Video encoding and decoding based on region dependent film grain metadata

Abstract

A method and device allow to define image regions, sets of film grain characteristics, and provides means to associate image regions with film grain characteristics. An encoded video bitstream comprises specific syntax allowing to carry such information from an encoding device to a decoding device. In one example of usage of the application, the determined film grain is synthetized and applied to an image of a decoded video. This brings a differentiation of the film grain characteristics of different regions, for example in relation with different types of video sources.

Description

[0001] VIDEO ENCODING AND DECODING BASED ON

[0002] REGION DEPENDENT FILM GRAIN METADATA

[0003] TECHNICAL FIELD

[0004] At least one of the present embodiments generally relates to a method and a device for encoding and decoding video comprising region dependent film grain metadata.

[0005] BACKGROUND ART

[0006] To achieve high compression efficiency, image and video coding schemes usually employ prediction and transform to leverage spatial and temporal redundancy in the video content. Generally, intra or inter prediction is used to exploit the intra or inter frame correlation, then the differences between the original image block and the predicted image block, often denoted as prediction errors or prediction residuals, are transformed, quantized and entropy coded. During encoding the original image block is usually partitioned / split into sub-blocks for example using quad-tree partitioning. To reconstruct the video, the compressed data is decoded by inverse processes corresponding to the prediction, transform, quantization and entropy coding.

[0007] SUMMARY

[0008] According to a first aspect of at least one embodiment, a method comprises obtaining a bitstream comprising encoded video data and region-dependent film grain metadata, determining film grain characteristics for one or more regions of a picture of the video based on the region-dependent film grain metadata for a region, and providing the determined film grain characteristics.

[0009] According to a second aspect of at least one embodiment, a method comprises obtaining a bitstream comprising encoded video data and region-dependent film grain metadata, determining film grain characteristics for one or more regions of a picture of the video based on the region-dependent film grain metadata for a region, and providing the determined film grain characteristics. A variant embodiment of second aspect further comprises decoding a picture based on the encoded video data, determining film grain samples for a region based on the determined film grain characteristics, adding the film grain samples to the decoded picture, and providing the modified decoded picture. According to a third aspect of at least one embodiment, an apparatus comprises one or more processors configured to obtain video data, determining region-dependent film grain metadata representative of film grain characteristics, insert the region-dependent film grain metadata into an encoded bitstream comprising the video data and the region-dependent film grain metadata, and provide the bitstream.

[0010] According to a fourth aspect of at least one embodiment, an apparatus comprises one or more processors configured to obtain a bitstream comprising encoded video data and regiondependent film grain metadata, determine film grain characteristics for one or more regions of a picture of the video based on the region-dependent film grain metadata for a region, and provide the determined film grain characteristics. In a variant of the fourth aspect, the one or more processors are further configured to decode a picture based on the encoded video data, determine film grain samples for a region based on the determined film grain characteristics, add the film grain samples to the decoded picture, and provide the modified decoded picture.

[0011] One or more of the present embodiments also provide a computer readable storage medium having stored thereon instructions according to at least part of any of the methods described above. One or more embodiments also provide a computer readable storage medium having stored thereon a bitstream generated according to the encoding methods described above. One or more embodiments also provide a computer program product including instructions for performing at least part of any of the methods described above.

[0012] BRIEF SUMMARY OF THE DRAWINGS

[0013] Figure 1 illustrates a block diagram of an example of a system in which various aspects and embodiments are implemented.

[0014] Figure 2 describes an example of a context in which following embodiments can be implemented.

[0015] Figure 3 illustrates a block diagram of an example of video encoder.

[0016] Figure 4 illustrates a block diagram of an example of video decoder.

[0017] Figure 5 illustrates an example of partitioning undergone by an image of an original video sequence.

[0018] Figure 6 illustrates examples of film grain parameters comprising a frequency cut-off and a gain. Figure 7 illustrates an example of reproduction of a film scan.

[0019] Figure 8 illustrates an example of regions for a picture according to embodiments.

[0020] Figure 9A illustrates an example process for encoding a bitstream comprising a FGRC- SEI message according to embodiments.

[0021] Figure 9B illustrates an example process for decoding a bitstream comprising a FGRC- SEI message according to embodiments.

[0022] Figure 9C illustrates an example process for decoding a bitstream comprising a FGRC- SEI message according to embodiments and applying the determined film grain characteristics on a decoded image.

[0023] DETAILED DESCRIPTION

[0024] Various embodiments relate to embedding metadata that describe region dependent film grain metadata in a SEI message. On the encoding side, a SEI message comprising region dependent film grain metadata is inserted into a bitstream. On the decoding side, the SEI message is extracted from the bitstream and the region dependent film grain metadata may be used to generate synthetic film grain samples, for example to be added to the decoded picture for an artistic effect.

[0025] The present aspects, although describing principles in the context of VVC (Versatile Video Coding) or HEVC (High Efficiency Video Coding) specifications, are not limited to these video coding standards, and can be applied, for example, to other standards and recommendations and extensions of any such standards and recommendations (including VVC and HEVC). Unless indicated otherwise, or technically precluded, the aspects described in this application can be used individually or in combination.

[0026] Figure 1 illustrates a block diagram of an example of a system in which various aspects and embodiments are implemented. System 1000 can be embodied as a device or apparatus including the various components described below and is configured to perform one or more of the aspects described in this document. Examples of such devices include, but are not limited to, various electronic devices such as computers, smartphones, tablets, digital multimedia set top boxes, digital television receivers, personal video recording systems, connected home appliances, vehicle entertainment systems, vehicle control systems, drones, video surveillance cameras, and more generally data servers. Elements of system 1000, 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 processing and encoder / decoder elements of system 1000 are distributed across multiple Ics and / or discrete components. In various embodiments, the system 1000 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. In various embodiments, the system 1000 is configured to implement one or more of the aspects described in this document.

