Method for encoding and decoding an image, encoding and decoding device and corresponding computer program product

Abstract

The invention relates to the encoding of an image (ICj) divided into blocks, said image comprising distinct first and second zones (Z1, Z2), characterized in that the encoding implements, for at least one current block (Bu) of the image, a step (C4) of determining whether the current block belongs to the first or second zone, and a step (C5a) of encoding the current block by a first encoding method (MC1) if the current block belongs to the first zone (Z1), and a step (C5b) of encoding the current block by a second encoding method (MC2) comprising, from the position of the current block in the second zone (Z2), identifying a previously encoded and then decoded block (Bref) located in the first zone of the image from the current block's position in the second zone (C51b) and regenerating the value of at least one encoding parameter (PRC1) associated with the identified block.

Description

[Technical field]

[0001] The present invention relates generally to the field of image processing, and more particularly to the coding and decoding of parameters of digital images, whether these are fixed or form part of a sequence of digital images.

[0002] Specifically, the coding / decoding of such image parameters includes the following steps: images originating from one and the same camera and succeeding each other in time (2D type coding / decoding), - images resulting from different cameras oriented according to different fields of view (3D type coding and decoding), - Corresponding texture and depth components (3D type coding / decoding), - Images obtained by projection of 360° video, - etc. The method is applied to images originating from at least one video sequence having

[0003] The invention applies in an analogous manner to the coding / decoding of image parameters of 2D or 3D type.

[0004] The present invention can be particularly, but without limitation, applied to video coding implemented in current AVC (English abbreviation for "Advanced Video Coding") and HEVC (English abbreviation for "High Efficiency Video Coding") video coders and their extensions (MVC, 3D-AVC, MV-HEVC, 3D-HEVC, etc.) and to corresponding decoding. [Background technology]

[0005] Current video coders (MPEG, H.265, HEVC, etc.) use a block-wise representation of video sequences: images are divided into blocks, and these blocks may be further divided in a recursive manner, as in the HEVC standard, for example.

[0006] For the current block to be coded, the image parameters associated with this block are coded, in the form of bits, with the aid of an adapted coding scheme implemented by a coder, for example an entropy coder, whose objective is to code these parameters without loss.

[0007] Such parameters are, for example, - residual prediction coefficients for the pixels of the current block, - the mode of prediction of the current block (intra prediction, inter prediction, default prediction (in English, "skip"), which performs a prediction whose information is not transmitted to the decoder); - Information specifying the type of prediction for the current block (orientation, base image, etc.), - type of division of the current block, - If necessary, the motion information of the current block, - etc. It is.

[0008] The bits obtained after entropy coding are written into a data signal intended for transmission to a decoder.

[0009] Once the coded data signal is received by the decoder, decoding is performed image by image, and for each image, block by block: for each block, bits representative of the image parameters associated with the block are read and then decoded with the aid of a decoding scheme implemented by the decoder.

[0010] For each image type or format considered, a specific coding is implemented. Thus, for example, AVC and HEVC coders / decoders are adapted to code and decode 2D images originating from one and the same camera and succeeding each other in time. Also, such coders and decoders: - images obtained by stereoscopic video projection and having two views each representing one and the same scene, intended to be viewed respectively through the left and right eye of a user, -Images obtained by two-dimensional projection of 360° stereoscopic video, etc. The present invention is adapted to code / decode the

[0011] According to another example, the 3D-HEVC coder / decoder is adapted to code / decode 3D images such as 3D images originating from various cameras oriented according to different fields of view and corresponding texture and depth components, images originating from mono 360° video, etc.

[0012] Therefore, by proposing a very specific type of coding / decoding for the image format or type considered, the coding / decoding performance obtained by current coders / decoders is not satisfactory. Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention therefore envisages a coder / decoder that proposes the use of two different coding / decoding schemes for a current image originating from a video content of a given type or format, while allowing optimization of the coding / decoding performance of the current image.

[0014] One of the objects of the present invention is to remedy the above-mentioned shortcomings of the prior art. [Means for solving the problem]

[0015] To this end, the subject of the present invention relates to a method for coding an image divided into blocks, said image comprising first and second distinct zones.

[0016] Such a coding method comprises the steps of: - determining whether the current block belongs to a first or a second zone; coding the current block with the aid of a first coding scheme if the current block belongs to a first zone; -If the current block belongs to the second zone, - identifying a previously coded and then decoded block located in the first zone of the image based on the position of the current block in the second zone, -duplicating the value of at least one coding parameter associated with the identified block; coding the current block with the aid of a second coding scheme having It is notable that it implements

[0017] Such a scheme makes it possible to select, within one and the same encoder, the coding scheme that is best adapted to the way the scene that the image represents was originally captured.

[0018] For example, if the current image is a two-dimensional image, in the case where the images originate from a video with 2D images that follow each other in time, selecting a first coding scheme implemented in the encoder, such as a conventional scheme of the AVC or HEVC type, selecting, in the encoder, either the first or the second coding scheme as described above depending on whether the current block is located in the first or the second zone of the image, when this image is formed from two image zones corresponding to the left and right eyes of the user, for example obtained by projection of a stereoscopic video captured according to a number of viewing angles covering an angle of 360°, Therefore, it will be decided.

[0019] The invention therefore makes it possible to propose an adaptive coding of video content taking into account its format. Furthermore, for a certain type of content format, the invention advantageously makes it possible to apply adaptive coding to a current image according to a zone of the image currently to be coded, where at least one current block of a first zone is coded according to a first coding scheme and at least one current block of a second zone of this image is coded according to a second coding scheme.

[0020] Advantageously, the second coding scheme used makes it possible to exploit the spatial correlation existing between the second zone and the first zone of the current image, in which the value of at least one coding parameter of a block located in the first zone is duplicated for the current block of the second zone, and thus it is not necessary to code the value of such coding parameter for the current block. This results in a relatively high-performance coding of the image, because in this case it is relatively accurate, relatively simple and requires relatively little bit rate.

[0021] According to a particular embodiment, the second coding scheme is applied to all blocks of the second zone of the current image.

[0022] Such a scheme allows for a reduction in complexity and cost optimization in terms of bit rate of the coding implemented in the encoder.

[0023] According to another particular embodiment, the coding method comprises the steps of: - coding said at least one current block of a second zone of the image with the aid of a first coding scheme; selecting a first coding scheme or a second coding scheme according to a predetermined coding performance criterion; - coding an item of information representative of said selection; is implemented.

[0024] In view of the fact that the first and second coding schemes are set in a competitive state, if the second coding scheme is first applied to the encoder for the current block, the coding method will be relatively flexible, thereby improving the coding efficiency.

[0025] According to yet another particular embodiment, the first and second zones of the image have the same shape, where the first zone is located above the second zone and is separated from the second zone by a horizontal boundary extending along the center of the image.

[0026] Such a spatial configuration of the first and second zones of the current image allows optimizing the coding performance by precisely predefining the location of already coded and then decoded blocks of the first zone of the image as a function of the position of the current block of the second zone.

