Efficient loudspeaker surface search for multichannel loudspeaker systems

An apparatus for spatial audio signal decoding and rendering associated with a plurality of speaker nodes placed within a three dimensional space having virtual surface arrangement comprising a plurality of virtual surfaces, wherein each of the plurality of virtual surfaces has corners positioned at at least three speaker nodes, wherein the virtual surface arrangement is defined at least in part by a virtual surface set comprising a plurality of virtual surfaces, wherein each of the plurality of virtual surfaces is each referenced by a reference means, and wherein the apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

• determine an azimuth angle for each virtual surface of the virtual surface set;
• arrange the virtual surfaces of the virtual surface set into an order based on the determined azimuth angles to give an ordered virtual surface set;
• determine at least two search sectors, wherein each of the at least two search sectors occupies a range of azimuth angles;
• associate a virtual surface of the ordered virtual surface set to each of the at least two search sectors;
• obtain a target panning direction comprising at least a target azimuth angle;
• determine a search sector from the at least two search sectors based on the target azimuth angle;
• and
• start from the associated virtual surface for the determined search sector, search the ordered virtual surface set to determine a virtual surface that encloses the target panning direction.