Data structure for higher order ambisonics audio data

1. A non-transitory machine readable medium containing a data structure for Higher Order Ambisonics (HOA) audio data including Ambisonics coefficients, which data structure includes 2D, or 3D, or both 2D and 3D, spatial audio content data for one or more different HOA audio data stream descriptions, and which data structure is also suited for HOA audio data that have on order of greater than ‘3’, and which data structure in addition can include single audio signal source data, or microphone array audio data, or both single audio signal source data and microphone array audio data, from fixed or time-varying spatial positions,

wherein said different HOA audio data stream descriptions are related to at least two of different loudspeaker position densities, coded HOA wave types, HOA orders and HOA dimensionality, and

wherein one HOA audio data stream description contains audio data for a presentation with a given loudspeaker arrangement located at a distinct area of a presentation site, and another HOA audio data stream description contains audio data for a presentation with a different loudspeaker arrangement surrounding said presentation site, wherein said different loudspeaker arrangement has a loudspeaker position density that is lower than that of said given loudspeaker arrangement.

2. The medium according to claim 1 , wherein said audio data for said given loudspeaker arrangement represent sphere waves and a first Ambisonics order, and said audio data for said different loudspeaker arrangement represent plane waves, or a second Ambisonics order, or both plane waves and a second Ambisonics order, wherein said second Ambisonics order is smaller than said first Ambisonics order.

3. The medium according to claim 1 , wherein said data structure serves as scene description where tracks of an audio scene can start and end at any time.

4. The medium according to claim 1 , wherein said data structure includes data items regarding one or more of a:

region of interest related to audio sources outside or inside a listening area;

normalization of spherical basis functions;

propagation directivity;

Ambisonics coefficient scaling information;

Ambisonics wave type, including a plane or spherical type;

in case of spherical waves, reference radius for decoding.

5. The medium according to claim 1 , wherein said Ambisonics coefficients are complex coefficients.

6. The medium according to claim 1 , wherein said data structure includes at least one of a metadata regarding the directions and characteristics for one or more microphones, and an encoding vector for single-source input signals.

7. The medium according to claim 1 , wherein

at least part of said Ambisonics coefficients are bandwidth-reduced, so that for different HOA orders the bandwidth of the related Ambisonics coefficients is different.

8. The medium according to claim 7 , wherein said bandwidth reduction is based on modified discrete cosine transform (MDCT) processing.

9. The medium according to claim 1 , wherein said presentation site is a listening or seating area in a cinema.

10. Method for encoding and arranging data for a data structure contained in a medium according to claim 1 .

11. Method for audio presentation, comprising:

receiving a Higher Order Ambisonics (HOA) audio data stream containing at least two different HOA audio data signals,

wherein at least a first one of the signals is used for presentation with a given loudspeaker arrangement located at a distinct area of a presentation site, and

wherein at least a second and different one of the signals is used for presentation with a different loudspeaker arrangement surrounding said presentation site, wherein said different loudspeaker arrangement has a loudspeaker position density that is lower than that of said given loudspeaker arrangement.

12. Method according to claim 11 , wherein said audio data for said given loudspeaker arrangement represent sphere waves and a first Ambisonics order, and said audio data for said different loudspeaker arrangement represent plane waves, or a second Ambisonics order, or both plane waves and a second Ambisonics order, wherein said second Ambisonics order is smaller than said first Ambisonics order.

13. Method according to claim 11 , wherein said presentation site is a listening or seating area in a cinema.

14. Apparatus for audio presentation, comprising:

means for receiving a Higher Order Ambisonics (HOA) audio data stream containing at least two different HOA audio data signals;

means for processing at least a first one of the signals for presentation with a given loudspeaker arrangement located at a distinct area of a presentation site; and

means for processing a second and different one of the signals for presentation with a different loudspeaker arrangement surrounding said presentation site, wherein said different loudspeaker arrangement has a loudspeaker position density that is lower than that of said given loudspeaker arrangement.