[0027] Various modes or features of the embodiments may be added, independently or in combination with one another, to operations implemented in a coding method such as those defined above.

[0028] In a related manner, the invention relates to a device for coding at least one image divided into blocks, said image comprising first and second distinct zones.

[0029] Such a coding device determines for at least one current block of an image: - determining whether the current block belongs to a first or a second zone; coding the current block with the aid of a first coding scheme if the current block belongs to a first zone; -If the current block belongs to the second zone, - identifying a previously coded and then decoded block located in the first zone of the image based on the position of the current block in the second zone, -duplicating the value of at least one coding parameter associated with the identified block; coding the current block with the aid of a second coding scheme having It is notable in that it has processing circuitry designed to implement

[0030] In a corresponding manner, the invention also relates to a method for decoding a data signal representative of an image divided into coded blocks, wherein said at least one image comprises first and second distinct zones.

[0031] The method comprises the steps of: for at least one current block of an image to be decoded: - determining whether the current block belongs to a first or a second zone; - decoding the current block with the aid of a first decoding scheme if the current block belongs to a first zone; -If the current block belongs to the second zone, - identifying a previously decoded block located in the first zone of the image based on the position of the current block in the second zone, - assigning at least one decoding parameter associated with said identified block to a current block; decoding the current block with the aid of a second decoding scheme having It is notable that it implements

[0032] According to a particular embodiment, the second decoding scheme is applied to all blocks of the second zone of the current image.

[0033] According to another particular embodiment, the second decoding scheme is applied to the current block of the second zone if an item of information regarding the selection of the second decoding scheme for the current block is read in the data signal, and the first decoding scheme is applied to the current block of the second zone if an item of information regarding the selection of the first decoding scheme for the current block is read in the data signal.

[0034] According to yet another particular embodiment, the first and second zones of the image have the same shape, where the first zone is located above the second zone and is separated from the second zone by a horizontal boundary extending along the center of the image.

[0035] The various above-mentioned modes or characteristics of the embodiments may be added, independently or in combination with one another, to operations implemented in a decoding method such as that defined above.

[0036] In a correlated manner, the invention relates to an apparatus for decoding a data signal representative of an image divided into coded blocks, where said at least one image comprises first and second distinct zones.

[0037] Such a decoding device performs the following steps for at least one current block of an image to be decoded: - determining whether the current block belongs to a first or a second zone; - decoding the current block with the aid of a first decoding scheme if the current block belongs to a first zone; -If the current block belongs to the second zone, - identifying a previously decoded block located in the first zone of the image based on the position of the current block in the second zone, - assigning at least one decoding parameter associated with said identified block to a current block; decoding the current block with the aid of a second decoding scheme having The present invention is characterized in that the present invention has processing circuitry designed to implement the above.

[0038] The invention further relates to a computer program comprising instructions which, when executed on a computer, implements one of the coding and decoding methods according to the invention.

[0039] Such programs may use any programming language and may have the form of source code, object code, or an intermediate code between source code and object code, such as a partially compiled form, or any other desired form.

[0040] A further subject of the invention is also considered to be a recording medium readable by a computer and comprising computer program instructions as described above.

[0041] The recording medium may be any entity or device capable of storing a program. For example, the medium may comprise a storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or else a magnetic recording means, a digital recording means, for example a USB key or a hard disk.

[0042] Furthermore, such a recording medium may be a transmittable medium, such as an electrical or optical signal, which may be conveyed via electrical or optical cable, wirelessly or by other means. The program according to the invention may in particular be downloaded over an Internet type network.

[0043] Alternatively, such a recording medium may be an integrated circuit having the program embedded therein, the circuit being adapted to perform, or for use in the performance of, the subject method.

[0044] Other features and advantages will become apparent from the following detailed description of the preferred embodiments, which are described with reference to the accompanying drawings. [Brief description of the drawings]

[0045] [Figure 1A] 2 illustrates the progress of a coding method according to a first embodiment of the invention; [Figure 1B] 5 illustrates the progress of a coding method according to a second embodiment of the present invention. [Figure 2A] 1 illustrates a coding device according to a first embodiment of the invention; [Figure 2B] 4 illustrates a coding device according to a second embodiment of the present invention; [Figure 3A] 3A-3C each show an example of a distinct zone within a current image to be coded or decoded. [Figure 3B] 3A-3C each show an example of a distinct zone within a current image to be coded or decoded. [Figure 3C] 3A-3C each show an example of a distinct zone within a current image to be coded or decoded. [Figure 4] 1A and 1B illustrate an exemplary conventional coding scheme implemented in the coding method of FIG. [Figure 5A] Figures 5A-5B respectively represent two different examples of identification of a reference block in a current image when applying to a current block a coding or decoding scheme according to the present invention, such as that implemented in the coding method of Figures 1A and 1B or in the decoding method of Figures 6A and 6B. [Figure 5B] Figures 5A-5B respectively represent two different examples of identification of a reference block in a current image when applying to a current block a coding or decoding scheme according to the present invention, such as that implemented in the coding method of Figures 1A and 1B or in the decoding method of Figures 6A and 6B. [Figure 6A] 4 illustrates the progress of a decoding method according to a first embodiment of the present invention; [Figure 6B] 4 illustrates the progress of a decoding method according to a second embodiment of the present invention; [Figure 7A] 1 illustrates a decoding device according to a first embodiment of the present invention. [Figure 7B] 4 illustrates a decoding device according to a second embodiment of the present invention. [Figure 8] 6A and 6B illustrate an exemplary conventional decoding scheme implemented in the decoding method of FIG. 6B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Detailed explanation of the coding part In the following, a first embodiment of the invention will be described, in which the coding method according to the invention is used to code an image or a sequence of images according to a binary stream close to that obtained by coding implemented in a coder according to any current or future video coding standard.

[0047] In this embodiment, the coding method according to the invention is implemented by software or hardware methods, for example by modification of such a coder. The coding method according to a first embodiment of the invention is represented in the form of an algorithm with operations C1 to C6a) or C1 to C6b) such as the one represented in Fig. 1A.

[0048] According to a first embodiment of the invention, the coding method is implemented in a coding device or coder CO represented in FIG. 2A.

[0049] As shown in Fig. 2A, the coder CO comprises a memory MEM_C having a buffer memory MT_C and a processor PROC_C driven by a computer program PG_C implementing the coding method according to the invention. During initialization, the code instructions of the computer program PG_C are for example loaded into a RAM memory denoted MR_C before being executed by the processor PROC_C.

[0050] The coding method depicted in FIG. 1A is based on a sequence of L images, fixed or otherwise, to be coded. 1 ,...,I ​​C j ,...,I ​​C L Any current image IC that forms part of (1≦j≦L) j This applies to.

