阅读说明：本技术 具有环境光补偿的显示器管理 (Display management with ambient light compensation ) 是由 R·阿特金斯 C·托德 J·A·皮特拉尔兹 T·孔克尔 于 2020-01-09 设计创作，主要内容包括：描述一种显示设备、显示器管理模块及用于环境光补偿的方法。所述显示器管理模块经配置以接收包括视频帧的序列的输入视频信号,并确定所述视频帧的序列的当前视频帧是否紧跟场景改变。所述显示器管理模块经进一步配置以仅响应于确定所述视频帧的序列的所述当前视频帧紧跟场景改变而依赖于指示环境光的强度的信号来调整应用到所述输入信号的环境光补偿。(A display device, a display management module and a method for ambient light compensation are described. The display management module is configured to receive an input video signal comprising a sequence of video frames and determine whether a current video frame of the sequence of video frames immediately follows a scene change. The display management module is further configured to adjust ambient light compensation applied to the input signal in dependence upon a signal indicative of an intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.)

1. A display apparatus, comprising:

-a display;

-an ambient light sensor configured to generate a signal indicative of an intensity of ambient light; and

-a display management module configured to:

receiving an input video signal comprising a sequence of video frames;

receiving metadata related to the sequence of video frames;

determining whether a current video frame of the sequence of video frames immediately follows a scene change using the metadata; and

transforming the input video signal into an output video signal suitable for the display, comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

wherein the display is configured to display the output video signal, an

Wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence on the signal indicative of the intensity of ambient light only in response to determining, using the metadata, that the current video frame of the sequence of video frames immediately follows a scene change.

2. The display apparatus of claim 1, wherein the metadata related to the sequence of video frames includes metadata indicative of a scene change, and the display management module is configured to use the metadata indicative of a scene change to determine whether the current video frame immediately follows a scene change.

3. The display apparatus of claim 1 or 2, wherein the metadata related to the sequence of video frames includes metadata indicative of characteristics of the current video frame and one or more previous video frames, wherein the display management module is configured to derive the characteristics from the metadata indicative of the characteristics, and compare derived characteristics of the current video frame with derived characteristics of the one or more previous video frames to determine whether the current video frame of the sequence of video frames immediately follows a scene change.

4. The display apparatus of any of claims 1-3, wherein the ambient light sensor is less sensitive to light of wavelengths corresponding to primary colors of the display than to light of other wavelengths of the visible spectrum.

5. The display device defined in claim 4 wherein the ambient light sensor comprises an optical filter that attenuates light of wavelengths corresponding to primary colors of the display.

6. The display apparatus of claim 5, wherein the optical filter comprises an optical band-stop filter.

7. The display apparatus of claim 4, wherein the ambient light sensor is sensitive only to one or more bands within the visible spectrum.

8. The display apparatus of claim 7, wherein the ambient light sensor is sensitive to only yellow light, only cyan light, or only yellow and cyan light.

9. The display device of claim 7 or 8, wherein the ambient light sensor comprises an optical bandpass filter.

10. The display apparatus of any of claims 1-9, wherein applying ambient light compensation comprises applying an ambient light compensation function that maps input intensity values of the video frames of the input video signal to output intensity values of corresponding video frames of the output video signal, wherein the display management module is configured to select one of a set of ambient light compensation functions in dependence on the signal indicative of intensity of ambient light.

11. The display apparatus of any of claims 1-10, wherein the display management module is further configured to determine a measured bias due to the light emitted by the display and recorded by the ambient light sensor based on at least one of the input video signal and metadata related to the input video signal,

wherein applying ambient light compensation by the display management module comprises: applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light compensated by the determined measurement bias.

12. The display apparatus of claim 11, wherein determining the measurement bias comprises:

determining an intensity level for each of a predetermined number of video frames prior to the current video frame; and

determining a sum of the intensity levels of the predetermined number of video frames.

13. A display management module configured to:

receiving an input video signal comprising a sequence of video frames;

receiving metadata related to the sequence of video frames;

receiving a signal indicative of the intensity of the ambient light;

determining whether a current video frame of the sequence of video frames immediately follows a scene change using the metadata;

transforming the input video signal into an output video signal suitable for a target display, comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light; and

outputting the output video signal for use by the target display;

wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence on the signal indicative of the intensity of ambient light only in response to determining, using the metadata, that the current video frame of the sequence of video frames immediately follows a scene change.

14. A method for applying ambient light compensation, comprising:

-receiving an input video signal comprising a sequence of video frames;

-receiving metadata relating to the sequence of video frames;

-receiving a signal indicative of an intensity of ambient light from an ambient light sensor;

-determining whether a current video frame of the sequence of video frames immediately follows a scene change using the metadata; and

-transforming the input video signal into an output video signal suitable for a target display comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

the method includes adjusting the ambient light compensation applied in dependence on the signal indication only in response to determining, using the metadata, that the current video frame of the sequence of video frames immediately follows a scene change.

15. A computer program product having instructions which, when executed by a computing device or system, cause the computing device or system to perform the method of claim 14.

Technical Field

The present disclosure relates generally to video technology. More particularly, embodiments of the present disclosure relate to video signal display in a viewing environment with variable ambient light.

Background

In a typical content creation pipeline, video is color graded in a low light environment, typically a 5 nit (nit) environment for color graded High Dynamic Range (HDR) video, and a 10 nit environment for color graded Standard Dynamic Range (SDR) video. In practice, viewers may display content in a variety of environments, for example, at 0 to 5 nits (e.g., watching a movie in a relatively dark home theater), at 100 to 150 nits (e.g., watching a movie in a relatively bright living room), or higher (e.g., watching a movie in a tablet computer in daylight in a very bright room or outdoors).

As appreciated by the inventors herein, improved techniques are desired for displaying video to compensate for ambient light conditions in a viewing environment.

Disclosure of Invention

Embodiments of the present disclosure relate to a Display Management (DM) module and corresponding method.

In an embodiment, a DM module is configured to receive an input video signal comprising a sequence of video frames and a signal indicative of an intensity of ambient light. The DM module is further configured to determine whether a current video frame of the sequence of video frames immediately follows a scene change. The DM module is further configured to transform the input video signal into an output video signal suitable for a target display device. Transforming the input video signal to the output signal includes applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light. The output video signal is output by the DM module for use by the target display device. The DM module is configured to adjust the ambient light compensation applied to the input signal in dependence upon the signal indicative of the intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

Other embodiments of the present disclosure relate to a display device comprising the DM module, an ambient light sensor and a display, and a computer program for performing the method.

Drawings

Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

FIGS. 1A-C show schematic diagrams of an exemplary display apparatus;

FIG. 2 shows a flow diagram of an example of a method for applying ambient light compensation;

FIGS. 3A-B show a flow diagram of an example of determining whether a video frame follows a scene change;

FIG. 4 shows an example function for ambient light compensation;

FIG. 5 shows a schematic diagram of an exemplary ambient light sensor;

FIG. 6A shows a schematic diagram of sensitivity as a function of wavelength for a first exemplary ambient light sensor;

FIG. 6B shows a schematic diagram of sensitivity as a function of wavelength for a second exemplary ambient light sensor; and is

Fig. 7 schematically illustrates adjusting the ambient light signal for a measurement bias caused by the detection of light emitted by the display device itself.

