Allocation, by sub-bands, of bits for quantifying spatial information parameters for parametric encoding
A method is provided for allocating bits for quantifying spatial information parameters by frequency sub-band for parametric encoding/decoding of a multichannel audio stream representative of a soundstage consisting of a plurality of sound sources. The method includes a step of quantifying or inversely quantifying, by frequency sub-band, spatial information parameters for the sound sources of the soundscape. The method further includes: assessing a spatial resolution of the current sub-band on the basis of the spectral properties of the sub-band; and determining a number of bits to be allocated to the current sub-band, the number of bits to be allocated being inversely proportional to the estimated spatial resolution. Also provided is a device for allocating quantification bits implementing the above-described method.
1. A method comprising:
allocating quantization bits for spatial information parameters per frequency sub-band, for a parametric coding or decoding of a multichannel audio stream representing a sound scene having a plurality of sound sources and including at least one of quantization or inverse quantization per frequency sub-band of spatial information parameters of the sound sources of the sound scene, wherein allocating comprises;
estimation by an allocation device of a spatial resolution of a current sub-band on the basis of spectral properties of the sub-band; and
determination by the allocation device of a number of bits to be allocated to the current sub-band, the number of bits to be allocated being inversely proportional to the estimated spatial resolution.
2. The method as claimed in claim 1 , wherein the spectral properties of a sub-band are represented by the central frequency of the sub-band.
3. The method as claimed in claim 1 , wherein the spectral properties of a sub-band are properties of energy in the sub-band.
4. The method as claimed in claim 1 , wherein the spectral properties of a sub-band are at one and the same time properties of energy in the sub-band and the central frequency of the sub-band.
5. The method as claimed in claim 4 , wherein the spatial resolution of a sub-band is estimated furthermore on the basis of the spectral properties of the other sub-bands of a set of sub-bands defining the sound sources.
6. The method as claimed in claim 1 , wherein the spectral properties of a sub-band are obtained on the basis of a decoded sum signal arising from a reduction processing of the channels of the multichannel audio stream.
7. The method as claimed in claim 3 , wherein the energy properties in a sub-band comprise the properties of primary energy and of ambient energy in the sub-band.
8. The method as claimed in claim 1 , wherein the number of bits to be allocated for a sub-band forms part of a predetermined number of bits plus a number of bits already allocated per sub-band.
9. The method as claimed in claim 8 , wherein the determination of the number of bits to be allocated for a sub-band is adjusted as a function of the difference between the resolution in this sub-band and a predetermined reference resolution, to which there corresponds a predetermined allocation of reference bits.
10. The method as claimed in claim 1 , wherein the method is implemented for a set of non-masked sub-bands which is determined by a step of analysis of energy-related masking between sub-bands.
11. A device for allocating quantization bits for spatial information parameters per frequency sub-band, for a parametric coder or decoder of a multichannel audio stream representing a sound scene consisting of a plurality of sound sources and comprising a module for at least one of quantization or inverse quantization per frequency sub-band of spatial information parameters of the sound sources of the sound scene, wherein the device comprises:
a module configured to estimate a spatial resolution of a current sub-band on the basis of spectral properties of the sub-band; and
a module configured to determine a number of bits to be allocated to the current sub-band, the number of bits to be allocated being inversely proportional to the estimated spatial resolution.
12. The device of claim 11 , wherein the device comprises a parametric coder of a multichannel audio stream.
13. The device of claim 11 , wherein the device comprises a parametric decoder of a multichannel audio stream.
14. A computer-readable memory device comprising a computer program stored thereon and comprising code instructions for implementation of a method for allocating quantization bits for spatial information parameters per frequency sub-band, for a parametric coding or decoding of a multichannel audio stream representing a sound scene having a plurality of sound sources and including at least one of quantization or inverse quantization per frequency sub-band of spatial information parameters of the sound sources of the sound scene, when these instructions are executed by a processor, wherein the method comprises the following steps;
estimation by an allocation device of a spatial resolution of a current sub-band on the basis of spectral properties of the sub-band; and
determination by the allocation device of a number of bits to be allocated to the current sub-band, the number of bits to be allocated being inversely proportional to the estimated spatial resolution.