Layered coding for compressed sound or sound field representations
The present document relates to a method of layered encoding of a compressed sound representation of a sound or sound field. The compressed sound representation comprises a basic compressed sound representation comprising a plurality of components, basic side information for decoding the basic compressed sound representation to a basic reconstructed sound representation of the sound or sound field, and enhancement side information including parameters for improving the basic reconstructed sound representation. The method comprises sub-dividing the plurality of components into a plurality of groups of components and assigning each of the plurality of groups to a respective one of a plurality of hierarchical layers, the number of groups corresponding to the number of layers, and the plurality of layers including a base layer and one or more hierarchical enhancement layers, adding the basic side information to the base layer, and determining a plurality of portions of enhancement side information from the enhancement side information and assigning each of the plurality of portions of enhancement side information to a respective one of the plurality of layers, wherein each portion of enhancement side information includes parameters for improving a reconstructed sound representation obtainable from data included in the respective layer and any layers lower than the respective layer. The document further relates to a method of decoding a compressed sound representation of a sound or sound field, wherein the compressed sound representation is encoded in a plurality of hierarchical layers that include a base layer and one or more hierarchical enhancement layers, as well as to an encoder and a decoder for layered coding of a compressed sound representation.
1. A method of decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or sound field, the method comprising:
receiving a bit stream containing the compressed HOA representation, wherein the bit stream comprises a plurality of hierarchical layers that include a base layer and two or more hierarchical enhancement layers, and wherein the bit stream further comprises basic side information that is associated with the base layer and enhancement side information that is associated with the two or more hierarchical enhancement layers,
wherein the two or more hierarchical enhancement layers comprises a highest usable hierarchical enhancement layer;
determining that no coefficient sequences of the original HOA representation are contained in a basic compressed sound representation of the base layer and, based on this determination, determining that dependent basic side information for each vector-based signal consists of all the vector components and has its greatest size; and
decoding the compressed HOA representation based on the dependent basic side information that is associated with the base layer and based on the portion of the enhancement side information that is associated with the highest usable hierarchical enhancement layer, and not based on a second portion of the enhancement side information that is associated with any other layer of the two or more hierarchical enhancement layers.
2. A non-transitory carrier medium carrying computer executable code that, when executed on a processor, causes the processor to perform a method according to claim 1 .
3. An apparatus for decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or sound field, the apparatus comprising:
a receiver for receiving a bit stream containing the compressed HOA representation, wherein the bit stream comprises a plurality of hierarchical layers that include a base layer and two or more hierarchical enhancement layers, and wherein the bit stream further comprises basic side information that is associated with the base layer and enhancement side information that is associated with the two or more hierarchical enhancement layers,
wherein the two or more hierarchical enhancement layers comprises a highest usable hierarchical enhancement layer;
a processor for determining that no coefficient sequences of the original HOA representation are contained in a basic compressed sound representation of the base layer and, based on this determination, determining that dependent basic side information for each vector-based signal consists of all the vector components and has its greatest size;
a decoder for decoding the compressed HOA representation based on the dependent basic side information that is associated with the base layer and based on the portion of the enhancement side information that is associated with the highest usable hierarchical enhancement layer, and not based on a second portion of the enhancement side information that is associated with any other layer of the two or more hierarchical enhancement layers.