Patent Publication Number: US-11653025-B2

Title: Coding and decoding of an omnidirectional video

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a Section 371 National Stage Application of International Application No. PCT/FR2019/052254, filed Sep. 25, 2019, which is incorporated by reference in its entirety and published as WO 2020/070409 A1 on Apr. 9, 2020, not in English. 
     1. FIELD OF THE INVENTION 
     The present invention generally relates to the field of omnidirectional videos, such as in particular 360°, 180°, etc. videos. More particularly, the invention relates to the coding and decoding of 360°, 180°, etc. views which are captured to generate such videos, and to the synthesis of uncaptured intermediate viewpoints. 
     The invention may in particular, but not exclusively, be applied to the video coding implemented in AVC and HEVC current video coders and their extensions (MVC, 3D-AVC, MV-HEVC, 3D-HEVC, etc.), and to the corresponding video decoding. 
     2. PRIOR ART 
     To generate an omnidirectional video, such as for example a 360° video, it is common practice to use a 360° camera. Such a 360° camera is formed of a plurality of 2D (two-dimensional) cameras installed on a spherical platform. Each 2D camera captures a particular angle of a 3D (three-dimensional) scene, the set of views that are captured by the cameras making it possible to generate a video representing the 3D scene with a 360°×180° field of view. It is also possible to use a single 360° camera to capture the 3D scene with a 360°×180° field of view. Such a field of view may of course be smaller, for example 270°×135°. 
     Such 360° videos then allow the user to watch the scene as if they were positioned in the center of it and to look all around them, over 360°, thus providing a new way of watching videos. Such videos are generally reproduced on virtual reality headsets, also known as HMDs for “head mounted devices”. However, they may also be displayed on 2D screens equipped with suitable user interaction means. The number of 2D cameras for capturing a 360° scene varies depending on the platforms used. 
     To generate a 360° video, the divergent views captured by the various 2D cameras are placed end to end, taking into account the overlaps between views, in order to create a panoramic 2D image. This step is also known as “stitching”. For example, an equirectangular projection (ERP) is one possible projection for obtaining such a panoramic image. According to this projection, the views captured by each of the 2D cameras are projected onto a spherical surface. Other types of projections are also possible, such as a cube mapping-type projection (projection onto the faces of a cube). The views projected onto a surface are then projected onto a 2D plane in order to obtain a 2D panoramic image comprising, at a given time, all of the views of the scene which have been captured. 
     To increase the feeling of immersion, a plurality of 360° cameras of the aforementioned type may be used simultaneously to capture a scene, these cameras being positioned in the scene in an arbitrary manner. A 360° camera may be an actual camera, that is to say a physical object, or else a virtual camera, in which case the view is obtained by view generation software. In particular, such a virtual camera makes it possible to generate views representative of viewpoints of the 3D scene which have not been captured by actual cameras. 
     The image of the 360° view obtained using a single 360° camera or the images of 360° views obtained using a plurality of 360° cameras (actual and virtual) are then coded using, for example:
         a conventional 2D video coder, for example a coder conforming to the HEVC (abbreviation for “High Efficiency Video Coding”) standard,   a conventional 3D video coder, for example a coder conforming to the MV-HEVC and 3D-HEVC standards.       

     Such coders are not efficient enough in terms of compression, taking into account the very large amount of data of the image of one 360° view to be coded, let alone the images of a plurality of 360° views to be coded, and the particular geometry of the 360° representation of the 3D scene using such 360° views. Moreover, since the views captured by the 2D cameras of a 360° camera are divergent, the aforementioned coders are not suitable for coding the different images of 360° views, because inter-image prediction will be hardly or not used by these coders. Specifically, between two views captured respectively by two 2D cameras, there is little similar content that can be predicted. Therefore, all of the images of 360° views are compressed in the same way. In particular, no analysis is performed in these coders in order to determine, with respect to the image of a current 360° view to be coded, whether it makes sense to code all of the data of this image, or just some data of this image, as part of a synthesis of uncaptured intermediate view images which would use this image of the view which is coded, then decoded. 
     3. AIM AND SUMMARY OF THE INVENTION 
     One of the aims of the invention is to rectify drawbacks of the aforementioned prior art. 
     To that end, one subject of the present invention relates to a method for coding an image of a view forming part of a plurality of views, the plurality of views simultaneously representing a 3D scene from different viewing angles or positions, implemented by a coding device, comprising the following:
         selecting a first coding method or a second coding method for coding the image of the view,   generating a data signal containing information indicating whether it is the first coding method or the second coding method which is selected,   if the first coding method is selected, coding the original data of the image of the view, the first coding method providing coded original data,   if the second coding method is selected:
           coding processed data of the image of the view, these data having been obtained by means of an image processing applied to the original data of the image of the view, the coding providing coded processed data,   coding description information of the image processing which has been applied,   
           the generated data signal further containing:
           the coded original data of the image of the view, if the first coding method has been selected,   the coded processed data of the image of the view, and the coded description information of the image processing, if the second coding method has been selected.   
               

     By virtue of the invention, from among a plurality of images from current views to be coded of the aforementioned type, said images representing a very large amount of data to be coded, and therefore to be signaled, it is possible to combine two coding techniques for each image of each view to be coded:
         a first coding technique, according to which the images of one or more views are coded conventionally (HEVC, MVC-HEVC, 3D-HEVC, for example), so as to obtain, respectively, reconstructed images forming views of very good quality,   a second, innovative coding technique, according to which processed data of images of one or more other views are coded, so as to obtain, on decoding, processed image data which therefore do not correspond to the original data of these images, but with the benefit of a not-insignificant decrease in the signaling cost of the coded processed data of these images.       

     What will then be obtained on decoding, for each image of each other view, the processed data of which have been coded according to the second coding method, are the corresponding processed data of the image of the view, and the description information of the image processing applied, on coding, to the original data of the image of the view. Such processed data could then be processed using the corresponding image processing description information, in order to form an image of the view which, used with at least one of the images of a view reconstructed according to the first method of conventional decoding, will make it possible to synthesize images of uncaptured intermediate views, in a particularly efficient and effective manner. 
     The present invention also relates to a method for decoding a data signal representative of an image of a view forming part of a plurality of views, the plurality of views simultaneously representing a 3D scene from different viewing angles or positions, implemented by a decoding device, comprising the following:
         on the basis of the data signal, reading an item of information indicating whether the image of the view is to be decoded according to a first or a second decoding method,   if it is the first decoding method:
           reading, in the data signal, coded data associated with the image of the view,   reconstructing an image of the view on the basis of the coded data that have been read, the image of the reconstructed view containing the original data of the image of the view,   
           if it is the second decoding method:
           reading, in the data signal, coded data associated with the image of the view,   reconstructing an image of the view on the basis of the coded data that have been read, the reconstructed image of the view containing processed data of the image of the view, in association with description information of an image processing used to obtain the processed data.   
               

     According to one particular embodiment:
         the processed data of the image of the view are data of the image of the view which have not been deleted following the application of a cropping of the image of the view,   the description information of the image processing is information on the location, in the image of the view, of one or more cropped regions.       

     Such cropping processing applied to the image of said view makes it possible to avoid coding a portion of the original data thereof, with the benefit of a significant decrease in the transmission rate of the coded data associated with the image of said view, since the data belonging to the one or more regions which have been cropped are neither coded nor signaled to the decoder. The decrease in the rate will depend on the size of the one or more regions cropped. The image of the view which will be reconstructed after decoding, then potentially processing of its processed data, using the corresponding image processing description information, will therefore not contain all of its original data or at least will be different with respect to the original image of the view. Obtaining such an image of the view cropped in this way does not however harm the effectiveness of the synthesis of an intermediate image which would use such an image of said cropped view, once reconstructed. Indeed, such a synthesis using one or more images reconstructed using a conventional decoder (HEVC, MVC-HEVC, 3D-HEVC, for example), it is possible to retrieve the original region in the intermediate view, by virtue of the image of said view and conventionally reconstructed images. 
     According to another particular embodiment:
         the processed data of the image of the view are the data of at least one region of the image of the view which has undergone a sampling, according to a given sampling factor and in at least one given direction,   the description information of the image processing comprises at least one item of information on the location, in the image of the view, of the at least one sampled region.       

     Such processing favors a homogeneous degradation of the image of said view, again with the aim of optimizing the decrease in the rate of the data that result from the sampling applied, and are then coded. The subsequent reconstruction of such an image of the view sampled in this way, even though it provides a reconstructed image of the view which is degraded/different from the original image of the view, the original data of which have been sampled, then coded, does not harm the effectiveness of the synthesis of an intermediate image which would use such an image of said reconstructed sampled view. Indeed, such a synthesis using one or more images reconstructed using a conventional decoder (HEVC, MVC-HEVC, 3D-HEVC, for example), it is possible to retrieve the original region corresponding to the filtered region of the image of said view, in these one or more conventionally reconstructed images. 
     According to another particular embodiment:
         the processed data of the image of the view are the data of at least one region of the image of the view which has undergone a filtering,   the description information of the image processing comprises at least one item of information on the location, in the image of the view, of the at least one filtered region.       

     Such processing favors the deletion of the data of the image of said view which are considered to be unnecessary to code, with a view to optimizing the decrease in the rate of the coded data which are advantageously formed only by the filtered data of the image. 
     The subsequent reconstruction of such an image of the view filtered in this way, even though it provides a reconstructed image of the view which is degraded/different with respect to the original image of the view, the original data of which have been filtered, then coded, does not harm the effectiveness of the synthesis of an intermediate image which would use such an image of said reconstructed filtered view. Indeed, such a synthesis using one or more images reconstructed using a conventional decoder (HEVC, MVC-HEVC, 3D-HEVC, for example), it is possible to retrieve the original region in the intermediate view, by virtue of the filtered region of the image of said view and the conventionally reconstructed images. 
     According to another particular embodiment:
         the processed data of the image of the view are pixels of the image of the view, corresponding to an occlusion detected using an image of another view of the plurality,   the description information of the image processing comprises an indicator of the pixels of the image of the view which are found in the image of another view.       

