Partial Video Decoding Method, Device and System

A decoding device comprising

• a controller, configured to indicate a selection of a sub-array of a spatial array of independently decodable slices in a first video stream that comprises video images encoded on the basis of a video codec, preferably on the basis of the HEVC codec, said video images having an image region and being divided into the spatial array, said spatial-array preferably associated with a first picture size, the first video stream comprising network abstraction layer units that each contain video data for a respective slice preceded by a header, preferably a slice header, that comprises parameters relating to the respective slice in relation to the first video stream;
• a stream pre-processor, configured to receive meta data and network abstraction layer units that comprise the encoded video data for the respective slices in the sub-array, the meta data indicating one or more locations in the network abstraction layer units, said locations preferably comprising an indication of the spatial location of one or more slices, the stream pre-processor being configured to partially rewrite the network abstraction layer units for the sub-array of slices into rewritten network abstraction layer units, at a location in each of the respective network abstraction layer units, said location being preferably in said header, wherein said location is selected on the basis of the meta data, said location preferably comprising an indication of the spatial location of one or more slices, the rewritten network abstraction layer units forming a second video stream that comprises encoded video data only for the subarray of slices, said encoded video data representing partial video images that comprise a sub region of said image region, and wherein said rewritten network abstraction layer units are decodable into said partial video images on the basis of said video codec;
• a decoder, with an input coupled to the stream pre-processor, and configured to decode said rewritten network abstraction layer units, the decoder being initialized for a second picture size associated with said sub-array, wherein said second picture size is smaller than said first picture size.

A decoding system for decoding partial video images from a first video stream that encodes full video images divided into a spatial array of independently decodable slices, wherein the first video stream comprises network abstraction layer units that each contain video content data for a respective one of the slices preceded by a header that comprises parameters relating to the respective one of the slices in relation to the first video stream, and wherein information defining versions of network abstraction layer units corresponding to derived streams with differently sized images are provided, the decoding system comprising

• a storage system;
• a controller, configured to indicate a selection of a sub-array of a spatial array of independently decodable slices in the first video stream;
• a stream generator, configured to retrieve the information defining versions of the network abstraction layer units from the storage system and to obtain the versions of the network abstraction layer units with video content data corresponding to the first video stream and headers for network abstraction layer units of a second video stream with an image size corresponding to the selected sub-array, based on the retrieved information;
• a decoder, with an input coupled to a stream pre-processor, and configured to decode partial video images containing only video data from the sub-array, from the obtained versions of the network abstraction layer units.