[0051] Current image IC j As a non-exhaustive example, - images coming from one and the same camera and succeeding each other in time (2D type coding / decoding), - images coming from different cameras oriented according to different fields of view (3D type coding / decoding), - Corresponding texture and depth components (3D type coding / decoding) which ultimately represent one and the same scene, -Images obtained by mono 360° video projection, images obtained by stereoscopic video projection and having at least two fields of view each representing one and the same scene, - non-natural images of the type "screen content", for example images obtained by screen video capture, - etc. The video sequence is derived from at least one video sequence having

[0052] Referring to FIG. 1A, in C1, a plurality of blocks B 1 , B 2 , ..., B u , ..., B S Current image IC to (1≦u≦S) j The partitioning is carried out in a manner known per se. The partitioning is implemented by a partitioning device MP_C represented in Fig. 2A, which is driven by a processor PROC_C.

[0053] It should be noted that the term "block" in the sense of the present invention means a coding unit, this terminology being used in particular in the HEVC standard "ISO / IEC / 23008-2 Recommendation ITU-T H.265 High Efficiency Video Coding (HEVC)".

[0054] Specifically, such coding units group together rectangular or square shaped sets of pixels, also called blocks or macroblocks, or sets of pixels having other geometric shapes.

[0055] Block B 1 , B 2 , ..., B u , ..., B S are intended to be coded according to a predefined translation order, which may be, for example, of lexicographic type, meaning that the blocks are coded in order, from left to right.

[0056] Of course, other types of movement are possible. j into several sub-images called slices, and this type of division can be applied to each sub-image independently. It is also possible to code a sequence of columns rather than a sequence of rows, as mentioned above. It is also possible to shift the rows or columns in the volume direction.

[0057] According to one example, Block B 1 , B 2 , ..., B u , ..., B S have a square shape and all contain K pixels, where k > 1. As non-exhaustive examples, the blocks have sizes of 64x64 pixels, and / or 32x32 and / or 16x16 and / or 8x8 pixels.

[0058] As a function of the size of the image, which is not necessarily a multiple of the size of the blocks, the last block on the left and the last block on the bottom may not be square. In an alternative embodiment, the blocks may have, for example, a rectangular size and / or may not be aligned with each other.

[0059] Optionally, in C2, as represented by the dashed line in FIG. 1A, the current image IC j The coding of the syntax element activateStereoReuse associated with the property is performed.

[0060] The syntax element activateStereoReuse activates the current image IC j For this purpose, as a function of the coding context, this element is at the start of the coding of each image of the video sequence, or once only at the beginning of the coding of a sequence of images, or once only at the start of the coding of the video sequence, Can be coded.

[0061] The syntax element activateStereoReuse is intended to signal the type of format of the current image to be coded. According to a preferred embodiment, it is coded to the value 1 if the current image to be coded is obtained by projection of a stereoscopic video of 360°, 180° or other and if the current image is composed of several views captured at the same time and arranged in the current image to form a single field of view (rectangle of pixels). A method of arranging such an image uses, for example, a technique called "Frame Packing" (FP). On the other hand, if the current image to be coded is of 2D type or otherwise obtained by projection of a mono video of 360°, 180° or other, the syntax element activateStereoReuse is coded to the value 0.

[0062] The coding C2 is, for example, an entropy coding of the CABAC (in English "Context Adaptive Binary Arighmetic Coding") type or else an entropy coding of the arithmetic or Huffman type, which is implemented by a coding device MC_C represented in FIG. 2A, which device is driven by a processor PROC_C.

[0063] Such a coding C2 is a coder CO, a current image to be coded, of the 2D type or otherwise obtained by mono-video projection of 360 °, 180 ° or other; - a current image to be coded obtained by stereoscopic video projection of 360°, 180° or other and constructed according to a technique of the FP type; In cases where an autonomous method of discrimination between

[0064] In the following description, it is assumed that the current image to be coded has been obtained by stereoscopic video projection of 360°, 180°, or other, and that the current image is composed of several views captured at the same time and arranged within the current image to form a single field of view (rectangle of pixels).

[0065] Referring to FIG. 1A, the coder CO of FIG. 2A converts the image IC j The current block B to be coded u is selected.

[0066] In C4, for example, image IC j The current block B of the image ICj is then determined by determining its coordinates for the first pixel located at the top left of the block B and having coordinates (0,0). uThe effect of such position detection is that the current block is located at the current image IC j In this case, the first and second zones are distinct. According to the present invention, the first and second zones are distinct in the sense that they do not overlap.

[0067] The position detection C4 is implemented by a computing device CAL1_C, such as the one represented in FIG. 2A, which is driven by a processor PROC_C.

[0068] According to a first embodiment, which is a preferred embodiment and is illustrated in FIG. 3A, the current image IC j has a first zone Z1 extending in the upper half of the image and a second zone Z2 extending in the lower half of the image. Zones Z1 and Z2 have the same shape and are separated from each other by a horizontal boundary FH extending along the center of the image.

[0069] According to a second embodiment illustrated in FIG. 3B, the current image IC j has a first zone Z1 extending in the left half of the image and a second zone Z2 extending in the right half of the image. Zones Z1 and Z2 have the same shape and are separated from each other by a vertical boundary FV extending along the center of the image.

[0070] According to a third embodiment illustrated in FIG. 3C, the current image IC j has a first zone Z1 extending in a first upper left quarter of the image and a second zone Z2 extending in a second upper left quarter of the image. Zones Z1 and Z2 have the same shape and are separated from each other by a horizontal boundary FH extending in the quarters of the image.

[0071] Of course, other configurations are possible, for example, zones Z1 and Z2 may be swapped, and further, zones Z1 and Z2 may or may not have the same shape.

[0072] Current Block B u Image IC j If the current block belongs to a first zone Z1, see Fig. 1A, coding of the current block is performed with the aid of a first coding scheme MC1 in C5a), which is a conventional scheme, an example of which is shown in Fig. 4. The coding scheme MC1 is applied to any current block of zone Z1.

[0073] Referring to FIG. 4, the conventional coding scheme MC1 predicts a current block B by a conventional prediction technique such as intra and / or inter and / or skip and / or merge. u For this purpose, the current Block B u is predicted for at least one predictor block according to a mode of prediction belonging to one of the prediction techniques mentioned immediately above.

[0074] In a manner known per se, the current block B u is predicted with respect to multiple candidate predictor blocks, each of which is a block of pixels that has already been coded and then decoded.

[0075] Upon completion of the prediction C51a), the optimal predictor block BP is selected according to a predefined coding performance criterion, for example by minimizing a distortion bit rate criterion known to those skilled in the art, after setting said predefined prediction technique in a competitive state. opt The block BP is obtained. opt is the current block B uThis prediction related information is intended to be written, in the form of syntax elements, into the data signal or stream transmitted to the decoder.

[0076] Then, in C52a), the predictor block BP opt Between the data of the current block B u A comparison of the data relating to the obtained predictor block BP opt and the current block B u Calculating the difference between:

[0077] As a result, the residual block Br u This results in a data set called

[0078] The operations C51a) and C52a) are implemented by a predictive coding device PRED_C represented in FIG. 2A, which device is driven by a processor PROC_C.