     Similar to the preceding embodiment, such processing favors the deletion of the data of the image of said view which are considered to be unnecessary to code, with a view to optimizing the decrease in the rate of the coded data which are advantageously formed only by the pixels of the image of said view, the absence of which has been detected in another image of a current view of said plurality. 
     The subsequent reconstruction of such an image of the view, even though it provides a reconstructed image of the view which is degraded/different with respect to the original image of the view, only the occluded region of which has been coded, does not harm the effectiveness of the synthesis of an intermediate image which would use such a reconstructed image of said view. Indeed, such a synthesis using one or more images reconstructed using a conventional decoder (HEVC, MVC-HEVC, 3D-HEVC, for example), it is possible to retrieve the original region in the intermediate view, by virtue of the image of the current view and the conventionally reconstructed images. 
     According to another particular embodiment:
         the processed data of the image of the view, which have been coded/decoded, are pixels which are calculated:
           on the basis of the original data of the image of the view,   on the basis of the original data of an image of at least one other view which is coded/decoded using the first coding/decoding method,   and potentially on the basis of the original data of an image of at least one other view, for which processed data are coded/decoded using the second coding/decoding method,   
           the description information of said image processing comprises:
           an indicator of the pixels of the image of the view which have been calculated,   information on the location, in the image of at least one other view which has been coded/decoded using the first coding/decoding method, of the original data which have been used to calculate the pixels of the image of the view,   and potentially, information on the location, in the image of at least one other view, for which processed data have been coded/decoded, of the original data which have been used to calculate the pixels of the image of the view.   
               

     According to another particular embodiment, the processed data of an image of a first view and the processed data of an image of at least one second view are combined into a single image. 
     Correspondingly with respect to the above embodiment, the processed data of the image of the view which are obtained according to the second decoding method comprise the processed data of an image of a first view and the processed data of an image of at least one second view. 
     According to one particular embodiment:
         the coded/decoded processed data of the image of the view are image-type data,   the coded/decoded description information of the image processing are image-type and/or text-type data.       

     The invention also relates to a device for coding an image of a view forming part of a plurality of views, the plurality of views simultaneously representing a 3D scene from different viewing angles or positions, the coding device comprising a processor which is configured to implement the following, at a current time:
         selecting a first coding method or a second coding method for coding the image of the view,   generating a data signal containing information indicating whether it is the first coding method or the second coding method which is selected,   if the first coding method is selected, coding the original data of the image of the view, the first coding method providing coded original data,   if the second coding method is selected:
           coding processed data of the image of the view, the processed data having been obtained by means of an image processing applied to the original data of the image of the view, the coding providing coded processed data,   coding description information of the image processing which has been applied,   
           the generated data signal further containing:
           the coded original data of the image of the view, if the first coding method has been selected,   the coded processed data of the image of the view, and the coded description information of the image processing, if the second coding method has been selected.   
               

     Such a coding device is in particular able to implement the aforementioned coding method. 
     The invention also relates to a device for decoding a data signal representative of an image of a view forming part of a plurality of views, the plurality of views simultaneously representing a 3D scene from different viewing angles or positions, the decoding device comprising a processor which is configured to implement the following, at a current time:
         reading, in the data signal, an item of information indicating whether the image of the view is to be decoded according to a first or a second decoding method,   if it is the first decoding method:
           reading, in the data signal, coded data associated with the image of the view,   reconstructing an image of the view on the basis of the coded data that have been read, the image of the reconstructed view containing the original data of the image of the view,   
           if it is the second decoding method:
           reading, in the data signal, coded data associated with the image of the view,   reconstructing an image of the view on the basis of the coded data that have been read, the reconstructed image of the view containing processed data of the image of the view, in association with description information of an image processing used to obtain the processed data.   
               

     Such a decoding device is in particular able to implement the aforementioned decoding method. 
     The invention also relates to a data signal containing data coded according to the aforementioned coding method. 
     The invention also relates to a computer program comprising instructions for implementing the decoding method or the coding method according to the invention, according to any one of the particular embodiments described above, when said program is executed by a processor. 
     This program may use any programming language and be in the form of source code, object code or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form. 
     The invention also targets a computer-readable recording medium or information medium containing computer program instructions, such as mentioned above. 
     The recording medium may be any entity or device capable of storing the 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, for example a USB key or a hard disk. 
     Moreover, the recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from an Internet-type network. 
     Alternatively, the recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the aforementioned coding or decoding method. 
    
    
     
       4. BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages will become more clearly apparent from reading several preferred embodiments, given purely by way of illustrative and non-limiting examples, and described below with reference to the appended drawings, in which: 
         FIG.  1    shows the main actions performed by the coding method according to one embodiment of the invention, 
         FIG.  2 A  shows a first type of data signal capable of being generated following the implementation of the coding method of  FIG.  1   , 
         FIG.  2 B  shows a second type of data signal capable of being generated following the implementation of the coding method of  FIG.  1   , 
         FIG.  2 C  shows a third type of data signal capable of being generated following the implementation of the coding method of  FIG.  1   , 
         FIG.  3 A  shows a first embodiment of a method for coding all of the images of views available at a current time, 
         FIG.  3 B  shows a second embodiment of a method for coding all of the images of views available at a current time, 
         FIGS.  4 A to  4 E  each show an example of a processing applied to the image of a view, according to a first embodiment, 
         FIGS.  5 A to  5 D  each show an example of a processing applied to the image of a view, according to a second embodiment, 
         FIG.  6    shows an example of a processing applied to the image of a view, according to a third embodiment, 
         FIG.  7    shows an example of a processing applied to the image of a view, according to a fourth embodiment, 
         FIG.  8    shows an example of a processing applied to the image of a view, according to a fifth embodiment, 
         FIG.  9    shows an example of a processing applied to the image of a view, according to a sixth embodiment, 
         FIG.  10    shows a coding device implementing the coding method of  FIG.  1   , 
         FIG.  11    shows the main actions performed by the decoding method according to one embodiment of the invention, 
         FIG.  12 A  shows a first embodiment of a method for decoding all of the images of views available at a current time, 
         FIG.  12 B  shows a second embodiment of a method for decoding all of the images of views available at a current time, 
         FIG.  13    shows a decoding device implementing the decoding method of  FIG.  11   , 
         FIG.  14    shows one embodiment of a synthesis of images of views, in which images of views reconstructed according to the decoding method of  FIG.  11    are used, 
         FIGS.  15 A to  15 D  each show an example of a processing applied to the image of a view after reconstruction thereof, according to a first embodiment, 
         FIG.  16    shows an example of a processing applied to the image of a view after reconstruction thereof, according to a second embodiment, 
         FIG.  17    shows an example of a processing applied to the image of a view after reconstruction thereof, according to a third embodiment, 
         FIG.  18    shows an example of a processing applied to the image of a view after reconstruction thereof, according to a fourth embodiment. 
     
    
    
     5. DESCRIPTION OF THE GENERAL PRINCIPLE OF THE INVENTION 
     The invention mainly proposes a scheme for coding a plurality of current images of, respectively, a plurality of views, the plurality of views representing, at the current time, a 3D scene according to a given position or a given viewing angle, in which two coding techniques are available:
         a first coding technique, according to which at least one current image of a view is coded using a conventional coding mode, such as for example HEVC, MV-HEVC, 3D-HEVC,   a second, innovative coding technique, according to which the processing data of at least one current image of a view, which result from the application of a processing of the original data of this image, using a particular image processing, are coded using a conventional coding mode of the aforementioned type and/or any other suitable coding mode, so as to significantly decrease the signaling cost of the coded data of this image, resulting from the processing implemented before the coding step.       

     Correspondingly, the invention proposes a decoding scheme which makes it possible to combine two decoding techniques:
         a first decoding technique, according to which at least one current image of a coded view is reconstructed using a conventional decoding mode, such as for example HEVC, MV-HEVC, 3D-HEVC, and corresponding to a conventional coding mode used in the coding and having been signaled to the decoder, so as to obtain at least one reconstructed image of a view which is of very good quality,   a second, innovative decoding technique according to which the coded processing data of at least one image of a view are decoded using a decoding mode corresponding to the coding mode signaled to the decoder, namely either the conventional coding mode and/or the other suitable coding mode, so as to obtain processed image data and description information of the image processing from which the obtained processed data originate. The processed data obtained on decoding for this image therefore do not correspond to the original data thereof, unlike the image data decoded according to the first decoding technique.       

     The image of the view which will be subsequently reconstructed on the basis of such decoded processed image data and the image processing description information will be different from the original image of the view, i.e. before processing, then coding of its original data. However, such a reconstructed image of the view will constitute the image of a view which, used with images of other views reconstructed according to the first conventional decoding technique, will make it possible to synthesize images of intermediate views, in a particularly efficient and effective manner. 
     6. EXEMPLARY CODING SCHEME IMPLEMENTATIONS 
     A method for coding 360°, 180° or other omnidirectional videos is described below, which may use any type of multiview video coder, for example conforming to the 3D-HEVC or MV-HEVC standard, or the like. 
     With reference to  FIG.  1   , such a coding method applies to a current image of a view which forms part of a plurality of views V 1 , . . . , V N , the plurality of views representing a 3D scene according to, respectively, a plurality of viewing angles or a plurality of positions/orientations. 
     According to a common example, in the case where three omnidirectional cameras are used to generate a video, for example a 360° video:
         a first omnidirectional camera may for example be placed in the center of the 3D scene, with a 360°×180° viewing angle,   a second omnidirectional camera may for example be placed on the left in the 3D scene, with a 360°×180° viewing angle,   a third omnidirectional camera may for example be placed on the right in the 3D scene, with a 360°×180° viewing angle.       

