Multi-Layer Video Stream Encoding and Decoding

Abstract

Multi-layer dependencies are signaled in an efficient way for a multi-view video stream ( 1 ). Coding or decoding relationship information defining coding or decoding dependencies is represented in bit-efficient syntax code, preferably through usage of hierarchical layer dependencies using layer indices for representing layer dependencies.

1 . A method, in a processing circuit, of determining decoding relationships for a digitally coded multi-layer video stream defining multiple layers of pictures, said method comprising:
 retrieving, based on said digitally coded multi-layer video stream, a direct decoding flag indicating a direct coding relationship between a layer with layer index i of said multiple layers and a layer with layer index j of said multiple layers, where i is not equal to j; and   determining information defining an indirect decoding relationship between the layer index i and a layer of said multiple layers other than the layer with layer index j, based on said at least one direct decoding flag.   
     
     
         2 . The method of  claim 1 , wherein
 retrieving said at least one direct decoding flag comprises retrieving, for said layer with layer index i, a respective direct dependency flag for each layer index k based on said coded multi-layer video stream, wherein k<i and said direct dependency flag indicates whether said layer with layer index k is a direct reference layer for said layer with layer index i; and   wherein determining said information comprises determining information defining the layer with layer index j<i which said layer with layer index i depends on, based on said direct dependency flags.   
     
     
         3 . The method of  claim 1 , wherein retrieving the direct decoding flag comprises retrieving, from a video parameter set or video parameter set extension associated with said coded multi-layer video stream, the direct decoding flag indicating said direct coding relationship between said layer with layer index i and said layer with layer index j. 
     
     
         4 . A method, in a processing circuit, of decoding a digitally coded multi-layer video stream defining multiple layers of pictures, each layer of said multiple layers having a respective layer identifier, said method comprising:
 retrieving, for a layer with a layer index of said multiple layers, decoding relationship information based on said digitally coded multi-layer video stream, said decoding relationship information defining a respective layer index of each reference layer of said multiple layers on which said layer directly depends;   mapping, for each reference layer and for said layer, its layer index to a layer identifier based on mapping information of a hierarchical mapping relationship between layer identifiers and layer indices, wherein said mapping information is retrieved based on said digitally coded multi-layer video stream; and   decoding a picture of said layer based on at least one previously decoded picture in a layer of said multiple layers identified based on said layer identifiers mapped from layer indices.   
     
     
         5 . The method of  claim 4 , wherein retrieving the decoding relationship information comprises:
 retrieving, based on said coded multi-layer video stream, at least one direct decoding flag indicating a direct coding relationship between a layer with layer index i of said multiple layers and a layer with layer index j of said multiple layers, where i is not equal to j; and   determining information defining an indirect decoding relationship between the layer index i and a layer of said multiple layers other than the layer with layer index j, based on said at least one direct decoding flag.   
     
     
         6 . The method of  claim 5 , wherein retrieving the direct decoding flag comprises retrieving, from a video parameter set or video parameter set extension associated with said coded multi-layer video stream, the direct decoding flag indicating said direct coding relationship between said layer with layer index i and said layer with layer index j. 
     
     
         7 . A device configured to determine decoding relationships for a digitally coded multi-layer video stream defining multiple layers of pictures, said device comprising a non-transitory computer readable medium and an associated processor configured to process computer program instructions stored in the computer readable medium, wherein the stored computer program instructions, when run on said processor, are configured to cause the processor to:
 retrieve, based on said digitally coded multi-layer video stream, a direct decoding flag indicating a direct coding relationship between a layer with layer index i of said multiple layers and a layer with layer index j of said multiple layers, where i is not equal to j; and   determine information defining an indirect decoding relationship between the layer index i and a layer of said multiple layers other than the layer with layer index j, based on said at least one direct decoding flag.   
     
     
         8 . The device of  claim 7 , wherein the stored computer program instructions are configured to cause the processor to:
 retrieve, for said layer with layer index i, a respective direct dependency flag for each layer index k based on said coded multi-layer video stream, wherein k<i and said direct dependency flag indicates whether said layer with layer index k is a direct reference layer for said layer with layer index i; and   determine information defining the layer with layer index j<i which said layer with layer index i depends on, based on said direct dependency flags.   
     
     
         9 . The device of  claim 7 , wherein the stored computer program instructions are configured to cause the processor to retrieve, from a video parameter set or video parameter set extension associated with said coded multi-layer video stream, the direct decoding flag indicating said direct coding relationship between said layer with layer index i and said layer with layer index j. 
     
     
         10 . A decoder device configured to decode a coded multi-layer video stream defining multiple layers of pictures, each layer of said multiple layers having a respective layer identifier, said decoder comprising a non-transitory computer readable medium and an associated processor configured to process computer program instructions stored in the computer readable medium, wherein the stored computer program instructions, when run on said processor, are configured to cause the processor to:
 retrieve, for a layer with a layer index of said multiple layers, decoding relationship information based on said coded multi-layer video stream, said decoding relationship information defining a respective layer index of each reference layer of said multiple layers on which said layer directly depends;   map, for each reference layer and for said layer, its layer index to a layer identifier based on mapping information of a hierarchical mapping relationship between layer identifiers and layer indices, said mapping information is retrieved based on said coded multi-layer video stream; and   decode a picture of said layer based on at least one previously decoded picture in a layer of said multiple layers identified based on said layer identifiers mapped from layer indices.   
     
     
         11 . The decoder device of  claim 10 , wherein the stored computer program instructions are configured to cause the processor to:
 retrieve, based on said coded multi-layer video stream, at least one direct decoding flag indicating a direct coding relationship between a layer with layer index i of said multiple layers and a layer with layer index j of said multiple layers, where i is not equal to j; and   determine information defining an indirect decoding relationship between the layer index i and a layer of said multiple layers other than the layer with layer index j, based on said at least one direct decoding flag.