Detailed Description

Numerous specific details are described below to provide a thorough understanding of the present invention. However, the invention may be practiced without these specific details. In addition, well-known parts may be described in less detail. The figures are schematic and include parts relevant for understanding the present disclosure, while other parts may be omitted or merely suggested.

Fig. 1A-C show examples of display apparatuses 100, 200, 300 applying ambient light compensation. In the context of the present disclosure, a display apparatus may include, for example, a television, a laptop computer, a tablet computer, a smartphone, a projector, or any other electronic device for displaying video.

As used herein, the term "dynamic range" (DR) may relate to the ability of the Human Visual System (HVS) to perceive a range of intensities (e.g., illumination, brightness) in an image, for example, from the darkest grayscale (dark or black) to the brightest white (highlight). In this sense, DR relates to "scene reference" intensity. DR may also relate to the ability of a display device to adequately or approximately exhibit a range of intensities of a particular width. In this sense, DR relates to "show reference" intensity. Unless a particular meaning is explicitly stated to have a particular meaning at any point in the description herein, it is to be inferred that this term can be used in either sense, e.g., interchangeably.

As used herein, the term "display management" refers to the process of adapting an image or picture (e.g., frame) of an input video signal to a target display device. Display management may include mapping images or pictures of an input video signal of a first dynamic range (e.g., 1000 nits) to a display device having a second dynamic range (e.g., 500 nits). Display management may include tone mapping and/or gamut mapping.

Display device 100 (fig. 1A) includes a display 102, an ambient light sensor 104, and a Display Management (DM) module 106. In this example, the ambient light sensor 104 is in communication with the DM module 106, and the DM module 106 is in communication with the display 102. The DM module 106 receives an input video signal 108 comprising a sequence of video frames. Optionally, the DM module 106 further receives metadata 110 related to the input video signal 108. For example, the DM module 106 may receive the input video signal 108 and the metadata 110 from a decoder internal or external to the device 100.

The DM module 106 receives a signal 112 from the sensor 104 indicative of ambient light. The signal is indicative of at least the intensity of the ambient light recorded by the sensor 104. Optionally, the signal may further indicate the color of the ambient light recorded by the sensor.

Typically, the sensor 104 is positioned on the front side of the device 100 corresponding to the front side of the display 102 to measure the illumination on the display screen, which is an ambient component that raises the black level of the display in terms of reflectivity. In such a scenario, the sensor 104 measures the intensity and optionally the color of the light present at the front side of the display 102. However, the present disclosure is not limited to a particular location of the sensor 104, and alternatively, the sensor 104 may be positioned at a different location, such as along an edge of the display device or at the back of the device.

In the example of the figure, a single sensor 104 is shown. However, the present disclosure is not limited to the use of a single sensor, and multiple sensors 104 may be used to generate the signal 112 indicative of ambient light used by the DM module 106.

The DM module 106 is configured to transform the input video signal 108 into an output video signal 114 suitable for the display 102. The transformation may include: tone mapping, e.g., to adjust the dynamic range of the input signal 108 to the dynamic range supported by the display 102; and/or gamut mapping, e.g., to adjust the color of the input signal 108 to a gamut supported by the display 102.

The optional metadata 110 may include parameters for tone mapping and/or gamut mapping operations. The DM module 106 may thus adjust tone mapping and/or gamut mapping operations to be applied to the input video signal 108 based on the metadata 108. The tone mapping and/or gamut mapping may further use parameters related to the characteristics of the display 102, which may be stored internally in the device 100 and thus accessible by the DM module 106.

An example of Display management including tone mapping is described in PCT/US2014/016304, entitled "Display management for high dynamic range video", the entire contents of which are incorporated herein by reference. PCT/US2014/016304 describes a tone mapping curve that maps an input luminance value to an output luminance value in accordance with

Wherein C is₁、C₂And C₃Is a constant number, Y_inFor inputting the luminance value, Y_outTo output the luminance values, n and m are parameters. C₁、C₂And C₃Based on the luminance characteristics of the reference (or source) display and the luminance characteristics of the target display. The luminance characteristics of the reference (or source) display are typically extracted from the input metadata, e.g. minimum luminance (S)_min) Average or median value (S)_mid) And maximum brightness (S)_max). Brightness characteristics of the target display, e.g. minimum brightness (T)_min) Average or median value (T)_mid) And maximum luminance (T)_max) Typically stored internally in the display device and thus accessible by the DM module. Parameter S_min、S_mid、S_max、T_min、T_mid、T_maxThree anchor points defining a tone mapping curve, i.e. (S)_min、T_min)、(S_mid、T_mid)、(S_max、T_max) The three anchor points determine a constant C in sequence₁、C₂And C₃The value of (c).

Another example of display management including Tone mapping is described in PCT/US2018/017830, entitled "Tone mapping for high dynamic range images", the entire contents of which are incorporated herein by reference. PCT/US2018/017830 describes a tone mapping curve that uses the same three anchor points, but has four segments in total: a value less than (S)_min、T_min) First linear section of (S), from_min、T_min) To (S)_mid、T_mid) First spline curve of (S)_mid、T_mid) To (S)_max、T_max) And a second spline curve of greater than (S)_max、T_max) The second linear section of (1).

Other examples of display management including tone mapping are described in PCT/US2011/025366, entitled "display management methods and apparatus," which is incorporated herein by reference in its entirety.

The transformation performed by the DM module 106 may further include applying ambient light compensation to the input video signal 108. Ambient light compensation is applied in response to a signal 112 received from the sensor 104 indicative of at least the intensity of the ambient light. The DM module 106, for example, in addition to applying the tone mapping operation, also applies ambient light compensation to the input signal 108 to thereby generate an output video signal 114 for presentation by the display 102. The ambient light compensation may be applied before or after applying the tone mapping and/or the gamut mapping. In another example, ambient light compensation is combined with tone mapping and/or gamut mapping into a single mapping operation. In such examples, the mapping applied by the DM module 106 to the input video signal 108 has parameters that depend on the signal 112, as well as parameters related to tone mapping and/or gamut mapping, which may be included in the metadata 110 or derived from the metadata 110, for example, or derived from the input video signal 108 itself.

The DM module 106 is further configured to determine whether a current video frame of the input video signal 108 immediately follows a scene change (also referred to as a "scene cut").

In other words, the DM module 106 may be configured to determine whether the current video frame starts a new scene that follows a previous scene that includes a video frame immediately preceding the current video frame.

A scene includes a set of consecutive video frames having similar luminance characteristics and/or similar color characteristics. The scene may be defined during the authoring of the video. For example, scene changes may be included in an Edit Decision List (EDL) used, for example, by a director and/or editor to create a movie from a number of different shots. These indications of scene changes may be included in metadata of the video signal.

Thus, in embodiments, metadata 110 includes metadata indicating a scene change. DM module 106 is configured to determine whether a current video frame of a sequence of video frames included in video signal 108 follows a scene change using metadata indicative of the scene change. For example, the metadata may include frame-by-frame metadata that includes a flag indicating whether the current frame immediately follows a scene change, i.e., whether the current frame is the first frame of a new scene. In another example, the metadata includes frame-by-frame metadata that includes an identifier, such as a scene number, that identifies a scene associated with the respective frame. In such a scenario, DM module 106 may determine whether the current video frame is located in a different scene than the video frame immediately preceding the current video frame by comparing the scene identifier of the current frame to the scene identifier of the previous frame. If the scene identifiers of two consecutive video frames are different, then it is determined that the current video frame immediately follows the scene change.