[0027] The system 1000 includes at least one processor 1010 configured to execute instructions loaded therein for implementing, for example, the various aspects described in this document. Processor 1010 can include embedded memory, input output interface, and various other circuitries as known in the art. The system 1000 includes at least one memory 1020 (e.g., a volatile memory device, and / or a non-volatile memory device). System 1000 includes a storage device 1040, 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-based memory, magnetic disk drive, solid-state drive (SSD), and / or optical disk drive. The storage device 1040 can include an internal storage device, an attached storage device (including detachable and non-detachable storage devices), and / or a network accessible storage device (a.k.a. cloud storage), as non-limiting examples.

[0028] System 1000 includes an encoder / decoder module 1030 configured, for example, to process data to provide an encoded video or decoded video, and the encoder / decoder module 1030 can include its own processor and memory. The encoder / decoder module 1030 represents module(s) that can be included in a device to perform the encoding and / or decoding functions described further below. As is known, a device can include one or both of the encoding and decoding modules. Additionally, encoder / decoder module 1030 can be implemented as a separate element of system 1000 or can be incorporated within processor 1010 as a combination of hardware and software as known to those skilled in the art.

[0029] Program code to be loaded onto processor 1010 or encoder / decoder 1030 to perform one or more of the aspects described in this document can be stored in storage device 1040 and subsequently loaded onto memory 1020 for execution by processor 1010. In accordance with various embodiments, one or more of processor 1010, memory 1020, storage device 1040, and encoder / decoder module 1030 can store one or more of various items during the performance of the processes described in this document. Such stored items can include, but are not limited to, the input video, the decoded video or portions of the decoded video, the bitstream, matrices, variables, and intermediate or final results from the processing of equations, formulas, operations, and operational logic.

[0030] In some embodiments, memory inside of the processor 1010 and / or the encoder / decoder module 1030 is used to store instructions and to provide working memory for processing that is needed during encoding or decoding. In other embodiments, however, a memory external to the processing device (for example, the processing device can be either the processor 1010 or the encoder / decoder module 1030) is used for one or more of these functions. The external memory can be the memory 1020 and / or the storage device 1040, for example, a dynamic volatile memory and / or a non-volatile flash memory. In several embodiments, an external nonvolatile flash memory is used to store the operating system of, for example, a television. In at least one embodiment, a fast external dynamic volatile memory such as a RAM is used as working memory for video coding and decoding operations, such as for MPEG-2 (MPEG refers to the Moving Picture Experts Group, MPEG-2 is also referred to as ISO / IEC 13818, and 13818-1 is also known as H.222, and 13818-2 is also known as H.262), HEVC (HEVC refers to High Efficiency Video Coding, also known as H.265), or VVC (Versatile Video Coding, also known as H.266).

[0031] The input to the elements of system 1000 can be provided through various input devices as indicated in block 1130. Such input devices include, but are not limited to, a radio frequency (RF) portion that receives an RF signal transmitted, for example, over the air by a broadcaster, a Component (COMP) input terminal (or a set of COMP input terminals), a Universal Serial Bus (USB) input terminal, and / or a High-Definition Multimedia Interface (HDMI) input terminal. Other examples include composite video.

[0032] In various embodiments, the input devices of block 1130 have associated respective input processing elements as known in the art. For example, the RF portion can be associated with elements suitable for selecting a desired frequency (also referred to as selecting a signal, or band- limiting a signal to a band of frequencies), down converting the selected signal, bandlimiting 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, demodulating the down converted and band-limited signal, performing error correction, and demultiplexing to select the desired stream of data packets. The RF portion 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. In one set-top box embodiment, the RF portion and its associated input processing element receives an RF signal transmitted over a wired (for example, cable) medium, and performs frequency selection by filtering, down converting, and filtering again to a desired frequency band. Various embodiments rearrange the order of the above-described (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 portion includes an antenna. The RF portion may comply with standard specifications such as those published by Digital Video Broadcasting (DVB), Advanced Television Systems Committee (ATSC), Association of Radio Industries and Businesses (ARIB) or others.

[0033] Additionally, the USB and / or HDMI terminals can include respective interface processors for connecting system 1000 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 processor 1010 as necessary. Similarly, aspects of USB or HDMI interface processing can be implemented within separate interface Ics or within processor 1010 as necessary. The demodulated, error corrected, and demultiplexed stream is provided to various processing elements, including, for example, processor 1010, and encoder / decoder 1030 operating in combination with the memory and storage elements to process the data stream as necessary for presentation on an output device.

[0034] Various elements of system 1000 can be provided within an integrated housing, Within the integrated housing, the various elements can be interconnected and transmit data therebetween using suitable connection arrangement 1140, for example, an internal bus as known in the art, including the Inter- IC (I2C) bus, wiring, and printed circuit boards.

[0035] The system 1000 includes communication interface 1050 that enables communication with other devices via communication channel 1060. The communication interface 1050 can include, but is not limited to, a transceiver configured to transmit and to receive data over communication channel 1060. The communication interface 1050 can include, but is not limited to, a modem or network card and the communication channel 1060 can be implemented, for example, within a wired and / or a wireless medium.

[0036] Data is streamed, or otherwise provided, to the system 1000, 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 Wi-Fi signal of these embodiments is received over the communications channel 1060 and the communications interface 1050 which are adapted for Wi-Fi communications. The communications channel 1060 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. Other embodiments provide streamed data to the system 1000 using a set- top box that delivers the data over the HDMI connection of the input block 1130. Still other embodiments provide streamed data to the system 1000 using the RF connection of the input block 1130. As indicated above, various embodiments provide data in a non-streaming manner. Additionally, various embodiments use wireless networks other than Wi-Fi, for example a cellular network or a Bluetooth network.