[0079] Referring again to FIG. 4, the current remaining block Br u The data are coded in the conventional manner in C53a).

[0080] According to a non-limiting exemplary embodiment, such a coding C53a) is u This implements the application of a transformation to pixels in C531a).

[0081] In a manner known per se, as a function of the context or of the coding standard used, such a transform may be, for example, a transform of the DCT (English abbreviation for "Discrete Cosine Transform"), DST (English abbreviation for "Discrete Sine Transform") type, DWT (English abbreviation for "Discrete Wavelet Transform") or else of the LT (English abbreviation for "Lapped Transform") type. These transforms are previously stored in a list LST1 in the buffer memory MT_C of the coder CO of FIG. 2A.

[0082] Upon completion of the application of this transformation, the current transformed data block Bt u is obtained.

[0083] Such operations are performed by a transformation and computation device MTR_C such as the one represented in FIG. 2A, which is driven by a processor PROC_C.

[0084] The coding C53a) is carried out by converting the transformed block Bt u This further implements the quantization of the data C532a). The result is a block of quantized coefficients Bq u is obtained.

[0085] The quantization C 532a) is implemented by a quantization device MQ_C such as the one represented in FIG. 2A, which device is driven by a processor PROC_C.

[0086] The transform calculation device MTR_C and the quantization device MQ_C are contained in the device for the coding block MCB_C represented in FIG. 2A, which device is driven by a processor PROC_C.

[0087] Coding C53a) is done by dividing a block of quantized coefficients Bq uThe coding C533a) is implemented by the coding device MC_C of FIG. 2A. Upon completion of the coding C53a), the current block B u The coded data set DC u is obtained.

[0088] Referring to FIG. 1A, in C6a), -C5a) Data obtained by coding DC u , -for example, Current Block B u the type of prediction applied to the block (inter, intra, skip, or merge), and, where appropriate, the selected prediction mode, the index of the resulting prediction block, Block B u If is partitioned, then current block B u The type of partitioning, Current Block B u The type of transformation applied to the data in Specific information encoded by the coder CO, such as - etc. The construction of the signal part F containing

[0089] According to the invention, the stream F optionally contains the value 0 / 1 of the syntax element activateStereoReuse if it is coded at picture level.

[0090] The construction of the stream F is implemented by a data signal construction device MCF, such as the one represented in FIG. 2A.

[0091] When position detection C4 is completed, the current block B u Image IC jIf the current block belongs to the second zone Z2, then in C5b) coding of the current block is performed with the aid of the second coding scheme MC2. According to the first embodiment, the second coding scheme MC2 is applied to any current block located within the second zone Z2.

[0092] According to the invention, referring to FIG. 1A, in C51b), a current image IC is pre-coded and then decoded. j A reference block B is located in the first zone Z1 of ref Identification is being carried out.

[0093] The identification C51b) is implemented by a computing device CAL2_C, such as the one represented in FIG. 2A, which device is driven by a processor PROC_C.

[0094] According to a preferred embodiment, the current block located in the second zone Z2 corresponds to the current image IC j Within the coordinate (x u ,y u ), then the reference block B' ref In the first zone Z1, x' ref =x u and y' ref =y u The first pixel p' at the top left is -h / 2. ref is the coordinate (x' ref ,y' ref ), where h is the current image IC j The height is

[0095] FIG. 5A shows the determined reference block B' ref However, for example, a current image IC similar to that shown in FIG. j5A shows an example of such a determination in the case where the block B' does not overlap with other adjacent reference blocks in the first zone Z1. In FIG. 5A, the adjacent reference blocks are represented by points. ref As a result, the identified block B ref is deemed to be.

[0096] FIG. 5B shows the determined reference block B'. ref However, for example, a current image IC similar to that shown in FIG. j This illustrates another example of such a determination in the case where the block B′ overlaps with other adjacent reference blocks r1, r2, r3, r4 in the first zone Z1. According to such a configuration, according to one example embodiment, which of the adjacent reference blocks r1, r2, r3, r4 overlaps with the block B′ ref In FIG. 5B, the identified block B ref It is the reference block r4 that is considered to be.

[0097] Naturally, Block B' ref The current image IC j There are also other schemes for selecting adjacent reference blocks when they overlap with adjacent reference blocks in the first zone Z1.

[0098] According to another example, in the case of FIG. 5B, which of the adjacent reference blocks r1, r2, r3, and r4 is the block B' ref It may be possible to determine whether the center of the

[0099] According to yet another exemplary embodiment, reference block B' ref In the first zone Z1, the coordinate x' ref =x c and y' ref =y c−h / 2, in which case (x c ,y c ) are the coordinates of the center of the current block.

[0100] Reference Block B ref In the state where the reference block B is identified in the first zone Z1, referring to FIG. 1A, in C52b), ref At least one coding parameter PRC associated with 1 A reading of the coding parameters PRC is performed. 1 are stored in the list LST2 of the buffer memory MT_C of the coder of FIG. 2A.

[0101] The read C 52b) is implemented by a read device LEC_C, such as the one represented in FIG. 2A, which is driven by a processor PROC_C.

[0102] As a non-exhaustive example, the list LST2 may include the identified reference blocks B ref and the associated K coding parameters PRC 1 , P.R.C. 2 , ..., P.R.C. K Including, among which: -Block B ref The type of prediction chosen to predict,intra, inter, skip, merge, etc. - Intra prediction is performed for block B during coding. ref the selected intra prediction direction when applied to Block B ref the motion vector index when the prediction applied to is inter-type, - Block B during coding ref the nullity of the residual part of the prediction applied to - Block B during coding ref The type of partitioning applied to - the type of conversion selected, - The value of the selected quantization interval, - The type of filtering applied to block B, such as the SAO ("Sample Adaptive Offset") mode used in the HEVC standard, ref etc., - and so on, exist.

[0103] Therefore, during reading C52b), one or more of the above-described coding parameters related to block B ref can be read.

[0104] Referring to Figure 1A, in C53b), a copy of the value of the coding parameter PRC 1 read in C52b) for the current block is being executed. Therefore, advantageously, the coding of the coding parameter PRC 1 is unnecessary.

[0105] According to one embodiment, in C54b), the coding of the syntax element ES_PRC ref that notifies whether the coding parameter PRC 1 of the reference block B has a parameter whose value is copied for the current block is being executed. 1 etc.

[0106] Coding C54b) is, for example, CABAC - type entropy coding, or alternatively, arithmetic or Huffman - type entropy coding. This coding is implemented by the coding device MC_C in Figure 2A.

[0107] For example, the syntax element ES_PRC 1 is - Set to a value 1 that notifies that the value of the coding parameter PRC 1 is copied for the current block, - The coding parameter PRC 1to the value 0, which signals that the value of has not been duplicated for the current block and is therefore coded in the conventional manner, It is coded.

[0108] Syntax element ES_PRC 1 In the case where is coded to the value 0, the coding parameter PRC 1 is coded according to the conventional method.