In another embodiment, the scene change is determined by the DM module 106 by comparing characteristics of the current video frame with characteristics of one or more previous video frames. For example, the characteristics may include luminance characteristics and/or color characteristics.

In an example, the DM module 106 determines whether a change in the characteristic between the current frame and the previous frame satisfies a predetermined threshold condition, e.g., exceeds a predetermined threshold. If the change satisfies the threshold condition, the DM module 106 determines that a scene change occurs between the current video frame and the previous video frame, i.e., the current scene immediately follows the scene change.

In another example, the DM module 106 determines an average illumination value for each frame j<I_j>And comparing the average illumination values of the current frame<I_j>Average illumination value from previous frame<I_j-1>The difference between and the threshold T. If the difference is-<I_j>-<I_j-1>| exceeding the threshold T, i.e. |<I_j>-<I_j-1>|>T, then the DM module 106 determines that the current frame immediately follows the scene change. Instead of an average luminance value, a different function of the luminance values of the frames may be used. For example, instead of an average luminance value, an intermediate luminance value may be used, which may for example be calculated as the maximum luminance value (I) of a video frame_max) And a minimum value (I)_min) Average value of (I), i.e. (I)_max+I_min)/2。

In another example, a characteristic of a video frame is derived from metadata indicative of the characteristic. For example, referring to the example of the previous paragraph, the intermediate luminance value or the average luminance value may be, for example, the metadata value S described above_midIs available as frame-by-frame metadata contained in the metadata 110 received by the DM module 106.

In another embodiment, DM module 106 is capable of determining a scene change based on the metadata indicative of a scene change and determining a scene change by the comparison of characteristics of a current video frame to characteristics of one or more previous video frames. In another example of this embodiment, the DM module 106 is configured to-in the presence of metadata indicative of a scene change-determine a scene change based on the metadata rather than by the comparison. An advantage of metadata indicating that the scene change overrules the automatic detection of the DM module 106 is that the display management process follows the creator's intent more closely.

In fig. 1B and 1C, elements similar to those of fig. 1A are given the same reference numerals, increased by 100 or 200, respectively. These elements have the same characteristics, configurations, and functionality as described with respect to fig. 1A, unless described otherwise in the following description.

The display device 200 (fig. 1B) differs from the display device 100 in that it includes a display controller 216 that controls the operation of the display 202. The DM module 206 communicates with a display controller 216, and the display controller communicates with the display 202. The DM module 206 receives an input video signal 208 comprising a sequence of video frames. In addition, the DM module 206 optionally receives metadata 210, such as metadata including metadata for dynamic range mapping and/or metadata indicating scene changes. The DM module 206 receives information 218 from the display controller 216 regarding characteristics of the display 202.

In an example, the information 218 includes brightness characteristics of the target display for use by the DM module 206 in tone mapping, such as a minimum brightness (min), an average or median value (mid), and a maximum brightness (max). In this example, the DM module 206 is based on source brightness characteristics (e.g., S) contained in the metadata 210_min、S_mid、S_max) And target brightness characteristics (e.g., T) included in or derivable from information 218 received from display controller 216_min、T_mid、T_max) Tone mapping is applied to the input video signal 208. In addition, the DM module 206 receives a signal 212 from the ambient light sensor 204 indicative of the intensity of the ambient light (and optionally the color of the ambient light) and applies an ambient light compensation in dependence on the signal 212. The DM module 206 transmits the tone-mapped (and optionally gamut-mapped) and ambient light compensated output video signal 214 to the display controller 216. The display controller 216 controls the display 202 to present the output signal 214.

Instead of using the metadata 210 to determine source brightness characteristics, the DM module 206 may determine these characteristics by analyzing the video signal 208 (e.g., by determining a minimum, an intermediate, and a maximum of one or more images of the video signal 208). Additionally, as described above with respect to the display device 100, instead of using the optional metadata 210, a scene change may be determined by the DM module 206 of the display device 200 by comparing characteristics of a current video frame with characteristics of one or more previous video frames.

In an example, the display 202 includes a backlight. For example, the display 202 may be an LCD type display. In this scenario, the display controller 216 is configured to control the backlight of the LCD display based on the video signal 214 received from the DM module 206. In other examples, display 202 may not include a backlight. For example, display 202 may be an OLED type display.

The display device 300 (fig. 1C) differs from the display device 200 in that the ambient light sensor 304 communicates with the display controller 316 rather than with the DM module 306. The display controller 316 receives a signal 312 from the sensor 304 indicative of the intensity of the ambient light. The display controller 316 transmits information 320 regarding the intensity of the ambient light (and optionally information regarding the color of the ambient light) to the DM module 306. In the illustrated example, the signal 312 of the sensor 304 is passed to the DM module 306. Alternatively, the display controller 316 may process the signal 312 of the sensor 304 to generate a parameter indicative of the intensity of the ambient light and communicate the parameter to the DM module 306.

Similar to in FIG. 1B, also in FIG. 1C, the display controller 316 communicates information to the DM module 306 regarding characteristics of the display 302, e.g., communicates brightness characteristics for tone mapping operations of the DM module 306. The DM module 306 applies a tone mapping operation and ambient light compensation to the input video signal 308, wherein the tone mapping operation is controlled via parameters of the source characteristics contained in the metadata 310 (or determined directly from the video signal 308 by the DM module 306) and parameters of the characteristics of the display 302 contained in the signal 318, and wherein the ambient light compensation is applied in dependence on the signal 320 indicative of the intensity of the ambient light received from the display controller 316.

The display devices 100, 200, and 300 include displays 102, 202, 302. In some embodiments, the display device 100, 200, 300 may comprise a projector instead of a display. For example, the projector includes a laser projector.

In the above embodiments, the ambient light sensor 104, 204, 304 is depicted as part of the display device 100, 200, 300. Alternatively, the ambient light sensor may be located external to the display device 100, 200, 300, in which case the DM module 106, 206, 306 is configured to receive a signal indicative of the intensity of the ambient light from the external ambient light sensor, e.g., via a wired or wireless connection 112, 212, 312.

Since the ambient light is generally not constant over time, the signal 112, 212, 320 indicative of the intensity of the ambient light will also generally vary over time. However, compensating for transient ambient light may cause "flicker": a significant rapid fluctuation in the brightness of the displayed image. Measurement noise inherent to the ambient light sensor may, for example, cause the brightness to be adjusted in response to the measured intensity of ambient light, even if the intensity of the ambient light is not actually changed. In another example, if the ambient light sensor is temporarily blocked, such as by a person standing in front of the ambient light sensor, the brightness may drop significantly, rising again only immediately after the person leaves and no longer blocks the sensor.

In the embodiment of fig. 1A-C, the DM module 106, 206, 306 is configured to adjust the ambient light compensation only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change. In other words, the adjustment of the ambient light compensation is synchronized with the scene change of the input video signal. The inventors have found that adjusting ambient light compensation is not noticeable to the viewer when limiting the adjustment to the scene change. In a typical video, a scene change occurs every 1 to 5 seconds. The inventors have found that even if the ambient light compensation is adjusted every 1 to 5 seconds, the change in ambient light compensation is not significant if the adjustment is limited to only scene changes. Thus, by synchronizing the ambient light adjustment with the scene change, flicker is avoided or at least reduced. Furthermore, a fast response to changes in the ambient light is ensured, since the next scene will have an ambient light adjustment adapted to the actual ambient light conditions.

