U.S. patent application number 17/152912 was filed with the patent office on 2022-03-31 for cinema projection method and system.
The applicant listed for this patent is CFGDC(BeiJing)Technology Co., Ltd.. Invention is credited to Jie Wang.
Application Number | 20220103793 17/152912 |
Document ID | / |
Family ID | 1000005412971 |
Filed Date | 2022-03-31 |
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United States Patent
Application |
20220103793 |
Kind Code |
A1 |
Wang; Jie |
March 31, 2022 |
CINEMA PROJECTION METHOD AND SYSTEM
Abstract
A cinema projection method and system are provided, 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. By adjusting the PWM,
the brightness of a screen display is reduced. 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.
Inventors: |
Wang; Jie; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CFGDC(BeiJing)Technology Co., Ltd. |
Beijing |
|
CN |
|
|
Family ID: |
1000005412971 |
Appl. No.: |
17/152912 |
Filed: |
January 20, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 9/3182 20130101;
G03B 21/005 20130101; H04N 9/3123 20130101; G03B 21/14 20130101;
G03B 21/32 20130101 |
International
Class: |
H04N 9/31 20060101
H04N009/31 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2020 |
CN |
202011029263.7 |
Claims
1. A cinema projection method, wherein the cinema projection method
comprises: 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,
wherein 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.
2. The cinema projection method according to claim 1, wherein 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 comprises: 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 Y.sub.SDR of each pixel of each frame of the
original DCP by using a formula Y GDR = INT .function. ( Y SDR
.times. 4095 percent_pixel ) , ##EQU00010## to obtain the
transformed luminance component Y.sub.GDR of each pixel of each
frame of the transformed DCP, wherein 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.
3. The cinema projection method according to claim 1, wherein an
EOTF corresponding to the standard PWM level is L = ( Y GDR .times.
percent_pixel 4095 2 ) 2.6 .times. 48 , ##EQU00011## wherein L is a
display luminance of each pixel of each frame of the transformed
DCP of a standard cinema on the screen, Y.sub.GDR is the
transformed luminance component, and percent_pixel is a right
boundary value of the standard luminance component interval.
4. The cinema projection method according to claim 1, wherein
obtaining the luminance adjustment consistency mapping model of the
local cinema comprises: 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.
5. A cinema projection system, wherein the cinema projection system
comprises a processor and a local cinema projector, wherein: the
processor is 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, wherein all transformed frames
form a transformed DCP; 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; and 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; and
the local cinema projector is 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.
6. The cinema projection system according to claim 5, wherein the
processor is further 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 Y.sub.SDR of each pixel of each frame of the
original DCP by using a formula Y GDR = INT .function. ( Y SDR
.times. 4095 percent_pixel ) , ##EQU00012## to obtain the
transformed luminance component Y.sub.GDR of each pixel of each
frame, wherein 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.
7. The cinema projection system according to claim 5, wherein an
EOTF corresponding to the standard PWM level is L = ( Y GDR .times.
percent_pixel 4095 2 ) 2.6 .times. 48 , ##EQU00013## wherein L is a
display luminance of each pixel of each frame of the transformed
DCP of a standard cinema on the screen, Y.sub.GDR is the
transformed luminance component, and percent_pixel is a right
boundary value of the standard luminance component interval.
8. The cinema projection system according to claim 5, wherein the
processor is further 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; 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; determine a display
luminance difference between the first display luminance and the
second display luminance; 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; 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
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.
Description
CLAIM OF PRIORITY UNDER 35 U.S.C. .sctn. 119
[0001] 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
[0002] The present disclosure relates to the technical field of
cinema projection, and in particular, to a cinema projection method
and system.
BACKGROUND
[0003] 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
[0004] The present disclosure aims to provide a cinema projection
method and system to improve the ANSI contrast of a digital
projector.
[0005] To achieve the above objective, the present disclosure
provides the following solutions:
[0006] 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.
[0007] 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 Y.sub.SDR of each pixel
of each frame of the original DCP by using a formula
Y GDR = INT .function. ( Y SDR .times. 4095 percent .times. .times.
pixel ) , ##EQU00001##
to obtain the transformed luminance component Y.sub.GDR of 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.
[0008] Optionally, an EOTF corresponding to the standard PWM level
is
L = ( Y GDR .times. percent_pixel 4095 2 ) 2.6 .times. 48 ,
##EQU00002##
where L is a display luminance of each pixel of each frame of the
transformed DCP of a standard cinema on the screen, Y.sub.GDR is
the transformed luminance component, and percent_pixel is a right
boundary value of the standard luminance component interval.