     According to another more atypical example, in the case where three omnidirectional cameras are used to generate an α° video, with 0°&lt;α≤360°:
         a first omnidirectional camera may for example be placed in the center of the 3D scene, with a 360°×180° viewing angle,   a second omnidirectional camera may for example be placed on the left in the 3D scene, with a 270°×135° viewing angle,   a third omnidirectional camera may for example be placed on the right in the 3D scene, with a 180°×90° viewing angle.       

     Other configurations are of course possible. 
     At least two views of said plurality of views may represent the 3D scene from the same viewing angle, or not. 
     The coding method according to the invention consists in coding, at a current time:
         an image IV 1  of a view V 1 ,   an image IV 2  of a view V 2 ,   etc.,   an image IV k  of a view V k ,   . . . ,   an image IV N  of a view V N ,       

     An image of a view in question may equally be a texture image or a depth image. The image of a view in question, for example the image IV k , contains an amount Q (Q≥1) of original data (d 1   k , . . . , dQ k ), such as for example Q pixels. 
     The coding method then comprises the following, for at least one image IV k  of a view V k , to be coded: 
     In C 1 , a first coding method MC 1  or a second coding method MC 2  for the image IV k  is selected. 
     If the first coding method MC 1  is selected, in C 10 , information flag_proc is coded, for example on a bit set to 0, to indicate that the coding method MC 1  has been selected. 
     In C 11   a,  the Q original data (pixels) d 1   k , . . . , dQ k  of the image IV k  are coded using a conventional coder, such as for example conforming to the HEVC, MV-HEVC, 3D-HEVC, etc. standard. On completion of the coding C 11   a,  a coded image IVC k  of the view V k  is obtained. The coded image IVC k  then contains Q coded original data dc 1   k , dc 2   k , . . . , dcQ k . 
     In C 12   a,  a data signal F 1   k  is generated. As shown in  FIG.  2 A , the data signal F 1   k  contains the information flag_proc=0 relating to the selection of the first coding method MC 1 , and the coded original data dc 1   k , dc 2   k , . . . , dcQ k . 
     If the second coding method MC 2  is selected, in C 10 , information flag_proc is coded, for example on a bit set to 1, to indicate that the coding method MC 2  has been selected. 
     In C 11   b,  the coding method MC 2  is applied to data DT k  resulting from a processing of the image IV k , carried out before the coding step. 
     Such data DT k  comprise:
         data of image type (pixels) corresponding to all or some of the original data of the image IV k  which have been processed using a particular image processing, before the coding step, various detailed examples of which will be described further on in the description,   description information of the image processing that has been applied to the image IV k , before the coding step C 11   b,  such description information being for example of text and/or image type.       

     On completion of the coding C 11   b,  coded processed data DTC k  are obtained. They are representative of a coded processed image IVTC k . 
     Thus, the processed data DT k  do not correspond to the original data of the image IV k . 
     For example, these processed data DT k  correspond to an image of which the resolution is higher or lower than that of the image IV k  before processing. Thus, the processed image IV k  could for example be larger, since it is obtained on the basis of images of other views, or conversely be smaller, since it results from the deletion of one or more original pixels from the image IV k . 
     According to another example, these processed data DT k  correspond to an image of which the format of representation (YUV, RGB, etc.) of the processed image IV k  is different from the original format of the image IV k  before processing, as well as the number of bits for representing a pixel (16 bits, 10 bits, 8 bits, etc.). 
     According to yet another example, these processed data DT k  correspond to a color or texture component which is degraded with respect to the original texture or color component of the image IV k  before processing. 
     According to yet another example, these processed data DT k  correspond to a particular representation of the original content of the image IV k  before processing, for example a representation of the filtered original content of the image IV k . 
     In the case where the processed data DT k  are only image data, that is to say are for example in the form of a grid of pixels, the coding method MC 2  may be implemented by a coder which is similar to the coder implementing the first coding method MC 1 . It could be a lossy or lossless coder. In the case where the processed data DT k  are different from the image data, such as for example data of text type, or else comprise both image data and data of a type other than image data, the coding method MC 2  may be implemented:
         by a lossless coder in order to code specifically the data of text type,   by a lossy or lossless coder in order to code specifically the image data, such a coder possibly being identical to the coder implementing the first coding method MC 1  or else different.       

     In C 12   b,  a data signal F 2   k  is generated. As shown in  FIG.  2 B , the data signal F 2   k  contains the information flag_proc=1 relating to the selection of the second coding method MC 2  and the coded processed data DTC k , in the case where these data are all image data. 
     As an alternative, in C 12   c,  in the case where the coded processed data DTC k  comprise both image data and data of text type, two signals F 3   k  and F′ 3   k  are generated. 
     As shown in  FIG.  2 C :
         the data signal F′ 3  contains the information flag_proc=1 relating to the selection of the second coding method MC 2  and the coded processed data DTC k  of image type,   the data signal F′ 3   k  contains the coded processed data DTC k  of text type.       

     The coding method which has just been described above may then be implemented for each image IV 1 , IV 2 , . . . , IV N  of the N views to be coded that are available, for some of them only or else may be limited to the image IV k , with for example k=1. 
     According to two exemplary embodiments shown in  FIGS.  3 A and  3 B , it is assumed for example that among the N images IV 1 , . . . , IV N  to be coded:
         the n first images IV 1 , . . . , IV n  are coded using the first coding technique MC 1 : the n first views V 1  to V n  are called master views because, once reconstructed, the images of the n master views will contain all of their original data and will be suitable for use with one or more of the N-n other views in order to synthesize the images of arbitrary views required by a user,   the N-n other images IV n+1 , . . . , IV N  are processed before being coded using the second coding method MC 2 : these N-n other images processed belong to what are called additional views.       

     If n=0, all of the images IV 1 , . . . , IV N  of all of the views are processed. If n=N−1, the image of a single view among N is processed, for example the image of the first view. 
     On completion of the processing of the N-n other images IV n+1 , . . . , IV N , M-n processed data are obtained. If M=N, there are as many processed data as there are views to be processed. If M&lt;N, at least one of the N-n views has been deleted during the processing. In this case, on completion of the coding C 11   b  according to the second coding method MC 2 , processed data relating to this image of the deleted view are coded, using a lossless coder, which comprise only information indicating the absence of this image and of this view. No pixel will then be coded, using the second coding method MC 2 , using a coder of HEVC, MVC-HEVC, 3D-HEVC, etc. type, for this image deleted by the processing. 
     In the example of  FIG.  3 A , in C 11   a,  the n first images IV 1 , . . . , IV n  are coded using a conventional coder of HEVC type, independently of one another. On completion of the coding C 11   a,  n coded images IVC 1 , . . . , IVC n  are respectively obtained. In C 12   a,  n data signals F 1   1 , . . . , F 1   n  are respectively generated. In C 13   a,  these n data signals F 1   1 , . . . , F 1   n  are concatenated, generating a data signal F 1 . 
     As represented by the dashed arrows, the images IV 1 , . . . , IV n  may be used during the processing of the N-n other images IV n+1 , . . . , IV N . 
     Still with reference to  FIG.  3 A , in C 11   b,  the M-n processed data DT n+1 , . . . , DT M  are coded using a conventional coder of HEVC type, independently of each other, if these M-n processed data are all of image type or, if they are both of image type and of text type, are coded using a conventional coder of HEVC type, independently of each other, for the processed data of image type, and are coded by means of a lossless coder for the processed data of text type. On completion of the coding C 11   b,  N-n coded processed data DTC n+1 , . . . , DTC N  are obtained as, respectively, N-n coded data associated, respectively, with the N-n images IV n+1 , . . . , IV N . In C 12   b,  in the case where the M-n processed data are all of image type, N-n data signals F 2   n+1  , . . . , F 2   N  are generated, respectively, containing, respectively, the N-n coded processed data DTC n+1 , . . . , DTC N . In C 12   c,  in the case where the M-n processed data are both of image type and of text type:
         N-n data signals F 3   n+1 , . . . , F 3   N  are generated containing, respectively, the N-n coded processed data of image type, and   N-n data signals F′ 3   n+1 , . . . , F′ 3   N  are generated containing, respectively, the N-n coded processed data of text type.       

     In C 13   c,  the data signals F 3   n+1 , . . . , F 3   N  and F′ 3   n+1 , . . . , F′ 3   N  are concatenated, generating a data signal F 3 . 
     In C 14 , either the signals F 1  and F 2  are concatenated, or the signals F 1  and F 3  are concatenated, providing a data signal F capable of being decoded by a decoding method which will be described further on in the description. 
     In the example of  FIG.  3 B , in C 11   a,  the n first images IV 1 , . . . , IV n  are coded simultaneously using a conventional coder of MV-HEVC or 3D-HEVC type. On completion of the coding C 11   a,  n coded images IVC 1 , . . . , IVC n  are respectively obtained. In C 12   a,  a single signal F 1  is generated which contains the coded original data associated with each of these n coded images. 
     As represented by the dashed arrows, the first images IV 1 , . . . , IV n  may be used during the processing of the N-n other images IV n+1 , . . . , IV N . 
     Still with reference to  FIG.  3 B , in C 11   b,  the M-n processed data DT n+1 , . . . , DT M  of image type are coded simultaneously using a conventional coder of MV-HEVC or 3D-HEVC type if these M-n processed data are all of image type or, if they are both of image type and of text type, are coded simultaneously using a conventional coder of MV-HEVC or 3D-HEVC type for the processed data of image type, and are coded by means of a lossless coder for the processed data of text type. On completion of the coding C 11   b,  N-n coded processed data DTC n+1 , . . . , DTC N  are obtained, respectively, as, respectively, N-n coded processed data associated, respectively, with the N-n images IV n+1 , . . . , IV N  which have been processed. In C 12   b,  in the case where the M-n processed data are all of image type, a single signal F 2  is generated which contains the N-n coded processed data DTC n+1 , . . . , DTC N  of image type. In C 12   c,  in the case where the M-n processed data are both of image type and of text type:
         a signal F 3  is generated which contains the coded processed data of image type,   a signal F′ 3  is generated which contains the coded processed data of text type.       