The above description relates to sensor adaptive ambient light compensation, i.e. ambient light compensation that is automatically adjusted in response to a signal indicative of the intensity of the ambient light. Other types of adjusting the brightness and/or color of the displayed image may be useful. For example, the DM module 106, 206, 306 and/or the display controller 216, 316 may allow a user to manually set brightness levels and/or color settings. In embodiments, the DM module 106, 206, 306 does not limit the other types of adjusting brightness and/or color to scene changes, e.g., brightness settings may be adjusted by a user intermediate to a scene.

Optionally, a temporally smoothed version may be applied to the signals 112, 212, 312 of the sensors 104, 204, 304 while limiting the adjustment of ambient light compensation to scene changes, as described above. In an embodiment, a temporal smoothing filter is applied to the signal indicative of the intensity of the ambient light, wherein the filter is reset in response to determining that the current video frame closely follows the scene change. For example, the smoothing filter includes a moving average filter, a weighted moving average filter, and an exponential smoothing filter. Resetting the filter may include clearing previously stored values of the filter, for example setting these values to zero or a currently measured value.

For example, the cumulative average filter is implemented as:

y(n)＝y(n-1)+I(n)，

where I (n) represents the ambient intensity measured by the sensor at discrete time instance n, and y (n) represents the cumulative average, where y (0) may be initialized to I (0). In this example, y (n) is reset to i (n) in response to determining that the current video frame immediately follows the scene change.

Fig. 1A-C show an exemplary display apparatus for ambient light compensation. However, the present disclosure is not limited to these examples. In particular, additional components of the display apparatus not related to ambient light compensation have not been described.

Fig. 2 illustrates a method for applying ambient light compensation. The method may be implemented by a display device. In an embodiment, the method is performed by a display management module of a display device. For example, the method may be performed by any of the DM modules 106, 206, 306 described above.

The method begins at step 402. A current video frame of a sequence of video frames is received in step 404. It is determined whether a scene change has occurred 406. In particular, in step 406, it is determined whether the current frame immediately follows a scene change, which will be described in more detail with respect to fig. 3A and 3B.

In response to determining that the current video frame immediately follows the scene change, the method moves to step 408, where an ambient light signal is received. The ambient light signal comprises at least an indication of the intensity of the ambient light. Optionally, the ambient light signal further comprises an indication of the color of the ambient light. In step 410, the current setting of the ambient light compensation is adjusted in dependence on the ambient light signal received in step 408. The method then moves to step 412 where the current setting of the-ambient light compensation-updated in step 410-is applied.

In response to determining that the current video frame does not immediately follow the scene change, the method moves from step 406 to step 412. In such cases, the setting of the ambient light compensation is not adjusted, i.e. the previous setting of the ambient light compensation is maintained. Thus, in this case, at least step 410 is omitted. At step 412, the current setting is applied, in this scenario the current setting is the same as the ambient light setting of the previous frame.

After step 412, it is determined in step 414 whether the current frame is a final video frame. If not, i.e., the next video frame is available, then the next video frame is set as the current video frame and the method returns to step 404. If the current frame is the final video frame, the method ends at step 418.

In the example of fig. 2, step 408 is performed immediately before step 410. However, step 408 may also be performed between steps 404 and 406. In another example, step 408 is performed before step 404 as a first step of a loop over the illustrated video frame, followed by step 404.

Fig. 3A shows a first example of the substeps of step 406, namely the step of determining whether the current video frame immediately follows a scene change. In the example of FIG. 3A, metadata is received in sub-step 406-1. The metadata contains metadata indicating a scene change. In an example, the metadata indicating a scene change includes a frame-by-frame flag indicating whether the current frame starts a new scene. In sub-step 406-2, the method determines whether a flag is set, i.e., whether the current frame starts a new scene. In response to determining that the flag is set, the method continues to step 408 as described above. In response to determining that the flag has not been set, the method continues to step 412 as described above. In another example, the metadata indicating the scene change includes a frame-by-frame identifier for the scene with which the current frame is associated. For example, the identifiers may include unique numeric, alphabetic, or alphanumeric identifiers to identify different scenes. In such a scenario, step 406-2 compares the identifier of the current video frame with the identifier of the previous video frame (i.e., the video frame immediately preceding the current video frame). If it is determined that the current video frame and the previous video frame have the same scene identifier, i.e. they are associated to the same scene, the metadata thus indicates that no scene change has occurred and the method continues to step 412. If it is determined that the current video frame and the previous video frame have different scene identifiers, i.e., they are associated with different scenes, the method continues to step 408.

Fig. 3B shows a second example of the substeps of step 406. In sub-step 406-a, characteristics of the current video frame are determined. For example, a luminance characteristic of the current video frame is determined. For example, a median or average luminance value for the current video frame may be calculated or extracted from the metadata, as described above.

In sub-step 406-B, a difference between one or more characteristics of the current video frame and the same one or more characteristics of at least one previous video frame is calculated. For example, the difference between the intermediate illumination level of the current video frame and the intermediate illumination level of the previous video frame is calculated. In another example, the difference between the characteristic of the current video frame and the average (or weighted average) of the same characteristics of the N previous video frames is calculated, such as the difference between the median illumination of the current video frame and the average (or weighted average) of the median illumination of the N previous frames.

In step 406-C, it is determined whether the difference calculated in step 406-B satisfies a threshold condition. In the example shown, it is determined whether the difference exceeds a threshold. In response to determining that the difference exceeds the threshold, the method proceeds to step 408. In response to determining that the difference does not exceed the threshold, the method proceeds to step 412.

In another embodiment, the same functionality is implemented by determining whether the difference is less than a threshold. In response to determining that the difference is less than the threshold, the method proceeds to step 412. In response to determining that the difference is not less than the threshold, the method proceeds to step 408.

As described above, the DM module 106, 206, 306 applies ambient light compensation to the input video signal 108, 2 depending on the ambient light intensity08. 308. For example, applying ambient light compensation comprises adjusting the brightness in dependence of the ambient light intensity, wherein the brightness increases with increasing ambient light intensity. Let v be_ijDenotes the luminance component of a video frame j having P pixels I0.. P-1, and let I denote the ambient light intensity. The output video frame may then be calculated as:where f (I) represents a function of ambient light intensity. Here, the ambient light intensity I is calculated based on the signals 112, 212, 312 received from the ambient light sensors 104, 204, 304. For example, the signal may be temporally smoothed as described above to obtain the ambient light intensity. The function f (i) may take both negative and positive values. For example, when an input video signal is composed in a 5 nit reference environment, f (I) may take a negative value for a value of I corresponding to an ambient light intensity smaller than 5 nit, f (I) is 0 for a value of I corresponding to an ambient light intensity of 5 nit, and f (I) > 0 for a value of I corresponding to an ambient light intensity exceeding 5 nit. The function f (i) may be a linear or non-linear function.

In an embodiment, applying ambient light compensation includes adjusting the brightness as a function of both the ambient light intensity and an intensity value of the input video frame (e.g., a pixel value of a brightness component of the input video frame). Thirdly, v_ijDenotes the luminance component of a video frame j having P pixels I0.. P-1, and I denotes the ambient light intensity. The output video frame may then be calculated as: wherein g (v)_ijI) represents a function of both the ambient light intensity and the luminance value of pixel I of frame j.

