CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

This application claims the priority of Chinese Patent Application No. 202010236443.6, entitled “Cinema Projection Method and System” filed with the China National Intellectual Property Administration on Sep. 27, 2020, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of cinema projection, and in particular, to a cinema projection method and system.

BACKGROUND

When a movie is shown in the theater, if the image luminance of the movie is low while the traditional light source luminance is constant, the electrical information of image pixels (that is, the luminance component Y of the image YVU color space) is more densely concentrated in the low value area. In this case, it is difficult to achieve the theoretical effect (Gamma 2.6 for cinemas) through precise control because the projector cannot darken the dark part of the image enough, and therefore the ANSI contrast of a single-frame image is low.

SUMMARY

The present disclosure aims to provide a cinema projection method and system to improve the ANSI contrast of a digital projector.

To achieve the above objective, the present disclosure provides the following solutions:

A cinema projection method includes: performing global dynamic range (GDR) transformation on an original digital cinema package (DCP) based on a standard luminance component interval of a luminance component of each pixel of each frame of the original DCP, to obtain a transformed luminance component of each pixel of each transformed frame, where all transformed frames form a transformed DCP; determining a standard pulse width modulation (PWM) level of each frame of the original DCP based on a standard luminance component interval of a maximum luminance value of all pixels in each frame of the original DCP; transforming the standard PWM level by using a luminance adjustment consistency mapping model of a local cinema, to obtain a local PWM level of each frame of the local cinema; and based on the transformed luminance component of each pixel of each frame of the transformed DCP, determining a display luminance of each pixel of each frame of the transformed DCP on a local cinema screen by using an electro-optical transfer function (EOTF) corresponding to the local PWM level, to show the transformed DCP in the local cinema.

Optionally, the performing GDR transformation on an original DCP based on a standard luminance component interval of a luminance component of each pixel of each frame of the original DCP, to obtain a transformed luminance component of each pixel of each transformed frame specifically includes: based on the standard luminance component interval of the luminance component of each pixel of each frame of the original DCP, performing GDR transformation on the luminance component YSDRof each pixel of each frame of the original DCP by using a formula

YGDR=INT⁡(YSDR×4095percent⁢⁢pixel)
to obtain the transformed luminance component YGDRof each pixel of each frame of the transformed DCP, where percent_pixel is a right boundary value of the standard luminance component interval, all values of percent_pixel are standard luminance components corresponding to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% of a maximum display luminance of the screen, percent_pixel=1689, 2205, 2577, 2879, 3137, 3365, 3570, 3758, 3932, 4095, and INT ( ), is a rounding function.

Optionally, an EOTF corresponding to the standard PWM level is

L=(YG⁢D⁢R×percent_pixel4⁢0⁢9⁢52)2.6×4⁢8
where L is a display luminance of each pixel of each frame of the transformed DCP of a standard cinema on the screen, YGDRis the transformed luminance component, and percent_pixel a right boundary value of the standard luminance component interval.

Optionally, before the transforming the standard PWM level by using a luminance adjustment consistency mapping model of a local cinema, to obtain a local PWM level of each frame of the local cinema, the method further includes: obtaining a first display luminance on a local cinema screen corresponding to a maximum luminance value of all pixels in each frame of an original DCP sample; based on a transformed luminance component of each pixel of each frame of a transformed DCP sample, determining a second display luminance of each pixel of each frame of the transformed DCP sample on the local cinema screen by using an EOTF corresponding to a standard PWM level of the original DCP sample; determining a display luminance difference between the first display luminance and the second display luminance; when the display luminance difference is not within a digital cinema initiatives (DCI) luminance tolerance range, adjusting the standard PWM level of the original DCP sample to obtain an updated standard PWM level of the original DCP sample, and returning to the step of “based on a transformed luminance component of each pixel of each frame of a transformed DCP sample, determining a second display luminance of each pixel of each frame of the transformed DCP sample on the local cinema screen by using an EOTF corresponding to a standard PWM level of the original DCP sample”; when the display luminance difference is within the DCI luminance tolerance range, using the updated standard PWM level of the original DCP sample as a local PWM level of the original DCP sample of the local cinema; and determining a mapping relationship between the standard PWM level of the original DCP sample and the local PWM level of the original DCP sample, and using the mapping relationship as the luminance adjustment consistency mapping model of the local cinema.

