Apparatus, method and computer program for encoding, decoding, scene processing and other procedures related to dirac based spatial audio coding using direct component compensation

Abstract

An apparatus for generating a sound field description from an input signal having at least two channels has: an input signal analyzer for obtaining direction data and diffuseness data from the input signal; an estimator for estimating a first energy- or amplitude-related measure for an omnidirectional component derived from the input signal and for estimating a second energy- or amplitude-related measure for a directional component derived from the input signal, and a sound component generator for generating sound field components of the sound field, wherein the sound component generator is configured to perform an energy compensation of the directional component using the first energy- or amplitude-related measure, the second energy- or amplitude-related measure, the direction data and the diffuseness data.

1 . An apparatus for generating a sound field description from an input signal comprising at least two channels, the apparatus comprising:
 an input signal analyzer for acquiring direction data and diffuseness data from the input signal;   an estimator for estimating a first energy- or amplitude-related measure for an omnidirectional component derived from the input signal and for estimating a second energy- or amplitude-related measure for a directional component derived from the input signal, and   a sound component generator for generating sound field components of the sound field description, wherein the sound component generator is configured to perform an energy compensation of the directional component using the first energy- or amplitude-related measure, the second energy- or amplitude-related measure, the direction data and the diffuseness data.   
     
     
         2 . The apparatus of  claim 1 , wherein the input signal comprises the at least two channels, wherein the estimator is configured to calculate the omnidirectional component using an addition of the at least two channels, and to calculate the directional component using a subtraction between a first channel of the at least two channels and a second channel of the at least two channels. 
     
     
         3 . The apparatus of  claim 1 , wherein the input signal comprises the omnidirectional component and one or more directional components, and wherein the estimator is configured to calculate the first energy- or amplitude-related measure for the omnidirectional component using the input signal and to calculate the second energy- or amplitude-related measure for each of the one or more directional components from the input signal. 
     
     
         4 . The apparatus of  claim 1 , wherein the input signal comprises an A-format with at least two channel signals, and
 wherein the estimator is configured to derive the omnidirectional component using a first weighted linear combination of the at least two channel signals and to derive the directional components using second weighted linear combinations of the at least two channel signals.   
     
     
         5 . The apparatus of  claim 1 , wherein the input signal analyzer is configured to extract the diffuseness data from metadata associated with the input signal or to extract the diffuseness data from the input signal by a signal analysis of the input signal comprising the at least two channels or components. 
     
     
         6 . The apparatus of  claim 1 , wherein the estimator is configured to calculate the first energy- or amplitude-related measure or the second energy- or amplitude-related measure from an absolute value of a complex amplitude or a magnitude raised to a power greater than 1 and lower than 5 or being equal to 2 or 3. 
     
     
         7 . The apparatus of  claim 1 ,
 wherein the sound component generator comprises an energy compensator for performing the energy compensation, the energy compensator comprising a compensation gain calculator for calculating a compensation gain using the first energy- or amplitude-related measure, the second energy- or amplitude-related measure, the direction data and the diffuseness data.   
     
     
         8 . The apparatus of  claim 1 , wherein the sound component generator is configured to calculate, from the direction data, a directional gain and to combine the directional gain and the diffuseness data for performing the energy compensation. 
     
     
         9 . The apparatus of  claim 1 , wherein the estimator is configured to estimate the second energy- or amplitude-related measure for a first directional component and a third energy- or amplitude-related measure for a second directional component, to calculate a first compensation gain for the first directional component using the first and the second energy- or amplitude-related measures, and to calculate a second compensation gain for the second directional component using the first and the third energy- or amplitude-related measures. 
     
     
         10 . The apparatus of  claim 7 ,
 wherein the compensation gain calculator is configured to calculate, as a diffuse compensation gain, a first gain factor depending on the diffuseness data and at least one of the number of sound field components in the second group, the maximum order of sound field components of the first group and the maximum number of sound field components of the second group, to calculate, as a direct compensation gain, a second gain factor depending on the first energy- or amplitude-related measure for the omnidirectional component, the second energy- or amplitude-related measure for the directional component, the direction data and the diffuseness data, and to calculate the compensation gain using the first gain factor and the second gain factor, and   wherein the sound component generator is configured to use the same direction data and diffuseness data for calculating the first compensation gain and the second compensation gain.   
     
