Energy aware TV sl-hdr

Abstract

A method comprising: obtaining (140) reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance; deriving (141), using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance; and, reconstructing (143) the HDR data using the second tone mapping function, the HDR data being intended to be displayed on a display panel; wherein: the second peak luminance is based on an average picture level representative of a percentage of the display panel that is illuminated or a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target.

Description

[0001] ENERGY AWARE TV SL-HDR

[0002] 1. TECHNICAL FIELD

[0003] At least one of the present embodiments generally relates to the field of display of High Dynamic Range (HDR) video and more particularly to a method and a device for controlling an energy consumed for displaying HDR video.

[0004] 2. BACKGROUND

[0005] Recent advancements in display technologies allow for an extended dynamic range of color, luminance and contrast in images to be displayed. The term image refers here to an image content that can be for example a video or a still picture or image.

[0006] High-dynamic-range video (HDR video) describes video having a dynamic range greater than that of standard-dynamic-range video (SDR video). HDR-video based applications involve capture, production, content / encoding, and display. HDR capture and display devices are capable of brighter whites and deeper blacks. To accommodate this, HDR encoding standards allow for a higher maximum luminance and use at least a 10-bit dynamic range (compared to 8-bit (for non-professional) and 10-bit (for professional) dynamic ranges for SDR video) in order to maintain precision across this extended range.

[0007] HDR technology offers a better viewer experience (or Quality of Experience (QoE)) of video contents, but the energy consumption is much more significant than SDR. Indeed, the display of a HDR video consumes up to two times more energy than a SDR video. A current trend in many domains being to reduce the consumption of energy, it is desirable to overcome the above drawbacks.

[0008] It is particularly desirable to propose a solution allowing controlling or reducing the energy consumed by the display of HDR videos while preserving as much as possible the improvement of the QoE provided by the HDR technology and the artistic intent of the content creator.

[0009] 3. BRIEF SUMMARY

[0010] In a first aspect, one or more of the present embodiments provide a method comprising: obtaining reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance; deriving, using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance; and, reconstructing the HDR data using the second tone mapping function, the HDR data being intended to be displayed on a display panel; wherein: the second peak luminance is based on an average picture level representative of a percentage of the display panel that is illuminated or a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target.

[0011] In an embodiment, the second peak luminance is further based on a modulation factor depending on a profile selected by a user and on the average picture level.

[0012] In an embodiment, the second peak luminance guaranty a deactivation of an Auto Brightness Limiter process implemented by the display panel limiting an illumination of the display panel in function of a maximum power consumption of the display panel.

[0013] In an embodiment, responsive to the second peak luminance is based on a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target, a recursive process is applied on an image basis until the energy consumption target is met when displaying the HDR data, the recursive process comprising for a current image of the HDR data applying an adaptation coefficient to a second peak luminance used for a previous image of the HDR data to obtain the second peak luminance to be used for the current image of the HDR data.

[0014] In an embodiment, the adaptation coefficient is fixed or is a function of a ratio between the energy consumption target and the measured energy consumption of the display panel. In an embodiment, the recursive process is applied responsive to a ratio between the energy consumption target and the measured energy consumption of the display panel respect a condition.

[0015] In an embodiment, a Proportional Derivative Controller uses an error between the energy consumption target and the measured energy consumption of the display panel to compute the adaptation coefficient.

[0016] In a second aspect, one or more of the present embodiments provide a device comprising electronic circuitry configured for: obtaining reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance; deriving, using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance; and, reconstructing the HDR data using the second tone mapping function, the HDR data being intended to be displayed on a display panel; wherein: the second peak luminance is based on an average picture level representative of a percentage of the display panel that is illuminated or a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target.

[0017] In an embodiment, the second peak luminance is further based on a modulation factor depending on a profile selected by a user and on the average picture level.

[0018] In an embodiment, the second peak luminance guaranty a deactivation of an Auto Brightness Limiter process implemented by the display panel limiting an illumination of the display panel in function of a maximum power consumption of the display panel.

[0019] In an embodiment, responsive to the second peak luminance is based on a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target, the electronic circuitry is further configured for applying a recursive process on an image basis until the energy consumption target is met when displaying the HDR data, the recursive process comprising for a current image of the HDR data applying an adaptation coefficient to a second peak luminance used for a previous image of the HDR data to obtain the second peak luminance to be used for the current image of the HDR data.

[0020] In an embodiment, the adaptation coefficient is fixed or is a function of a ratio between the energy consumption target and the measured energy consumption of the display panel.

[0021] In an embodiment, the recursive process is applied responsive to a ratio between the energy consumption target and the measured energy consumption of the display panel respect a condition.

[0022] In an embodiment, a Proportional Derivative Controller uses an error between the energy consumption target and the measured energy consumption of the display panel to compute the adaptation coefficient.

[0023] In a third aspect, one or more of the present embodiments provide a non- transitory information storage medium storing program code instructions for implementing the method according to the first aspect.

[0024] In a fourth aspect, one or more of the present embodiments provide a computer program comprising program code instructions for implementing the method according to the first aspect.

[0025] 4. BRIEF SUMMARY OF THE DRAWINGS

[0026] Fig. 1 illustrates schematically an example of context in which the various embodiments are implemented;

[0027] Fig. 2A illustrates a tone mapping curve;

[0028] Fig. 2B illustrates an inverse tone mapping curve without display adaptation;

[0029] Fig. 2C illustrates inverse tone mapping curves with display adaptation;

[0030] Fig. 3 presents some energy consumption values for different kinds of scenes, i.e., bright, intermediate, dim scene luminance.