[0037] The system 1000 can provide an output signal to various output devices, including a display 1100, speakers 1110, and other peripheral devices 1120. The display 1100 of various embodiments includes one or more of, for example, a touchscreen display, an organic lightemitting diode (OLED) display, a curved display, and / or a foldable display. The display 1100 can be for a television, a tablet, a laptop, a cell phone (mobile phone), or other device. The display 1100 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 1120 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 1120 that provide a function based on the output of the system 1000. For example, a disk player performs the function of playing the output of the system 1000.

[0038] In various embodiments, control signals are communicated between the system 1000 and the display 1100, speakers 1110, or other peripheral devices 1120 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 1000 via dedicated connections through respective interfaces 1070, 1080, and 1090. Alternatively, the output devices can be connected to system 1000 using the communications channel 1060 via the communications interface 1050. The display 1100 and speakers 1110 can be integrated in a single unit with the other components of system 1000 in an electronic device such as, for example, a television. In various embodiments, the display interface 1070 includes a display driver, such as, for example, a timing controller chip.

[0039] The display 1100 and speaker 1110 can alternatively be separate from one or more of the other components, for example, if the RF portion of input 1130 is part of a separate set- top box. In various embodiments in which the display 1100 and speakers 1110 are external components, the output signal can be provided via dedicated output connections, including, for example, HDMI ports, USB ports, or COMP outputs.

[0040] The embodiments can be carried out by computer software implemented by the processor 1010 or by hardware, or by a combination of hardware and software. As a nonlimiting example, the embodiments can be implemented by one or more integrated circuits. The memory 1020 can be of any type appropriate to the technical environment and can be implemented using any appropriate data storage technology, such as optical memory devices, magnetic memory devices, semiconductor-based memory devices, fixed memory, and removable memory, as non-limiting examples. The processor 1010 can be of any type appropriate to the technical environment, and can encompass one or more of microprocessors, general purpose computers, special purpose computers, and processors based on a multi-core architecture, as non-limiting examples.

[0041] Figure 2 describes an example of a context in which following embodiments can be implemented. In this context 200, a system 210 transmits a video stream to a system 230 using a communication channel 220. Examples of system 210 comprise a camera, a storage device, a computer, a drone, a video surveillance camera, a server or any device capable of delivering a video stream. The video stream is either encoded and transmitted by the system 210 or received and / or stored by the system 210 and then transmitted. The communication channel 220 is a wired (for example Internet, Ethernet, Cable network) or a wireless (for example WiFi, 3G, 4G or 5G, satellite TV, terrestrial TV) network link. The system 230 receives and decodes the video stream to generate a sequence of decoded pictures. An example of system 230 is a set top box. The obtained sequence of decoded pictures is then transmitted to a display system 250 using a communication channel 240, that could be a wired or wireless network as introduced above. The display system 250 then displays said pictures. An example of display system 250 is a television or display monitor.

[0042] In an embodiment, the system 230 and the display system 250 are comprised in a single device, thus combining the reception, decoding and display of the video stream. Examples of such device are a television, a computer, a tablet, a smartphone, a head-mounted display, a vehicle entertainment system, a medical device.

[0043] Figure 3 illustrates a block diagram of an example of video encoder. Variations of this encoder 300 are contemplated, but the encoder 300 is described below for purposes of clarity without describing all expected variations. Before being encoded, the video sequence may go through pre-encoding processing 301, for example, applying a color transform to the input color picture (e.g., conversion from RGB 4:4:4 to YcbCr 4:2:0), or performing a remapping of the input picture components in order to get a signal distribution more resilient to compression (for instance using a histogram equalization of one of the color components). Metadata can be associated with the pre-processing and attached to the bitstream, for example in the form of supplemental enhancement information (SEI) messages, for the standards that include such mechanism.

[0044] In the encoder, a picture is encoded by the encoder elements as described below. The picture to be encoded is partitioned (302), for example as further described in figure 5, and processed in units such as coding units. Each unit is encoded using, for example, either an intra or inter mode. When a unit is encoded in an intra mode, it performs intra prediction (360). In an inter mode, motion estimation (375) and compensation (370) are performed. The encoder decides (305) which one of the intra mode or inter mode to use for encoding the unit, and indicates the intra / inter decision by, for example, a prediction mode flag. Prediction residuals are calculated, for example, by subtracting (320) the predicted block from the original image block. The prediction residuals are then transformed (325) and quantized (330). The quantized transform coefficients, as well as motion vectors and other syntax elements, are entropy coded (345) to output a bitstream. The encoder can skip the transform and apply quantization directly to the non-transformed residual signal. The encoder can bypass both transform and quantization, i.e., the residual is coded directly without the application of the transform or quantization processes.

[0045] The encoder decodes an encoded block to provide a reference for further predictions. The quantized transform coefficients are de-quantized (340) and inverse transformed (350) to decode prediction residuals. Combining (355) the decoded prediction residuals and the predicted block, an image block is reconstructed. In-loop filters (365) are applied to the reconstructed picture to perform, for example, deblocking / SAO (Sample Adaptive Offset), Adaptive Loop-Filter (ALF) filtering to reduce encoding artifacts. The filtered image is stored at a reference picture buffer (380) for further use.

[0046] The encoder also generally performs video decoding as part of encoding video data.

[0047] Figure 4 illustrates a block diagram of an example of video decoder. In the decoder 400, a bitstream is decoded by the decoder elements as described below. Video decoder 400 generally performs a decoding pass reciprocal to the encoding pass as described in previous figure. The input of the decoder includes a video bitstream, which can be generated by video encoder 300 of figure 3. The bitstream is first entropy decoded (430) to obtain transform coefficients, motion vectors, and other coded information. The picture partition information indicates how the picture is partitioned. The decoder may therefore divide (435) the picture according to the decoded picture partitioning information. The transform coefficients are de-quantized (440) and inverse transformed (450) to decode the prediction residuals. Combining (455) the decoded prediction residuals and the predicted block, an image block is reconstructed. The predicted block can be obtained (470) from intra prediction (460) or motion-compensated prediction (i.e., inter prediction) (475). In-loop filters (465) are applied to the reconstructed image. The filtered image is stored at a reference picture buffer (480).

