US 11,869,525 B2
Method and apparatus for processing an audio signal, audio decoder, and audio encoder to filter a discontinuity by a filter which depends on two fir filters and pitch lag
Emmanuel Ravelli, Erlangen (DE); Manuel Jander, Hemhofen (DE); Grzegorz Pietrzyk, Nuremberg (DE); Martin Dietz, Nuremberg (DE); and Marc Gayer, Erlangen (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 Feb. 3, 2022, as Appl. No. 17/592,423.
Application 17/592,423 is a continuation of application No. 15/412,920, filed on Jan. 23, 2017, abandoned.
Application 15/412,920 is a continuation of application No. PCT/EP2015/065219, filed on Jul. 3, 2015.
Claims priority of application No. 14178821 (EP), filed on Jul. 28, 2014.
Prior Publication US 2022/0157328 A1, May 19, 2022
Int. Cl. G10L 19/005 (2013.01); G10L 19/03 (2013.01); G10L 19/12 (2013.01); H04B 1/10 (2006.01); G10L 19/26 (2013.01); G10L 19/022 (2013.01); G10L 19/20 (2013.01); G10L 21/0364 (2013.01); G11B 27/038 (2006.01)
CPC G10L 19/26 (2013.01) [G10L 19/005 (2013.01); G10L 19/022 (2013.01); G10L 19/03 (2013.01); G10L 19/12 (2013.01); G10L 19/20 (2013.01); G10L 21/0364 (2013.01); G11B 27/038 (2013.01); H04B 1/1027 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A method for decoding an audio signal, the method comprising:
receiving the audio signal; and
decoding the audio signal;
wherein decoding the audio signal comprises processing consecutive audio frames of the audio signal to remove a discontinuity by linear predictive filtering, the discontinuity being between a filtered past frame and a filtered current frame of the audio signal, the filtered past frame being a past frame filtered using a set of past filter frame parameters, the filtered current frame being a current frame filtered using a set of current frame filter parameters, and the past filter frame parameters being different from the current frame filter parameters, and the processing comprising:
acquiring, by a decoder, a signal by linear predictive filtering a predefined signal with initial states of a linear predictive filter, the initial states defined on basis of a last part of an unfiltered past frame filtered using the set of current frame filter parameters for filtering the current frame,
filtering the current frame of the audio signal, and
removing the discontinuity by modifying a beginning portion of the filtered current frame by the signal acquired by linear predictive filtering,
wherein the linear predictive filter is defined as
A(z)=1/(Σm=0Mamz−m)
with M the filter order and am the filter coefficients, with a0=1, and
wherein decoding the audio signal comprises filtering the audio frames using the following filter:
H(z)=(1−B(z))/(1−C(z)·z−T)
where B(z) and C(z) are two FIR filters and the H(z) filter parameters are the coefficients of the FIR filters B(z) and C(z), and T indicates the pitch lag.