[0031] Fig. 4A illustrates schematically an example of hardware architecture of a processing module able to implement various aspects and embodiments; Fig. 4B illustrates a block diagram of an example of a first system in which various aspects and embodiments are implemented; and,

[0032] Fig. 4C illustrates a block diagram of an example of a second system in which various aspects and embodiments are implemented;

[0033] Fig. 5 illustrates a post-processing process allowing controlling the energy consumed by a display device when displaying an HDR video; and, Fig. 6 illustrates four sigmoid functions.

[0034] 5. DETAILED DESCRIPTION

[0035] Even if display devices with HDR capabilities have recently appeared, some of them have limited HDR capabilities. For instance, a HDR capable display may have a luminance capability that is lower than a luminance of a HDR signal as defined by the content creator it has to display. For instance, if the reconstructed HDR signal has a peak luminance of “1000” nits and the display can only render up to “500” nits.

[0036] An adaptation of the reconstructed signal to the capacity of the display device is therefore required. An adaptation solution would be to clip the reconstructed signal in a range of values admissible by the display device before displaying it. However, this solution is far from preserving the artistic intent of the content creator and QoE allowed by the HDR signal.

[0037] When speaking about images, the artistic intent often relies on how tones, i.e., shadows, midtones, highlights, are distributed within the scenes. This is part of a color grading that an artist (i.e., a content creator) has to do in order to convey a desired emotion and / or to define a visual signature of the content.

[0038] Tonal zones can be defined as follows:

[0039] • Shadows: this corresponds to the lowest part of the color distribution (represented for example by an histogram of luminance values of an image) of a considered content;

[0040] • Midtones: this corresponds to the middle part of the color distribution of the considered content;

[0041] • Highlights: this corresponds to the highest part of the color distribution of a considered content. In addition to these three tonal zones, it is common to define a black point as the pixel with the lowest sample value found within the shadows whereas the white point corresponds to the pixel with the lightest sample value found within the highlights.

[0042] Obviously, defining such black and white points is key during the color grading performed by artists. Increasing the black point leads to a scene in which areas darker than the black point are clipped. Similarly, decreasing the white point leads to a scene in which areas lighter than the white point are clipped. Clipping the highlights can result in a loss of valuable highlight details.

[0043] More “artistic intent” friendly solutions based on a display adaptation were proposed. Display adaptation allows adapting the reconstructed HDR signal to the display device luminance capacities while allowing getting the highest QoE and preserving the artistic intent of the HDR signal. For instance, display adaptation adjusts tones to preserve highlights which cannot be clipped.

[0044] By definition, the QoE is higher when the display adaptation adapts the reconstructed HDR signal to the luminance capability of the display device. However, this still comes with a high energy consumption. To make possible a trade-off between energy consumption and QoE, various embodiments described in the following propose to take account the energy consumption in the display adaptation.

[0045] Fig- 1 illustrates schematically an example of context in which the various embodiments are implemented.

[0046] In Fig. 1, a source device 10, such as a camera or a streaming system providing a video content, generates a video content. The source device 10 is for instance a SDR or HDR camera generating respectively a SDR or HDR video content.

[0047] The video content is then provided to a pre-processing module 11. The preprocessing module 11, for example, adapts a content to a SL-HDRx standard. For instance, the SL-HDRx standard is SL-HDR1. Therefore when the video content is a HDR video, the pre-processing module applies a tone mapping (TM) to the HDR video to generate a SDR video and generates SL-HDR1 metadata. When the video content is a SDR video, the pre-processing module first estimates a HDR video and then applies a TM to the estimated HDR video to generate the SL-HDR1 metadata. The HDR video has a peak of luminance called master display peak luminance corresponding generally to a peak luminance defined by the content creator. The SL-HDR1 metadata comprise information representative of an inverse tone mapping function and of a color correction function allowing to obtain a HDR video from a SDR video. These metadata could be dynamic and adapted to each image or group of images.

[0048] The SDR video and the SL-HDR1 metadata are then provided to an encoding module 12. The SDR video and the SL-HDR1 metadata are encoded by the encoding module 12 in a bitstream (i.e., in video data) using a video compression format such as AVC ((ISO / CEI 14496-10 / ITU-T H.264), HEVC (ISO / IEC 23008-2 - MPEG-H Part 2, High Efficiency Video Coding / ITU-T H.265)), VVC (ISO / IEC 23090-3 - MPEG- I, Versatile Video Coding / ITU-T H.266), AV1,VP9, EVC (ISO / CEI 23094-1 Essential Video Coding) or any other video compression format adapted to encode a SDR video and SL-HDR1 metadata. The output of the encoding module 12 is a bitstream (i.e., video data) representing the encoded SDR video and the SL-HDR1 metadata.

[0049] The encoding module 12 then provides the video data to a decoding module 13 for instance via a network. The decoding module 13 decodes the bitstream to obtain a decoded (i.e., reconstructed) version of the SDR video and the SL-HDR1 metadata.

[0050] The reconstructed SDR video is provided directly to a display device 16 adapted to display SDR contents.

[0051] The SDR video and the SL-HDR1 metadata are also provided to a postprocessing module 14. The post-processing module 14 applies an inverse tone mapping (ITM) step and a color correction step to the SDR video to obtain an HDR video.

[0052] The color correction comprises a computation of a Look-Up-Table (LUT) lutCC() from the SL-HDR1 metadata. The LUT lutCC() is then used to reconstruct the HDR chrominance signal of the HDR video.