[0048] The decoded picture can further go through post-decoding processing (485), for example, an inverse color transform (e.g., conversion from YCbCr 4:2:0 to RGB 4:4:4) or an inverse remapping performing the inverse of the remapping process performed in the preencoding processing (301 of figure 3). The post-decoding processing can use metadata derived in the pre-encoding processing and signaled in the bitstream.

[0049] Figure 5 illustrates an example of partitioning undergone by an image of an original video sequence. An original video sequence 500 comprises a plurality of pictures 510. A picture comprises a plurality of pixels, generally arranged in a grid comprising rows and columns. It is considered in this document that a pixel is composed of three components: a luminance component and two chrominance components. Other types of pixels are however possible comprising less or more components such as only a luminance component or an additional depth component or an additional transparency component.

[0050] A picture is divided into a plurality of coding entities. First, as represented by reference 530, a picture is divided in a grid of blocks called coding tree units (CTU). A CTU consists of a block of luminance samples together with two corresponding blocks of chrominance samples. The size of such block is generally NxN, and N is generally a power of two having a maximum value of “128” for example. Second, a picture is divided into one or more groups of CTU. For example, it can be divided into one or more tile rows and tile columns, a tile being a sequence of CTU covering a rectangular region of a picture. In some cases, a tile could be divided into one or more bricks, each of which consisting of at least one row of CTU within the tile. Above the concept of tiles and bricks, another encoding entity, called slice, exists, that can contain at least one tile of a picture or at least one brick of a tile. In the example represented by reference 520, the picture 21 is divided into three slices SI, S2 and S3 of the raster-scan slice mode, each comprising a plurality of tiles (not represented), each tile comprising only one brick.

[0051] As represented by reference 540, a CTU may be partitioned into the form of a hierarchical tree of one or more sub-blocks called coding units (CU). The CTU is the root (i.e., the parent node) of the hierarchical tree and can be partitioned in a plurality of CU (i.e., child nodes). Each CU becomes a leaf of the hierarchical tree if it is not further partitioned in smaller CU or becomes a parent node of smaller CU (i.e., child nodes) if it is further partitioned. During the coding of a picture, the partitioning is adaptive, each CTU being partitioned to optimize a compression efficiency.

[0052] For example, the CTU 540 is first partitioned in four square CU using a quadtree type partitioning. The upper left CU 541 is a leaf of the hierarchical tree since it is not further partitioned, i.e., it is not a parent node of any other CU. The upper right CU is further partitioned in four smaller square CU 551, 552, 553, 554 using again a quadtree type partitioning. The bottom left CU is vertically partitioned in three rectangular CU 561, 562, 563 using a ternary tree type partitioning. The bottom right CU is vertically partitioned in two rectangular CU 571, 572 using a binary tree type partitioning.

[0053] In HEVC appeared the concept of prediction unit (PU) and transform unit (TU). Indeed, in HEVC, the coding entity that is used for prediction (i.e., a PU) and transform (i.e., a TU) can be a subdivision of a CU. For example, as represented in the figure, a CU of size 2Nx2N, can be divided in PU 580 of size Nx2N or of size 2NxN. In addition, said CU can be divided in four TU 590 of size NXN or in “16” TU of size (N / 2)x(N / 2). Other video coding standards also use these notions. In VVC, except in some particular cases, frontiers of the TU and PU are aligned on the frontiers of the CU. Consequently, a CU comprises generally one TU and one PU.

[0054] In the present application, the terms “reconstructed” and “decoded” may be used interchangeably, the terms “pixel” and “sample” may be used interchangeably, the terms “image,” “picture”, “sub-picture”, “slice” and “frame” may be used interchangeably. Usually, but not necessarily, the term “reconstructed” is used at the encoder side while “decoded” is used at the decoder side. In the present application, the term “block” or “picture block” can be used to refer to any one of a CTU, a CU, a PU and a TU. In addition, the term “block” or “picture block” can be used to refer to a macroblock, a partition and a sub-block as specified in H.264 / A VC or in other video coding standards, and more generally to refer to an array of samples of numerous sizes.

[0055] Video coding standards like A VC, HEVC and VVC enable embedding of metadata in video bitstreams through SEI (Supplemental Enhancement information) messages. Those messages are defined either in the core standard or companion standard like VSEI (Versatile Supplemental Enhancement Information), and more get added in successive versions of these standards.

[0056] A SEI message is a syntax structure that is defined in various MPEG standards to allow carriage of metadata. It is a specific type of NAL (Network Access Layer) unit, which is the elementary packet in MPEG bitstream formats. The SEI syntax may vary slightly across different standards, but it commonly contains at least a pay load type, a pay load length, and the payload itself. The SEI syntax defined for VVC is illustrated in Table 1 as an example. Table 1

[0057] In addition, a specific syntax structure is typically defined for each payload type and instantiated by a sei_payload syntax structure according to each payload type.

[0058] Various video coding specifications, including AVC, HEVC and VVC / VSEI standards, allow embedding specific metadata that describe film grain characteristics as parameters of a statistical model (film grain characteristics are sometimes referred to as model parameters). Such model typically defines grain strength and spatial properties as a function of picture sample value or intensity. The parameters can be different for each color component. Spatial properties can be described as frequency cutoffs, or coefficients of a 2D autoregressive filter. This model can be used to describe the grain present in the source video, that is potentially lost in the encoded bitstream. A decoder can then use this model to add a synthetic grain on top of the decoded video, recovering a grainy aspect as close as possible to the original.

[0059] Film grain is a random optical texture of photographic film introduced by the development process of the film. When used properly, film grain is an artistic effect that makes a video feel more natural and more believable, which helps increasing the viewing experience for the audience. However, in the today’s digital world, digitally captured and digitally generated content do not exhibit film grain anymore since there is no film. In addition, natural film grain tends to be suppressed by some features of video coding algorithms since it is a kind of noise. The visual and artistic effect of film grain can be simulated by adding grain to a digital image. Thus, in a digital video ecosystem, film grain can be introduced at the decoder side by adding film grain to a digital image to simulate the visual and artistic effect of film grain.