[0009] 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.
[0010] 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.
[0011] 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 Y.sub.SDR of each pixel of each frame of the
original DCP by using a formula
Y GDR = INT .function. ( Y SDR .times. 4095 percent_pixel ) ,
##EQU00003##
to obtain the transformed luminance component Y.sub.GDR of 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.
[0012] Optionally, an EOTF corresponding to the standard PWM level
is
L = ( Y GDR .times. percent_pixel 4095 2 ) 2.6 .times. 48 ,
##EQU00004##
where L is a display luminance of each pixel of each frame of the
transformed DCP of a standard cinema on the screen, Y.sub.GDR is
the transformed luminance component, and percent_pixel is a right
boundary value of the standard luminance component interval.
[0013] 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.
[0014] 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.
BRIEF DESCRIPTION OF DRAWINGS
[0015] To describe the technical solutions in the embodiments of
the present disclosure or in the prior art more clearly, the
following briefly introduces the accompanying drawings required for
describing the embodiments or the prior art. Notably, the
accompanying drawings in the following description show some
embodiments of the present disclosure, and those of ordinary skill
in the art may still derive other drawings from these accompanying
drawing without any creative efforts.
[0016] FIG. 1 is a flowchart of a cinema projection method
according to the present disclosure.
[0017] FIG. 2 is a principle diagram of a GDT standard model
transformation process according to the present disclosure.
[0018] FIG. 3 is a principle diagram of obtaining a luminance
adjustment consistency mapping model according to the present
disclosure.
[0019] FIG. 4 is a principle diagram of local cinema projection
according to the present disclosure.
[0020] FIG. 5 is a schematic diagram of a standard SDR
electro-optical transfer function (EOTF) curve.
[0021] FIG. 6 is a schematic diagram of standard GDR EOTF curves
under different PWM levels.
DETAILED DESCRIPTION
[0022] The following clearly and completely describes the technical
solutions in the embodiments of the present disclosure with
reference to accompanying drawings in the embodiments of the
present disclosure. Apparently, the described embodiments are
merely a part rather than all of the embodiments of the present
disclosure. All other embodiments obtained by a person of ordinary
skill in the art based on the embodiments of the present disclosure
without creative efforts shall fall within the protection scope of
the present disclosure.
[0023] An objective of the present disclosure is to provide a
cinema projection method and system to improve the ANSI contrast of
a digital projector.
[0024] To make the foregoing objective, features, and advantages of
the present disclosure clearer and more comprehensible, the present
disclosure is further described in detail below with reference to
the accompanying drawings and specific embodiments.
[0025] FIG. 1 is a flowchart of a cinema projection method
according to the present disclosure. The cinema projection method
includes the following steps. S101: Perform 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, where all transformed frames form a
transformed DCP. S102: 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. S103: 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. S104: 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.
[0026] FIG. 4 is a principle diagram of local cinema projection
according to the present disclosure.
[0027] A production process of GDR transformation of original
images based on different PWM levels includes steps S101 and S102.
Step S101 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 Y.sub.SDR of each pixel of each frame of the
original DCP by using a formula
Y GDR = INT .function. ( Y SDR .times. 4095 percent_pixel ) ,
##EQU00005##
to obtain the transformed luminance component Y.sub.GDR of each
pixel of each transformed 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.
[0028] A process of transforming the original DCP into a GD-DCP
(transformed DCP) is a standard GDT model transformation process.
The entire transformation process is completed by a plate making
tool, which contains a standard GDT model, as shown in the FIG.
2.
[0029] The formula of the standard GDT model is:
Y GDR = INT .function. ( Y SDR .times. 4095 percent_pixel ) ,
##EQU00006##
Y.sub.SDR.di-elect cons.[0, percent_pixel] where
Percent_pixel=1689, 2205, 2577, 2879, 3137, 3365, 3570, 3758, 3932,
4095.
[0030] After the original DCP is processed by the standard GDT
model. Therefore, except for frames in the original DCP with the
maximum luminance within the interval [3932, 4095], luminance
components Y of all other frames increase. After the processing by
the standard GDT model, a brightened DCP is obtained. A
corresponding PWM level is determined based on the maximum
luminance of the luminance component Y of each frame of the
original DCP. The brightened DCP and the corresponding standard PWM
levels form a standard GD-DCP.