In an embodiment, the function f (I) or g (v)_ijI) is implemented as a look-up table (LUT).

FIG. 4 shows the function g (v) of the ambient light intensity I at four different levels_ijExamples of I). In the graph of FIG. 4, the abscissa shows candelas per square meter as a unitInput illuminance in bit representation, which is dependent on input brightness value v_ijAnd correspond to each other. The ordinate shows the output illuminance expressed in candelas per square meter, in relation to the output brightness valueAnd correspond to each other. The graph shows the relationship between input illumination and output illumination at 5 nits (405), 100 nits (410), 500 nits (415), and zero nits (420).

As depicted in fig. 4, when the viewing environment matches the reference environment (e.g., 5 nits), the function 505 represents a straight line with a slope of 1, i.e., no environmental compensation is applied. For a darker (e.g., function 520) or lighter (e.g., function 510 or function 515) viewing environment, the ambient light compensation is reduced or increased as needed. As can be seen from fig. 4, the ambient light compensation depends on both the ambient light intensity and the input illumination of the input video frame.

The DM module 106, 206, 306 may access a predetermined number of ambient light compensation maps (e.g., in the form of one or more LUTs or 3D LUTs) stored internally in the display device 100, 200, 300 (e.g., stored in a memory of the DM module 106, 206, 306). In this example, the DM module 106, 206, 306 may be configured to select one of a set of ambient light compensation maps in dependence on a signal indicative of the intensity of the ambient light. For ambient light intensities that are not represented in the stored LUT, interpolation techniques may be applied to derive an appropriate LUT. For example, for two ambient light values I₁And I₂Given a pre-calculated curve g (v)_ij，I₁) And g (v)_ij，I₂) Can be prepared by reaction of compounds in g (v)_ij，I₁) And g (v)_ij，I₂) Interpolating between values to generate I₁＜I＜I₂New curve g (v) of_ij，I)。

As described above, light sensors for ambient light compensation in display devices are typically positioned at the front side of the display device to obtain a measure of the light intensity that increases the black level of the displayed image. However, the positioning of the sensor close to the front of the display device may cause the sensor to also register some of the light emitted by the display device itself. Thus, the signal generated by the sensor may not be an accurate measure of ambient light. Instead, the signal of the sensor depends on both the ambient light and the light emitted by the display device. This may also affect the output of the light sensor, since the light emitted by the display device may change rapidly due to changes in the input video signal, and in conventional display devices, may be another cause of the occurrence of flicker. The synchronization of the environmental adjustments to the scene changes as described above is also effective in reducing or eliminating flicker caused by the sensor recording the light emitted by the display device itself. However, the signal generated by the sensor may be an inaccurate quantity of ambient light intensity. Thus, ambient light compensation applied based on sensor output may unnecessarily increase or decrease the brightness of the displayed image in view of the actual ambient light.

The LCD display may empty the screen at certain time intervals. Thus, the above problem of reduced accuracy can be solved by taking measurements from the ambient light sensor only during the time the screen is emptied. However, this approach has the disadvantage that the amount of time the screen is emptied is relatively short, otherwise the average display brightness will be affected. If the screen is off 10% of the time, the sensor will only measure ambient light 10% of the time and a 10-fold gain needs to be applied, resulting in more noise being generated in the measurement. This is undesirable because noise in the output signal of the sensor is a cause of flicker.

The problem of the display device interfering with the measurement of the ambient light sensor increases with increasing brightness. Therefore, the interference is larger for HDR display devices that typically have higher maximum luminance. However, the problem also exists in SDR display devices, so the present disclosure is not limited to HDR, but covers both HDR and SDR implementations.

The inventors have recognized that by using an ambient light sensor that is less sensitive to light of wavelengths corresponding to the primary colors of the display device than to other wavelengths of the visible spectrum, the accuracy of ambient light compensation can be improved without increasing the occurrence of flicker.

For displaying color images, the display device comprises three or more different color pixels, referred to as the primary colors of the display device. For example, a display device may include red (R), green (G), and blue (B) pixels. The ambient light sensor (e.g., sensors 104, 204, 304) is of a type that is less sensitive to the primary colors of the display device (e.g., to wavelengths corresponding to the RGB colors of the pixels of the display device).

The embodiment of fig. 5 shows an example of such an ambient light sensor. The ambient light sensor 604 of fig. 5 includes a photodetector 603a and an optical filter 603 b. The photodetector 603a may, for example, comprise a photodiode, a phototransistor, a resistor, one or more reverse biased LEDs, any other suitable type of photodetector. Optical filter 603b reduces or blocks one or more primary colors of the display device. For example, optical filter 603b may be an optical band-stop filter (also referred to as an optical notch filter) that attenuates light of wavelengths corresponding to the primary colors of the display device. In other words, the stopband of the optical band-stop filter corresponds to the spectral power distribution of the light emitted by the display device. An example of such sensor characteristics is shown schematically in fig. 6A. The abscissa corresponds to the wavelength and the ordinate corresponds to the sensor sensitivity. The sensor typically has a flat response across the visible spectrum, except for three notches, each corresponding to one of the primary colors of the exemplary display apparatus.

For example, an optical band-stop filter may be used as optical filter 603b to achieve the response of fig. 6A. In another example, instead of having a band-stop characteristic as shown in fig. 6A, a sensor having a band-pass characteristic may be provided, wherein the pass-band of the sensor corresponds to a band that does not include the primary colors of the display device. For example, an optical bandpass filter may be provided as the optical filter 603 b. Figure 6B schematically shows the sensitivity of a sensor having such a band pass characteristic. The solid line illustrates a first pass band, which corresponds to cyan light, e.g., light having a wavelength of 490 to 520 nm. The dashed line illustrates a second pass-band, which corresponds to yellow light, e.g. light with a wavelength of 570 to 590 nm. The response of the sensor may include only the first pass band, only the second pass band, or may include both the first pass band and the second pass band. The band pass characteristic of the sensor is realized, for example, by using a yellow filter as the optical filter 603b, or by using a cyan filter as the optical filter 603b, or by using the optical filter 603b having a double pass band, or by using the optical filter 603b including a mosaic of a yellow filter and a cyan filter.

In another example, optical filters 603B may comprise a color filter mosaic comprising a red filter (R), a green filter (G), a blue filter (B), a yellow filter (Y), and a cyan filter (C). This may be labeled as a RYGCB sensor. Optionally, a magenta filter (M) is also included. The mosaic R, G and the B filter correspond to the R, G, B primary color of the display device. For ambient light compensation, only the Y and C pixels of the RYGCB sensor are considered to avoid adjusting the ambient light compensation to the light emitted by the display device itself. R, G and the B pixels may be used to determine the color of the ambient light for adjusting the color mapping of the video signal to be displayed. Thus, the present disclosure further relates to such sensors themselves: a light sensor comprising an optical filter in the form of a RYGCB mosaic (optionally a RYGCBM mosaic).

The optical filter 603b may thus block or attenuate other wavelengths, such as red, green, and blue light used in RGB display devices.

The use of an ambient light sensor that is less sensitive to the primary colors of the display device is particularly effective for display devices that include one or more lasers (e.g., laser projectors) because the laser light sources have very narrow bandwidths. Thus, the laser light illuminating the sensor can be filtered out very effectively.