[0060] In AVC, HEVC and VVC / VSEI, film grain characteristics can be described using a FGC (Film Grain Characteristics) SEI message; the model used is based on intensity intervals, with model parameters (strength and spatial properties) specified for each interval. Intervals and model parameters are specific to each color component. After having extracted the film grain characteristics, a decoder may then generate corresponding film grain samples and add them to a decoded picture to obtain the expected artistic effect. Table 2 illustrates the film grain characteristics metadata structure currently defined in VSEI.

[0061] Table 2

[0062] In the structure of Table 2, the syntax element fg_characteristics_cancel_flag is used to handle the persistence of any previous film grain characteristics SEI message. The syntax element fg_model_id is used to identify the film grain simulation model, selected amongst frequency_filtering when the value is 0 and auto-regression when the value is 1. The syntax element fg_separate_colour_description_present_flag equal to 1 indicates that a distinct colour space description for the film grain characteristics specified in the SEI message is present and the colour is further specified. The colour space definition is not represented in Table 2, replaced by the three dots between bracket on the seventh line. The syntax element fg_blending_mode_id identifies the blending mode used to blend the simulated film grain with the decoded images, selected amongst additive when the value is 0 and multiplicative when the value is 1. The syntax element fg_log2_scale_factor specifies a scale factor used in the film grain characterization equations. The syntax element table fg_comp_model_present_flag[c] indicates if the film grain is modelled on the color components, the components referring for example to Y / Cb / Cr components or to RGB components. fg_comp_model_present_flag[c] equal to 1 indicates that syntax elements specifying modelling of film grain on colour component c are present in the SEI message. The syntax element fg_num_intensity_intervals_minusl[ c ] plus 1 specifies the number of intensity intervals for which a specific set of parameters is provided. The syntax element fg_num_model_values_minusl[ c ] plus 1 specifies the number of model values present for each intensity interval in which the film grain has been modelled. Its value shall be in the range of 0 to 5, inclusive. The syntax element fg_intensity_interval_lower_bound[ c ][ i ] specifies the lower bound of the interval i of intensity levels for which the set of model values applies. The syntax element fg_intensity_interval_upper_bound[ c ][ i ] specifies the upper bound of the interval i of intensity levels for which the set of model values applies. The syntax element fg_comp_model_value[ c ][ i ][ j ] represents each one of the model values present for the colour component c and the intensity interval i. The set of model values has different meaning depending on the value of fg_film_grain_model_id. The fg_film_grain_characteristics_persistence_flag specifies the persistence of the film grain characteristics SEI message for the current layer. A value equal to 0 specifies that the film grain characteristics SEI message applies to the current decoded picture only.

[0063] Figure 6 illustrates examples of film grain parameters comprising a frequency cut-off and a gain. The diagram 600 shows the film grain model parameters as a function of intensity. The intensity used in this example is the luma component (Y). The plot 610 represents grain strength, also called (or “gain”), with intensity interval boundaries represented by dashed vertical lines. The plot 620 represents grain sharpness or size, here in the form of a spatial frequency cutoff. In this example, intensity intervals cover the full range without holes nor overlaps, but this needs not be the case: the FGC SEI message syntax allows holes, overlaps, and out-of-order interval definitions.

[0064] Figure 7 illustrates an example of reproduction of a film scan. It shows that film grain characteristics differ significantly between shadows and highlights, justifying different model parameters, including spatial properties, depending on intensity.

[0065] Embodiments described hereafter have been designed with the foregoing in mind and propose to define image regions, sets of film grain characteristics, and provides means to associate image regions with film grain characteristics. An encoded video bitstream comprises specific syntax allowing to carry such information from an encoding device to a decoding device and allowing to regenerate the corresponding film grain to be applied to an image of a decoded video. Variations of such embodiment are described hereunder.

[0066] At least one embodiment proposes to define a film grain region characteristics metadata structure taking the form of a specific SEI message hereafter abbreviated FGRC-SEI to carry region-dependent film grain metadata. Such FGRC-SEI is inserted into a video bitstream so that a decoder can generate the appropriate synthetic film grain samples for different regions of a picture according to film grain characteristics (i.e., parameters) extracted from the metadata carried by the FGRC-SEI. The film grain samples are then added to the decoded picture.

[0067] Different techniques may be used to associate image regions with film grain characteristics. A first technique is to assign a region to an intensity interval. A second technique is to assign model parameters to a region. A third technique is to assign a tag identifier to model parameters and to assign a tag identifier to a region, thus using an indirect reference system to a set of film characteristics.

[0068] Different methods may be used to define image regions. Regions may be defined as a list of rectangular areas, each region being identified by its list index, or a dedicated identifier and being characterized by a position and size. A single region (or area) may be determined by a top left corner and a size of the region, or by a couple of positions of opposite comers, or by horizontal and vertical boundaries of the region, or by the location of the center of the region and the size of the region. A region may be defined by re-using a list of externally defined image areas, such as regions from Annotated Regions SEI message, with their identifier, subpictures and their identifiers, such as defined for VVC bitstreams, tiles and their identifiers, such as defined for VVC an HEVC bitstreams, slices, being either rectangular or non- rectangular, or object masks defined by sample values of auxiliary pictures, as in the proposed OMI SEI message. In some cases, the syntax describing the object masks characteristics (sample value(s), bounding box or other parameters associated to each object mask) may be included in the film grain regions characteristics metadata structure. In embodiments, the image regions may be updated independently. Indeed, the list of regions embedded in the film grain regions characteristics metadata structure needs not be fully specified in each message regularly inserted inside the bitstream. Part of it (for example, a subset of regions) can be updated either, for example, by defining its new position, by translating its position by a specified motion vector, by transforming its position and size (or two opposite comers) using a specified parametric transformation such as an affine transformation. Other parametric transformations such as an homographic transformation can also be considered. When defining region transformations, the transformation can be specified to apply repetitively for subsequent frames without needing new Film grain regions characteristics SEI messages, until cancelled by a subsequent FGRC-SEI message (or end of sequence). In at least one embodiment, the regions do not overlap. Figure 8 illustrates an example of regions for a picture according to embodiments. In this example, the picture 800 is split in three different regions identified in the figure as A, B, and C. These regions may have different film grain characteristics. This is for example the case when the picture is a composite of different sources such as film scan, video from a digital camera or synthetic content. Embodiments described herein allow to generate a picture with consistent film grain all over the pixels thanks to specific film grain metadata for each of the region.