[0109] According to one embodiment, during the coding C54b), K syntax elements ES_PRC 1 , ES_PRC 2 , ..., ES_PRC K are coded, in this case, as the reference block B ref and associated coding parameters PRC 1 , P.R.C. 2 , ..., RPC K Each of these tells us whether its value is a replicated parameter for the current block.

[0110] Of course, it may be decided to code only some of the above K syntax elements. According to one embodiment, by assuming that in C2 the syntax element activateStereoReuse is coded to the value 1, the binary sequence 1101 may be, for example, the syntax element activateStereoReuse is coded in C2 with the value 1, - Reference Block B ref The partitioning type value applied to the current block is replicated. - Reference Block B ref The value of the type of transformation applied to the current block is not duplicated for the current block, and therefore the type of transformation applied to the current block is coded in the conventional manner as - Reference Block B refThe value of the quantization interval used in coding of is copied for the current block. This means that...

[0111] With reference to FIG. 1A, the device MCF of FIG. 2A, in C6a), according to the invention, determines said at least syntax element ES_PRC 1 We are now performing the construction of a signal part F containing the values ​​0 / 1.

[0112] Signal portion F also contains all the data of the current block that is conventionally coded.

[0113] According to the invention, the stream F optionally contains the syntax element activateStereoReuse with the value 0 / 1 if it is coded at the picture level.

[0114] The data signal F is then transmitted by a communication network (not represented) to a remote terminal, which comprises a decoder DO, represented in Figure 7A.

[0115] According to the first embodiment described immediately above with reference to FIG. The coding operations C1 to C6a) are performed on the current image IC j is implemented for each block in the first zone Z1, The coding operations C1 to C6b) are performed on the current image IC j This is implemented for each block in the second zone Z2.

[0116] We will now describe a second embodiment of the coding method according to the invention with reference to FIG. 1B.

[0117] According to this second embodiment of the invention, the coding method is implemented in a coding device or coder CO' represented in Fig. 2B, which has elements similar to those of the coder CO of Fig. 2A. For reasons of clarity, similar elements such as these are repeated in Fig. 2B with the same reference numerals as in Fig. 2A.

[0118] According to a second embodiment, a first coding scheme MC1 is applied to any current block located in the first zone Z1 in exactly the same manner as in the first embodiment of Fig. 1A. This second embodiment, with reference to Fig. 1B, in addition to the coding C5b) implemented for the current block located in the second zone Z2, also includes the coding of the current block B100b) with the aid of the first coding scheme MC1 applied to any block of the first zone Z1 of the current image, for example the coding scheme represented in Fig. 4. u 1A is distinguished from the one of FIG. 1A by the fact that a coding 100b) is performed. Such a coding 100b) is implemented by a predictive coding device PRED_C, a device for coding blocks MCB_C and a coding device MC_C, which are shown in FIG. 2B.

[0119] Referring to FIG. 1B, the coding schemes MC1 and MC2 applied to the current block in C5b) and C100b), respectively, are set to a competitive state in C200b) according to a predefined coding performance criterion, for example by minimizing a distortion bit rate criterion, as is well known to those skilled in the art.

[0120] The setting to a race condition C200b) is implemented by a computing device CPT such as the one represented in FIG. 2B, which device is driven by a processor PROC_C.

[0121] Upon completion of the competition setting C200b), MC opt =MC1 or MC opt The optimal coding scheme MC such that =MC2.opt Then, in C300b), the syntax element ES_MC opt is coded.

[0122] The coding C 300b) is for example an entropy coding of the CABAC type or else an entropy coding of the arithmetic or Huffman type, which coding is implemented by the coding device MC_C of Fig. 2B.

[0123] For example, the syntax element ES_MC opt teeth, - Current Block B of Zone 2 Z2 u is coded using the first conventional coding scheme MC1 selected after the setting C200b) in the race condition, - Current Block B of Zone 2 Z2 u is coded using the second coding scheme MC2 according to the invention selected after the setting in the race condition C200b), is coded as follows:

[0124] Referring to FIG. 1B, the device MCF of FIG. 2B includes, in C400b), If the first conventional coding scheme MC1 is selected after the setting C200b) in the competitive state, · Data DC obtained from coding in C100b) u , ·for example, Current Block B u the type of prediction applied to the block (inter, intra, skip, or merge), and, where appropriate, the selected prediction mode, the index of the resulting prediction block, The current block B if it is partitioned u The type of partitioning, Current Block B u The type of transformation applied to the data in etc. The specific information encoded by the coder CO', such as if the second coding scheme MC2 according to the invention has been selected after the setting C200b) in the competitive state, said at least syntax element ES_PRC 1 Values ​​0 / 1, All data in the current block coded using the conventional method, Then, the construction of the signal part F' is carried out, which includes:

[0125] The signal portion F' is then transmitted by a communication network (not represented) to a remote terminal, which comprises a decoder DO, which is represented in Fig. 7B.

[0126] According to a second embodiment of the coding method described immediately above, The coding operations C1 to C6a) are performed on the current image IC j is implemented for each block of the first zone Z1, The coding operations C1 to C400b) are performed on the current image IC j This is implemented for each block in the second zone Z2.

[0127] Detailed explanation of the decoding part In the following, a first embodiment of the invention will be described, in which a decoding method according to the invention is used to decode a data signal or stream representing an image or a sequence of images which can be decoded by a decoder in accordance with any of the current or future video decoding standards.

[0128] In this embodiment, the decoding method according to the invention is implemented in software or hardware form, for example by modification of such a decoder.

[0129] The decoding method according to the first embodiment of the invention is represented in the form of an algorithm having operations D1 to D7a) or D1 to D7b) such as the one represented in FIG. 6A.

[0130] According to this first embodiment, the decoding method according to the invention is implemented in a decoding device or decoder DO represented in FIG. 7A.

[0131] As shown in figure 7A, according to a first embodiment of the invention, the decoder DO comprises a memory MEM_D which itself comprises a buffer memory MT_D, and a processor PROC_D driven by a computer program PG_D implementing the decoding method according to the invention. During initialization, the code instructions of the computer program PG_D are for example loaded into a RAM memory, denoted RAM_D, before execution by the processor PROC_D.

[0132] The decoding method depicted in FIG. 6A is based on a sequence of L images, fixed or otherwise, to be decoded, IC 1 ,...,I ​​C j ,...,I ​​C L It is applied to any current coded image ICj forming part of (1≦j≦L).

[0133] Current image to be decoded IC j As a non-exhaustive example, - images coming from one and the same camera and succeeding each other in time (2D type coding / decoding), - images coming from different cameras oriented according to different fields of view (3D type coding / decoding), - Corresponding texture and depth components (3D type coding / decoding) which ultimately represent one and the same scene, -Images obtained by mono 360° video projection, - images obtained by stereoscopic video projection and intended to be observed respectively through the left and right eyes of a user, each having two fields of view representing one and the same scene, - non-natural images of the type "screen content", for example images obtained by screen video capture, - etc. The video sequence is derived from at least one video sequence having

[0134] Optionally, as represented in dashed lines in FIG. 6A, at D1, a current image IC to be decoded is j A reading D1 is performed in the data signal F of the coded value 0 or 1 of the syntax element activateStereoReuse associated with the property of the current image IC. j This is implemented only in cases where the property is coded at the property level.