     In C 14 , either the signals F 1  and F 2  are concatenated, or the signals F 1 , F 3  and F′ 3  are concatenated, providing a data signal F capable of being decoded by a decoding method which will be described further on in the description. 
     Of course, other combinations of coding methods are possible. 
     According to one possible variant of  FIG.  3 A , the coder implementing the coding method MC 1  could be a coder of HEVC type and the coder implementing the coding method MC 2  could be a coder of MV-HEVC or 3D-HEVC type or else comprise a coder of MV-HEVC or 3D-HEVC type and a lossy coder. 
     According to one possible variant of  FIG.  3 B , the coder implementing the coding method MC 1  could be a coder of MV-HEVC or 3D-HEVC type and the coder implementing the coding method MC 2  could be a coder of HEVC type or else comprise a coder of HEVC type and a lossless coder. 
     A description will now be given, with reference to  FIGS.  4 A to  4 E , of a first embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in these figures, the processing applied to the original data of the image IV k  is a cropping of one or more regions of this image, in a horizontal or vertical direction or else in both directions at the same time. 
     In the example of  FIG.  4 A , the left-hand border B 1  and the right-hand border B 2  of the image IV k  are cropped, which means the deletion of the pixels of the rectangular region of the image IV k  formed by each of the borders B 1  and B 2 . 
     In the example of  FIG.  4 B , the top border B 3  and the bottom border B 4  of the image IV k  are cropped, which means the deletion of the pixels of the rectangular region of the image IV k  formed by each of the borders B 3  and B 4 . 
     In the example of  FIG.  4 C , the cropping is applied in a vertical direction to a rectangular region Z 1  located in the image IV k . 
     In the example of  FIG.  4 D , the cropping is applied in a horizontal direction to a rectangular region Z 2  located in the image IV k . 
     In the example of  FIG.  4 E , the cropping is applied in both a horizontal and a vertical direction to a region Z 3  located in the image IV k . 
     The processed data DT k  to be coded then comprise:
         the pixels of the remaining region Z R  of the image IV k  which have not been deleted following the cropping ( FIGS.  4 A,  4 B,  4 E ), or else the pixels of the remaining regions Z 1   R  and Z 2   R  ( FIGS.  4 C,  4 D ) of the image IV k  which have not been deleted following the cropping,   information describing the cropping applied.       

     In the case for example of  FIGS.  4 A,  4 B,  4 E , the information describing the cropping applied is of text type and contains:
         the coordinates of the pixel located at the top, the furthest to the left, in the remaining region Z R  of the image IV k ,   the coordinates of the pixel located at the bottom, the furthest to the right, in the remaining region Z R  of the image IV k .       

     In the case for example of  FIGS.  4 C and  4 D , the information describing the cropping applied contains:
         the coordinates of the pixel located at the top, the furthest to the left, in the remaining region Z 1   R  of the image IV k ,   the coordinates of the pixel located at the bottom, the furthest to the right, in the remaining region Z 1   R  of the image IV k ,   the coordinates of the pixel located at the top, the furthest to the left, in the remaining region Z 2   R  of the image IV k ,   the coordinates of the pixel located at the bottom, the furthest to the right, in the remaining region Z 2   R  of the image IV k .       

     The original data (pixels) of the rectangular region defined by the coordinates of the pixel located at the top, the furthest to the left in the remaining region Z R  (resp. Z 1   R  and Z 2   R ) and the coordinates of the pixel located at the bottom, the furthest to the right, in the remaining region Z R  (resp. Z 1   R  and Z 2   R ) are then coded in C 11   b  ( FIG.  1   ) by a coder of HEVC, 3D-HEVC, MV-HEVC, etc. type. The description information of the cropping applied is for its part coded in C 11   b  ( FIG.  1   ) by a lossless coder. 
     As a variant, the information describing the cropping applied contains the number of rows and/or columns of pixels to be deleted, and the position of these rows and/or columns in the image IV k . 
     According to one embodiment, the amount of data to be deleted by cropping is fixed. It may for example be decided to systematically delete X rows and/or Y columns from the image of a view in question. In this case, the description information contains only the information on the cropping or not for each view. 
     According to another embodiment, the amount of data to be deleted by cropping is variable between the image IV k  of the view V k  and an image of another view that is available. 
     The amount of data to be deleted by cropping may also depend for example on the position in the 3D scene of the camera which has captured the image IV k . Thus, for example, if the image of another view among said N views has been captured by a camera having a position/orientation in the 3D scene that is different from that of the camera which has captured the image IV k , an amount of data to be deleted that is different from the amount of data deleted for the image IV k  will for example be used. 
     The application of a cropping may further depend on the time at which the image IV k  is coded. At the current time, it may for example be decided to apply a cropping to the image IV k , while at the times preceding or following the current time, it may be decided not to apply such a cropping, or any processing for that matter, to the image IV k . 
     Finally, the cropping may be applied to the images of one or more views at the current time. The cropped region in the image IV k  of the view V k  may or may not be the same as the cropped region of an image of another view to be coded at the current time. 
     A description will now be given, with reference to  FIGS.  5 A to  5 D , of a second embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in these figures, the processing applied to the original data of the image IV k  is a downsampling of one or more regions of this image, in a horizontal or vertical direction. 
     In the example of  FIG.  5 A , a downsampling is applied to a region Z 4  of the image IV k , in a vertical direction. 
     In the example of  FIG.  5 B , a downsampling is applied to a region Z 5  of the image IV k , in a horizontal direction. 
     In the example of  FIG.  5 C , a downsampling is applied to the entire image IV k . 
     In the example of  FIG.  5 D , a downsampling is applied to a region Z 6  of the image IV k , in both a horizontal direction and a vertical direction. 
     The processed data DT k  to be coded then comprise:
         the downsampled image data (pixels),   information describing the downsampling applied, such as for example:
           the downsampling factor used,   the downsampling direction used,   in the case of  FIGS.  5 A,  5 B,  5 D , the location of the filtered region Z 4 , Z 5 , Z 6  in the image IV k  or else,   in the case of  FIG.  5 C , the coordinates of the pixel located at the top, the furthest to the left, in the image IV k , and the coordinates of the pixel located at the bottom, the furthest to the right, in the image IV k  thus defining the complete area of this image.   
               

     The downsampled image data (pixels) are then coded in C 11   b  ( FIG.  1   ) by a coder of HEVC, 3D-HEVC, MV-HEVC, etc. type. The description information of the downsampling applied is for its part coded in C 11   b  ( FIG.  1   ) by a lossless coder. 
     The value of the downsampling factor may be fixed or depend on the position in the 3D scene of the camera which has captured the image IV k . Thus, for example, if the image of another view among said N views has been captured by a camera having a position/orientation in the 3D scene that is different from that of the camera which has captured the image IV k , another downsampling factor will for example be used. 
     The application of a downsampling may further depend on the time at which the image of the view V k  is coded. At the current time, it may for example be decided to apply a downsampling to the image IV k , while at the times preceding or following the current time, it may be decided not to apply such a downsampling, or any processing for that matter, to the image of the view V k . 
     Finally, the downsampling may be applied to the images of one or more views at the current time. The downsampled region in the image IV k  may or may not be the same as the downsampled region of an image of another view to be coded at the current time. 
     A description will now be given, with reference to  FIG.  6   , of a third embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in  FIG.  6   , the processing applied to the original data of the image IV k  is a detection of contours by filtering this image. Two contours ED 1  and ED 2  are for example present in an image IV k . In a manner known per se, such filtering comprises, for example, the following:
         applying a contour detection filter to the contours ED 1  and ED 2 ,   applying an expansion of the contours ED 1  and ED 2  so as to enlarge the region surrounding each contour ED 1  and ED 2 , such a region being represented by hatching in  FIG.  6   ,   deleting all of the original data from the image IV k  which do not form part of the hatched regions and which are therefore considered unnecessary to code.       

     The processed data DT k  to be coded, in the case of such filtering, then comprise:
         the original pixels which are contained in the hatched regions,   information describing the filtering applied, such as for example a predefined value for each pixel not comprised in the hatched region, represented for example by a predefined value YUV=000.       

     The image data (pixels) corresponding to the hatched regions are then coded in C 11   b  ( FIG.  1   ) by a coder of HEVC, 3D-HEVC, MV-HEVC, etc. type. The description information of the filtering applied is for its part coded in C 11   b  ( FIG.  1   ) by a lossless coder. 
     The filtering which has just been described in relation to the image IV k  may be applied to one or more images of other views among said N views, to regions of these one or more images which may be different from one image of a view to another image of a view. 
     A description will now be given, with reference to  FIG.  7   , of a fourth embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in  FIG.  7   , the processing applied to the original data of the image IV k  is a detection of occlusion of at least one region Z OC  of the image IV k  using at least one image IV p  of another view V p  among N views (1≤p≤N). 
     In a manner known per se, such an occlusion detection consists in looking for the region Z OC  of the image IV k  on the basis of the image IV p , using for example a disparity estimate. The occluded region Z OC  is then expanded, for example using a mathematical morphology algorithm. The region Z OC  thus expanded is represented by hatching in  FIG.  7   . All of the original data of the image IV k  which do not form part of the hatched region Z OC  and which are therefore considered unnecessary to code are deleted. 
     The processed data DT k  to be coded, in the case of such an occlusion detection, then comprise:
         the original pixels which are contained in the hatched region,   information describing the occlusion detection applied, such as for example a predefined value for each pixel not comprised in the hatched region, represented for example by a predefined value YUV=000.       