[0069] Different methods may be used to define the film grain characteristics. Film grain characteristics may be defined as common parameters part (e.g., selection of color space, selection of model, number of model parameters) and a list of intensity intervals, with model parameters specific to each interval. In addition, image regions may be defined and associated with intervals and interval- specific parameters. The intervals and model parameters for a region can be grouped in a specific structure, and / or identified by an identifier, allowing a more efficient reuse of a set of parameters by several image regions. An existing structure may be used, such as the film_grain_characteristics introduced in Table 2, as defined in AVC, HEVC, and VSEI standards. In that case, some common parts may be constrained to have the same value (e.g., selection of model: either frequency-filtering or auto-regressive). Different parts of film grain characteristics (e.g., for different regions) may be updated independently. Indeed, the list of intervals (potentially associated with different image regions) embedded in the film grain regions characteristics metadata structure needs not be fully specified in each message: part of it can be updated, for example, by specifying which intervals (of which regions) are updated.

[0070] All these techniques may be mixed together in order to design the most appropriate mechanism to associate specific image regions with specific film grain characteristics.

[0071] Embodiments described herein are applicable to AVC, HEVC, VVC / VSEI as well as to other video coding systems based on the same principles and using similar data structures.

[0072] In at least one embodiment, a new FGRC-SEI message type is created to describe region-dependent film grain characteristics using a statistical model, where sets of model parameters are specified, each set being associated with a sample intensity interval and an image region. In such embodiment, the syntax structure specifies a set of intensity intervals, model parameters for each interval and one or more region for each interval.

[0073] In at least one embodiment, a new FGRC-SEI message defines a set of image regions and defines the film grain characteristics for each region. This can comprise a list of intensity intervals and interval-specific model parameters, or model parameters that are parametric functions of intensity (e.g., a piecewise linear function to define grain strength).

[0074] In at least one embodiment, film grain characteristics are associated with image regions through tag identifiers. In an implementation based on intervals as described above, a tag identifier is specified for each intensity interval and a set of tag identifiers is specified for each image region. Several intensity intervals can have the same tag identifier. In an implementation based on parametric function as described above, a tag identifier is specified for each parametric function and a set of tag identifiers is specified for each image region.

[0075] In at least one embodiment, the syntax for the FGRC-SEI message comprising the film grain region characteristics metadata structure is defined as illustrated in Table 3. In such embodiment, common parameters are specified, such as the selection of model or the color components. An interval tag identifier named fgr_intensity_interval_tag is specified for each of the intensity intervals. This interval tag identifier can be the same for several intervals. The film grain metadata structure comprises a list of regions. Each region is defined by the corresponding area, represented using one of the different techniques introduced above such as the top-left comer and size of the region. For each region, a list of interval tag identifier refers to one of the intensity intervals so that the corresponding film grain characteristics are used. When using such syntax, different regions may be defined and each of these regions may use specific film grain parameters. The syntax of Table 3 does not comprise the partial update mechanism mentioned above.

[0076] Table 3

[0077] In the structure of Table 2, the syntax element with same name as in Table 2 have the same meaning. In addition, the syntax element fgr_intensity_interval_tag[ c ][ i ] specifies an identifier for the intensity interval i of the color component c. The syntax element fgr_num_regions_minusl plus 1 specifies the number of regions for which a specific set of parameters is provided. The syntax element fg_num_region_interval_tags_minusl[ i ] plus 1 specifies the number of tag identifiers used by region i. The syntax element fgr_region_interval_tag[ i ][ j ] specifies an identifier used by the region i. This identifier is matched with one of the fgr_intensity_interval_tag: the film grain characteristics of region i includes all intervals specifying the same identifier, for all j in region i.

[0078] In embodiments, the prefix ‘fg’ and ‘fgr’ may be replaced by other prefixes and the labels of the elements may vary while expressing the same functions.

[0079] The syntax elements for the region definition can use any of the conventional syntax elements used to describe a region. One example is given in table 4 below where the region is defined by its position using the fg_rect_region_position_top and fg_rect_region_position_left syntax element and the size of the region using the fg_rect_region_width and fg_rect_region_height syntax elements. Table 4

[0080] In a variant embodiment, instead of using interval tag ids for each interval as shown in Table 3, a range of interval indices is specified for each region, as illustrated in Table 5. Film grain characteristics corresponding to the specified intervals are used for the region.

[0081] Table 5

[0082] In variant embodiments as introduced above, region definitions can be updated independently as in Annotated Regions SEI message (using a flag to indicate update, specifying which region is updated, and the new region definition or the region modification, e.g., translation vector and / or size change). In variant embodiments as introduced above, parameters describing the temporal evolution (transformation) of the region shape may be also inserted. In variant embodiments as introduced above, intensity intervals can be updated independently (using a flag to indicate update, specifying which intervals are updated, and the new model parameters). Minor modifications to the syntax proposed in tables 3 and 4 would allow to implement these variant embodiments.

[0083] The examples described herein are based on SEI messages to carry the regiondependent film grain metadata but any other means providing the same functionality may be used.

