Method and apparatus for decoding stereo loudspeaker signals from a higher-order ambisonics audio signal
Decoding of Ambisonics representations for a stereo loudspeaker setup is known for first-order Ambisonics audio signals. But such first-order Ambisonics approaches have either high negative side lobes or poor localisation in the frontal region. The invention deals with the processing for stereo decoders for higher-order Ambisonics HOA.
1 . A method for decoding an Higher-Order Ambisonics (HOA) audio signal, the method comprising:
receiving the HOA audio signal;
determining a matrix G of panning function values, wherein the matrix G comprises, for each of a number S of virtual sampling points on a sphere, gain vectors g 1 . . . g s , wherein at least a first panning function value for a first virtual sampling point located opposite to a loudspeaker position approaches zero, and at least a second panning function value for a source located close to the loudspeaker position has a value not approaching zero;
receiving a mode matrix, wherein the mode matrix was determined based on the number S of virtual sampling points and an order of the HOA audio signal;
determining a decoding matrix D based on the matrix G and the mode matrix; and
rendering, by at least one processor, the HOA audio signal to stereo loudspeaker signals based on the decoding matrix D.
2 . The method of claim 1 , wherein the matrix G has a size L x S, wherein L corresponds to a number of loudspeakers.
3 . The method of claim 2 , wherein the gain vectors g 1 . . . g s , are directed to achieve a panned mix in S directions of the L loudspeakers.
4 . A non-transitory computer-readable medium having stored thereon instructions, that when executed by one or more processors, cause one or more processors to perform the method of claim 1 .
5 . An apparatus for decoding an Higher-Order Ambisonics (HOA) audio signal, the apparatus comprising:
a first receiver configured to receive the HOA audio signal;
a first processor for determining a matrix G of panning function values, wherein the matrix G comprises, for each of a number S of virtual sampling points on a sphere, gain vectors g 1 . . . g s , wherein at least a first panning function value for a first virtual sampling point located opposite to a loudspeaker position approaches zero, and at least a second panning function value for a source located close to the loudspeaker position has a value not approaching zero;
a second receiver for receiving a mode matrix, wherein the mode matrix was determined based on the number S of virtual sampling points and an order of the HOA audio signal;
a second processor for determining a decoding matrix D based on the matrix G and the mode matrix; and
a renderer for rendering the HOA audio signal to stereo loudspeaker signals based on the decoding matrix D.
6 . The apparatus of claim 5 , wherein the matrix G has a size L×S, wherein L corresponds to a number of loudspeakers.
7 . The apparatus of claim 6 , wherein the gain vectors g 1 . . . g s , are directed to achieve a panned mix in S directions of the L loudspeakers.