Coding of audio scenes

1. A method for encoding a time/frequency tile of an audio scene which at least comprises N audio objects, the method comprising:

receiving the N audio objects;

generating M downmix signals based on at least the N audio objects;

generating a reconstruction matrix with matrix elements for reconstruction of at least the N audio objects from the M downmix signals, wherein approximations of at least the N audio objects are obtainable as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations; and

generating a bit stream comprising the M downmix signals and at least some of the matrix elements of the reconstruction matrix.

2. The method of claim 1 , wherein the M downmix signals are arranged in a first field of the bit stream using a first format, and the matrix elements are arranged in a second field of the bit stream using a second format, thereby allowing a decoder that only supports the first format to decode and playback the M downmix signals in the first field and to discard the matrix elements in the second field.

3. The method of claim 2 , further comprising the step of receiving positional data corresponding to each of the N audio objects, wherein the M downmix signals are generated based on the positional data.

4. The method of claim 1 , wherein the audio scene further comprises a plurality of bed channels, wherein the M downmix signals are generated based on at least the N audio objects and the plurality of bed channels.

5. The method of claim 4 , wherein the reconstruction matrix comprises matrix elements for reconstruction of the bed channels from the M downmix signals, wherein approximations of the N audio objects and the bed channels are obtainable as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations.

6. The method of any claim 1 , further comprising:

forming L auxiliary signals from the N audio objects;

including matrix elements in the reconstruction matrix for reconstruction of at least the N audio objects from the M downmix signals and the L auxiliary signals, wherein approximations of at least the N audio objects are obtainable as linear combinations of the M downmix signals and the L auxiliary signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations; and

including the L auxiliary signals in the bit stream.

7. The method of claim 6 , wherein the M downmix signals span a hyperplane, and wherein at least one of the plurality of auxiliary signals does not lie in the hyperplane spanned by the M downmix signals.

8. The method of claim 7 , wherein the at least one of the plurality of auxiliary signals is orthogonal to the hyperplane spanned by the M downmix signals.

9. A non-transitory computer-readable medium comprising computer code instructions adapted to carry out the method of claim 1 when executed on a device having processing capability.

10. An encoder that encodes a time/frequency tile of an audio scene which at least comprises N audio objects, comprising at least one of hardware and a processor in association with a memory configured to implement:

a receiver that receives the N audio objects;

a downmix generator that-receives the N audio objects from the receiver and generates M downmix signals based on at least the N audio objects;

an analyzer that generates a reconstruction matrix with matrix elements for reconstruction of at least the N audio objects from the M downmix signals, wherein approximations of at least the N audio objects are obtainable as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations; and

a bit stream generator that receives the M downmix signals from the downmix generator and the reconstruction matrix from the analyzer and generates a bit stream comprising the M downmix signals and at least some of the matrix elements of the reconstruction matrix.

11. A method for decoding a time-frequency tile of an audio scene which at least comprises N audio objects, the method comprising the steps of:

receiving a bit stream comprising M downmix signals and at least some matrix elements of a reconstruction matrix;

generating the reconstruction matrix using the matrix elements; and

reconstructing the N audio objects from the M downmix signals using the reconstruction matrix, wherein approximations of at least the N audio objects are obtained as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations.

12. The method of claim 11 , wherein the M downmix signals are arranged in a first field of the bit stream using a first format, and the matrix elements are arranged in a second field of the bit stream using a second format, thereby allowing a decoder that only supports the first format to decode and playback the M downmix signals in the first field and to discard the matrix elements in the second field.

13. The method of claim 11 , wherein the audio scene further comprises a plurality of bed channels, the method further comprising reconstructing the bed channels from the M downmix signals using the reconstruction matrix, wherein approximations of the N audio objects and the bed channels are obtained as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations.

14. The method of claim 11 , further comprising:

receiving L auxiliary signals being formed from the N audio objects;

reconstructing the N audio objects from the M downmix signals and the L auxiliary signals using the reconstruction matrix, wherein approximations of at least the N audio objects are obtained as linear combinations of the M downmix signals and the L auxiliary signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations.

15. The method of claim 14 , wherein the M downmix signals span a hyperplane, and wherein at least one of the plurality of auxiliary signals does not lie in the hyperplane spanned by the M downmix signals.

16. The method of claim 15 , wherein the at least one of the plurality of auxiliary signals that does not lie in the hyperplane is orthogonal to the hyperplane spanned by the M downmix signals.

17. The method of claim 11 , further comprising:

receiving positional data corresponding to the N audio objects, and

rendering the N audio objects using the positional data to create at least one output audio channel.

18. The method of claim 17 , wherein the reconstruction matrix is represented with respect to a second frequency domain corresponding to a second filter bank, and the rendering is performed in a third frequency domain corresponding to a third filter bank, wherein the second filter bank and the third filter bank are at least partly the same filter bank.

19. A non-transitory computer-readable medium comprising computer code instructions adapted to carry out the method of claim 11 when executed on a device having processing capability.

20. A decoder that decodes a time-frequency tile of an audio scene which at least comprises N audio objects, comprising at least one of hardware and a processor in association with a memory configured to implement:

a receiver that receives a bit stream comprising M downmix signals and at least some matrix elements of a reconstruction matrix;

a reconstruction matrix generator that receives the matrix elements from the receiver and based thereupon generates the reconstruction matrix; and

a reconstructor that receives the reconstruction matrix from the reconstruction matrix generator and reconstructs the N audio objects from the M downmix signals using the reconstruction matrix, wherein approximations of at least the N audio objects are obtained as linear combinations of at least the M downmix signals with the matrix elements of the reconstruction matrix as coefficients in the linear combinations.