[0084] Figure 9A illustrates an example process for encoding a bitstream comprising a FGRC- SEI message comprising region-dependent film grain metadata according to embodiments. The process 910 is for example implemented by a processor 1010 of a device 1000 of figure 1, a system 210 of figure 2, or an encoder 300 of figure 3. In step 912, the processor obtains video data. In step 914, the processor determines region-dependent film grain characteristics and region-dependent film grain metadata representative of the region-dependent film grain characteristics. In step 916, processor packages the metadata into a FGRC-SEI message, for example according to the syntax of tables 3 or 4. In step 918, the processor provides the bitstream that comprises encoded video data and the FGRC-SEI message comprising the region-dependent film grain characteristics.

[0085] Figure 9B illustrates an example process for decoding a bitstream comprising a FGRC- SEI message comprising region-dependent film grain metadata according to embodiments. The process 930 is for example implemented by a device 1000 of figure 1, a system 230 of figure 2, or a decoder 400 of figure 4. In step 935, the processor obtains the bitstream that comprises an encoded video data and metadata representing region-dependent film grain characteristics packaged into a FGRC-SEI message, for example based on the syntax of tables 3 or 4. In step 950, the processor obtains the FGRC-SEI message and determines the metadata representing region-dependent film grain characteristics. In step 954, the processor determines, for one or more regions, the film grain characteristics (e.g., parameters needed to synthetize the film grain), based on the region-dependent film grain metadata and for example using intervals and regions characteristics defined in the metadata. In step 990, the processor provides the determined film grain characteristics for further use. Figure 9C illustrates an example process for decoding a bitstream comprising a FGRC- SEI message according to embodiments and applying the determined film grain characteristics on a decoded image. This process 931 builds upon the process 930 of figure 9B and further proposes one application of use for the determined film grain characteristics. In this case, the determined characteristics are provided (Step 990 of Figure 9B) internally to the process and directly exploited in further steps. Steps 935, 950, 954 are identical to the corresponding steps of process 930. In addition to these steps, in step 940, the processor decodes a picture. In step 956, the processor generates, for the region, film grain samples based on the extracted film grain characteristics. Steps 954 and 956 may be iterated (arrow 958) over a plurality of regions, for example over each region defined in the FGRC-SEI message. In step 970, the processor adds the generated film grain samples to the decoded picture, according to the respective position and size of the regions with regards to the decoded picture. In step 980, the processor provides the picture that comprises the film grain as specified in the FGRC-SEI message.

[0086] This application describes a variety of aspects, including tools, features, embodiments, models, approaches, etc. Many of these aspects are described with specificity and, at least to show the individual characteristics, are often described in a manner that may sound limiting. However, this is for purposes of clarity in description, and does not limit the application or scope of those aspects. Indeed, all of the different aspects can be combined and interchanged to provide further aspects. Moreover, the aspects can be combined and interchanged with aspects described in earlier filings as well.

[0087] The aspects described and contemplated in this application can be implemented in many different forms. Figures provide some embodiments, but other embodiments are contemplated and the discussion of these figures does not limit the breadth of the implementations. At least one of the aspects generally relates to video encoding and decoding, and at least one other aspect generally relates to transmitting a bitstream generated or encoded. These and other aspects can be implemented as a method, an apparatus, a computer readable storage medium having stored thereon instructions for encoding or decoding video data according to any of the methods described, and / or a computer readable storage medium having stored thereon a bitstream generated according to any of the methods described.

[0088] Various methods are described herein, and each of the methods comprises one or more steps or actions for achieving the described method. Unless a specific order of steps or actions is required for proper operation of the method, the order and / or use of specific steps and / or actions may be modified or combined.

[0089] Various methods and other aspects described in this application can be used to modify modules, for example, the motion compensation and motion estimation modules of a video encoder 300 and decoder 400 as respectively shown in figures 3 and 4.

[0090] Various numeric values are used in the present application, for example, 128 for the block size. The specific values are for example purposes and the aspects described are not limited to these specific values.

[0091] Various implementations involve decoding. “Decoding”, as used in this application, can encompass all or part of the processes performed, for example, on a received encoded sequence in order to produce a final output suitable for display. In various embodiments, such processes include one or more of the processes typically performed by a decoder, for example, entropy decoding, inverse quantization, inverse transformation, and differential decoding. In various embodiments, such processes also, or alternatively, include processes performed by a decoder of various implementations described in this application, for example, adapting the illumination compensation process.

[0092] As further examples, in one embodiment “decoding” refers only to entropy decoding, in another embodiment “decoding” refers only to differential decoding, and in another embodiment “decoding” refers to a combination of entropy decoding and differential decoding. Whether the phrase “decoding process” is intended to refer specifically to a subset of operations or generally to the broader decoding process will be clear based on the context of the specific descriptions and is believed to be well understood by those skilled in the art.

[0093] Various implementations involve encoding. In an analogous way to the above discussion about “decoding”, “encoding” as used in this application can encompass all or part of the processes performed, for example, on an input video sequence in order to produce an encoded bitstream. In various embodiments, such processes include one or more of the processes typically performed by an encoder, for example, partitioning, differential encoding, transformation, quantization, and entropy encoding. In various embodiments, such processes also, or alternatively, include processes performed by an encoder of various implementations described in this application.

[0094] As further examples, in one embodiment “encoding” refers only to entropy encoding, in another embodiment “encoding” refers only to differential encoding, and in another embodiment “encoding” refers to a combination of differential encoding and entropy encoding. Whether the phrase “encoding process” is intended to refer specifically to a subset of operations or generally to the broader encoding process will be clear based on the context of the specific descriptions and is believed to be well understood by those skilled in the art.

[0095] Note that the syntax elements as used herein, are descriptive terms. As such, they do not preclude the use of other syntax element names.

[0096] 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.