     The image data (pixels) corresponding to the hatched region are then coded in C 11   b  ( FIG.  1   ) by a coder of HEVC, 3D-HEVC, MV-HEVC, etc. type. The description information of the occlusion detection applied is for its part coded in C 11   b  ( FIG.  1   ) by a lossless coder. 
     A description will now be given, with reference to  FIG.  8   , of a fifth embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in  FIG.  8   , the processing applied to the original data of the image IV k  consists in calculating pixels:
         on the basis of the original pixels of the image IV k ,   on the basis of the original pixels of an image IV j  of one or more other views (1≤j≤n) which are coded in C 11   a  ( FIG.  1   ) using the first coding method MC 1 ,   and potentially on the basis of the original pixels of an image IV l  (n+1≤l≤N) of at least one other view, for which processed pixels are coded in C 11   b  ( FIG.  1   ) using the second coding method MC 2 .       

     The processed data DT k  to be coded, in the case of such a calculation, then comprise:
         an indicator of the pixels of the image IV k  of said view which have been calculated,   information on the location, in the image IV j , of the original pixels which have been used to calculate the pixels of the image IV k ,   and potentially information on the location, in the image IV j , of the original pixels which have been used to calculate the pixels of the image IV k .       

     The aforementioned calculation consists, for example, in subtracting the original pixels of the image IV k  of a view and potentially the original pixels of the image IV l  from the original pixels of the image IV j . 
     A description will now be given, with reference to  FIG.  9   , of a sixth embodiment of a processing applied to the original data of an image IV k , before the coding step C 11   b  ( FIG.  1   ) according to the second coding method MC 2 . 
     In the example shown in  FIG.  9   , the processing applied to the original data of the image IV k  consists:
         in processing the original pixels of the image IV k , providing processed data DT′ k ,   in processing the original pixels of an image IV s  of a view V s  (1≤s≤N), providing processed data DT s ,   in bringing together the processed data DT′ k  of the image IV k  and the processed data DT s  of the image IV s  in a single image IV one , of which the original processed data obtained DT k  are coded in C 11   b  ( FIG.  1   ) using the second coding method MC 2 .       

       FIG.  10    shows the simplified structure of a coding device COD designed to implement the coding method according to any one of the particular embodiments of the invention. 
     According to one particular embodiment of the invention, the actions performed by the coding method are implemented by computer program instructions. To that end, the coding device COD has the conventional architecture of a computer and comprises in particular a memory MEM_C, a processing unit UT_C, equipped for example with a processor PROC_C, and driven by the computer program PG_C stored in memory MEM_C. The computer program PG_C comprises instructions for implementing the actions of the coding method such as described above when the program is executed by the processor PROC_C. 
     On initialization, the code instructions of the computer program PG_C are for example loaded into a RAM memory (not shown), before being executed by the processor PROC_C. The processor PROC_C of the processing unit UT_C implements in particular the actions of the coding method described above, according to the instructions of the computer program PG_C. 
     7. EXEMPLARY DECODING SCHEME IMPLEMENTATIONS 
     A method for decoding a 360°, 180° or other omnidirectional video is described below, which may use any type of multiview video decoder, for example conforming to the 3D-HEVC or MV-HEVC standard, or the like. 
     With reference to  FIG.  11   , such a decoding method applies to a data signal representative of a current image of a view which forms part of said plurality of views V 1 , . . . , V N . 
     The decoding method according to the invention consists in decoding:
         a data signal representative of the coded data associated with the image IV 1  of a view V 1 ,   a data signal representative of the coded data associated with the image IV 2  of a view V 2 ,   . . . ,   a data signal representative of the coded data associated with the image IV k  of a view V k ,   . . . ,   a data signal representative of the coded data associated with the image IV N  of a view V N .       

     An image of a view in question to be reconstructed using the aforementioned decoding method may equally be a texture image or a depth image. 
     The decoding method comprises the following, for a data signal F 1   k , F 2   k  or F 3   k  and F′ 3   k  representative of at least one image IV k  of a view V k , to be reconstructed: 
     In D 1 , the information flag_proc, indicating whether the image IV k  has been coded using the first coding method MC 1  or the second coding method MC 2 , is read in the data signal F 1   k , F 2   k  or F 3   k  and F′ 3   k , as shown, respectively, in  FIGS.  2 A,  2 B and  2 C . 
     If it is the signal F 1   k , the information flag_proc is at 0. 
     In D 11   a,  the coded data dc 1   k , dc 2   k , . . . , dcQ k  associated with the coded image IVC k  are read in the data signal F 1   k . 
     In D 12   a,  an image IVD k  is reconstructed on the basis of the coded data dc 1   k , dc 2   k , . . . , dcQ k  that are read in D 11   a,  using a decoding method MD 1  corresponding to the coding method MC 1  applied to the coding, in C 11   a  in  FIG.  1   . To that end, the image IV k  is reconstructed using a conventional decoder, such as for example conforming to the HEVC, MVC-HEVC, 3D-HEVC, etc. standard. 
     On completion of the decoding D 12   a,  the image IVD k  thus reconstructed contains the original data d 1   k , d 2   k , . . . , dQ k  of the image IV k  which has been coded in C 11   a  in  FIG.  1   . 
     Since the image IVD k  is in keeping with the original image IV k , it thus constitutes a master image which is suitable for use, in the context for example of a synthesis of intermediate views. 
     In D 1 , if it is the signal F 2   k  or F 3   k , the determined information flag_proc is at 1. 
     If it is the signal F 2   k , in D 11   b,  the coded processed data DTC k  associated with the coded processed image IVTC k , as obtained in C 11   b  in  FIG.  1   , are read in the data signal F 2   k . 
     These coded processed data DTC k  that are read are only data of image type. 
     In D 12   b,  a processed image IVTD k  is reconstructed on the basis of the coded data DTC k  that are read in D 11   b,  using a decoding method MD 2  corresponding to the coding method MC 2  applied to the coding, in C 11   b  in  FIG.  1   . To that end, coded data DTC k  are decoded using a conventional decoder, such as for example conforming to the HEVC, MVC-HEVC, 3D-HEVC, etc. standard. 
     On completion of the decoding D 12   b,  the processed image thus reconstructed IVTD k , corresponding to the decoded data DTC k , contains the processed data DT k  of the image IV k  before their coding in C 11   b  in  FIG.  1   . 
     The reconstructed processed image IVTD k  contains image data (pixels) corresponding to all or some of the original data of the image IV k  which have been processed using a particular image processing, various detailed examples of which have been described with reference to  FIGS.  4  to  9   . 
     If it is the signal F 3   k , the coded processed data DTC k  associated with the coded processed image IVTC k , are read in D 11   c.    
     To that end:
         coded processed data DTC k  of image type are read in the signal F 3   k ,   coded processed data DTC k , different from the image data, such as for example data of text type, or else comprising both image data and data of a type other than image data, are read in the signal F′ 3   k .       

     The coded processed data DTC k  are decoded in D 12   b,  using the decoding method MD 2 , which may be implemented:
         by a lossy or lossless decoder in order to decode specifically the image data, such a decoder possibly being identical to the decoder implementing the first decoding method MD 1  or else different,   by a lossless decoder in order to decode specifically the data of text type.       

     On completion of the decoding D 12   b,  the following are obtained:
         the processed image thus reconstructed IVTD k , corresponding to the data DTC k  of image type which have been decoded,   processed data of text type corresponding to description information of the processing applied to the image IV k  before the coding C 11   b  ( FIG.  1   ).       

     Such a reconstructed processed image IVTD k  according to the second decoding method MD 2  does not contain all of the original data of the image IV k  before processing then coding in C 11   b.  Such a reconstructed image of a view according to the second decoding method MD 2  may however be used in addition to an image of a master view which will have been reconstructed using the first decoding method MD 1 , in the context for example of a synthesis of intermediate images, in order to obtain synthesized images of views which are of good quality. 
     The decoding method which has just been described above may then be implemented at the current time for each of the coded images IVC 1 , IVC 2 , . . . , IVC N  to be reconstructed that are available, for some of them only or else may be limited to the image IV k , with for example k=1. 
     According to two exemplary embodiments shown in  FIGS.  12 A and  12 B , it is assumed for example that among the N coded images IVC 1 , . . . , IVC N  to be reconstructed:
         the n first coded images IVC 1 , . . . , IVC n  are reconstructed using the first decoding technique MD 1  to obtain, respectively, the image of each of the n master views,   the N-n other coded images IVC n+1 , . . . , IVC N  are reconstructed using the second decoding method MD 2  to obtain, respectively, the image of each of the N-n additional views.       

     If n=0, the images IVC 1 , . . . , IVC N  of the views from 1 to N are reconstructed using the second decoding method MD 2 . If n=N−1, the image of a single view is reconstructed using the second decoding method MD 2 . 
     In the example of  FIG.  12 A , in D 100 , the data signal F, as generated in C 14  in  FIG.  3 A  is separated:
         either into two data signals: the data signal F 1 , as generated in C 13   a  in  FIG.  3 A , and the data signal F 2 , as generated in C 13   b  in  FIG.  3 A ,   or into three data signals: the data signal F 1 , as generated in C 13   a  in  FIG.  3 A , and the data signals F 3  and F′ 3 , as generated in C 13   c  in  FIG.  3 A .       

