Display system, display method, and display apparatus

1. A display system comprising:

a conversion apparatus; and

a display apparatus,

wherein the conversion apparatus comprises: one or more memories, and circuitry which, in operation, performs:

acquiring a first luminance signal indicating a first code value obtained by quantization of a luminance value of a video, the luminance of the video being included in a first luminance range;

converting the first code value into a second luminance value compatible with a second luminance range, a maximum value of the second luminance range being determined based on a luminance range of the display apparatus, the maximum value of the second luminance range being smaller than a maximum value of the first luminance range, and the maximum value of the second luminance range being larger than 100 nit;

determining a third luminance value associated with the second luminance value in advance, the third luminance value being compatible with a third luminance range with a maximum value of 100 nit;

converting the second luminance value compatible with the second luminance range into the third luminance value compatible with the third luminance range;

determining a second code value by quantization of the determined third luminance value;

converting the third luminance value compatible with the third luminance range into a third luminance signal indicating the second code value; and

outputting the third luminance signal to the display apparatus, and

wherein the display apparatus comprises one or more memories, and circuitry which, in operation, performs:

acquiring the third luminance signal and setting information indicating a display setting recommended to the display apparatus in display of the video;

performing setting of the display setting of the display apparatus by using the acquired setting information;

converting the second code value indicated by the acquired third luminance signal into the second luminance value compatible with the second luminance range by using the display setting of the display apparatus; and

displaying the video on the display apparatus based on the second luminance value obtained by the third luminance conversion.

2. A display method for displaying a video on the display apparatus of the display system according to claim 1 , the display method comprising:

acquiring the third luminance signal and the setting information indicating the display setting recommended to the display apparatus in display of the video;

performing setting of the display setting of the display apparatus by using the acquired setting information;

converting the second code value indicated by the acquired third luminance signal into the second luminance value compatible with the second luminance range by using the display setting of the display apparatus; and

displaying the video on the display apparatus based on the second luminance value obtained by the converting the second code value.

3. The display method according to claim 2 , wherein the converting the second code value comprises:

by using an electro-optical transfer function (EOTF) that associates the luminance value in the third luminance range with a plurality of second code values, determining the third luminance value associated with the second code value indicated by the acquired third luminance signal, the third luminance value being compatible with the third luminance range;

determining the second luminance value associated with the third luminance value in advance, the second luminance value being compatible with the second luminance range; and

performing third luminance conversion to convert the third luminance value compatible with the third luminance range into the second luminance value compatible with the second luminance range.

4. The display method according to claim 3 , wherein

performing setting of the display setting comprises setting the EOTF that is set for the display apparatus as a recommended EOTF according to the acquired setting information, and

determining the third luminance value comprises determining the third luminance value by using the recommended EOTF.

5. The display method according to claim 4 , wherein performing setting of the display setting comprises, when the EOTF that is set for the display apparatus cannot be switched, displaying a message on the display apparatus for prompting a user to switch the EOTF that is set for the display apparatus to the recommended EOTF.

6. The display method according to claim 3 , wherein performing setting of the display setting comprises setting a display parameter that is set for the display apparatus as a recommended display parameter according to the acquired setting information.

7. The display method according to claim 6 , wherein performing setting of the display setting comprises, when the display parameter that is set for the display apparatus cannot be switched, displaying a message on the display apparatus for prompting a user to switch the display parameter that is set for the display apparatus to the recommended display parameter.

8. The display method according to claim 3 , wherein the performing the third luminance conversion comprises:

by using luminance-related information according to a display parameter indicating the display setting of the display apparatus, determining a luminance value associated with the third luminance value in advance as the second luminance value; and

switching luminance conversion processing according to the display parameter.

9. The display method according to claim 8 , wherein the performing the third luminance conversion comprises:

when the display parameter is a normal mode, performing luminance conversion to convert the second luminance value into a direct proportion value in direct proportion to the third luminance value; and

when the display parameter is a dynamic mode in which a high-luminance pixel becomes brighter and a low-luminance pixel becomes darker than pixels in the normal mode, performing luminance conversion to convert the second luminance value of the low-luminance pixel into a value lower than the direct proportion value in direct proportion to the third luminance value, and to convert the second luminance value of the high-luminance pixel into a value higher than the direct proportion value in direct proportion to the third luminance value.