[0053] For both constant luminance (CL) and non-constant luminance (NCL) modes, lutCC(Y) =f(Y).(l / Y) with f(Y) = 1 / (R . sgf(l / Y)) and Y being a value representative of a luminance. Function sgf(l / Y) corresponds to the color correction function encoded in the SL-HDR1 metadata.

[0054] In NCL mode, f(Y) is a constant function, i.e., f(Y) = so that lutCC(Y) = Q.(l / Y).

[0055] In CL mode, / (%) is not a constant function.

[0056] The ITM step comprises a derivation of a LUT lutMapY() from the SL-HDR1 metadata. The LUT lutMapY() is then used to perform the inverse tone mapping of the luminance signal of the SDR video to reconstruct the HDR luminance signal of the HDR video.

[0057] When a display adaptation is required (i.e., responsive to the HDR display 15 have a display peak luminance (called target display peak luminance in the following) lower than the master display peak luminance), the target display peak luminance is taken into account during the inverse tone mapping. Three cases are considered:

[0058] • the target display peak luminance is the same as the master display peak luminance. In that case the ITM curve is the inverse of the TM curve applied by the pre-processing module 11. The LUT lutMapY() is therefore derived directly from the SL-HDR1 metadata.

[0059] • the target display peak luminance is “100” nits (i.e., the HDR display 15 is a SDR display). In that case, the ITM curve is equal to the identity in the linear domain. In other words, when the target display peak luminance is “100” nits, the luminance of the reconstructed HDR signal is equal to the luminance of the reconstructed SDR signal. One can note that this latter is true for NCL mode but is not true for CL mode.

[0060] • the target display peak luminance is between “100” nits and the master display peak luminance. An ITM curve that is between the identity and the Inverse Tone Mapping curve specified in the SL-HDR1 metadata.

[0061] Fig. 2A illustrates a TM curve used by the pre-processing module 11 to generate a SDR video from an original HDR video.

[0062] Fig. 2B illustrates an ITM curve resulting from the inversion of the TM curve of Fig. 2A. The sequential application of the TM curve of Fig. 2A and of the ITM curve of Fig. 2B allows (in theory) obtaining back the original HDR video.

[0063] Fig. 2C illustrates a plurality of ITM curves obtained from the TM curve of Fig. 2A when a display adaptation process is applied.

[0064] An example of process of deriving the LUT lutMapY() when the target display peak luminance is between “100” nits and the master display peak luminance is described in annex E of document ETSI TS 103 433-1 VI.2.1 (High-Performance Single Layer High Dynamic Range (HDR) System for use in Consumer Electronics devices; Part 7: Directly Standard Dynamic Range (SDR) Compatible HDR System (SL-HDRl ) called simply SL-HDR1 in the following. Basically, this process consists in applying the process described in Fig. 4 of section 7.2.3.1.2 of document SL-HDR1 to compute a first LUT lutMapY’O representative of the ITM curve without display adaption (i.e. the first LUT lutMapY’O allows transforming the reconstructed SDR signal into the HDR signal with a peak of luminance equal to the master display peak luminance) and then to compute a second LUT lutMapY’ ’() allowing mapping the HDR signal with a peak of luminance equal to the master display peak luminance to a HDR signal with a peak luminance equal to the target display peak luminance. The LUT lutMapY is then the combination of the first LUT lutMapY’O and the second LUT lutMapY”(). In annex E of document SL-HDR1, the target display peak luminance is called maximum luminance of the presentation display and is represented by a variable pdisp-

[0065] One benefit of the display adaptation process of Annex E of document SL- HDR1 is to preserve as much as possible the artistic intent defined by the content creator.

[0066] Once reconstructed, the HDR video is then provided to a HDR display 15.

[0067] One can note that the post-processing module 14 could be integrated in the HDR display 15.

[0068] Fig. 3 presents some energy consumption values for different kinds of HDR scenes, i.e., bright, intermediate, dim scene luminance. The energy consumption values are function of a peak luminance expressed in nits. In this example, an OLED (Organic Light-Emitting Diode) screen used for the test has a target display peak luminance of “1000” nits. Its energy consumption is therefore the highest for this value since the full capability of the screen is used. Decreasing the peak luminance of the displayed content allows to decrease the energy consumption. Interestingly, the amount of reduction significantly depends on the scene luminance.

[0069] Fig. 4A illustrates schematically an example of hardware architecture of a processing module 40 used for instance in the pre-processing module 11 or in the postprocessing module 14. The processing module 40 comprises, connected by a communication bus 405: a processor or CPU (central processing unit) 400 encompassing one or more microprocessors, general purpose computers, special purpose computers, and processors based on a multi-core architecture, as non-limiting examples; a random access memory (RAM) 401; a read only memory (ROM) 402; a storage unit 403, which can include non-volatile memory and / or volatile memory, including, but not limited to, Electrically Erasable Programmable Read-Only Memory (EEPROM), Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), flash, magnetic disk drive, and / or optical disk drive, or a storage medium reader, such as a SD (secure digital) card reader and / or a hard disc drive (HDD) and / or a network accessible storage device; at least one communication interface 404 for exchanging data with other modules, devices, systems or equipment. The communication interface 404 can include, but is not limited to, a transceiver configured to transmit and to receive data over a communication network 41. The communication interface 404 can include, but is not limited to, a modem or a network card.

[0070] For example, the communication interface 404 enables for instance the processing module 40 to receive the HDR or SDR data and to output HDR or SDR data along with SL-HDR1 metadata.

