Methods, apparatus and systems for encoding and decoding of multi-channel Ambisonics audio data

An apparatus for decoding an encoded bitstream of multi-channel audio data and associated metadata, the apparatus comprising:

• a decoder configured to decode the encoded bitstream of multi-channel audio data into multi-channel audio data and associated metadata;
• a detecting unit for detecting, based on the associated metadata, that the multi-channel audio data includes a first set of channels in a first Ambisonics format and a second set of channels in a format other than Ambisonics;
• and
• a processing unit configured to transform, using the associated metadata, the first set of channels in the first Ambisonics format to a second Ambisonics format,
• wherein the associated metadata further includes re-mixing information comprising a mixing matrix, wherein the mixing matrix includes mixing weights to transform the first Ambisonics format to the second Ambisonics format and mixing weights to transform the second set of channels to the format other than Ambisonics.

A method for encoding audio data, comprising:

• encoding Ambisonics audio data and other audio data into encoded multi-channel audio data, wherein the Ambisonics audio data is encoded based on a first Ambisonics format;
• determining auxiliary data that includes re-mixing information, the re-mixing information comprising a mixing matrix, wherein the mixing matrix includes mixing weights to transform the Ambisonics audio data from the first Ambisonics format to a second Ambisonics format and mixing weights to transform the other audio data to a format other than Ambisonics;
• and
• transmitting a bitstream containing the encoded multi-channel audio data and associated metadata relating to the auxiliary data.

An apparatus for encoding audio data, comprising:

• an encoder configured to encode Ambisonics audio data and other audio data into encoded multi-channel audio data, wherein the Ambisonics audio data is encoded based on a first Ambisonics format;
• a processing unit configured determine auxiliary data that includes re-mixing information for re-mixing the encoded multi-channel audio data into the Ambisonics audio data, the remixing information comprising a mixing matrix, wherein the mixing matrix includes mixing weights to transform the first Ambisonics format into a second Ambisonics format and mixing weights to transform the other audio data into a format other than Ambisonic;
• and
• transmitting a bitstream containing the encoded multi-channel audio data and associated metadata relating to the auxiliary data.