US 11,996,110 B2
Apparatus and method for synthesizing an audio signal, decoder, encoder, system and computer program
Guillaume Fuchs, Bubenrath (DE); Tom Baeckstroem, Nuremberg (DE); Ralf Geiger, Erlangen (DE); Wolfgang Jaegers, Erlangen (DE); and Emmanuel Ravelli, 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 May 27, 2022, as Appl. No. 17/827,316.
Application 17/827,316 is a continuation of application No. 16/549,878, filed on Aug. 23, 2019, granted, now 11,373,664.
Application 16/549,878 is a continuation of application No. 14/811,386, filed on Jul. 28, 2015, granted, now 10,431,232, issued on Oct. 1, 2019.
Application 14/811,386 is a continuation of application No. PCT/EP2014/051592, filed on Jan. 28, 2014.
Claims priority of provisional application 61/758,098, filed on Jan. 29, 2013.
Prior Publication US 2022/0293114 A1, Sep. 15, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. G10L 19/02 (2013.01); G10L 19/087 (2013.01); G10L 19/12 (2013.01); G10L 19/26 (2013.01); G10L 19/06 (2013.01)
CPC G10L 19/087 (2013.01) [G10L 19/02 (2013.01); G10L 19/12 (2013.01); G10L 19/26 (2013.01); G10L 19/06 (2013.01)] 25 Claims
OG exemplary drawing
 
1. An apparatus for synthesizing an audio signal, comprising:
an input for receiving an encoded audio signal,
a decoder for decoding the encoded audio signal, the decoder comprising an adaptive codebook and a fixed codebook, and the encoded audio signal being an encoded speech signal,
a filter coupled to the fixed codebook and configured to apply a spectral tilt to a code of the fixed codebook for obtaining a filtered code of the fixed codebook,
a summer coupled to the adaptive codebook and to the filter, the summer configured to combine a code from the adaptive codebook and the filtered code of the fixed codebook for obtaining a combined code, and
a LPC synthesis filter coupled to the summer and configured to synthesize the audio signal,
wherein the spectral tilt is based on the spectral tilt of the current frame of the audio signal,
wherein the apparatus is configured to determine the spectral tilt of the current frame of the audio signal on the basis of spectral envelope information for the current frame of the audio signal, and
wherein the filter is configured to apply the spectral tilt by filtering the code of the fixed codebook based on a transfer function modeling the spectral tilt.