[0071] The processor 400 is capable of executing instructions loaded into the RAM 401 from the ROM 402, from an external memory (not shown), from a storage medium, or from a communication network. When the processing module 40 is powered up, the processor 400 is capable of reading instructions from the RAM 401 and executing them. When the processing module 40 is comprised in the pre-processing module 11, these instructions form a computer program causing, for example, the implementation by the processor 400 of a TM process (when the source module generates a HDR video). When the processing module 40 is comprised in the post-processing module 14, these instructions form a computer program causing, for example, the implementation by the processor 400 of an ITM process comprising a display adaptation according to embodiments described in the following of this disclosure.

[0072] All or some of the algorithms and steps of said processes may be implemented in software form by the execution of a set of instructions by a programmable machine such as a DSP (digital signal processor) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component such as a FPGA (field- programmable gate array) or an ASIC (application-specific integrated circuit). Microprocessors, DSP, FPGA and ASIC are considered as electronic circuitry.

[0073] Fig. 4C illustrates a block diagram of an example of a system A implementing a post processing module in which various aspects and embodiments are implemented. System A can be embodied as a device including various components or modules and is configured to generate a HDR displayable video. Examples of such system include, but are not limited to, various electronic systems such as personal computers, laptop computers, smartphones, tablet, TV, or set top boxes. Components of system A, singly or in combination, can be embodied in a single integrated circuit (IC), multiple ICs, and / or discrete components. For example, in at least one embodiment, the system A comprises one processing module 40 that implements the post-processing module 14. In various embodiments, the system A is communicatively coupled to one or more other systems, or other electronic devices, via, for example, a communication bus or through dedicated input and / or output ports.

[0074] The input to the processing module 40 can be provided through various input modules as indicated in a block 42. Such input modules include, but are not limited to, (i) a radio frequency (RF) module that receives an RF signal transmitted, for example, over the air by a broadcaster, (ii) a component (COMP) input module (or a set of COMP input modules), (iii) a Universal Serial Bus (USB) input module, and / or (iv) a High Definition Multimedia Interface (HDMI) input module. Other examples, not shown in FIG. 4C, include composite video.

[0075] In various embodiments, the input modules of block 42 have associated respective input processing elements as known in the art. For example, the RF module can be associated with elements suitable for (i) selecting a desired frequency (also referred to as selecting a signal, or band-limiting a signal to a band of frequencies), (ii) down-converting the selected signal, (iii) band-limiting again to a narrower band of frequencies to select (for example) a signal frequency band which can be referred to as a channel in certain embodiments, (iv) demodulating the down-converted and bandlimited signal, (v) performing error correction, and (vi) demultiplexing to select the desired stream of data packets. The RF module of various embodiments includes one or more elements to perform these functions, for example, frequency selectors, signal selectors, band-limiters, channel selectors, filters, downconverters, demodulators, error correctors, and demultiplexers. The RF portion can include a tuner that performs various of these functions, including, for example, down-converting the received signal to a lower frequency (for example, an intermediate frequency or a near-baseband frequency) or to baseband. Various embodiments rearrange the order of the abovedescribed (and other) elements, remove some of these elements, and / or add other elements performing similar or different functions. Adding elements can include inserting elements in between existing elements, such as, for example, inserting amplifiers and an analog-to-digital converter. In various embodiments, the RF module includes an antenna.

[0076] Additionally, the USB and / or HDMI modules can include respective interface processors for connecting system A to other electronic devices across USB and / or HDMI connections. It is to be understood that various aspects of input processing, for example, Reed-Solomon error correction, can be implemented, for example, within a separate input processing IC or within the processing module 40 as necessary. Similarly, aspects of USB or HDMI interface processing can be implemented within separate interface ICs or within the processing module 40 as necessary. The demodulated, error corrected, and demultiplexed stream is provided to the processing module 40.

[0077] Various elements of system A can be provided within an integrated housing. Within the integrated housing, the various elements can be interconnected and transmit data therebetween using suitable connection arrangements, for example, an internal bus as known in the art, including the Inter-IC (I2C) bus, wiring, and printed circuit boards. For example, in the system A, the processing module 40 is interconnected to other elements of said system A by the bus 405.

[0078] The communication interface 404 of the processing module 40 allows the system A to communicate on the communication network 41. The communication network 41 can be implemented, for example, within a wired and / or a wireless medium.

[0079] Data is streamed, or otherwise provided, to the system A, in various embodiments, using a wireless network such as a Wi-Fi network, for example IEEE 802.11 (IEEE refers to the Institute of Electrical and Electronics Engineers). The WiFi signal of these embodiments is received over the communications network 41 and the communications interface 404 which are adapted for Wi-Fi communications. The communications network 41 of these embodiments is typically connected to an access point or router that provides access to external networks including the Internet for allowing streaming applications and other over-the-top communications. Still other embodiments provide streamed data to the system A using the RF connection of the input block 42. As indicated above, various embodiments provide data in a nonstreaming manner, for example, when the system A is a smartphone or a tablet. Additionally, various embodiments use wireless networks other than Wi-Fi, for example a cellular network or a Bluetooth network.

[0080] The system A can provide an output signal to various output devices using the communication network 41 or the bus 405. For example, the system A can provide a reconstructed HDR video.