An advantage of using a sensor sensitive only to yellow light is that in a typical viewing environment, the main contribution to the intensity of the ambient light is emitted by a lamp that typically emits predominantly yellow light.

Some displays include blue and yellow phosphors, in which case it is advantageous to use a sensor sensitive to cyan light only.

Instead of using optical filters 603b, ambient light sensors may be selected that are inherently insensitive to the primary colors of the display device. For example, the ambient light sensor comprises a light sensitive semiconductor device (e.g. a photodiode or a reverse biased LED) having a bandgap corresponding to a wavelength different from the wavelength of the primary color of the display device. For example, a semiconductor device having a bandgap corresponding to a wavelength in the yellow portion of the spectrum (e.g., 570 to 590 nm). In another example, two or more photosensitive semiconductor devices with different bandgaps are used, each corresponding to a wavelength different from the wavelength of the primary color of the display apparatus. For example, the ambient light sensor includes a photodiode having a bandgap corresponding to a wavelength of the yellow portion of the spectrum (e.g., 570-590 nm) and another photodiode having a bandgap corresponding to a wavelength of the cyan portion of the spectrum (e.g., 490-520 nm).

The above combinations describe a) synchronizing ambient light compensation with scene changes, and b) using a metric of an ambient light sensor having reduced sensitivity to light of a wavelength corresponding to a primary color of the display device. However, the present disclosure is not limited to such a combination, and these features may be implemented as independent metrics. It should be noted that the effect of reduced flicker may also be achieved in case an ambient light sensor having a reduced sensitivity to the primary colors of the display device is used as an independent measure, i.e. in case the ambient light adjustment is not synchronized with the scene change, since flicker caused by detecting light emitted by the display device is prevented.

In an embodiment, a display apparatus comprises an ambient light sensor configured to generate a signal indicative of an intensity of ambient light, wherein the apparatus is configured to receive an input video signal and to apply an ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of ambient light, wherein the ambient light sensor is less sensitive to light of wavelengths corresponding to a primary color of the display apparatus than to light of other wavelengths of the visible spectrum.

For example, the display device includes a projector such as a laser projector or a display such as an LCD or OLED display.

For example, the display apparatus includes a controller and/or DM module configured to receive the input video signal and apply ambient light compensation to the input signal in dependence on a signal indicative of an intensity of ambient light.

As described above, by using an ambient light sensor with reduced sensitivity to the primary colors of the display device, interference of light emitted by the display device itself with measurements performed by the ambient light sensor is avoided or at least reduced. Additionally or alternatively, the apparatus (e.g., a DM module of the apparatus) may be configured to determine an expected measurement bias based on the input video signal and to consider the expected measurement bias when applying ambient light compensation based on the sensor output.

Fig. 7 illustrates an example of a process for accounting for expected measurement bias caused by sensors recording light emitted by the display device itself. The input video signal 702 includes a sequence of video frames 704-1 through 704-4. The current frame is depicted as "frame n" and the first three video frames are depicted as "frame n-3", "frame n-2", and "frame n-1", respectively. The input video signal 702 may further include metadata (not shown), such as frame-based metadata and/or scene-based metadata, as described in more detail above.

The function block 706 performs operation f for each video frame 704 to extract a measure of the overall intensity level of each video frame. The function block 706 is the same for each video frame 704, so that operation f is also the same for each video frame 704. Operation f may be performed on image data of each video frame or metadata of the video frame. For example, operation f may analyze pixel intensity values of the image data to determine an overall intensity level of the video frame 704. In another example, operation f uses frame metadata (e.g., S described above)_min、S_midOr S_maxMetadata) to determine the overall intensity level of the video frame 704. The result of operation f is a scalar indicating the overall intensity level of the corresponding video frame.

For example, the overall intensity of the video frame 704 may be calculated as the average pixel intensity value of the video frame. Let P denote the number of pixels in each frame, i denotes 0 ≦ i<Pixel index of P, and L_iRepresenting pixel intensity values. Then, in this example:

alternatively, an average strength of the intensity values for the video frames may be available in the frame metadata, and operation f extracts the average strength from the metadata for each frame.

In another example, the overall intensity of the video frame 704 is calculated as an average or median of the pixel intensity values of the video frame. In yet another example, the overall intensity of the video frame 704 is calculated as the average of the maximum pixel intensity value and the minimum pixel intensity value of the video frame:

alternatively, max (L)_i) Or min (L)_i) May be available in the frame metadata and operation f extracts those values from the metadata and calculates their sum and divides by 2. In another example, instead of calculating the average of max and min, the operation extracts S directly from the frame metadata_midThe value is obtained.

The term "pixel intensity value" refers to a per-pixel measure of intensity for the pixel. For example, the pixel intensity values may correspond to pixel values of a luminance component of the image data. In another example, pixel intensity values are calculated from pixel values of the image data, e.g., in an RGB image, the intensity values of the pixels may be calculated as a linear combination of R, G and B pixel values.

In block 708, a desired measurement bias is calculated 712, which includes the step of summing the intensity levels generated by block 706. In an embodiment, the expected measurement bias 712 simply corresponds to the calculated sum, as illustrated by the sigma (sigma) sign in block 708. In another embodiment, the desired measured offset 712 is calculated by dividing the sum by the number of video frames 704 used in the calculation to obtain an average of the intensities of the video frames 704. In another embodiment, the desired measured bias 712 is calculated by calculating a linear combination (e.g., a weighted average) of the intensities of the video frames 704. For example, a weighted average having a greater weighting factor for intensities of more recent video frames (e.g., 704-3) than for older video frames (e.g., 704-1).

The measurement configuration 712 calculated in block 708 is used in a function block 710 to adjust the ambient light intensity value 714 based on the measurement performed by the ambient light sensor. The measured value 714 may be obtained directly from the ambient light sensor, or a pre-processing step such as analog-to-digital conversion, scaling or offset may be performed on the sensor's signal to convert it to a measured value of the ambient intensity 714. In block 710, the measured value 714 is adjusted by compensating for an expected measured bias 712 determined based on the input video signal 702. The output of block 710 is a correction value for the ambient light intensity, based on which the subsequent ambient light compensation will be based.

For example, the compensation performed in block 710 may include subtracting the expected measured offset 712 from the measured value 714: i is_corrected＝I_measured-I_bias. In another example, the compensation performed in block 710 includes scaling the expected bias before subtracting: i is_corrected＝I_measured–a*I_bias. For example, 0<a is less than or equal to 1. In another example, the expected bias determined in block 708 is converted via a second order polynomial before subtraction: i is_corrected＝I_measured–(αI_bias ²+βI_bias+ γ). In yet another example, in slave I_measuredThe expected bias determined in block 708 is translated via the LUT prior to subtraction. In yet another example, the compensation performed in block 710 uses a 2D lookup table (LUT) to pair data (I)_measured,I_bias) Conversion into corrected intensity values I_corrected。

For example, a calibration procedure may be used to determine the scaling factor a, the parameters α, β, γ, LUT or 2D LUT. In a first step of the calibration procedure, the display device is configured to display the test image with minimal light emission. For example, the display apparatus is configured to display a black image. In the example of a display device having a display with a backlight, the backlight may be turned off for said first step of the calibration process. A response from the ambient light sensor is measured. In a second step of the calibration procedure, which may be performed before or after the first step, at least one test image is displayed and the response from the ambient light sensor is measured. For example, a series of test images are displayed in sequence, each of the test images having a different overall intensity. The first and second steps are performed in a relatively small time frame, not exceeding 2 to 3 minutes, but typically less than 30 seconds. Therefore, the difference between the sensor output when displaying a black image and the sensor output when displaying a test image is mainly attributable to the sensor that records the light emitted by the display device itself. In an embodiment, the difference is calculated to obtain a calibration bias level for each test image. Each test image has a known overall intensity. Thus, a LUT can be constructed that correlates the overall intensity of the image shown on the display device with the calibrated sensor bias. In an example, interpolation is used to obtain other entries of the LUT. Additionally or alternatively, a function may be fitted to pairs of measured overall image intensity and bias values, e.g., to obtain the parameters a, α, β, or γ described above. In an embodiment, instead of measuring once with a black screen and then measuring a series of test images, black screen measurements are alternated with measuring one or more test images.

