Method and device for multi-view video decoding and method and device for image processing

1. A decoding method for decoding a data stream representative of a multi-view video, implemented by a decoding device, the method comprising:

obtaining syntax elements from at least one part of the stream data;

reconstructing at least one image of a view of the video from the syntax elements obtained;

receiving a request from an image synthesis module indicating at least one item of metadata required by the image synthesis module, said at least one item of metadata being associated with said at least one reconstructed image, and said at least one item of metadata corresponding to a map associated to said at least one reconstructed image;

obtaining said at least one item of metadata from at least one syntax element; and

providing said at least one item of metadata to the image synthesis module, said image synthesis module being configured to synthesize at least one virtual view, distinct from the views of the multi-view video, from said at least one reconstructed image and said at least one item of metadata.

2. The decoding method according to claim 1 , wherein obtaining at least one item of metadata further comprises calculating said at least one item of metadata from at least one part of the syntax elements.

3. The decoding method according to claim 1 , wherein said at least one item of metadata is not used for reconstructing the at least one image.

4. The decoding method according to claim 1 , wherein the metadata are obtained in a predetermined form corresponding to an indexed table in which at least one item of metadata is stored in association with an index.

5. The decoding method according to claim 1 , wherein said at least one item of metadata is obtained based on a granularity level specified in the decoding device.

6. The decoding method according to claim 1 , wherein the request comprises at least one index indicating the required item of metadata among a predetermined list of available metadata.

7. A device for decoding a data stream representative of a multi-view video, wherein the device comprises:

a processor; and

a non-transitory computer-readable medium comprising instructions stored thereon which when executed by the processor configure the decoding device to:

obtain syntax elements from at least one part of the stream data;

reconstruct at least one image of a view of the video from the syntax elements obtained;

receive a request from an image synthesis module indicating at least one item of metadata required by the image synthesis module, said at least one item of metadata being associated with said at least one reconstructed image, and said at least one item of metadata corresponding to a map associated to said at least one reconstructed image;

obtain said at least one item of metadata in a predetermined form from at least one syntax element; and

provide said at least one item of metadata to the image synthesis module, said image synthesis module being configured to synthesize at least one virtual view, distinct from the views of the multi-view video, from said at least one reconstructed image and said at least one item of metadata.

8. An image synthesis method implemented by a synthesis device, the method comprising:

generating at least one image of a virtual view, from at least one image of a view of a multi-view video decoded by a decoding device, said virtual view being distinct from views of the multi-view video, by:

sending to the decoding device a request indicating at least one item of metadata required to generate the at least one image of a view, said at least one item of metadata being associated with said at least one image of a view, and said at least one item of metadata corresponding to a map associated to said at least one image of a view;

reading said at least one item of metadata, said at least one item of metadata being obtained by the decoding device from at least one syntax element obtained from a data stream representative of a multi-view video; and

generating said at least one image of a virtual view comprising using said at least one read item of metadata and said decoded image.

9. An image synthesis device configured to generate at least one image of a virtual view, from at least one image of a view of a multi-view video decoded by a decoding device, said virtual view being distinct from views of the multi-view video, the image synthesis device comprising:

a processor; and

a non-transitory computer-readable medium comprising instructions stored thereon which when executed by the processor configure the image synthesis device to:

send to the decoding device a request indicating at least one item of metadata required to generate the at least one image of a view, said at least one item of metadata being associated with said at least one image of a view, and said at least one item of metadata corresponding to a map associated to said at least one image of a view;

read said at least one item of metadata, said at least one item of metadata being obtained by the decoding device from at least one syntax element obtained from a data stream representative of a multi-view video; and

generate said at least one image using said at least one read item of metadata and said decoded image.

10. A non-transitory computer-readable medium comprising a computer program stored thereon comprising instructions for implementing a decoding method when said program is executed by a processor of a decoding device, wherein the instructions configure the decoding device to:

decode a data stream representative of a multi-view video by:

obtaining syntax elements from at least one part of the stream data;

reconstructing at least one image of a view of the video from the syntax elements obtained;

receiving a request from an image synthesis module indicating at least one item of metadata required by the image synthesis module, said at least one item of metadata being associated with said at least one reconstructed image, and said at least one item of metadata corresponding to a map associated to said at least one reconstructed image;

obtaining said at least one item of metadata from at least one syntax element; and

providing said at least one item of metadata to the image synthesis module, said image synthesis module being configured to synthesize at least one virtual view, distinct from the views of the multi-view video, from said at least one reconstructed image and said at least one item of metadata.