     
         11 . The apparatus of  claim 7 , wherein the compensation gain calculator is configured
 to increase the compensation gain with an increasing first energy- or amplitude-related measure, or   to decrease the compensation gain with an increasing second energy- or amplitude-related measure, or   to increase the compensation gain using an increasing direction gain, or to increase the compensation gain with a decreasing number of directional components.   
     
     
         12 . The apparatus of  claim 7 ,
 wherein the sound component generator is configured for generating, from the input signal, one or more sound field components of a first group of sound field components comprising for each sound field component a direct component and a diffuse component, and for generating, from the input signal, a second group of sound field components comprising only a direct component,   wherein the compensation gain calculator is configured to calculate the compensation gain using the diffuseness data and at least one of the number of sound field components in the second group, the number of diffuse components in the first group, a maximum order of sound field components of the first group, and a maximum order of sound field components of the second group.   
     
     
         13 . The apparatus of  claim 7 , wherein the compensation gain calculator is configured to perform a gain factor manipulation using a limitation with a fixed maximum threshold or a fixed minimum threshold or using a compression function for compressing low or high gain factors towards medium gain factors to acquire the compensation gain. 
     
     
         14 . The apparatus of  claim 1 ,
 wherein the sound component generator is configured to generate other sound field components of other orders, wherein a combiner is configured to combine the sound field components of the sound field description and the other sound field components of other orders to acquire the sound field description.   
     
     
         15 . The apparatus of  claim 7 , wherein the energy compensator comprises a compensation gain applicator for applying the compensation gain to at least one sound field component. 
     
     
         16 . The apparatus of  claim 1 , wherein the sound component generator comprises a low-order component generator for generating a low-order sound field description from the input signal up to a predetermined order and the predetermined mode, wherein the low-order component generator is configured to derive the low-order sound field description by copying or taking the input signal or forming a weighted combination of the channels of the input signal,
 wherein the low order sound field description comprises the omnidirectional component and the directional component generated by the copying or the taking or the weighted combination.   
     
     
         17 . The apparatus of  claim 1 ,
 wherein a first group of sound field components up to an order l of coefficients and a second group of sound field components above the order l of coefficients are orthogonal to each other, or wherein the sound field components are at least one of coefficients of orthogonal basis functions, coefficients of spatial basis functions, coefficients of spherical or circular harmonics, and Ambisonics coefficients.   
     
     
         18 . The apparatus of  claim 1 ,
 an analysis filter bank for generating the one or more sound field components for a plurality of different time-frequency tiles, wherein the input signal analyzer is configured to acquire a diffuseness data item for each time-frequency tile, and wherein the sound component generator is configured to perform the energy compensation separately for each time-frequency tile.   
     
     
         19 . A method for generating a sound field description from an input signal comprising at least two channels, comprising:
 acquiring direction data and diffuseness data from the input signal;   estimating a first energy- or amplitude-related measure for an omnidirectional component derived from the input signal and estimating a second energy- or amplitude-related measure for a directional component derived from the input signal, and   generating sound field components of the sound field description, wherein the generating comprises performing an energy compensation of the directional component using the first energy- or amplitude-related measure, the second energy- or amplitude-related measure, the direction data and the diffuseness data.   
     
     
         20 . A non-transitory digital storage medium having stored thereon a computer program for performing a method for generating a sound field description from an input signal comprising at least two channels, comprising:
 acquiring direction data and diffuseness data from the input signal;   estimating a first energy- or amplitude-related measure for an omnidirectional component derived from the input signal and estimating a second energy- or amplitude-related measure for a directional component derived from the input signal, and   generating sound field components of the sound field description, wherein the generating comprises performing an energy compensation of the directional component using the first energy- or amplitude-related measure, the second energy- or amplitude-related measure, the direction data and the diffuseness data,   when said computer program is run by a computer.