Spatial audio parameter encoding and associated decoding

An apparatus comprising 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:

• obtain a multichannel audio signal;
• obtain direction parameter values associated with at least two time-frequency parts of the multichannel audio signal, the direction parameter values associated with at least two time-frequency parts comprising an elevation element and an azimuth element associated with at least two time-frequency parts;
• and
• compand encode the obtained direction parameter values, wherein the apparatus caused to compand encode the obtained direction parameter values is further caused to:
• quantize the elevation element;
• determine a companding function based on the quantized elevation element and/or multichannel audio signal format;
• generate a companded azimuth element based on the companding function applied to the azimuth element;
• and
• quantize the companded azimuth element.

An apparatus comprising 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:

• obtain at least one encoded bitstream comprising:
• an encoded multichannel audio signal and compand encoded direction parameter values, the compand encoded direction parameter values associated with at least two time-frequency parts of the encoded multichannel audio signal, and the encoded direction parameter values associated with at least two time-frequency parts comprising an encoded elevation element and a companded encoded azimuth element associated with at least two time-frequency parts;
• decode the encoded elevation element;
• determine a decompanding function based on the quantized elevation element and/or multichannel format;
• and
• generate a decompanded azimuth element based on the decompanding function applied to the companded encoded azimuth element.

A method comprising:

• obtaining a multichannel audio signal;
• obtaining direction parameter values associated with at least two time-frequency parts of the multichannel audio signal, the direction parameter values associated with at least two time-frequency parts comprising an elevation element and an azimuth element associated with at least two time-frequency parts;
• and
• compand encoding the obtained direction parameter values, wherein compand encoding the obtained direction parameter values comprises:
• quantizing the elevation element;
• determining a companding function based on the quantized elevation element and/or multichannel audio signal format;
• generating a companded azimuth element based on the companding function applied to the azimuth element;
• and
• quantizing the companded azimuth element.

A method comprising:

• obtaining at least one encoded bitstream comprising:
• an encoded multichannel audio signal and compand encoded direction parameter values, the compand encoded direction parameter values associated with at least two time-frequency parts of the encoded multichannel audio signal, and the encoded direction parameter values associated with at least two time-frequency parts comprising an encoded elevation element and a companded encoded azimuth element associated with at least two time-frequency parts;
• decoding the encoded elevation element;
• determining a decompanding function based on the encoded elevation element and/or encoded multichannel audio signal format;
• and
• generating a decompanded azimuth element based on the decompanding function applied to the companded encoded azimuth element.