk playback operation.

  First, the playback apparatus determines whether the playback target optical disk is a dual disk (S401). If it is determined that the disk is a dual disk (Yes in S401), it is determined whether the output TV is HDRTV or SDRTV (S402). If it is determined that it is HDRTV (Yes in S402), the process proceeds to step S403. If it is determined that it is SDRTV (No in S402), the process proceeds to step S404. In step S403, an HDR video signal is acquired from the multiplexed stream including the HDR signal in the dual disc, decoded, and output to HDRTV. In step S404, an SDR video signal is acquired from the multiplexed stream including the SDR signal in the dual disc, decoded, and output to SDRTV. If it is determined in step S401 that the playback target is not a dual disc (No in S401), whether or not playback is possible is determined by a predetermined method, and a playback method is determined based on the determination result (S405).

  In the conversion method of the present disclosure, when HDR video is displayed in SDRTV, the HDR video is converted to SDR video of 100 nit or less by using the peak brightness of SDRTV to be displayed exceeds 100 nit (usually 200 nit or more). Instead, it realizes a “HDR → pseudo HDR conversion process” that can be converted to maintain a certain level of gradation in a region exceeding 100 nits, converted into pseudo HDR video close to the original HDR, and displayed on SDRTV.

  In the conversion method, the conversion method of “HDR → pseudo HDR conversion processing” may be switched depending on the display characteristics (maximum luminance, input / output characteristics, and display mode) of SDRTV.

  The display characteristic information can be acquired by (1) automatically acquiring it via HDMI (registered trademark) or a network, (2) generating it by allowing the user to input information such as manufacturer name and product number, and (3) manufacturer. It can be obtained from the cloud using information such as name and product number.

  In addition, the display characteristic information acquisition timing of the conversion device 100 includes (1) acquisition immediately before pseudo-HDR conversion, and (2) when connecting to the display device 200 (such as SDRTV) for the first time (when connection is established). ) Can be considered.

  In the conversion method, the conversion method may be switched according to the luminance information (CAL, CPL) of the HDR video.

  For example, as the method of acquiring the luminance information of the HDR video of the conversion device 100, (1) acquiring as meta information attached to the HDR video, (2) acquiring by causing the user to input content title information, And (3) It is conceivable to acquire from the cloud or the like using input information that has been instructed by the user.

  The details of the conversion method are as follows: (1) Conversion so as not to exceed DPL; (2) Conversion so that CPL becomes DPL; (3) CAL and its surrounding luminance are not changed; 4) Conversion using natural logarithm, (5) Clip processing by DPL.

  Further, in the conversion method, in order to enhance the effect of the pseudo HDR, display settings such as the SDRTV display mode and display parameters can be transmitted to the display device 200 and switched. For example, the user is prompted to perform display settings. A message may be displayed on the screen.

  In each of the above embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

  Although the display method and the display device according to one or more aspects of the present invention have been described based on the embodiment, the present invention is not limited to this embodiment. Without departing from the spirit of the present invention, one or more of the present invention may be applied to various modifications conceived by those skilled in the art in the present embodiment, forms constructed by combining components in different embodiments, and the like. It may be included within the scope of the embodiments.

  The present disclosure is useful as a conversion method, a conversion apparatus, and the like that can appropriately convert luminance from the first luminance range to the second luminance range in which the luminance range is reduced.

DESCRIPTION OF SYMBOLS 100 Conversion apparatus 101 Conversion part 102 Brightness conversion part 103 Reverse brightness conversion part 104 Inverse SDR EOTF conversion part 200 Display apparatus 201 Display setting part 202 SDR EOTF conversion part 203 Brightness conversion part 204 Display part

Claims (10)

A conversion method executed in a conversion device that converts luminance of a video whose luminance is defined by a first dynamic range into luminance defined by a second dynamic range that can be displayed by the display device,
The second dynamic range has a smaller maximum value and a narrow dynamic range than the first dynamic range,
The conversion method is:
The display device connected to the conversion device displays a UI (User Interface) for determining the second dynamic range,
Receiving input from the user for the UI displayed on the display device;
Determining the second dynamic range according to the received input;
A conversion method for converting the luminance of the video into luminance defined by the determined second dynamic range. further,
The conversion method according to claim 1, wherein a sample image in which luminance is defined in the second dynamic range determined in the determination is displayed on the display device. In the display, a slider for determining the maximum value of the second dynamic range is displayed on the display device as the UI,
The conversion method according to claim 1, wherein in the reception, a value corresponding to a position of a knob of the slider is received as an input from the user. The conversion method according to claim 3, wherein each of the minimum value and the maximum value of the slider is a predetermined fixed value. The minimum value of the slider is a predetermined fixed value,
The conversion method according to claim 3, wherein the maximum value of the slider is a value determined based on metadata relating to luminance of the video. The conversion method according to claim 5, wherein the metadata is a peak luminance of the video. The conversion method according to claim 5, wherein the metadata is an average luminance of the video. The conversion device is connected to the display device via HDMI (registered trademark),
The first dynamic range is HDR (High Dynamic Range),
In the conversion method, further,
Obtaining information indicating whether or not the display device is capable of displaying a video corresponding to HDR;
8. The message for performing the conversion is displayed on the display device when the acquired information indicates that the display device cannot display an image corresponding to HDR. 8. Conversion method. further,
The conversion method according to claim 8, wherein the UI is displayed when the acquired information indicates that the display device cannot display an image corresponding to HDR. A conversion device that converts luminance of a video whose luminance is defined by a first dynamic range into luminance defined by a second dynamic range that can be displayed by the display device,
The second dynamic range has a smaller maximum value and a narrow dynamic range than the first dynamic range,
The converter is
A UI display unit for displaying a UI (User Interface) for determining the second dynamic range on a display device connected to the conversion device;
An input receiving unit that receives an input from the user for the UI displayed on the display device;
A determination unit that determines the second dynamic range according to the input received by the input reception unit;
A conversion unit configured to convert luminance of the video into luminance defined by the second dynamic range determined by the determination unit.