     In the case of the signals F 1  and F 2 , in D 110   a,  the data signal F 1  is in turn separated into n data signals F 1   1 , . . . , F 1   n  that are representative, respectively, of the n coded images of views IVC 1 , . . . , IVC n . 
     In D 11   a,  in each of the n data signals F 1   1 , . . . , F 1   n , the coded original data dc 1   1 , . . . , dcQ 1 , . . . , dc 1   n , . . . , dcQ n  which are associated with each of these n coded images are determined, respectively. 
     In D 12   a,  the images IVD 1 , . . . , IVD n  are reconstructed on the basis of their respective coded original data, read in D 11   a,  using a conventional decoder of HEVC type, independently of one another. 
     Still with reference to  FIG.  12 A , in D 110   b,  the data signal F 2  is in turn separated into N-n data signals F 2   n+1 , . . . , F 2   N  that are representative, respectively, of the N-n coded processed data DTC n+1 , . . . , DTC N . 
     In D 11   b,  in each of the N-n data signals F 2   n+1 , . . . , F 2   N , N-n coded processed data DTC n+1 , . . . , DTC N  are read, respectively, which correspond, respectively, to each of the N-n images IV n+1 , . . . , IV N  to be reconstructed. 
     In D 12   b,  the processed images are reconstructed, respectively, on the basis of N-n coded processed data DTC n+1 , . . . , DTC N  read in D 11   b,  using a conventional decoder of HEVC type, independently of one another. The reconstructed processed images IVTD n+1 , . . . , IVTD N  are then obtained. 
     In the case of the signals F 1 , F 3  and F′ 3 , in D 110   a,  the data signal F 1  is in turn separated into n data signals F 1   1 , . . . , F 1   n  that are representative, respectively, of the n coded images IVC 1 , . . . , IVC n . 
     In D 11   a,  in each of the n data signals F 1   1 , . . . , F 1   n , the coded original data dc 1   1 , . . . , dcQ 1 , . . . , dc 1   n , . . . , dcQ n  which are associated with each of these n coded images are read, respectively. 
     In D 12   a,  the images IVD 1 , . . . , IVD n  are reconstructed on the basis of their respective coded original data, read in D 11   a,  using a conventional decoder of HEVC type, independently of one another. 
     In D 110   c:  
         the data signal F 3  is in turn separated into N-n data signals F 3   n+1 , . . . , F 3   N  that are representative, respectively, of the N-n coded processed data DTC n+1 , . . . , DTC N  of image type and,   the data signal F′ 3  is in turn separated into N-n data signals F′ 3   n+1 , . . . , F′ 3   N  that are representative, respectively, of the N-n coded processed data DTC n+1 , . . . , DTC N  of text or another type.       

     In D 11   c:  
         in each of the N-n data signals F 3   n+1 , . . . , F 3   N , N-n coded processed data DTC n+1 , . . . , DTC N  of image type are read, respectively, which correspond, respectively, to each of the N-n images IV n+1 , . . . , IV N  to be reconstructed,   in each of the N-n data signals F′ 3   n+1 , . . . , F′ 3   N , N-n coded processed data DTC n+1 , . . . , DTC N  of text or another type are read, respectively, which correspond, respectively, to the description information of the processing for each of the N-n images IV n+1 , . . . , IV N  to be reconstructed.       

     In D 12   b,  the N-n processed images are reconstructed, respectively, on the basis of N-n coded processed data DTC n+1 , . . . , DTC N  read in D 11   b,  using a conventional decoder of HEVC type, independently of one another. The reconstructed processed images IVTD n+1 , . . . , IVTD N  are then obtained. 
     Also in D 12   b,  there is reconstructed description information of the processing applied to each of the images IV n+1 , . . . , IV N , before the coding thereof C 11   b  ( FIG.  3 A ), on the basis of N-n coded processed data DTC n+1 , . . . , DTC N  of text or other type read in D 11   c,  using a decoder corresponding to the lossless coder used in the coding. 
     In the example of  FIG.  12 B , in D 100 , the data signal F, as generated in C 14  in  FIG.  3 B  is separated:
         either into two data signals: the data signal F 1 , as generated in C 12   a  in  FIG.  3 B , and the data signal F 2 , as generated in C 12   b  in  FIG.  3 B ,   or into three data signals: the data signal F 1 , as generated in C 12   a  in  FIG.  3 B , and the data signals F 3  and F′ 3 , as generated in C 12   c  in  FIG.  3 B .       

     In the case of the signals F 1  and F 2 , in D 11   a,  in the data signal F 1 , the coded original data dc 1   1 , . . . , dcQ 1 , . . . , dc 1   n , . . . , dcQ n  are read which are associated, respectively, with each of the images IVC 1, i , . . . , IVC n, i  of n coded views. 
     In D 12   a,  the images IVD 1, i , . . . , IVD n, i  are reconstructed on the basis of their respective coded original data, read in D 11   a,  simultaneously, using a conventional decoder of MV-HEVC or 3D-HEVC type. 
     In D 11   b,  in  FIG.  12 B , in the data signal F 2 , the N-n coded processed data DTC n+1 , . . . , DTC N  are read which are associated, respectively, with each of the images IV n+1 , . . . , IV N  of the N-n views to be reconstructed. 
     In D 12   b,  the N-n processed images are reconstructed, respectively, on the basis of the N-n coded processed data DTC n+1 , . . . , DTC N , read in D 11   b,  simultaneously, using a conventional decoder of MV-HEVC or 3D-HEVC type. The reconstructed processed images IVTD n+1 , . . . , IVTD N  are then obtained. 
     In the case of the signals F 1 , F 3  and F′ 3 , in D 11   a,  in the data signal F 1 , the coded original data dc 1   1 , . . . , dcQ 1 , . . . , dc 1   n , . . . , dcQ n  are read which are associated, respectively, with each of the images IVC 1 , . . . , IVC n  of then coded views. 
     In D 12   a,  the images IVD 1 , . . . , IVD n  are reconstructed on the basis of their respective coded original data, read in D 11   a,  simultaneously, using a conventional decoder of MV-HEVC or 3D-HEVC type. 
     In D 11   c,  in  FIG.  12 B , in the data signal F 3 , the N-n coded processed data DTC n+1 , . . . , DTC N  of image type are read which are associated, respectively, with each of the N-n images IV n+1 , . . . , IV N  to be reconstructed. 
     In D 12   b,  the processed images are reconstructed, respectively, on the basis of N-n coded processed data DTC n+1 , . . . , DTC N , read in D 11   c,  simultaneously, using a conventional decoder of MV-HEVC or 3D-HEVC type. The reconstructed processed images of views IVTD n+1 , . . . , IVTD N  are then obtained. 
     Also in D 12   b,  in  FIG.  12 B , there is reconstructed description information of the processing applied to each of the images IV n+1 , . . . , IV N , before the coding thereof C 11   b  ( FIG.  3 B ), on the basis of the N-n coded processed data DTC n+1 , . . . , DTC N  of text or other type read in D 11   c,  and decoded using a decoder corresponding to the lossless coder used in the coding. 
     Of course, other combinations of decoding methods are possible. 
     According to one possible variant of  FIG.  12 A , the decoder implementing the decoding method MD 1  could be a decoder of HEVC type and the decoder implementing the decoding method MD 2  could be a decoder of MV-HEVC or 3D-HEVC type. 
     According to one possible variant of  FIG.  12 B , the decoder implementing the decoding method MD 1  could be a decoder of MV-HEVC or 3D-HEVC type and the decoder implementing the decoding method MD 2  could be a coder of HEVC type. 
       FIG.  13    shows the simplified structure of a decoding device DEC designed to implement the decoding method according to any one of the particular embodiments of the invention. 
     According to one particular embodiment of the invention, the actions performed by the decoding method are implemented by computer program instructions. To that end, the decoding device DEC has the conventional architecture of a computer and comprises in particular a memory MEM_D, a processing unit UT_D, equipped for example with a processor PROC_D, and driven by the computer program PG_D stored in memory MEM_D. The computer program PG_D comprises instructions for implementing the actions of the decoding method such as described above when the program is executed by the processor PROC_D. 
     On initialization, the code instructions of the computer program PG_D are for example loaded into a RAM memory (not shown), before being executed by the processor PROC_D. The processor PROC_D of the processing unit UT_D implements in particular the actions of the decoding method described above, according to the instructions of the computer program PG_D. 
     According to one embodiment, the decoding device DEC is for example comprised in a terminal. 
     8. EXEMPLARY APPLICATIONS OF THE INVENTION TO AN IMAGE PROCESSING 
     As already explained above, the N reconstructed images IVD 1 , . . . , IVD n  and IVTD n+1 , . . . , IVTD N  may be used to synthesize an image of an intermediate view required by a user. 
     As shown in  FIG.  14   , in the case where a user requires the synthesis of an image of an arbitrary view, the n first reconstructed images of views IVD 1 , . . . , IVD n  which are considered to be master views, are transmitted in S 1  to an image synthesis module. 
     The N-n reconstructed processed images of views IVTD n+1 , . . . , IVTD N , in order to be able to be used in the synthesis of images, as additional images of the views, may need to be processed in S 2 , using decoded image processing description information, which are respectively associated therewith. 
     On completion of the processing S 2 , N-n reconstructed images of views IVD n+1 , . . . , IVD N  are obtained. 
     The N-n reconstructed images IVD n+1 , . . . , IVD N  are then transmitted in S 3  to the image synthesis module. 
     In S 4 , an image of a view is synthesized using at least one of the images IVD 1 , . . . , IVD n  of the n first reconstructed views and potentially at least one of the N-n images IVD n+1 , . . . , IVD N  of the N-n reconstructed views. 
     An image of a synthesized view IV SY  is then obtained on completion of the synthesis S 4 . 
     It should be noted that the n reconstructed images IVD 1 , . . . , IVD n  may also undergo a processing S 2 . Such a processing S 2  may prove to be necessary, in the case where the user UT requires an image of a view of which the viewing angle represented does not correspond to the one or more viewing angles of the n reconstructed images IVD 1 , . . . , IVD n . The user UT could for example request an image of a view representing a field of view of 120×90, whereas the n reconstructed images IVD 1 , . . . , IVD n  each represent a viewing angle of 360×180. Such a possibility of processing for the reconstructed images IVD 1 , . . . , IVD n  is represented by dashed arrows in  FIG.  14   . Additionally, in relation to the types of processing described with reference to  FIGS.  8  and  9   , the reconstructed images IVD 1 , . . . , IVD n  may be used during the processing of the N-n other images IV n+1 , . . . , IV N . 
     A first embodiment of a processing applied to the data of a reconstructed processed image IVTD k  will now be described with reference to  FIGS.  15 A to  15 C . Such a processing consists in obtaining the initial resolution of the image IV k  of the corresponding view which has been sampled before being coded in C 11   b  in  FIG.  1   . 
     In the example of  FIG.  15 A , it is assumed that the processing applied before coding is a downsampling of a region Z 4  of the image IV k , in a vertical direction, as shown in  FIG.  5 A . 
     The processing applied to the reconstructed processed image IVTD k  consists in applying an upsampling to the region Z 4 , corresponding to the downsampling applied in  FIG.  5 A , so as to return to the initial resolution of the image IV k , using the information describing the downsampling applied, such as in particular:
         the downsampling factor used, which makes it possible to determine the corresponding upsampling factor,   the downsampling direction used, which makes it possible to determine the corresponding upsampling direction,   the location of the downsampled region Z 4  in the image IV k .       