[0135] According to a preferred embodiment, the syntax element activateStereoReuse is read, for example: the value 1 if the current image to be coded was obtained by stereoscopic video projection of 360 degrees, 180 degrees or other, and if the current image to be decoded was constructed according to the above-mentioned FP technique, the value 0, if the current image to be decoded is of 2D type or has otherwise been obtained by mono-video projection of 360°, 180° or other, Take.

[0136] The read D1 is implemented by a stream analysis device PARS_D, such as the one represented in FIG. 7A, said device being driven by a processor PROC_D.

[0137] In the identification case, referring to FIG. 6A, in D2, decoding of the coded value 0 or 1 obtained by the syntax element activateStereoReuse is performed.

[0138] Such a decoding D2 is implemented by a decoding device MD_D represented in FIG. 7A, which device is driven by a processor PROC_D.

[0139] For example, the decoding may be a CABAC type entropy decoding or else an arithmetic or Huffman type entropy decoding.

[0140] Such a decoding D2 is performed by the decoder DO: a current image to be decoded, of the 2D type or otherwise obtained by mono-video projection of 360 °, 180 ° or other; - a current image to be decoded obtained by stereoscopic video projection of 360°, 180° or other and constructed according to a technique of the FP type; In cases where the discrimination between is performed autonomously, this is not necessary.

[0141] In the following description, it is assumed that the current image to be decoded has been obtained by stereoscopic video projection of 360°, 180° or other, and that the current image is composed of several views captured at the same time and arranged within the current image to form a single field of view (rectangle of pixels).

[0142] 6A, in D3, the previously coded lexicographic order B obtained upon completion of the coding operation C5a) or C5b) of FIG. 1A is 1 , B 2 , ..., B u , ..., BS and DC 1 , D.C. 2 , ..., DC u , ..., DC S A discrimination is carried out within the signal F for (1≦u≦S), which means that the blocks are decoded in sequence from left to right in a manner that corresponds to the coding order described above.

[0143] Such identification D3 is implemented by the stream analysis unit PARS_D in FIG. 7A.

[0144] Of course, other types of movements than those described above are possible and depend on the order of movements chosen during coding.

[0145] According to one example, Block B 1 , B 2 , ..., B u , ..., B S have a square shape and all contain K pixels, where K > 1. As non-exhaustive examples, the blocks may have 64x64 pixels, and / or 32x32 and / or 16x16 and / or 8x8 pixels.

[0146] As a function of the size of the image, which is not necessarily a multiple of the size of the blocks, the last block on the left and the last block on the bottom may not be square. In an alternative embodiment, the blocks may have, for example, a rectangular size and / or may not be aligned with each other.

[0147] Referring to FIG. 6A, at D4, the decoder DO of FIG. 7A receives the image IC j Coded Data DC u The current set of blocks B u is associated with.

[0148] In D5, the image ICj is reconstructed by determining its coordinates for the first reconstructed pixel of the image ICj, for example. j The current block B to be decoded u A location has been performed for a pixel, which is located in the top left of the image and has coordinates (0,0).

[0149] The position detection D5 is implemented by a computing device CAL1_D such as the one represented in FIG. 7A, which is driven by a processor PROC_D.

[0150] Current Block B u Image IC j If the current block belongs to a first zone Z1 of the current block, then, referring to Fig. 6A, in D6a) decoding of the current block is performed with the aid of a first decoding scheme MD1 corresponding to the coding scheme MC1 applied for coding in C5a) of Fig. 1A. The first decoding scheme MD1 is a conventional scheme, an example of which is shown in Fig. 8. The decoding scheme MD1 is applied to any current block of the zone Z1.

[0151] Referring to FIG. 8, the conventional decoding method MD1 performs the following steps: u The type of prediction applied to the BP 1 block (inter, intra, skip, or merge) and, where appropriate, the selected prediction mode, the prediction implemented during coding C51a (FIG. 4), the predictor block BP opt , and implements the decoding of prediction information previously read in signal F, such as the index of

[0152] Upon completion of the decoding D61a), the predictor block BP associated with the decoded index opt is obtained.

[0153] Current Block B uCoded Data DC u is decoded in D62a). Such decoding is implemented by a device for decoding blocks MDB_D represented in Fig. 7A, which device is driven by a processor PROC_D.

[0154] Decoding D62a) is performed by decoding the current block B u and coded in C5a) of FIG. 1A, u Upon completion of such decoding, a set of numerical information is obtained, which in this case is associated with the block of quantized coefficients Bqu obtained in C532a) of FIG.

[0155] The decoding D621a) is implemented by a decoding device MD_D represented in FIG. 7A.

[0156] Decoding D62a) follows a conventional inverse quantization operation, which is the inverse operation of the quantization C532a) of FIG. 4, to dequantize the quantized coefficients Bq u The result is the inverse quantization of the block of coefficients BDq u Such an inverse quantization may be, for example, of scalar or vector type and may be implemented using an inverse quantizer MQ such as the one depicted in FIG. -1 _D, and the device is driven by a processor PROC_D.

[0157] Decoding D62a) is performed by dequantizing the dequantized coefficients BDq u7A. In a manner known per se, such a transform is the inverse transform applied for coding in C531a) of FIG. 4, such as, for example, a DCT, DST, DWT, LT or other transform. In a manner corresponding to the coder CO of FIG. 2A, these transforms are stored in a list of transforms LTS1 prestored in a buffer memory MT_D of the decoder DO of FIG. 7A. -1 The type of transform applied can be determined in the decoder in a conventional manner by reading, in the data signal F, the index of the transform applied for coding.

[0158] The transform application D623a) is implemented by a transform calculation device MTR such as the one depicted in FIG. -1 _D, which is driven by processor PROC_D.

[0159] Inverse quantizer MQ -1 _D and conversion calculation device MTR -1 _D is included within the block decoding device MDB_D represented in FIG. 7A, which device is driven by a processor PROC_D.

[0160] Upon completion of the decoding D62a) of the data of the current block, the currently decoded residual block BDR u is obtained.

[0161] Referring to FIG. 8, in D63a), a currently decoded residual block BDR u However, the predictor block BP obtained in D61a) opt has been added.

[0162] The operation D63a) is implemented by a predictive decoding device PRED_D represented in FIG. 7A, which device is driven by a processor PROC_D.

[0163] Upon completion of operation D63a), the currently decoded block BD u is obtained.

[0164] Referring again to FIG. 6A, in D7a), the decoded image ID j The currently decoded block BD u A write is being performed.

[0165] Write D7a) is implemented by an image reconstruction device URI such as the one represented in FIG. 7A, which is driven by a processor PROC_D.