In the example of fig. 7, the current video frame "frame n" is also used to calculate the sum in block 708. However, as indicated by the dashed line, the inclusion of "frame n" is optional, and in some embodiments, the calculation is based only on video frames preceding the current video frame. In the example shown, the summing is performed over four frames, but the disclosure is not limited to summing over four frames. In one embodiment, the predetermined number of video frames used to calculate the measured offset may be in the range of 2 to 120 video frames, for example in the range of 30 to 90 video frames. Additionally, in the illustrated example, the calculations are performed on successive video frames. However, the present disclosure is not limited to using consecutive video frames for the calculation of the measurement bias, e.g., other video frames may be used.

The predetermined number of video frames used in the calculation corresponds to a certain duration. For example, in the case of 60 frames per second, 60 video frames correspond to a duration of 1 second. In an embodiment, the predetermined number of video frames to be used in the calculation (and optionally also during calibration) corresponds to a duration arranged in the order of the integration constants of the sensor. Typical values for the duration are 0.01 to 2 seconds, for example 0.5 to 1.5 seconds.

The embodiments described herein may be implemented in hardware, software, firmware, and combinations thereof. For example, embodiments may be implemented on a system including electronic circuitry and components, such as a computer system. Examples of computer systems include desktop computer systems, portable computer systems (e.g., notebook computers), handheld devices (e.g., smart phones or tablets), and network devices. A system for implementing an embodiment may, for example, include at least one of an Integrated Circuit (IC), a Programmable Logic Device (PLD), such as a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP), an application specific IC (asic), a Central Processing Unit (CPU), and a Graphics Processing Unit (GPU).

Certain implementations of the embodiments described herein may include a computer program product comprising instructions that, when executed by a data processing system, cause the data processing system to perform the method of any of the embodiments described herein. The computer program product may include non-transitory media that store the instructions, such as physical media (e.g., magnetic data storage media including floppy disks and hard drives), optical data storage media including CD ROMs and DVDs, and electronic data storage media including ROMs, flash memory (e.g., flash RAM or USB flash drives). In another example, the computer program product comprises a data stream comprising the instructions, or a file comprising the instructions stored in a distributed computing system (e.g., in one or more data centers).

The present disclosure is not limited to the embodiments and examples described above. Many modifications and variations are possible without departing from the scope of the disclosure, which is defined by the appended claims.

Various aspects of the disclosure may be understood from the example embodiments (EEEs) listed below:

EEE 1. a display device, comprising:

an ambient light sensor configured to generate a signal indicative of an intensity of ambient light,

wherein the display apparatus is configured to:

-receiving an input video signal; and

-applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

wherein the ambient light sensor is less sensitive to light of wavelengths corresponding to primary colors of the display device than to light of other wavelengths of the visible spectrum.

EEE 2. the display device according to EEE 1, wherein the ambient light sensor comprises an optical filter attenuating light of wavelengths corresponding to primary colors of the display device.

EEE 3. the display device according to EEE 2, wherein the optical filter comprises an optical band-stop filter.

EEE 4. the display apparatus according to EEE 1, wherein the ambient light sensor is sensitive only to one or more bands within the visible spectrum.

EEE 5. the display device according to EEE 4, wherein the ambient light sensor is sensitive to yellow light only.

EEE 6. the display device according to EEE 4, wherein the ambient light sensor is sensitive to cyan light only.

EEE 7. the display device according to EEE 4, wherein the ambient light sensor is sensitive to yellow light and cyan light only.

EEE 8. the display device according to any one of EEEs 4 to 7, wherein the ambient light sensor comprises an optical bandpass filter.

EEE 9. the display apparatus according to any one of EEEs 1-8, further comprising a display, wherein the display apparatus is configured to transform the input video signal into an output video signal suitable for the display, comprising applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light, and wherein the display is configured to display the output video signal.

EEE 10. the display apparatus according to any one of EEEs 1-8, further comprising a projector, wherein the display apparatus is configured to transform the input video signal into an output video signal suitable for the projector, comprising applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light.

EEE 11. the display device according to EEE 10, wherein the projector is a laser projector.

EEE 12. a display device, comprising:

an ambient light sensor configured to generate a signal indicative of an intensity of ambient light,

wherein the display apparatus is configured to:

-receiving an input video signal; and

-applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

wherein the display apparatus is further configured to determine a measurement bias due to the light emitted by the display apparatus and recorded by the ambient light sensor based on at least one of the input video signal and metadata related to the input video signal, and

wherein applying ambient light compensation comprises: applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light compensated by the determined measurement bias.

EEE 13. the display device according to EEE 12, wherein determining the measurement offset comprises:

determining an intensity level for each of a predetermined number of video frames prior to the current video frame; and

determining a sum of the intensity levels of the predetermined number of video frames.

EEE 14. the display apparatus according to EEE 12 or EEE 13, further comprising a display, wherein the display apparatus is configured to transform the input video signal into an output video signal suitable for the display, comprising the application of ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light, and wherein the display is configured to display the output video signal.

EEE 15. a method for applying ambient light compensation, comprising:

-receiving an input video signal comprising a sequence of video frames;

-receiving a signal indicative of an intensity of ambient light from an ambient light sensor;

-determining whether a current video frame of the sequence of video frames immediately follows a scene change; and

-transforming the input video signal into an output video signal suitable for a target display device comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

the method further comprises:

determining a measured bias due to the light emitted by the display apparatus and recorded by the ambient light sensor based on at least one of the input video signal and metadata related to the input video signal,

wherein applying ambient light compensation comprises: applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light compensated by the determined measurement bias.

EEE 16. the method of EEE 15, wherein determining the measurement offset comprises:

determining an intensity level for each of a predetermined number of video frames prior to the current video frame; and

determining a sum of the intensity levels of the predetermined number of video frames.

EEE 17. a display device, comprising:

-an ambient light sensor configured to generate a signal indicative of an intensity of ambient light; and

-a display management module configured to:

receiving an input video signal comprising a sequence of video frames;

determining whether a current video frame of the sequence of video frames immediately follows a scene change; and

applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light,

wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence upon the signal indicative of intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 18. the display apparatus of EEE 17, wherein the display management module is configured to receive metadata relating to the sequence of video frames, the metadata including metadata indicative of a scene change, and the display management module is configured to determine whether the current video frame immediately follows a scene change using the metadata indicative of the scene change.