A cinema projection system includes: a transformed luminance component obtaining module, configured to transform an original DCP based on a standard luminance component interval of a luminance component of each pixel of each frame of the original DCP by using GDR transformation, to obtain a transformed luminance component of each pixel of each transformed frame, where all transformed frames form a transformed DCP; a standard PWM level determining module, configured to determine a standard PWM level of each frame of the original DCP based on a standard luminance component interval of a maximum luminance value of all pixels in each frame of the original DCP; a local PWM level determining module, configured to transform the standard PWM level by using a luminance adjustment consistency mapping model of a local cinema, to obtain a local PWM level of each frame of the local cinema; a local cinema projection module, configured to, based on the transformed luminance component of each pixel of each frame of the transformed DCP, determine a display luminance of each pixel of each frame of the transformed DCP on a local cinema screen by using an EOTF corresponding to the local PWM level, to show the transformed DCP in the local cinema.

Optionally, the transformed luminance component obtaining module specifically includes: a transformed luminance component obtaining submodule, configured to, based on the standard luminance component interval of the luminance component of each pixel of each frame of the original DCP, perform GDR transformation on the luminance component YSDRof each pixel of each frame of the original DCP by using a formula

YGDR=INT⁡(YSDR×4095percent_pixel)
to obtain the transformed luminance component YGDRof each pixel of each frame, where percent_pixel is a right boundary value of the standard luminance component interval, all values of percent_pixel are standard luminance components corresponding to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% of a maximum display luminance of the screen, percent_pixel=1689, 2205, 2577, 2879, 3137, 3365, 3570, 3758, 3932, 4095, and INT ( ) is a rounding function.

Optionally, an EOTF corresponding to the standard PWM level is

L=(YG⁢D⁢R×percent_pixel4⁢0⁢9⁢52)2.6×4⁢8
where L is a display luminance of each pixel of each frame of the transformed DCP of a standard cinema on the screen, YGDRis the transformed luminance component, and percent_pixel is a right boundary value of the standard luminance component interval.

Optionally, the system further includes: a first display luminance obtaining submodule, configured to obtain a first display luminance on the local cinema screen corresponding to a maximum luminance value of all pixels in each frame of an original DCP sample; a second display luminance determining submodule, configured to, based on a transformed luminance component of each pixel of each frame of a transformed DCP sample, determine a second display luminance of each pixel of each frame of the transformed DCP sample on the local cinema screen by using an EOTF corresponding to a standard PWM level of the original DCP sample; a display luminance difference determining submodule, configured to determine a display luminance difference between the first display luminance and the second display luminance; a standard PWM level update submodule, configured to, when the display luminance difference is not within a DCI luminance tolerance range, adjust the standard PWM level of the original DCP sample to obtain an updated standard PWM level of the original DCP sample, and return to the step of “based on a transformed luminance component of each pixel of each frame of a transformed DCP sample, determining a second display luminance of each pixel of each frame of the transformed DCP sample on the local cinema screen by using an EOTF corresponding to a standard PWM level of the original DCP sample”; a local PWM level determining submodule, configured to, when the display luminance difference is within the DCI luminance tolerance range, use the updated standard PWM level of the original DCP sample as a local PWM level of the original DCP sample of the local cinema; and a luminance adjustment consistency mapping model determining submodule, configured to determine a mapping relationship between the standard PWM level of the original DCP sample and the local PWM level of the original DCP sample, and use the mapping relationship as the luminance adjustment consistency mapping model of the local cinema.

According to specific embodiments of the present disclosure, the present disclosure has the following technical effects. The present disclosure provides a cinema projection method and system, to perform GDR transformation on an original DCP while keeping a luminance component value of pure black unchanged. A transformed DCP has a brighter display luminance than the original DCP, and a display luminance of pure black remains unchanged. To ensure that the transformed DCP has a consistent display luminance with the original DCP, a luminance adjustment consistency mapping model of a local cinema is used to transform a standard PWM level of each frame of the original DCP, to obtain a local PWM level of each frame of the local cinema, and an electro-optical transformation function corresponding to the local PWM level is used to adjust the display luminance, so that a display luminance of pure white of each frame of the transformed DCP is unchanged while the display luminance of pure black is reduced. This improves the ANSI contrast of different cinemas, thereby enhancing the cinema projection effect.