[0081] The system A can provide an output signal to various output devices, including the HDR display 15, speakers 46, and other peripheral devices 47. The HDR display 15 of various embodiments includes one or more of, for example, a touchscreen display, an organic light-emitting diode (OLED) display, a curved display, and / or a foldable display. The HDR display 15 can be for a television, a tablet, a laptop, a cell phone (mobile phone), or other devices. The HDR display 15 can also be integrated with other components (for example, as in a smart phone), or separate (for example, an external monitor for a laptop). The other peripheral devices 47 include, in various examples of embodiments, one or more of a stand-alone digital video disc (or digital versatile disc) (DVR, for both terms), a disk player, a stereo system, and / or a lighting system. Various embodiments use one or more peripheral devices 47 that provide a function based on the output of the system A. For example, a disk player performs the function of playing the output of the system A.

[0082] In various embodiments, control signals are communicated between the system A and the HDR display 15, speakers 46, or other peripheral devices 47 using signaling such as AV. Link, Consumer Electronics Control (CEC), or other communications protocols that enable device-to-device control with or without user intervention. The output devices can be communicatively coupled to system A via dedicated connections through respective interfaces 43, 44, and 45. Alternatively, the output devices can be connected to system A using the communication network 41 via the communication interface 404. The HDR display 15 and speakers 46 can be integrated in a single unit with the other components of system A in an electronic device such as, for example, a television. In various embodiments, the display interface 43 includes a display driver, such as, for example, a timing controller (T Con) chip.

[0083] The HDR display 15 and speakers 46 can alternatively be separate from one or more of the other components, for example, if the RF module of block 42 is part of a separate set-top box. In various embodiments in which the HDR display 15 and speakers 46 are external components, the output signal can be provided via dedicated output connections, including, for example, HDMI ports, USB ports, or COMP outputs.

[0084] Fig. 4B illustrates a block diagram of an example of the system B adapted to implement the pre-processing module 11 in which various aspects and embodiments are implemented.

[0085] System B can be embodied as a device including the various components and modules described above and is configured to perform one or more of the aspects and embodiments described in this document.

[0086] Examples of such devices include, but are not limited to, various electronic devices such as personal computers, laptop computers, a camera, a smartphone and a server. Elements or modules of system B, singly or in combination, can be embodied in a single integrated circuit (IC), multiple ICs, and / or discrete components. For example, in at least one embodiment, the system B comprises one processing module 40 that implement the pre-processing module 11. In various embodiments, the system B is communicatively coupled to one or more other systems, or other electronic devices, via, for example, a communications bus or through dedicated input and / or output ports.

[0087] The input to the processing module 40 can be provided through various input modules as indicated in block 42 already described in relation to Fig. 4C.

[0088] Various elements of system B can be provided within an integrated housing. Within the integrated housing, the various elements can be interconnected and transmit data therebetween using suitable connection arrangements, for example, an internal bus as known in the art, including the Inter-IC (I2C) bus, wiring, and printed circuit boards. For example, in the system B, the processing module 40 is interconnected to other elements of said system B by the bus 405.

[0089] The communication interface 404 of the processing module 40 allows the system B to communicate on the communication network 41. The communication network 71 can be implemented, for example, within a wired and / or a wireless medium.

[0090] Data is streamed, or otherwise provided, to the system B, in various embodiments, using a wireless network such as a Wi-Fi network, for example IEEE 802.11 (IEEE refers to the Institute of Electrical and Electronics Engineers). The WiFi signal of these embodiments is received over the communications network 41 and the communications interface 404 which are adapted for Wi-Fi communications. The communications network 41 of these embodiments is typically connected to an access point or router that provides access to external networks including the Internet for allowing streaming applications and other over-the-top communications. Still other embodiments provide streamed data to the system B using the RF connection of the input block 42. As indicated above, various embodiments provide data in a nonstreaming manner.

[0091] When a figure is presented as a flow diagram, it should be understood that it also provides a block diagram of a corresponding apparatus. Similarly, when a figure is presented as a block diagram, it should be understood that it also provides a flow diagram of a corresponding method / process.

[0092] The implementations and aspects described herein can be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method), the implementation of features discussed can also be implemented in other forms (for example, an apparatus or program). An apparatus can be implemented in, for example, appropriate hardware, software, and firmware. The methods can be implemented, for example, in a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable / personal digital assistants ("PDAs"), smartphones, tablets, and other devices that facilitate communication of information between end-users.

[0093] Reference to “one embodiment” or “an embodiment” or “one implementation” or “an implementation”, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” or “in one implementation” or “in an implementation”, as well any other variations, appearing in various places throughout this application are not necessarily all referring to the same embodiment.

[0094] Additionally, this application may refer to “determining” various pieces of information. Determining the information can include one or more of, for example, estimating the information, calculating the information, predicting the information, retrieving the information from memory or obtaining the information for example from another device, module or from user. Further, this application may refer to “accessing” various pieces of information. Accessing the information can include one or more of, for example, receiving the information, retrieving the information (for example, from memory), storing the information, moving the information, copying the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0095] Additionally, this application may refer to “receiving” various pieces of information. Receiving is, as with “accessing”, intended to be a broad term. Receiving the information can include one or more of, for example, accessing the information, or retrieving the information (for example, from memory). Further, “receiving” is typically involved, in one way or another, during operations such as, for example, storing the information, processing the information, transmitting the information, moving the information, copying the information, erasing the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0096] It is to be appreciated that the use of any of the following “and / or”, and “at least one of’, “one or more of’ for example, in the cases of “A / B”, “A and / or B” and “at least one of A and B”, “one or more of A and B” is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and / or C” and “at least one of A, B, and C”, “one or more of A, B and C” such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as is clear to one of ordinary skill in this and related arts, for as many items as are listed.