EEE 19. the display apparatus of EEE 17, wherein the display management module is configured to compare characteristics of the current video frame to characteristics of one or more previous video frames to determine whether the current video frame of the sequence of video frames immediately follows a scene change.

EEE 20. the display device according to any one of EEEs 17 to 19, wherein the ambient light sensor has a lower sensitivity to light of a wavelength corresponding to a primary color of the display device than to light of other wavelengths of the visible spectrum.

EEE 21. the display device according to EEE 20, wherein the ambient light sensor comprises an optical filter that attenuates light of a wavelength corresponding to a primary color of the display device.

EEE 22. the display device according to EEE 21, wherein the optical filter comprises an optical band-stop filter.

EEE 23. the display apparatus of EEE 22, wherein the ambient light sensor is sensitive only to one or more bands within the visible spectrum.

EEE 24. the display device according to EEE 23, wherein the ambient light sensor is sensitive to yellow light only, cyan light only, or yellow and cyan light only.

EEE 25. the display device according to EEE 23 or 24, wherein the ambient light sensor comprises an optical bandpass filter.

EEE 26. the display apparatus according to any of EEEs 17-25, wherein applying ambient light compensation comprises applying an ambient light compensation function that maps input intensity values of the video frames of the input video signal to output intensity values of corresponding video frames of the output video signal, wherein the display management module is configured to select one of a set of ambient light compensation functions in dependence on the signal indicative of the intensity of ambient light.

EEE 27. the display apparatus of any of EEEs 17-26, wherein the display management module is further configured to determine a measured offset due to the light emitted by the display apparatus and recorded by the ambient light sensor based on at least one of the input video signal and metadata related to the input video signal,

wherein applying ambient light compensation by the display management module comprises: applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light compensated by the determined measurement bias.

EEE 28. the display device of EEE 27, wherein determining the measurement bias comprises:

determining an intensity level for each of a predetermined number of video frames prior to the current video frame; and

determining a sum of the intensity levels of the predetermined number of video frames.

EEE 29. a display management module configured to:

receiving an input video signal comprising a sequence of video frames;

receiving a signal indicative of an intensity of ambient light;

determining whether a current video frame of the sequence of video frames immediately follows a scene change;

transforming the input video signal into an output video signal suitable for a target display device, including applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light; and

output the output video signal for use by the target display device;

wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence upon the signal indicative of intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 30. a method for applying ambient light compensation, comprising:

-receiving an input video signal comprising a sequence of video frames;

-receiving a signal indicative of an intensity of ambient light from an ambient light sensor;

-determining whether a current video frame of the sequence of video frames immediately follows a scene change; and

-transforming the input video signal into an output video signal suitable for a target display device comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

the method includes adjusting the ambient light compensation applied in dependence on the signal indication only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 31. the method of EEE 30, further comprising receiving metadata related to the sequence of video frames, the metadata including metadata indicating a scene change, wherein the determining whether the current video frame of the sequence of video frames immediately follows a scene change uses the metadata indicating the scene change.

EEE 32. the method of EEE 30, wherein said determining whether the current video frame of the sequence of video frames corresponds to a scene change comprises automatically detecting the scene change.

EEE 33. the method of EEE 32, wherein automatically detecting the scene change comprises comparing characteristics of the current video frame with characteristics of one or more previous video frames.

EEE 34, a computer program product having instructions that, when executed by a computing device or system, cause the computing device or system to perform a method according to any one of EEEs 15 or 30-33.

EEE 35. a non-transitory computer-readable storage medium having stored thereon computer-executable instructions for performing a method according to any one of EEEs 15 or 30-33.

EEE 36. a display apparatus, comprising:

-a display;

-an ambient light sensor configured to generate a signal indicative of an intensity of ambient light; and

-a display management module configured to:

receiving an input video signal comprising a sequence of video frames;

determining whether a current video frame of the sequence of video frames immediately follows a scene change; and

transforming the input video signal into an output video signal suitable for the display, including applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light,

wherein the display is configured to display the output video signal, an

Wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence upon the signal indicative of intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 37. the display apparatus of EEE 36, wherein the display management module is configured to receive metadata related to the sequence of video frames, the metadata including metadata indicative of a scene change, and the display management module is configured to determine whether the current video frame immediately follows a scene change using the metadata indicative of the scene change.

EEE 38. the display apparatus of EEE 36, wherein the display management module is configured to compare characteristics of the current video frame with characteristics of one or more previous video frames to determine whether the current video frame of the sequence of video frames immediately follows a scene change.

EEE 39. the display device according to any one of EEEs 36 to 38, wherein the ambient light sensor has a lower sensitivity to light of a wavelength corresponding to a primary color of the display than to light of other wavelengths of the visible spectrum.

EEE 40. the display device according to EEE 39, wherein the ambient light sensor comprises an optical filter that attenuates light of a wavelength corresponding to a primary color of the display.

EEE 41. the display device according to EEE 40, wherein the optical filter comprises an optical band-stop filter.

EEE 42. the display apparatus of EEE 39, wherein the ambient light sensor is sensitive only to one or more bands within the visible spectrum.

EEE 43. the display device according to EEE 42, wherein the ambient light sensor is sensitive to yellow light only, cyan light only, or yellow and cyan light only.

EEE 44. the display device according to EEE 42 or 43, wherein the ambient light sensor comprises an optical bandpass filter.

EEE 45. the display apparatus according to any one of EEEs 36-44, wherein applying ambient light compensation comprises applying an ambient light compensation function that maps input intensity values of the video frames of the input video signal to output intensity values of corresponding video frames of the output video signal, wherein the display management module is configured to select one of a set of ambient light compensation functions in dependence on the signal indicative of the intensity of ambient light.

EEE 46. the display apparatus of any of EEEs 36-45, wherein the display management module is further configured to determine a measured offset due to the light emitted by the display and recorded by the ambient light sensor based on at least one of the input video signal and metadata related to the input video signal,

wherein applying ambient light compensation by the display management module comprises: applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light compensated by the determined measurement bias.

EEE 47. the display device of EEE 46, wherein determining the measurement offset comprises:

determining an intensity level for each of a predetermined number of video frames prior to the current video frame; and

determining a sum of the intensity levels of the predetermined number of video frames.

EEE 48. a display management module configured to:

receiving an input video signal comprising a sequence of video frames;

receiving a signal indicative of an intensity of ambient light;

determining whether a current video frame of the sequence of video frames immediately follows a scene change;

transforming the input video signal into an output video signal suitable for a target display, including applying ambient light compensation to the input video signal in dependence on the signal indicative of the intensity of the ambient light; and

output the output video signal for use by the target display;

wherein the display management module is configured to adjust the ambient light compensation applied to the input signal in dependence upon the signal indicative of intensity of ambient light only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 49. a method for applying ambient light compensation, comprising:

-receiving an input video signal comprising a sequence of video frames;

-receiving a signal indicative of an intensity of ambient light from an ambient light sensor;

-determining whether a current video frame of the sequence of video frames immediately follows a scene change; and

-transforming the input video signal into an output video signal suitable for a target display comprising applying an ambient light compensation to the input video signal in dependence of the signal indicative of the intensity of the ambient light,

the method includes adjusting the ambient light compensation applied in dependence on the signal indication only in response to determining that the current video frame of the sequence of video frames immediately follows a scene change.

EEE 50 a computer program product having instructions which, when executed by a computing device or system, cause the computing device or system to perform the method according to EEE 49.