Multi-layer video stream decoding

A method of decoding a coded multi-layer video stream defining multiple layers of pictures, each layer of said multiple layers having a respective layer identifier, said method comprises:

• retrieving, 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 any 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, said mapping information is retrieved based on said coded multi-layer video stream;
• determining a type of prediction operation based on at least one scalability identifier of said layer and at least one scalability identifier of said any reference layer;
• 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.

A device for determining decoding relationship for a coded multi-layer video stream defining multiple layers of pictures, said device comprises:

• a flag retriever configured 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, wherein i≠j;
• an information determiner configured to determine information defining any decoding relationship between said multiple layers based on said at least one direct decoding flag;
• and
• a type determiner configured to determine a type of prediction operation based on at least one scalability identifier of said layer with layer index i and at least one scalability identifier of said layer with layer index j.

A device for determining decoding relationship for a coded multi-layer video stream defining multiple layers of pictures, said device comprises a processor configured to process code means of a computer program stored in a computer readable medium, said code means causes, when run on said processor, said 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, wherein i≠j;
• determine information defining any decoding relationship between said multiple layers based on said at least one direct decoding flag;
• and
• determine a type of prediction operation based on at least one scalability identifier of said layer with layer index i and at least one scalability identifier of said layer with layer index j.

A decoder 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 comprises:

• a decoding relationship information retriever configured 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 any reference layer of said multiple layers, on which said layer directly depends;
• an index-to-identifier mapping unit configured to 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;
• a type determiner configured to determine a type of prediction operation based on at least one scalability identifier of said layer and at least one scalability identifier of said any reference layer;
• and
• a decoding unit configured to 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.

A decoder 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 comprises a processor configured to process code means of a computer program stored in a computer readable medium, said code means causes, when run on said processor, said 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 any 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;
• determine a type of prediction operation based on at least one scalability identifier of said layer and at least one scalability identifier of said any reference layer;
• 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.