[0031] An EOTF corresponding to the standard PWM level is
L = ( Y GDR .times. percent_pixel 4095 2 ) 2.6 .times. 48 ,
##EQU00007##
where L is a display luminance of each pixel of each frame of the
transformed DCP screen in an ideal condition, Y.sub.GDR is the
transformed luminance component, and percent_pixel is the right
boundary value of the standard luminance component interval.
[0032] Step S103 is a cinema calibration process. Because different
cinemas have different projection devices and projection
environments, the standard GD-DCP obtained by the foregoing
standard transformation method may be inapplicable to other
cinemas. To be specific, the screen display luminance before and
after the transformation is beyond a digital cinema initiatives
(DCI) luminance tolerance range. The solution is to adjust the PWM
level. The PWM adjustment accuracy is 1%. Therefore, a PWM value
within the DCI luminance tolerance range can definitely be found
for a cinema.
[0033] The cinema calibration process is to find a mapping
relationship PWM.sub.stdPWM.sub.local between an appropriate PWM
level for the local cinema and the standard PWM level. This mapping
relationship is called the luminance adjustment consistency mapping
model. The entire calibration process is completed using a light
source calibration tool. The calibration flowchart is shown in FIG.
3. The specific process is as follows: 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 (GDR EOTF in
FIG. 4) 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 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. The luminance
adjustment consistency mapping model of the local cinema needs to
be calibrated periodically.
[0034] The DCI luminance tolerance range is .+-.10.2 cd/m.sup.2
(.+-.3.00 fL).
[0035] FIG. 5 shows a standard SDR EOTF curve. FIG. 6 shows
standard GDR EOTF curves under different PWM levels. As seen from
FIG. 6, the local GDR EOTF curve is theoretically consistent with
the standard GDR EOTF curve, except that the PWM levels are
different. In both FIG. 5 and FIG. 6, horizontal coordinates
represent the luminance component Y, and vertical coordinates
represent the screen display luminance in cd/m.sup.2.
[0036] The cinema projection method according to the present
disclosure has the following technical effects.
[0037] During the GD-DCP creation process, the Y values of the
luminance component of each frame is also adjusted according to the
formula, but the Y value of pure black (Y=0) remains unchanged.
Without PWM adjustment, the GD-DCP obtained by transformation has a
brighter display luminance than the original DCP, while the display
luminance of the dark field (pure black) is unchanged. To ensure
the consistent screen display luminance of each frame before and
after transformation, PWM adjustment is required, so that the
display luminance of the GD-DCP is consistent with that of the
original DCP in each frame, or is within the DCI luminance
tolerance range.
[0038] 1. The ANSI contrast is improved, which improves the cinema
projection effect. Adjusting the PWM level is actually adjusting
the output power of the projector. When the PWM level is not
adjusted, the output power of the projector always remains
unchanged. In this case, for frames with a small luminance
component Y, there will be excess power, and because the output
power cannot be adjusted, the display luminance of the dark field
cannot be reduced to a very low level. According to the
transformation formula, for any frame, when the maximum value of
the luminance component Y of the frame is in the interval [3933,
4095], all Y values of the frame before and after the
transformation remain unchanged, and the projector output power
should remain unchanged; for frames with the maximum value of the
luminance component Y in [0, 3932], after transformation, the value
of the luminance component Y increases. Therefore, for these
frames, the PWM level needs to be adjusted to keep the display
luminance consistent before and after transformation of the DCP.
The output power of the projector should be reduced, and a display
luminance darker than that before the adjustment is achieved for
the pure black part based on the PWM adjustment. For a frame in the
GD-DCP, the display luminance of pure white remains unchanged,
while the display luminance of pure black is reduced and the ANSI
contrast is increased. Although the display luminance of pure white
needs to be kept unchanged, the output power cannot be adjusted to
a very low level, and the dark field cannot be reduced to nearly
full darkness, but tests show that the ANSI contrast always remains
at 137:1 to 138:1, which is always far higher than the minimum
100:1 required by cinemas. Table 1 shows the ANSI contrast under
different PWM levels.
TABLE-US-00001 TABLE 1 ANSI contrast under different PWM levels PWM
10% 15% 20% 25% 30% 35% 40% 45% 50% ANSI -- 138 138 137 138 137 138
137 138 contrast PWM 55% 60% 65% 70% 75% 80% 85% 90% 95% ANSI 138
137 138 137 137 138 138 138 137 contrast
[0039] 2. The sequential contrast is improved. For the sequential
contrast, the luminance of the full-white frame remains unchanged,
and the full-black dark field can achieve a nearly full-dark effect
by adjusting the PWM level, so the sequential contrast is greatly
improved. The sequential contrast of the image can be increased
from 1660:1 without dimming to 7000:1 or even higher, especially
the luminance of the dark field image can reach 9.03614E-05 nits,
which is close to full darkness and darker than a luminance of 0.33
nits without dimming by more than 10,000 times.