[0097] As will be evident to one of ordinary skill in the art, implementations or embodiments can produce a variety of signals formatted to carry information that can be, for example, stored or transmitted. The information can include, for example, instructions for performing a method, or data produced by one of the described implementations or embodiments. For example, a signal can be formatted to carry a SDR image or video sequence and SL-HDRx metadata of a described embodiment. Such a signal can be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting can include, for example, encoding a SDR image or video sequence with SL-HDR1 metadata in an encoded stream (i.e., in video data) and modulating a carrier with the encoded stream. The information that the signal carries can be, for example, analog or digital information. The signal can be transmitted over a variety of different wired or wireless links, as is known. The signal can be stored on a processor-readable medium.

[0098] As seen above, display adaptation allows displaying a HDR video compliant with a target display peak luminance corresponding to the peak luminance supported by a display device on which is displayed the HDR video while preserving the artistic intent of the content creator. Nevertheless, in that case, the energy consumed by the display device corresponds to the maximum of the energy that can be consumed by the display device to display the HDR video.

[0099] A common objective of the various embodiments described in the following is to decrease the consumption of the display device when displaying the HDR video with respect to this maximum of energy. To do so, a peak luminance, called energy consumption based peak luminance in the following, lower than the target display peak luminance, is used in place of the target display peak luminance in the display adaptation process. Using an energy consumption based peak luminance lower than the target display peak luminance has a direct impact on the energy consumption reduction.

[0100] Before delving into a detailed description of the various embodiments, we introduce several notions and terminology:

[0101] The Auto Brightness Limiter (ABL) is an inherent limitation of OLED panels. The energy consumption of these panels depends on the content displayed. With a pure white image, every pixel needs to be lit and consumes maximum power depending on brightness settings. Conversely, with a perfectly black image, each pixel is off, so it consumes no energy. But for all the pixels, the OLED panel has a maximum power consumption. This means that an all-white image is limited by the maximum power consumption of the OLED panel. It is for this reason that an entirely white image on an OLED panel is always less bright than an isolated light point. Indeed, the isolated light point is limited by the maximum power consumption of the screen.

[0102] On OLED panels, the percentage of the OLED panel that is illuminated compared to an all-white OLED panel is known as the Average Picture Level (APL). For example, an OLED panel displaying a small window of white pixels has a small APL. This level of brightness then decreases as the size of the window of white pixels increases. As can be seen, this phenomenon is related to the ABL.

[0103] There is a maximum brightness that the OLED panel can reach and maintain for an image with perfect white (100% APL). If the APL is reduced, electrical power can be reallocated to brighter areas and therefore increase peak brightness in these areas.

[0104] As can be seen, the ABL is not controlled and cannot guarantee a preservation of the artistic intent.

[0105] One can note that the terms peak brightness and peak luminance are used equivalently in this document and represent the same notion.

[0106] Fig- 5 illustrates a post-processing process allowing controlling the energy consumed by a display device when displaying an HDR video.

[0107] The post-processing process described in Fig. 5 is for instance executed by the processing module 40 of the system A when this processing module 40 implements the post-processing module 14. The system A is supposed to have received encoded video data from the system B. The decoding module 13 of the system A has then decoded the encoded video data and has generated reconstructed SDR data and SL-HDR1 metadata. The post-processing module 14 then obtains the reconstructed SDR data and the SL- HDR1 metadata from the decoding module 13. The process of Fig. 5 is executed before the ABL process which is performed by the processing module 40 of the HDR display 15.

[0108] One can note that in the following description, we took the example of SL- HDR1. However, the various embodiments described in the following apply to any other HDR distribution technology using dynamic metadata such as SL-HDR2, SL- HDR3, Dolby Vision and HDR10+. In addition, the various embodiments use a modified version of the display adaptation process described in annex E of SL-HDR1. However, other display adaptation process can be used, the display adaptation process described in annex E of SL-HDR1 being just an example of such process.

[0109] In a step 140, the processing module 40 of the post-processing module 14 obtains the reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance. In the example of Fig. 5, the metadata are the SL-HDR1 metadata generated by the pre-processing module 11. The first peak luminance is the master display peak luminance corresponding to the peak luminance defined by the content creator.

[0110] In a step 141, the processing module 40 derives, using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance. The second peak luminance is typically the energy consumption based peak luminance mentioned above. To do so, the processing module 40 applies for example the display adaptation process described in annex E of document SL-HDR1 by replacing the variable Lpdisprepresenting the target display peak luminance (i.e. the maximum luminance of the presentation display) by a variable LenergyConsorepresenting the energy consumption based peak luminance. The computation of the first LUT lutMapY’O representative of the ITM curve without display adaption is not modified. The replacement of the variable Lpdispby the variable LenergyConsoallows obtaining a second LUT lutMapY" „ () allowing mapping the HDR signal with a peak of luminance equal to the master display peak luminance to a HDR signal with a peak luminance equal to the energy consumption based peak luminance. The LUT lutMapY() is then the combination of the first LUT lutMapY’O and the second LUT

[0111] In a step 143, the processing module 40 reconstructs the HDR data using the second tone mapping function (i.e. using the LUT lutMapY the HDR data being intended to be displayed on the HDR display 15.

[0112] One can note that the energy based peak luminance is lower than the target display peak luminance representing the peak luminance supported by the HDR display 15.

[0113] Optionally, when the SDR data comprise chroma components, the SL-HDR1 metadata comprise information representative of a color correction function and the processing module 40 derives the color correction function in a step 142 as described in the document SL-HDR1. In step 143, the processing module 40 applies the color correction function to the SDR data to obtain the chrominance components of the HDR data.