[0097] Various embodiments refer to rate distortion optimization. In particular, during the encoding process, the balance or trade-off between the rate and distortion is usually considered, often given the constraints of computational complexity. The rate distortion optimization is usually formulated as minimizing a rate distortion function, which is a weighted sum of the rate and of the distortion. There are different approaches to solve the rate distortion optimization problem. For example, the approaches may be based on an extensive testing of all encoding options, including all considered modes or coding parameters values, with a complete evaluation of their coding cost and related distortion of the reconstructed signal after coding and decoding. Faster approaches may also be used, to save encoding complexity, in particular with computation of an approximated distortion based on the prediction or the prediction residual signal, not the reconstructed one. Mix of these two approaches can also be used, such as by using an approximated distortion for only some of the possible encoding options, and a complete distortion for other encoding options. Other approaches only evaluate a subset of the possible encoding options. More generally, many approaches employ any of a variety of techniques to perform the optimization, but the optimization is not necessarily a complete evaluation of both the coding cost and related distortion.

[0098] This application describes a variety of aspects, including tools, features, embodiments, models, approaches, etc. Many of these aspects are described with specificity and, at least to show the individual characteristics, are often described in a manner that may sound limiting. However, this is for purposes of clarity in description, and does not limit the application or scope of those aspects. Indeed, all of the different aspects can be combined and interchanged to provide further aspects. Moreover, the aspects can be combined and interchanged with aspects described in earlier filings as well.

[0099] 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 in, for example, 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, tablets, smartphones, cell phones, portable / personal digital assistants, and other devices that facilitate communication of information between end-users.

[0100] 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.

[0101] 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, or retrieving the information from memory.

[0102] 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.

[0103] 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.

[0104] In the present application, the terms “reconstructed” and “decoded” may be used interchangeably, the terms “pixel” and “sample” may be used interchangeably, the terms “image,” “picture”, “frame”, “slice” and “tiles” may be used interchangeably. Usually, but not necessarily, the term “reconstructed” is used at the encoder side while “decoded” is used at the decoder side.

[0105] It is to be appreciated that the use of any of the following “ / ”, “and / or”, and “at least one of’, for example, in the cases of “A / B”, “A and / or B” and “at least one 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”, 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.

[0106] Also, as used herein, the word “signal” refers to, among other things, indicating something to a corresponding decoder. For example, in certain embodiments the encoder signals a particular one of an illumination compensation parameter. In this way, in an embodiment the same parameter is used at both the encoder side and the decoder side. Thus, for example, an encoder can transmit (explicit signaling) a particular parameter to the decoder so that the decoder can use the same particular parameter. Conversely, if the decoder already has the particular parameter as well as others, then signaling can be used without transmitting (implicit signaling) to simply allow the decoder to know and select the particular parameter. By avoiding transmission of any actual functions, a bit savings is realized in various embodiments. It is to be appreciated that signaling can be accomplished in a variety of ways. For example, one or more syntax elements, flags, and so forth are used to signal information to a corresponding decoder in various embodiments. While the preceding relates to the verb form of the word “signal”, the word “signal” can also be used herein as a noun.

[0107] As will be evident to one of ordinary skill in the art, implementations 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. For example, a signal can be formatted to carry the bitstream 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 data stream and modulating a carrier with the encoded data 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.

[0108] We describe a number of embodiments. Features of these embodiments can be provided alone or in any combination, across various claim categories and types.

Claims

CLAIMS1. A method comprising: obtaining video data; determining region-dependent film grain metadata representative of film grain characteristics; inserting the region-dependent film grain metadata into an encoded bitstream comprising the video data and the region-dependent film grain metadata; and providing the bitstream.

2. A method comprising: obtaining a bitstream comprising encoded video data and region-dependent film grain metadata; determining film grain characteristics for one or more regions of a picture of the video based on the region-dependent film grain metadata for a region; and providing the determined film grain characteristics.

3. The method of claim 2, further comprising decoding a picture based on the encoded video data; determining film grain samples for a region based on the determined film grain characteristics; adding the film grain samples to the decoded picture; and providing the modified decoded picture.

4. The method of any of claim 1 to 3, wherein the region-dependent film grain metadata is carried by a supplemental enhancement information message.

5. The method of any of claim 1 to 4, wherein the region-dependent film grain metadata comprises information related to a list of regions with, for each region of the list of regions, information related to a position and a size of the region.

6. The method of any of claim 1 to 5, wherein the region-dependent film grain metadata comprises information related to a list of intervals and wherein a region is associated with oneor more intervals.

7. The method of claim 6, wherein the association is performed by associating an interval with an characteristics identifier and associating one or more regions with one or more characteristics identifiers.

8. An apparatus comprising one or more processor configured to: obtain video data; determine region-dependent film grain metadata representative of film grain characteristics; insert the region-dependent film grain metadata into an encoded bitstream comprising the video data and the region-dependent film grain metadata; and provide the bitstream.

9. An apparatus comprising one or more processor configured to: obtain a bitstream comprising encoded video data and region-dependent film grain metadata; determine film grain characteristics for one or more regions of a picture of the video based on the region-dependent film grain metadata for a region; and provide the determined film grain characteristics.

10. The apparatus of claim 9, wherein the one or more processor is further configured to: decode a picture based on the encoded video data; determine film grain samples for a region based on the determined film grain characteristics; add the film grain samples to the decoded picture; and provide the modified decoded picture.

11. The apparatus of any of claim 8 to 10, wherein the region-dependent film grain metadata is carried by a supplemental enhancement information message.

12. The apparatus of any of claim 8 to 11, wherein the region-dependent film grain metadata comprises information related to a list of regions with, for each region of the list of regions, information related to a position and a size of the region.

13. The apparatus of any of claim 8 to 12, wherein the region-dependent film grain metadata comprises information related to a list of intervals and wherein a region is associated with one or more intervals.

14. A non-transitory computer readable medium containing data content generated according to the method of any one of claims 1 to 7.

15. A computer program product comprising instructions for performing the method of any one of claims 1 to 7 when executed by one of more processor.

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