[0166] Referring to FIG. 6A, upon completion of the position detection D5, the current block B u Image IC j If the current block belongs to the second zone Z2 of the current block, then in D6b) the decoding of the current block is performed with the aid of a second decoding scheme MD2 which corresponds to the coding scheme MC2 applied for coding in C5b) of Fig. 1A. According to the first embodiment, the second decoding scheme MD2 is applied to any current block to be decoded which is located in the second zone Z2.

[0167] According to the invention, referring to FIG. 6A, in D61b), a current image IC that has been previously decoded and is undergoing decoding is j A reference block B is located in the first zone Z1 of ref Identification is being carried out.

[0168] The identification D61b) is implemented by a computing device CAL2_D such as the one represented in Fig. 7A, which is driven by a processor PROC_D. The identification D61b) is identical to the identification C51b) performed during coding with reference to Fig. 1A.

[0169] According to a preferred embodiment, the current block located in the second zone Z2 corresponds to the current image ICj Coordinates (x u ,y u ), then the reference block B' has its first pixel in the upper left ref In the first zone Z1, x' ref =x u and y' ref =y u The first pixel p' at the top left is -h / 2. ref is the coordinate (x' ref ,y' ref ), where h is the block having the current image IC j The height is

[0170] Reference block B' ref An example of the determination has already been described with reference to FIGS. 5A and 5B, and a repeated description here will be omitted.

[0171] Reference Block B ref In the state where the reference block B is identified in the first zone Z1, referring to FIG. 6A, the device PARS_D of FIG. 7A detects the reference block B in D62b). ref Coding parameters of PRC 1 However, the value is the current block B u At least one syntax element ES_PRC that informs whether a parameter is a duplicated parameter 1 A read is performed in signal F.

[0172] Then, in D63b), the syntax element ES_PRC 1 Decoding of is being performed.

[0173] The decoding D63b) is for example an entropy decoding of the CABAC type or else an entropy decoding of the arithmetic or Huffman type, which is implemented by the coding device MD_D of Fig. 7A.

[0174] for example, -Syntax element ES_PRC 1 If the decoded value of is equal to 1, the coding parameter PRC 1 is the decoding parameter PRD of the current block 1 It is used directly as -Syntax element ES_PRC 1 If the decoded value of is equal to 0, the coding parameter PRC 1 is decoded with the aid of conventional decoding schemes.

[0175] According to one embodiment, during the coding D63b), K syntax elements ES_PRC 1 , ES_PRC 2 , ..., ES_PRC K are decoded, where these are the reference blocks B ref and associated coding parameters PRC 1 , P.R.C. 2 , ..., P.R.C. K Each of these signals whether its value is a parameter that was copied during the coding of the current block.

[0176] Of course, if only some of these K syntax elements are coded in C54b), it can be decided to decode only some of the K syntax elements (FIG. 1A). According to one embodiment, by assuming that the decoded value obtained in D2 of the syntax element activateStereoReuse has the value 1, the binary sequence 1101 can be, for example, the syntax element activateStereoReuse is coded in C2 with the value 1, - Reference Block B ref The type of partitioning applied to is used directly as a decoding parameter for the current block. - Reference Block Bref the type of transformation applied to is not directly used as a decoding parameter of the current block and is decoded in a conventional manner; - Reference Block B ref The value of the quantization interval used in coding of is directly used as the decoding parameter of the current block. This means that...

[0177] Referring to FIG. 7A, reference block B ref At least one decoding parameter PRD associated with 1 are stored in the list LST2 of the buffer memory MT_D of the decoder DO.

[0178] As a non-exhaustive example, the list LST2 of the decoder DO of FIG. 7A includes the identified reference block B ref and stored in the list LST2 of the coder CO of FIG. 2A. 1 , P.R.C. 2 , ..., P.R.C. K K decoding parameters PRD, each of which is identical to 1 , P.R.D. 2 , ..., PRD K Examples of such parameters have already been described in the coding method of FIG. 1A, and will not be described again here.

[0179] Referring to FIG. 6A, in D64b), the current block B u Regarding the syntax element ES_PRC 1 and associated coding parameters PRC 1 For this purpose, a duplication of the value of the decoding parameter PRD is performed. 1 The value decoded in D63b) is the current block B u is assigned to.

[0180] Upon completion of application of the second decoding method MD2 to the current block, the currently decoded block BD u is obtained.

[0181] The image reconstruction device URI in FIG. 7A is the decoded image ID in D7b). j Currently decoded block BD u is being written.

[0182] According to the first embodiment described immediately above with reference to FIG. The decoding operations D1 to D7a) are performed on the current image IC j is implemented for each block of the first zone Z1, The decoding operations D1 to D7b) are performed on the current image IC j This is implemented for each block in the second zone Z2.

[0183] We will now describe a second embodiment of the decoding method according to the present invention with reference to FIG. 6B.

[0184] According to this second embodiment of the invention, the decoding method is implemented in a decoding device or decoder DO' represented in Fig. 7B, which has elements similar to those of the decoder DO of Fig. 7A. For reasons of clarity, similar elements such as these are repeated in Fig. 7B with the same reference numerals as in Fig. 7A.

[0185] According to the second embodiment, the first decoding scheme MD1 is applied to any current block located in the first zone Z1 in exactly the same way as in the first embodiment of Fig. 6A. The second embodiment is distinguished from that of Fig. 6A by the fact that the second decoding scheme MD2 is not systematically applied to each current block located in the second zone Z2. For this purpose, the current block B uis found in the second zone Z2 of the current image to be decoded, then in D100b) a syntax element ES_MC opt In the signal F', a read is performed. The read D100b) is implemented by the device PARS_D of FIG.

[0186] Next, in D200b), the syntax element ES_MC opt Decoding of is being performed.

[0187] The decoding D200b) is for example an entropy decoding of the CABAC type or else an entropy decoding of the arithmetic or Huffman type, which is implemented by the coding device MD_D of Fig. 7B.

[0188] Syntax element ES_MC opt is equal to 1, the current block is decoded with the aid of the second decoding scheme MD2 according to the first embodiment in exactly the same way as in D5b) of FIG. 6A.

[0189] Syntax element ES_MC opt If the decoded value of is equal to 0, then in D300b) the current block is decoded according to the first embodiment in exactly the same way as in D5a) of FIG. 6A with the aid of the first decoding scheme MD1 applied to each current block of the first zone Z1 of the current image.

[0190] The decoding scheme MD1 is, for example, the decoding scheme represented in Fig. 8. Such a decoding 300b) is implemented by a decoding device MD_D, a device for decoding blocks MDB_D and a predictive decoding device PRED_D, which are shown in Fig. 7B.

[0191] Upon completion of application of the first decoding method MD1 or the second decoding method MD2 to the current block, the currently decoded block BD u is obtained.

[0192] The image reconstruction device URI in FIG. 7B is the decoded image ID in D400b). j Currently decoded block BD u is being written.

