Method of reading and generating a video stream containing compressed and encrypted images

Method of reading a video stream containing compressed and encrypted images, characterized in that this method comprises: - receiving (92) a video stream containing compressed and tile-encrypted images, a compressed and tile-encrypted image being an image divided into several contiguous tiles, each one defined by respective coordinates in the image, forming the union of these contiguous tiles an overlay of the entire surface of this image, each image tile in the video stream being associated with a first range of bits, which is called "high quality variant", compressed and encrypted, which is the only one to encode the information necessary to build a so-called "high quality" version of the part of the image located within this mosaic, this compressed and encrypted variant being able to high-quality encrypted be decrypted and decompressed independently of high-quality encrypted and compressed variants, associated with other tiles that do not have the same coordinates, - for each compressed and tiled encrypted image: - the acquisition (94) of the coordinates of the tiles that divide the image, - the acquisition (110) of the coordinates of a point of interest in the image, - the selection (112), from the acquired coordinates of the tiles and of the point of interest, of the mosaic or mosaics closest to the point of interest, the number of mosaics thus selected being strictly less than the total number of mosaics that divide this image, to obtain selected and non-selected mosaics, - for each selected tile, the decryption (118) and decompression (120) of the high quality variant, compressed and encrypted, associated with this selected tile, and for each unselected tile, the absence of decryption of the high quality variant quality, compressed and encrypted, associated with this unselected tile, and then - for each compressed and encrypted tiled image: - building (130) the high-quality version for each part of this image located within a tile selected from the decrypted and decompressed high-quality variant associated with this selected tile, - building (130) a version different, called "degraded", for each part of this image located within an unselected tile regardless of the high-quality, compressed and encrypted variant associated with this unselected tile, and then - the assembly (132) of these different image parts built to form the decrypted and decompressed image of the video stream where only some parts, selected based on the coordinates of the point of interest, contain the high quality version while that the other parts contain the downgraded version, where: - the received video stream (92) also includes, associated with each of the mosaics, a second range of bits, called "degraded variant", compressed and different from the high quality variant, compressed and encrypted, associated with this same mosaic, this degraded compressed variant being the only one that encodes the information necessary to build a so-called "degraded" version of the part of the image located within this mosaic, this compressed degraded variant being able to be decompressed, independently, from the associated degraded compressed variants for other tiles that do not have the same coordinates and independently of the high-quality compressed and encrypted variant associated with the same tile, encoding the compressed degraded variant the information about the content of the high-quality version of the part of the image located within the tile with which it is associated but in insufficient quantity to allow by itself to reconstruct this high-quality version, - for each tile unselected, the method comprises decompressing (126) the compressed degraded variant associated with this unselected tile in the received video stream, and then - building (130) the degraded version of each part of the image located within an unselected tile, comprising building this degraded version from the decompressed degraded variant associated with this unselected tile.