[0114] In a first embodiment of step 141, the display adaptation is driven by the APL. More precisely, the value of the energy consumption based peak luminance is determined based on the APL. In an example, a LUT is used for this purpose. Table TAB1 discloses an example of LUT in which APL values Apt (in the first column from left to right) are mapped to Energy consumption based peak luminance values E (in the second column from left to right). Thanks to this LUT, a value of the Energy consumption based peak luminance E is determined from the value of the APL Apl. The first embodiment allows limiting the activation of the ABL and allows (i) reducing the energy consumption; and (ii) keeping the artistic intent. In a variant, the Energy consumption based peak luminance values in the LUT are defined to guaranty that the ABL is never activated.

[0115] In an embodiment, the APL is estimated from the content to be displayed. We suppose here that the content is composed of YUV pictures, each pixel of the YUV pictures being represented by a luminance value Y and two chrominance values U and V. The APL value corresponding to an image is estimated based on a number of pixels of the image having a value of the luminance component Y above a threshold TH. For instance, if the YUV components are encoded on “8” bits, TH is equal to “240”. The APL is considered equal to the percentage of pixels of the image having a value of the luminance component Y above the threshold TH. When the APL value Apl is estimated for each image, the process of Fig. 5 is applied for each image. In a variant, the APL is estimated for groups of consecutive images, the APL value Apl being an average of the percentage of pixels having a value of the luminance component Y above the threshold TH determined for each image of the group of images. In that case, a single energy consumption based peak luminance value E is determined for the group of images.

[0116] In a variant of the first embodiment, a user can select a user profile to reduce even more the Energy consumption based peak luminance and then the energy consumption. Four user profiles are defined in table TAB1 in the four Tightest columns. Each profile defines a modulation factor MOD for each value of APL Apl. The modulation factor is applied to the Energy consumption based peak luminance E obtained from the APL value Apl to obtain a modulated energy consumption based peak luminance Emodused as the second peak luminance in step 141:

[0117] Emod = E x MOD Eq. 1

[0118] For example, if the selected user profile is low and the APL value is 50: mod=243 x 0.9

[0119] In a variant, the Energy consumption based peak luminance values E and the modulation factors MOD of the LUT are defined so that any obtained modulated energy consumption based peak luminance value Emodguaranty that the ABL is never activated.

[0120] In a second embodiment, an energy consumption target is given by the user, for instance, “75” Watt per hour. Then the energy consumption based peak luminance is modified based on a comparison of a measured energy consumption of the HDR display 15 when displaying the HDR data with the energy consumption target so that the energy consumption target is met. In this embodiment, it is considered that the HDR display 15 is able to monitor its energy consumption and to record an average of this energy consumption. Instead of a simple average, the HDR display 15 can compute a weighted average putting more emphasis on the most recent images.

[0121] To match the energy consumption target, the energy consumption based peak luminance is recursively decreased over the time. The process of Fig. 5 is applied for example on an image basis. At each image, a simple decrease of the energy consumption based peak luminance is applied. When the energy consumption target is reached, the decrease is stopped. Obviously, if the gain is higher than the energy consumption target, a recursive increase can be performed.

[0122] In an example of implementation, the energy consumption based peak luminance for image t Eft) is computed as follows in function of the energy consumption based peak luminance for image t-1 E(t-l).'

[0123] Where desiredTargetWattConsumption is the energy consumption target and actualWattConsumption is the current energy consumption for instance measured by the HDR display 15.

[0124] The function f is a function allowing to control the variations of the energy consumption based peak luminance. In a simple embodiment, the function f is the identity function. In a second example, the function is a sigmoid function centered on

[0125] The parameter a allows to adjust the sigmoid function behavior around “1 ”. Fig.

[0126] 6 illustrates “4” sigmoid functions with a=5, 10, 15 and 20.

[0127] If the ratio is smaller than “1”, the energy consumption based peak luminance is decreased. If the ratio is greater than “1”, the energy consumption based peak luminance is increased (and limited to the target display peak luminance (i.e. the maximum luminance of the HDR display 15)).

[0128] In a variant of the second embodiment, the function , , , , , , , , ■ replaced by a constant adaptationcoefficient as described below:

[0129] E(t) = E(t — 1) x adaptationcoefficient Eq. 4 where the constant adaptationcoefficient is equal to 5% for example.

[0130] In a variant of the second embodiment, the process to decrease (or increase) the energy consumption based peak luminance value is activated only if the energy consumption target is not reached. For example, If the ratio desiredTargetWattConsumption is in an interval [MinTH, MaxTH] (MinTH=0.95 and actualWattConsumption

[0131] MaxTH=\.05 for instance), the proposed process is disabled. Otherwise, the proposed process is applied to adjust the energy consumption based peak luminance value.

[0132] Another variant of the second embodiment consists in using a PID (Proportional Integral Derivative) controller. A PID controller is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control. A PID controller continuously calculates an error value as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively).

[0133] In the context of the second embodiment, the desired setpoint SP is the energy consumption target defined by the user. The measured process variable Eis the energy consumption measured by the HDR display 15. By measuring the energy consumption PV, and subtracting it from the energy consumption target SP, an error e is found, and from it the controller calculates a scalar value. The scalar value in the range [0,1], This scalar value is used to modulate the energy consumption based peak luminance value for example in Equation Eq. 4.