[0193] According to the second embodiment described immediately above with reference to FIG. The decoding operations D1 to D7a) are performed on the current image IC j is implemented for each block of the first zone Z1, The decoding operations D1 to D400b) are performed on the current image IC j This is implemented for each block in the second zone Z2.

[0194] It goes without saying that the above described embodiments are given purely as a completely non-limiting indication and that numerous modifications can be easily made by those skilled in the art without departing from the scope of the invention. [Explanation of symbols]

[0195] CO Coda MT_C Buffer Memory MEM_C Memory PG_C Computer Program PROC_C Processor CAL1_C Computing device CAL2_C Computing device Z1, Z2 Zone FH horizontal boundary ICj Images FV Vertical Boundary Bu Current block Bru Residual Block MTR_C conversion calculation device Btu Converted Blocks Bqu Block of quantized coefficients MQ_C Quantizer B'ref Reference block Bref Identified Block r1, r2, r3, r4 Adjacent reference blocks ES_PRC1 Syntax Element PRC1, PRC2, ..., RPCK coding parameters MCF device DO Decoder PRED_C predictive coding device MCB_C Block coding device MC_C coding device MT_D Buffer memory MEM_D Memory PG_D Computer Program PROC_D Processor PARS_D Stream Analysis Device PROC_D Processor MD_D Decoding Device BPopt predictor block MDB_D Block Decoding Device BDru Residual Block URI Image Reconstruction Device

Claims

1. Image divided into blocks (IC ｊ ), wherein the image comprises first and second distinct zones (Z1, Z2) defined prior to coding the image, At least one current block (B ｕ ) - a step (C4) of determining whether said current block belongs to said first or second zone; - coding (C5a) of the current block with the aid of a first coding scheme (MC1) for coding at least one coding parameter related to the current block if the current block belongs to the first zone (Z1); - if the current block belongs to the second zone (Z2), - based on the position of the current block in the second zone, a previously coded and then decoded block (B ｒｅｆ ) (C51b)); - at least one coding parameter (PRC) associated with said identified block; １ ) in said image (ICj), wherein said at least one copied coding parameter is not coded during the coding of said current block, and whether said at least one coding parameter is a copied parameter is indicated by means of a syntax element associated with said image (ICj), (C5b) coding the current block with the aid of a second coding scheme (MC2) having 16. A method comprising:

2. The method of claim 1 , wherein the second coding scheme is applied to all blocks of the second zone of the current image.

3. - coding (C100b) of said at least one current block of said second zone of said image with the aid of said first coding scheme (MC1); - selecting the first coding scheme or the second coding scheme according to a predefined coding performance criterion (C200b); - an item of information representative of said selection (ES_MC ｏｐｔ ) and The coding method of claim 1 , which implements:

4. 4. A method according to claim 1, wherein the first and second zones of the image have the same shape, the first zone being located above the second zone and separated from it by a horizontal boundary extending along the centre of the image.

5. At least one image (IC ｊ 1. An apparatus (CO) for coding an image of a pixel region, the image comprising first and second distinct zones defined before coding the image, the apparatus (CO) comprising: For at least one current block of said image, - determining whether said current block belongs to said first or second zone; - coding the current block with the aid of a first coding scheme (MC1) for coding at least one coding parameter related to the current block if the current block belongs to the first zone (Z1); - if the current block belongs to the second zone (Z2), - based on the position of the current block in the second zone, a previously coded and then decoded block (B ｒｅｆ ) to identify - at least one coding parameter (PRC) associated with said identified block; １ ) in said image (ICj), wherein said at least one copied coding parameter is not coded during the coding of said current block, and whether said at least one coding parameter is a copied parameter is indicated by means of a syntax element associated with said image (ICj), coding the current block with the aid of a second coding scheme (MC2) having An apparatus (CO) comprising a processing circuit (CT_C) designed to implement:

6. A computer program comprising program code instructions for the execution of the steps of the coding method according to any one of claims 1 to 4, when said computer program is run on a computer.

7. A computer-readable storage medium having a computer program recorded thereon, the computer program having program code instructions for the execution of the steps of the coding method according to any one of claims 1 to 4 when the computer program is executed by a computer.

8. Image divided into coded blocks (IC ｊ 1. A method for decoding a data signal (F) representing an image, at least one of which comprises first and second distinct zones (Z1, Z2) defined prior to decoding the image, comprising: at least one current block to be decoded of said image (B ｕ ) - a step (D5) of determining whether said current block belongs to said first or second zone; - decoding (D6a) of the current block with the aid of a first decoding scheme (MD1) for decoding at least one decoding parameter associated with the current block if the current block belongs to the first zone (Z1); - if the current block belongs to the second zone (Z2), - identifying a previously decoded block located in the first zone of the image based on the position of the current block in the second zone (D61b)); - at least one decoding parameter (PRD) associated with said identified block; １ ) to the current block, wherein the at least one assigned decoding parameter is not decoded during the decoding of the current block, and whether the at least one decoding parameter is a copied parameter for the current block is indicated using a syntax element associated with the image (ICj), (D6b) decoding the current block with the aid of a second decoding scheme having 16. A method comprising:

9. The method of claim 8, wherein the second decoding scheme is applied to all blocks of the second zone of the current image.

10. 9. The decoding method of claim 8, wherein if for the current block an item of information regarding the selection of the second decoding scheme is read in the data signal (F') (D100b), the second decoding scheme is applied to the current block of the second zone, and if for the current block an item of information regarding the selection of the first decoding scheme is read in the data signal (F') (D100b), the first decoding scheme is applied to the current block of the second zone.

11. 11. A method for decoding according to any one of claims 8 to 10, wherein the first and second zones of the image have the same shape, the first zone being located above the second zone and separated from it by a horizontal boundary extending along the centre of the image.

12. The coded image divided into blocks (IC ｊ 1. An apparatus for decoding a data signal (F) representing an image, the image being at least one of the images comprising first and second distinct zones defined prior to decoding the image, the apparatus comprising: For at least one current block to be decoded of said image, - determining whether said current block belongs to said first or second zone; - decoding the current block with the aid of a first decoding scheme (MD1) for decoding at least one decoding parameter associated with the current block if the current block belongs to the first zone (Z1); - if the current block belongs to the second zone (Z2), - identifying a previously decoded block located in the first zone of the image based on the position of the current block in the second zone; - at least one decoding parameter (PRD) associated with said identified block; １ ) to the current block, wherein the at least one assigned decoding parameter is not decoded during the decoding of the current block, and whether the at least one decoding parameter is a copied parameter for the current block is indicated using a syntax element associated with the image (ICj); decoding the current block with the aid of a second decoding scheme having 16. An apparatus comprising: a processing circuit (CT_D) designed to implement:

13. Computer program comprising program code instructions for the execution of the steps of the decoding method according to any one of claims 8 to 11, when said computer program is run on a computer.

14. A computer-readable recording medium having a computer program recorded thereon, the computer program having program code instructions for the execution of the steps of the decoding method according to any one of claims 8 to 11, when the computer program is executed by a computer.

Images