10. The display method according to claim 6 , wherein performing setting of the display setting comprises, when the acquired setting information indicates that an acquired luminance signal is the third luminance signal converted using the second luminance range, switching a brightness setting of the display apparatus to a setting of brightest display.

11. A display method for displaying a video on a display apparatus, the display method comprising:

converting a first code value obtained by quantization of a luminance value of the video into a second luminance value compatible with a second luminance range, the luminance value of the video being included in a first luminance range, a maximum value of the second luminance range being determined based on a luminance range of the display apparatus, the maximum value of the second luminance range being smaller than a maximum value of the first luminance range, and the maximum value of the second luminance range being larger than 100 nit;

converting the second luminance value into a third luminance value compatible with a third luminance range with a maximum value of 100 nit;

acquiring, by the display apparatus, a third luminance signal indicating a second code value obtained by quantization of the third luminance value;

acquiring setting information indicating a display setting recommended to the display apparatus in display of the video;

performing setting of the display setting of the display apparatus by using the acquired setting information;

converting the second code value indicated by the acquired third luminance signal into the second luminance value compatible with the second luminance range by using the set display setting; and

displaying the video on the display apparatus based on the second luminance value obtained by the converting the second code value.

12. The display method according to claim 11 , wherein converting the second code value comprises:

by using an electro-optical transfer function (EOTF) that associates the luminance value in the third luminance range with a plurality of second code values, determining the third luminance value associated with the second code value indicated by the acquired third luminance signal, the third luminance value being compatible with the third luminance range;

determining the second luminance value associated with the third luminance value in advance, the second luminance value being compatible with the second luminance range; and

performing third luminance conversion to convert the third luminance value compatible with the third luminance range into the second luminance value compatible with the second luminance range.

13. The display method according to claim 12 , wherein

performing setting of the display setting comprises setting the EOTF that is set for the display apparatus as a recommended EOTF according to the acquired setting information, and

determining the third luminance value comprises determining the third luminance value by using the recommended EOTF.

14. The display method according to claim 12 , wherein the performing setting of the display setting comprises setting a display parameter that is set for the display apparatus as a recommended display parameter according to the acquired setting information.

15. The display method according to claim 12 , wherein the performing the third luminance conversion comprises:

by using luminance-related information according to a display parameter indicating the display setting of the display apparatus, determining a luminance value associated with the third luminance value in advance as the second luminance value; and

switching luminance conversion processing according to the display parameter.

16. The display method according to claim 15 , wherein the performing the third luminance conversion comprises:

when the display parameter is a normal mode, performing luminance conversion to convert the second luminance value into a direct proportion value in direct proportion to the third luminance value; and

when the display parameter is a dynamic mode in which a high-luminance pixel becomes brighter and a low-luminance pixel becomes darker than pixels in the normal mode, performing luminance conversion to convert the second luminance value of the low-luminance pixel into a value lower than the direct proportion value in direct proportion to the third luminance value, and to convert the second luminance value of the high-luminance pixel into a value higher than the direct proportion value in direct proportion to the third luminance value.

17. A display apparatus for the display system according to claim 1 .

18. A display apparatus comprising:

one or more memories; and

circuitry which, in operation, performs:

converting a first code value obtained by quantization of a luminance value of a video into a second luminance value compatible with a second luminance range, the luminance value of the video being included in a first luminance range, a maximum value of the second luminance range being determined based on a luminance range of the display apparatus, the maximum value of the second luminance range being smaller than a maximum value of the first luminance range, and the maximum value of the second luminance range being larger than 100 nit;

converting the second luminance value into a third luminance value compatible with a third luminance range with a maximum value of 100 nit;

acquiring a third luminance signal indicating a second code value obtained by quantization of the third luminance value;

acquiring setting information indicating a display setting recommended to the display apparatus in display of the video;

performing setting of the display setting of display apparatus by using the acquired setting information;

converting the second code value indicated by the acquired third luminance signal into the second luminance value compatible with the second luminance range by using the set display setting; and

displaying the video on the display apparatus based on the second luminance value obtained by the converting the second code value.