Energy-ratio signalling and synthesis

1. An apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive at least one audio signal;

for the at least one audio signal over at least one frequency band, obtain at least one directional energy ratio, at least one diffuse energy ratio and a remainder energy ratio based on directional, diffuse and remainder portions of the received at least one audio signal;

determine at least one signal energy of the at least one frequency band;

determine energy weights for the directional and diffuse portions, for the at least one frequency band, based on the obtained at least one directional energy ratio, the at least one diffuse energy ratio and the determined at least one signal energy of the at least one frequency band; and

form directional and diffuse streams, associated with the at least one audio signal, by distributing the remainder portion into at least one of directional and diffuse portions using the determined energy weights and the obtained energy ratios.

2. An apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive at least one audio signal;

for the at least one audio signal over at least one frequency band, obtain at least one directional energy ratio, at least one diffuse energy ratio and a remainder energy ratio based on directional, diffuse and remainder portions of the received at least one audio signal, wherein said energy ratios are configured to, at least partially, form directional and diffuse sound streams associated with the at least one audio signal;

prepare a combined energy ratio, for the at least one frequency band, wherein the remainder energy ratio is combined with one of the at least one directional energy ratio or the at least one diffuse energy ratio to form a combined energy ratio; and

provide the at least one audio signal and the combined energy ratio to form said directional and diffuse sound streams, depending on the combined energy ratio.

3. The apparatus as claimed in claim 2 , wherein the apparatus is further caused to reduce a number of the ratios that are transmitted.

4. The apparatus as claimed in claim 1 , wherein the apparatus is caused to form the directional and diffuse streams by distributing the remainder portion into the directional portion and the diffuse portion based on the energy weights for the directional and diffuse portions, respectively.

5. The apparatus as claimed in claim 1 , further caused to:

determine a main direction of the directional portion; and

determine a spatial extent angle based upon the at least one directional energy ratio for the main direction, and

wherein the apparatus is further caused to form the directional and diffuse streams by distributing the remainder portion based on the spatial extent angle and the main direction.

6. The apparatus as claimed in claim 5 , wherein the apparatus is caused to determine the main direction by determining energy weights for each of a plurality of directions associated with the directional portion and selecting a direction having the largest signal energy weight as the main direction.

7. The apparatus as claimed in claim 2 , wherein the apparatus is further caused to select the energy ratios to be combined and to be provided with the at least one audio signal at least one of:

a long term classification; or

a short term classification.

8. The apparatus as claimed in claim 2 , wherein the apparatus is caused to prepare the combined energy ratio by combining the remainder energy ratio with the at least one diffuse energy ratio.

9. The apparatus as claimed in claim 2 , further caused to:

combine the at least one directional energy ratios for a plurality of directions; and

combine the plurality of directions.

10. The apparatus as claimed in claim 9 , wherein the apparatus is caused to combine the at least one directional energy ratios by determining a main direction and determining the at least one directional energy ratios for directions other than the main direction based upon an angular difference between the main direction and a respective direction for the at least one directional energy ratio.

11. The apparatus as claimed in claim 10 wherein the apparatus is caused to determine the main direction by determining energy weights for the plurality of directions of the at least one directional sound stream based on the directional energy ratios for the plurality of directions and selecting a direction for which the energy weight is largest as the main direction.

12. The apparatus as claimed in claim 10 wherein the apparatus is caused to determine the main direction by determining a weighted average for the plurality of directions of the directional portion of the at least one audio signal.

13. A method comprising:

receiving at least one audio signal;

for the at least one audio signal over at least one frequency band, obtaining at least one directional energy ratio, at least one diffuse energy ratio and a remainder energy ratio based on directional, diffuse and remainder portions of the received at least one signal;

determining at least one signal energy of the at least one frequency band;

determining energy weights for the directional and diffuse portions, for the at least one frequency band, based on the obtained at least one directional energy ratio, the at least one diffuse energy ratio and the determined at least one signal energy of the at least one frequency band; and

forming directional and diffuse streams, associated with the at least one audio signal, by distributing the remainder portion into at least one of the directional and diffuse portions using the determined energy weights and the obtained energy ratios.

14. The method as claimed in claim 13 , wherein forming the directional and diffuse streams comprises distributing the remainder portion into the directional portion and the diffuse portion based on the energy weights for the directional and diffuse portions, respectively.

15. The method as claimed in claim 13 , further comprising:

determining a main direction of the directional portion; and

determining a spatial extent angle based upon the at least one directional energy ratio for the main direction, and

wherein forming the directional and diffuse streams comprises distributing the remainder portion based on the spatial extent angle and the main direction.

16. The method as claimed in claim 15 , wherein determining the main direction comprises determining energy weights for each of a plurality of directions associated with the directional portion and selecting a direction having the largest signal energy weight as the main direction.

17. A method comprising:

receiving at least one audio signal;

for the at least one audio signal over at least one frequency band, obtaining at least one directional energy ratio, at least one diffuse energy ratio and a remainder energy ratio based on directional, diffuse and remainder portions of the received at least one audio signal, wherein said energy ratios are configured to, at least partially, form directional and diffuse sound streams associated with the at least one audio signal;

preparing a combined energy ratio, for the at least one frequency band, wherein the remainder energy ratio is combined with one of the at least one directional energy ratio and the at least one diffuse energy ratio; and

providing the at least one audio signal and the combined energy ratio to form said directional and diffuse sound streams, depending on the combined energy ratio.

18. The method as claimed in claim 17 , wherein forming the combined energy ratio comprises combining the remainder energy ratio with the at least one diffuse energy ratio to form the combined energy ratio.

19. The method as claimed in claim 17 , further comprising:

combining the at least one directional energy ratios for a plurality of directions; and

combining the plurality of directions.

20. The method as claimed in claim 19 , wherein combining the direct energy ratios comprises determining a main direction and determining the at least one directional energy ratios for directions other than the main direction based upon an angular difference between the main direction and a respective direction for the at least one directional energy ratio.

21. The method as claimed in claim 20 wherein determining the main direction comprises determining energy weights for the plurality of directions of the at least one directional sound stream based on the directional energy ratios for the plurality of directions and selecting a direction for which the energy weight is largest as the main direction.

22. The method as claimed in claim 20 wherein determining the main direction comprises determining a weighted average for the plurality of directions of the directional portion of the at least one audio signal.