Method and device for metadata for multi-channel or sound-field audio signals

An apparatus for pre-processing audio data, comprising:

• a pre-processor for transforming audio data of a first Higher-Order Ambisonics (HOA) format comprising of HOA time-domain coefficients to a common HOA format audio data which relates a multi-channel representation of the first HOA format audio data;
• a transmission unit for transmitting the common HOA format audio data and metadata that indicates a coding mode of the common HOA format audio data.

A method for post-processing audio data, comprising:

• receiving audio data of a common HOA format and metadata that indicates that the audio data is based on the common HOA format;
• extracting, based on the metadata, information about a first HOA format audio data;
• converting the common format HOA audio data to the first HOA format audio data based on the information about the first HOA format audio data.

An apparatus for post-processing audio data, the apparatus comprising

• a receiver for receiving audio data of a common HOA format and metadata that indicates that the audio data is based on the common HOA format;
• an extraction unit for extracting, based on the metadata, information about a first HOA format audio data;
• a processing unit for converting the common format HOA audio data to the first HOA format audio data based on the information about the first HOA format audio data.