     In the example of  FIG.  15 B , it is assumed that the processing applied before coding is a downsampling of a region Z 5  of the image IV k , in a horizontal direction, as shown in  FIG.  5 B . 
     The processing applied to the reconstructed processed image IVTD k  consists in applying an upsampling to the region Z 5 , corresponding to the downsampling applied in  FIG.  5 B , so as to return to the initial resolution of the image IV k , using the information describing the downsampling applied, such as in particular:
         the downsampling factor used, which makes it possible to determine the corresponding upsampling factor,   the downsampling direction used, which makes it possible to determine the corresponding upsampling direction,   the location of the downsampled region Z 5  in the image IV k .       

     In the example of  FIG.  15 C , it is assumed that the processing applied before coding is a downsampling of the entire image IV k , as shown in  FIG.  5 C . 
     The processing applied to the reconstructed processed image IVTD k  consists in applying an upsampling to all of the image data of the image IVTD k , corresponding to the downsampling applied in  FIG.  5 C , so as to return to the initial resolution of the image IV k , using the information describing the downsampling applied, such as in particular:
         the downsampling factor used, which makes it possible to determine the corresponding upsampling factor,   the downsampling direction used, which makes it possible to determine the corresponding upsampling direction.       

     In the example of  FIG.  15 D , it is assumed that the processing applied before coding is a downsampling of a region Z 6  of the image IV k , in both a horizontal direction and a vertical direction, as shown in  FIG.  5 D . 
     The processing applied to the reconstructed processed image IVTD k  consists in applying an upsampling to the region Z 6 , corresponding to the downsampling applied in  FIG.  5 D , so as to return to the initial resolution of the image IV k , using the information describing the downsampling applied, such as in particular:
         the downsampling factor used, which makes it possible to determine the corresponding upsampling factor,   the downsampling direction used, which makes it possible to determine the corresponding upsampling direction,   the location of the downsampled region Z 6  in the image IV k .       

     With reference to  FIG.  16   , a second embodiment of a processing applied to the data of a reconstructed processed image IVTD k  will now be described. Such a processing consists in restoring one or more contours of the image IV k  of the view which has been filtered before coding of the latter. 
     In the example of  FIG.  16   , it is assumed that the processing applied before coding is a filtering of the contours ED 1  and ED 2  of the image IV k , as shown in  FIG.  6   . 
     The processing applied to the image of the reconstructed processed view IVTD k  then consists in restoring the contours ED 1  and ED 2  of the image IV k , using the information describing the filtering applied, such as in particular the predefined value for each unfiltered pixel, in particular the predefined value YUV=000. 
     With reference to  FIG.  17   , a third embodiment of a processing applied to the data of a reconstructed processed image IVTD k  will now be described. Such a processing consists in reconstructing pixels of the image IV k  of the view which, before coding, have been calculated in accordance with the embodiment of the processing of  FIG.  8   . 
     The processing applied to the reconstructed processed image IVTD k  then consists:
         in retrieving pixels of the image IV k  of the view which have been calculated in the coding, using an indicator of the pixels of the image IV k  of said view which have been calculated, such an indicator being read in the data signal,   in retrieving pixels of an image of at least one other view IV j  (1≤j≤n) which has been reconstructed using the first decoding method MD 1 , using the information on the location, in the image IV j , of the pixels which have been used to calculate the pixels of the image IV k ,   and potentially in retrieving pixels of an image IV l  (n+1≤l≤N) of at least one other view, for which processed pixels have been decoded using the second decoding method MD 2 .       

     The decoding of the processed data DT k  then consists in calculating the pixels of the image IV k :
         on the basis of the pixels of the image of at least one other view IV j  (1≤j≤n),   and potentially on the basis of the pixels of the image IV l  (n+1≤l≤N) of at least one other view.       

     The aforementioned calculation consists for example in combining the pixels of the image IV k , with the pixels of the reconstructed image IV j  and potentially with the pixels of the reconstructed image IV l . 
     With reference to  FIG.  18   , a fourth embodiment of a processing applied to the data of a reconstructed processed image IVTD k  will now be described. Such a processing consists in reconstructing pixels of the image IV k  of the view which, before coding, have been calculated in accordance with the embodiment of the processing of  FIG.  9   . 
     A processing is first applied to the reconstructed image IVD one  according to the second decoding method MD 2 . It then consists in reconstructing, on the basis of the image IVD one , the pixels of the image IV k :
         on the basis of the processed data DT′ k  of the image IV k  which have been decoded according to the second decoding method MD 2 ,   on the basis of the processed data DT s  of an image IVD s  of a view V S  (1≤s≤N), which have been decoded.       

     9. EXEMPLARY CONCRETE APPLICATIONS OF THE INVENTION 
     According to a first example, it is considered that six images of the views with a resolution of 4096×2048 pixels are captured, respectively, by six cameras of 360° type. A depth estimation method is applied to provide six corresponding 360° depth maps. 
     The image IV 0 , of the view V 0 , is coded conventionally using the first coding method MC 1 , while the five other images IV 1 , IV 2 , IV 3 , IV 4 , IV 5  of the views V 1 , V 2 , V 3 , V 4 , V 5  undergo a cropping before coding. The processing applied to each of the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5  consists in removing a fixed number of columns, for example  200 , on the right and on the left of each of these images. The number of columns to be removed has been selected such that the viewing angle is reduced from 360° to 120°. Similarly, the processing applied to each of the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5  consists in deleting a fixed number of rows, for example 100, from the top and bottom portions, respectively, of each of these images. The number of rows to be deleted has been selected such that the viewing angle is reduced from 180° to 120°. 
     An item of information flag_proc is set to 0, in association with the image IV 0 , and an item of information flag_proc is set to 1, in association with the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5 . 
     The image of the view IV 0  is coded using an HEVC coder. A single data signal F 1   0  is generated, said data signal containing the coded original data of the image IV 0 , and the information flag_proc=0. 
     The data of the regions remaining after cropping of each of the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5  are coded using an HEVC coder. Five data signals F 2   1 , F 2   2 , F 2   3 , F 2   4 , F 2   5 , which contain, respectively, the coded data of the regions remaining after cropping of each of the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5 , in association with the information flag_proc=1, are generated. The data signals F 1   0 , F 2   1 , F 2   2 , F 2   3 , F 2   4 , F 2   5  are concatenated, then transmitted to a decoder. 
     The five data signals F 2   1 , F 2   2 , F 2   3 , F 2   4 , F 2   5  may additionally comprise the coordinates of the cropped regions in the following way: 
     IV 1 , IV 2 , IV 3 , IV 4 , IV 5 : flag_proc=1, point top_left (h, v)=(0+200, 0+100), point bot_right (h, v)=(4096−200, 2048−100), with “h” for horizontal and “v” for vertical. 
     At the decoder, the information flag_proc is read. 
     If flag_proc=0, the image of the view IV 0  is reconstructed using an HEVC decoder. 
     If flag_proc=1, the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5 , corresponding to the coded processed data, are reconstructed using an HEVC decoder. No processing is applied to the images IV 1 , IV 2 , IV 3 , IV 4 , IV 5  which have been reconstructed because it is not possible to reconstruct the data of these images which have been deleted by cropping. However, a synthesis algorithm uses the six images IV 0 , IV 1 , IV 2 , IV 3 , IV 4 , IV 5  which have been reconstructed in order to generate an image of an arbitrary view required by a user. 
     In the case where the five data signals F 2   1 , F 2   2 , F 2   3 , F 2   4 , F 2   5  additionally comprise the coordinates of the cropped regions, these coordinates are used by the synthesis algorithm to generate an image of a view required by a user. 
     According to a second example, 10 images IV 0 , . . . , IV 9  with a respective resolution 4096×2048 pixels are considered which are generated by computer in order to simulate 10 cameras of 360° type. It is decided not to process the images IV 0  and IV 9 . The texture components of the images IV 1  to IV 8  undergo for their part a downsampling by a factor of 2 in the horizontal direction and by a factor of 2 in the vertical direction and the corresponding depth components undergo for their part a downsampling by a factor of 4 in the horizontal direction and by a factor of 4 in the vertical direction. As a result, the resolution of the texture components of the images IV 1  to IV 8  becomes 2048×1024 and the resolution of the depth components of the images IV 1  to IV 8  becomes 1024×512. 
     The processing data, such as the image data relating to the images IV 1  to IV 8  contain the 8 downsampled texture components of resolution 2048×1024 of the images IV 1  to IV 8  and the 8 downsampled depth components of resolution 1025×512 of the images IV 1  to IV 8 . 
     Additionally, the aforementioned processing data contain data of text type which indicate the downsampling factors for each image IV 1  to IV 8  of the views 1 to 8. They are written as follows:
         IV 1  to IV 8  texture: se_h=2, se_v=2 (“se” for downsampling, “h” for horizontal and “v” for vertical),   IV 1  to IV 8  depth: se_h=4, ss_v=4.       