[0040] 3. Saving electricity. Because the GD-DCP transformation
process increases the Y values of all frames with the maximum
luminance component Y in the interval [0, 3932], adjusting the PWM
level accordingly will reduce the output power of the projector.
Statistical testing shows that for a cinema, if the average value
of the maximum luminance values of all frames is 70% of the maximum
luminance value, electricity can be saved by about 30%.
[0041] The present disclosure further provides a cinema projection
system. The system includes: a transformed luminance component
obtaining module, a standard PWM level determining module, a local
PWM level determining module, and a local cinema projection
module.
[0042] The transformed luminance component obtaining module is
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.
[0043] The standard PWM level determining module is 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.
[0044] The local PWM level determining module is 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.
[0045] The local cinema projection module is 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.
[0046] The transformed luminance component obtaining module
specifically includes a transformed luminance component obtaining
submodule.
[0047] The transformed luminance component obtaining submodule is
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
Y.sub.SDR of each pixel of each frame of the original DCP by using
a formula
Y GDR = INT .function. ( Y SDR .times. 4095 percent_pixel ) ,
##EQU00008##
to obtain the transformed luminance component Y.sub.GDR of 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.
[0048] An EOTF corresponding to the standard PWM level is
L = ( Y GDR .times. percent_pixel 4095 2 ) 2.6 .times. 48 ,
##EQU00009##
where L is a display luminance of each pixel of each frame of the
transformed DCP of a standard cinema on the screen, Y.sub.GDR is
the transformed luminance component, and percent_pixel is the right
boundary value of the standard luminance component interval.
[0049] A cinema projection system further includes: a first display
luminance obtaining submodule, a second display luminance
determining submodule, a display luminance difference determining
submodule, a standard PWM level update submodule, a local PWM level
determining submodule, and a luminance adjustment consistency
mapping model determining submodule.
[0050] The first display luminance obtaining submodule is
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.
[0051] The second display luminance determining submodule is
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.
[0052] The display luminance difference determining submodule is
configured to determine a display luminance difference between the
first display luminance and the second display luminance.
[0053] The standard PWM level update submodule is 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".
[0054] The local PWM level determining submodule is 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.
[0055] The luminance adjustment consistency mapping model
determining submodule is 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.
[0056] The present disclosure expands the high-density pixel
information to the theoretical maximum electrical information range
through remapping of the original image, and adjusts the luminance
of the light source, thereby ensuring that the actual presentation
effect reaches the theoretical projection effect, that is,
increasing the ANSI contrast and providing better cinema projection
effect
Terms
[0057] GD: Global Dimming, which means adjusting the overall
presentation effect by adjusting the luminance of the light source,
which is different from local dimming.
[0058] DCI: Digital Cinema Initiatives, which defines the screening
standards of digital movies.
[0059] EOTF: Electro-optical Transfer Function, a function used to
transform digital images to the luminance of light, which is the
commonly used Gamma transformation.
[0060] PWM: Pulse Width Modulation, which is used in this patent to
change the duty cycle of the pulse to notify the light source to
adjust the luminance.
[0061] SDR: Standard Dynamic Range, using the EOTF specified by DCI
(Gamma=2.6).
[0062] GDR: Global Dynamic Range, used to distinguish SDR and
HDR.
[0063] GD-DCP: GDR transformed cinema.
[0064] DCP: Digital Cinema Package, which is used to store and
transform the audio, image and data streams of digital images, and
is a media file package used by cinema projectors.
[0065] Each embodiment of the present specification is described in
a progressive manner, each embodiment focuses on the difference
from other embodiments, and the same and similar parts between the
embodiments may refer to each other. For a system disclosed in the
embodiments, since the system corresponds to the method disclosed
in the embodiments, the description is relatively simple, and
reference can be made to the method description.
[0066] In this specification, several specific examples are used
for illustration of the principles and implementations of the
present disclosure. The description of the foregoing embodiments is
used to help illustrate the method of the present disclosure and
the core ideas thereof. In addition, those of ordinary skill in the
art can make various modifications in terms of specific
implementations and scope of application in accordance with the
ideas of the present disclosure. In conclusion, the content of this
specification shall not be construed as a limitation to the present
disclosure.
* * * * *