[0134] In a variant of the second embodiment, it is assumed that it is known when the ABL is activated in function of the APL. Furthermore, a LUT (such as the LUT of table TAB1) allows associating energy consumption based peak luminance values Eft) to APL values. Thanks to the link between energy consumption based peak luminance values Eft) and the APL values and to the knowledge of condition on APL to activate the ABL, it is possible to know if a determined energy consumption based peak luminance value Eft) allows deactivating the ABL. In this variant of the second embodiment, when the determined energy consumption based peak luminance value Eft) doesn’t allow to deactivate the ABL, the energy consumption based peak luminance value Eft) is further decreased to a value guarantying the deactivation of the ABL.

[0135] Until now, the various embodiments were described in the context of OLED panels. However, all embodiments are also compliant with other display technologies such as LCD (Liquid Crystal Display) displays with or without local dimming, QLED (Quantum-dot Light Emitting Diode) displays, or micro LED displays. In that case, the APL is the percentage of the (LCD, QLED, Micro-LED, etc) display panel that is illuminated compared to an all-white panel.

[0136] We described above a number of embodiments. Features of these embodiments can be provided alone or in any combination. Further, embodiments can include one or more of the following features, devices, or aspects, alone or in any combination, across various claim categories and types:

[0137] • A TV, set-top box, cell phone, tablet, personal computer or other electronic device that performs at least one of the embodiments described, and that displays (e.g., using a monitor, screen, or other type of display) a resulting picture.

[0138] • A TV, set-top box, cell phone, tablet, personal computer or other electronic device that tunes (e.g., using a tuner) a channel to receive a signal including an encoded SDR video and metadata, and performs at least one of the embodiments described.

[0139] • A TV, set-top box, cell phone, tablet, or other electronic device that receives (e.g., using an antenna) a signal over the air that includes an encoded SDR video and metadata, and performs at least one of the embodiments described.

[0140] • A server, camera, cell phone, tablet, personal computer or other electronic device that tunes (e.g., using a tuner) a channel to transmit a signal including a SDR video and metadata, and performs at least one of the embodiments described.

[0141] • A server, camera, cell phone, tablet, personal computer or other electronic device that transmits (e.g., using an antenna) a signal over the air that includes a SDR video and metadata, and performs at least one of the embodiments described.

Claims

Claims1. A method comprising: obtaining (140) reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance; deriving (141), using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance; and, reconstructing (143) the HDR data using the second tone mapping function, the HDR data being intended to be displayed on a display panel; wherein: the second peak luminance is based on an average picture level representative of a percentage of the display panel that is illuminated or a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target.

2. The method of claim 1, wherein the second peak luminance is further based on a modulation factor depending on a profile selected by a user and on the average picture level.

3. The method of claim 1 or 2 wherein the second peak luminance guaranty a deactivation of an Auto Brightness Limiter process implemented by the display panel limiting an illumination of the display panel in function of a maximum power consumption of the display panel.

4. The method of claim 1 wherein, responsive to the second peak luminance is based on a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target, a recursive process is applied on an image basis until the energy consumption target is met when displaying the HDR data, the recursive process comprising for a current image of the HDR data applying an adaptation coefficient to a second peakluminance used for a previous image of the HDR data to obtain the second peak luminance to be used for the current image of the HDR data.

5. The method of claim 4 wherein the adaptation coefficient is fixed or is a function of a ratio between the energy consumption target and the measured energy consumption of the display panel.

6. The method according to claim 4 or 5 wherein the recursive process is applied responsive to a ratio between the energy consumption target and the measured energy consumption of the display panel respect a condition.

7. The method of claim 4 wherein a Proportional Derivative Controller uses an error between the energy consumption target and the measured energy consumption of the display panel to compute the adaptation coefficient.

8. A device comprising electronic circuitry configured for: obtaining (140) reconstructed SDR data and metadata representative of a first inverse tone mapping function allowing transforming the reconstructed SDR data into HDR data with a dynamic range having a first peak luminance; deriving (141), using the metadata, a second tone mapping function allowing transforming the SDR data into HDR data with a dynamic range having a second peak luminance lower than the first peak luminance; and, reconstructing (143) the HDR data using the second tone mapping function, the HDR data being intended to be displayed on a display panel; wherein: the second peak luminance is based on an average picture level representative of a percentage of the display panel that is illuminated or a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target.

9. The device of claim 8, wherein the second peak luminance is further based on a modulation factor depending on a profile selected by a user and on the average picture level.

10. The device of claim 8 or 9 wherein the second peak luminance guaranty a deactivation of an Auto Brightness Limiter process implemented by the display panel limiting an illumination of the display panel in function of a maximum power consumption of the display panel.

11. The device of claim 8 wherein, responsive to the second peak luminance is based on a comparison of a measured energy consumption of the display panel when displaying the HDR data with an energy consumption target, the electronic circuitry is configured for applying a recursive process on an image basis until the energy consumption target is met when displaying the HDR data, the recursive process comprising for a current image of the HDR data applying an adaptation coefficient to a second peak luminance used for a previous image of the HDR data to obtain the second peak luminance to be used for the current image of the HDR data.

12. The device of claim 11 wherein the adaptation coefficient is fixed or is a function of a ratio between the energy consumption target and the measured energy consumption of the display panel.

13. The device according to claim 11 or 12 wherein the recursive process is applied responsive to a ratio between the energy consumption target and the measured energy consumption of the display panel respect a condition.

14. The device of claim 11 wherein a Proportional Derivative Controller uses an error between the energy consumption target and the measured energy consumption of the display panel to compute the adaptation coefficient.

15. Non-transitory information storage medium storing program code instructions for implementing the method according to any previous claim from claim 1 to 7.

16. A computer program comprising program code instructions for implementing the method according to any previous claim from claim 1 to 7.

Images