     An item of information flag_proc is set to 0, in association with the images IV 0  and IV 9 , and an item of information flag_proc is set to 1, in association with the images IV 1  to IV 8 . 
     The images IV 0  and IV 9  are coded simultaneously using a coder of MV-HEVC type, which generates a single data signal F 1  containing the information flag_proc=0 and the coded original data of the images IV 0  and IV 9 . 
     The processing data, such as the image data relating to the images IV 1  to IV 8 , containing the 8 downsampled texture components of resolution 2048×1024 of the images IV 1  to IV 8  and the 8 downsampled depth components of resolution 1025×512 of the images IV 1  to IV 8 , are also coded simultaneously, using a coder of MV-HEVC type, which generates a single data signal F 2  containing the information flag_proc=1, in association with the coded downsampled texture and depth data. The data of text type which indicate the downsampling factors for each image IV 1  to IV 8  of the views 1 to 8 are for their part coded losslessly. The data signals F 1  and F 2  are concatenated, then transmitted to a decoder. 
     At the decoder, the information flag_proc is read. 
     If flag_proc=0, the images IV 0  and IV 9  are reconstructed simultaneously using an MV-HEVC decoder. Reconstructed images IVD 0  and IVD 9  which are at their initial resolution are then obtained. 
     If flag_proc=1, the images IV 1  to IV 8 , corresponding to their respective coded downsampled texture and depth data, are reconstructed simultaneously using an MV-HEVC decoder. Reconstructed downsampled images IVDT 1  to IVDT 8  are then obtained. The data of text type corresponding to each of the 8 images IV 1  to IV 8  are also decoded, providing the downsampling factors which have been used for each image IV 1  to IV 8 . 
     The reconstructed downsampled images IVDT 1  to IVDT 8  are then processed using their corresponding downsampling factors. On completion of the processing, reconstructed images IVD 1  to IVD 8  are obtained, the 8 respective texture components of which are at their initial resolution 4096×2048 and the 8 respective depth components of which are at their initial resolution 4096×2048. 
     A synthesis algorithm uses the images of the 10 views thus reconstructed at their initial resolution, in order to generate an image of a view required by a user. 
     According to a third example, 3 images IV 0  to IV 2  with a respective resolution 4096×2048 pixels are considered which are generated by computer in order to simulate 4 cameras of 360° type. 3 texture components and 3 corresponding depth components are then obtained. It is decided not to process the image IV 0  and to extract occlusion maps for the images IV 1  and IV 2 , respectively. To that end, a disparity estimate is made between the image IV 1  and the image IV 0  so as to generate the occlusion mask of the image IV 1 , that is to say the pixels of the image IV 1  which are not found in the image IV 0 . A disparity estimate is also made between the image IV 2  and image IV 0  so as to generate the occlusion mask of the image IV 2 . 
     The processing data, such as the image data relating to the images IV 1  and IV 2  contain the 2 texture components of the occlusion masks of the images IV 1  and IV 2  and the 2 depth components of the occlusion masks of the images IV 1  and IV 2 . 
     An item of information flag_proc is set to 0, in association with the image IV 0 , and an item of information flag_proc is set to 1, in association with the images IV 1  and IV 2 . 
     The image IV 0  is coded using an HEVC coder. A single data signal F 1   0  is generated, said data signal containing the coded original data of the image IV 0 , and the information flag_proc=0. 
     The image data (texture and depth) of the occlusion masks of each of the images IV 1 , IV 2  are coded using an HEVC coder. Two data signals F 2   1 , F 2   2 , which contain, respectively, the coded image data of the occlusion masks of each of the images IV 1 , IV 2 , in association with the information flag_proc=1, are generated. The data signals F 1   0 , F 2   1 , F 2   2  are concatenated, then transmitted to a decoder. 
     At the decoder, the information flag_proc is read. 
     If flag_proc=0, the image IV 0  is reconstructed using an HEVC decoder. 
     If flag_proc=1, the images IV 1 , IV 2 , corresponding to the coded image data (texture and depth) of the occlusion masks of each of the images IV 1 , IV 2 , are reconstructed using an HEVC decoder. No processing is applied to the images IV 1 , IV 2  which have been reconstructed because it is not possible to reconstruct the data of these images which have been deleted on completion of the occlusion detection. However, a synthesis algorithm may use the images IV 0 , IV 1 , IV 2  which have been reconstructed in order to generate an image of a view required by a user. 
     According to a fourth example, it is considered that two images IV 0  and IV 1  with a resolution of 4096×2048 pixels are captured, respectively, by two cameras of 360° type. The image IV 0  of the first view is coded conventionally using the first coding method MC 1 , while the image IV 1  of the second view is processed before being coded according to the second coding method MC 2 . Such a processing comprises the following:
         extracting the contours of the image IV 1 , using a filter, such as for example a Sobel filter,   applying an expansion to the contours, for example using a mathematical morphology operator, in order to increase the region around the contours.       

     The processing data, such as the image data relating to the image IV 1 , comprise the pixels inside the region around the contours, and pixels set to 0 corresponding, respectively, to the pixels located outside the region around the contours. 
     Additionally, data of text type are generated, for example in the form of marking information (e.g.: YUV=000) which indicates the setting to 0 of the pixels located outside the region around the contours. The pixels set to 0 will be neither coded nor signaled to the decoder. 
     The image IV 0  is coded using an HEVC coder, which generates a data signal F 1  containing the information flag_proc=0 and the coded original data of the image IV 0 . 
     The image data of the region around the contours of the image IV 1  are coded using an HEVC coder, while the marking information is coded using a lossless coder. A data signal F 2  is then generated, said signal containing the information flag_proc=1, the coded pixels of the region around the contours of the image IV 1  and the item of coded marking information. 
     At the decoder, the information flag_proc is read. 
     If flag_proc=0, the image IV 0  is reconstructed using an HEVC decoder, at its original resolution. 
     If flag_proc=1, the image IV 1 , corresponding to the image data of the region around the contours of the image IV 1 , is reconstructed by means of an HEVC decoder, using the marking information which makes it possible to restore the value set to 0 of the pixels surrounding said region. 
     A synthesis algorithm may use the two images IV 0  and IV 1  which have been reconstructed in order to generate an image of a view required by a user. 
     According to a fifth example, it is considered that four images IV 0  to IV 3  with a resolution of 4096×2048 pixels are captured, respectively, by four cameras of 360° type. The image IV 0  is coded conventionally using the first coding method MC 1 , while the images IV 1  to IV 3  are processed before being coded according to the second coding method MC 2 . Such a processing is a filtering of the images IV 1  to IV 3 , during which a region of interest ROI is calculated. A region of interest contains the one or more regions of each image IV 1  to IV 3  which are considered the most relevant, for example because they contain many details. 
     Such a filtering is carried out according for example to one of the two methods below:
         calculating saliency maps of each image IV 1  to IV 3 , by means of a filtering,   filtering of the depth maps of each image IV 1  to IV 3 : the depth map is characterized, for each texture pixel, by a near or far depth value in the 3D scene. A threshold is defined, such that each pixel of an image IV 1 , IV 2 , IV 3  which is located below this threshold is associated with an object in the scene which is close to the camera. All of the pixels located below this threshold are then considered to be the region of interest.       

     The processing data, such as the image data relating to the images IV 1  to IV 3 , comprise the pixels inside their respective regions of interest, and pixels set to 0 corresponding, respectively, to the pixels located outside these regions of interest. 
     Additionally, data of text type are generated, for example in the form of marking information which indicates the setting to 0 of the pixels located outside the region of interest. The pixels set to 0 will be neither coded nor signaled to the decoder. 
     The image IV 0  is coded using an HEVC coder, which generates a data signal F 1   0  containing the information flag_proc=0 and the coded original data of the image IV 0 . 
     The image data of the region of interest of each image IV 1 , IV 2 , IV 3  are coded using an HEVC coder, while the marking information is coded using a lossless coder. Three data signals F 2   1 , F 2   2 , F 2   3  which contain, respectively, the coded image data of the regions of interest of each of the images IV 1 , IV 2 , IV 3  in association with the information flag_proc=1, and corresponding item of coded marking information, are generated. The data signals F 1   0 , F 2   1 , F 2   2 , F 2   3  are concatenated, then transmitted to a decoder. 
     At the decoder, the information flag_proc is read. 
     If flag_proc=0, the image IV 0  is reconstructed using an HEVC decoder, at its original resolution. 
     If flag_proc=1, each image IV 1  to IV 3 , corresponding to the image data of its respective region of interest, is reconstructed by means of an HEVC decoder, using the marking information, which makes it possible to restore the value set to 0 of the pixels surrounding said region. 
     A synthesis algorithm may directly use the four images IV 0 , IV 1 , IV 2 , IV 3  which have been reconstructed in order to generate an image of a view required by a user. 
     It goes without saying that the embodiments described above have been given purely by way of completely non-limiting indication, and that numerous modifications may be easily made by a person skilled in the art without otherwise departing from the scope of the invention.