US 11,854,561 B2
Low-frequency emphasis for LPC-based coding in frequency domain
Stefan Doehla, Erlangen (DE); Bernhard Grill, Lauf (DE); Christian Helmrich, Erlangen (DE); and Nikolaus Rettelbach, Nuremberg (DE)
Assigned to Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V., Munich (DE)
Filed by Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V., Munich (DE)
Filed on Nov. 22, 2022, as Appl. No. 17/992,496.
Application 17/992,496 is a continuation of application No. 16/899,328, filed on Jun. 11, 2020, granted, now 11,568,883.
Application 16/899,328 is a continuation of application No. 15/956,591, filed on Apr. 18, 2018, granted, now 10,692,513, issued on Jun. 23, 2020.
Application 15/956,591 is a continuation of application No. 14/811,716, filed on Jul. 28, 2015, granted, now 10,176,817, issued on Jan. 8, 2019.
Application 14/811,716 is a continuation of application No. PCT/EP2014/051585, filed on Jan. 28, 2014.
Claims priority of provisional application 61/758,103, filed on Jan. 29, 2013.
Prior Publication US 2023/0087652 A1, Mar. 23, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. G10L 19/087 (2013.01); G10L 19/16 (2013.01); G10L 19/06 (2013.01); G10L 19/26 (2013.01); G10L 19/02 (2013.01); G10L 19/08 (2013.01)
CPC G10L 19/087 (2013.01) [G10L 19/06 (2013.01); G10L 19/16 (2013.01); G10L 19/26 (2013.01); G10L 19/265 (2013.01); G10L 19/0212 (2013.01); G10L 19/08 (2013.01)] 26 Claims
OG exemplary drawing
 
1. An audio encoder for encoding a non-speech audio signal so as to produce therefrom a bitstream, the audio encoder comprising:
a combination of a linear predictive coding filter comprising a plurality of linear predictive coding coefficients and a time-frequency converter, wherein the combination is configured to filter and to convert a frame of the audio signal into a frequency domain in order to output a spectrum based on the frame and on the linear predictive coding coefficients;
a low frequency emphasizer configured to calculate a processed spectrum based on the spectrum, wherein spectral lines of the processed spectrum representing frequencies lower than a reference spectral line are emphasized;
a control device configured to control the calculation of the processed spectrum by the low frequency emphasizer depending on the linear predictive coding coefficients of the linear predictive coding filter;
a quantization device configured to produce a quantized spectrum based on the processed spectrum;
and a bitstream producer configured to embed the quantized spectrum and the linear predictive coding coefficients into the bitstream;
wherein the control device comprises a spectral analyzer configured to estimate a spectral representation of the linear predictive coding coefficients and a minimum-maximum analyzer configured to estimate a minimum of the spectral representation below a further reference spectral line and a maximum of the spectral representation below the further reference spectral line;
wherein the control device is configured in such a way that the spectral lines of the processed spectrum representing frequencies lower than the reference spectral line are emphasized only if the maximum is less than the minimum multiplied with a first preset value.