Method and apparatus for controlling audio frame loss concealment
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorsStefan Bruhn, Jonas Svedberg
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Abstract
In accordance with an example embodiment of the present invention, disclosed is a method and an apparatus thereof for controlling a concealment method for a lost audio frame of a received audio signal. A method for a decoder of concealing a lost audio frame comprises detecting in a property of the previously received and reconstructed audio signal, or in a statistical property of observed frame losses, a condition for which the substitution of a lost frame provides relatively reduced quality. In case such a condition is detected, the concealment method is modified by selectively adjusting a phase or a spectrum magnitude of a substitution frame spectrum.
Claims23
A frame loss concealment method, wherein a segment of a previously synthesized audio signal is used to generate a prototype frame in order to create a substitution frame for a lost audio frame, the method comprising:
- transforming the prototype frame into a frequency domain;
- applying a sinusoidal model to the transformed prototype frame to identify the frequency of a sinusoidal component of the audio signal;
- calculating a phase shift θk for the sinusoidal component;
- shifting a phase of all spectral coefficients in the transformed prototype frame included in an interval Mk around a sinusoid k by the phase shift θk while retaining a magnitude of those spectral coefficients;
- randomizing phases of spectral coefficients in the transformed prototype frame that are not phase shifted;
- creating the substitution frame for the lost audio frame by performing an inverse frequency transform of a frequency spectrum of the transformed prototype frame, wherein the transformed prototype frame includes the phase shifted spectral coefficients included in the interval Mk and randomized phases of spectral coefficients that are not phase shifted;
- substituting the created substitution frame for the lost audio frame in the previously synthesized audio signal;
- and
- outputting the previously synthesized audio signal comprising the created substitution frame substituted for the lost audio frame.
An apparatus for creating a substitution frame for a lost audio frame, the apparatus comprising:
- at least one processor;
- and
- at least one memory storing instructions executable by the at least one processor to cause the at least one processor to
- generate a prototype frame from a segment of a previously synthesized audio signal;
- transform the generated prototype frame into a frequency domain;
- apply a sinusoidal model to the transformed prototype frame to identify the frequency of a sinusoidal component of the audio signal;
- calculate a phase shift θk for the sinusoidal component;
- shift a phase of all spectral coefficients in the transformed prototype frame included in an interval Mk around a sinusoid k by the phase shift θk while retaining a magnitude of those spectral coefficients;
- randomize phases of spectral coefficients in the transformed prototype frame that are not phase shifted;
- create the substitution frame for the lost audio frame by performing an inverse frequency transform of a frequency spectrum of the transformed prototype frame, wherein the transformed prototype frame includes the phase shifted spectral coefficients included in the interval Mk and randomized phases of spectral coefficients that are not phase shifted;
- substitute the created substitution frame for the lost audio frame in the previously synthesized audio signal;
- and
- output the previously synthesized audio signal comprising the created substitution frame substituted for the lost audio frame.
A computer program product comprising a non-transitory computer-readable medium storing instructions which, when executed on at least one processor of an apparatus for creating a substitution frame for a lost audio frame, cause the at least one processor to perform operations to:
- generate a prototype frame from a segment of a previously synthesized audio signal;
- transform the prototype frame into a frequency domain;
- apply a sinusoidal model to the transformed prototype frame to identify the frequency of a sinusoidal component of the audio signal;
- calculate a phase shift θk for the sinusoidal component;
- shift a phase of all spectral coefficients in the transformed prototype frame included in an interval Mk around a sinusoid k by the phase shift θk while retaining a magnitude of those spectral coefficients;
- randomize phases of spectral coefficients in the transformed prototype frame that are not phase shifted;
- and
- create the substitution frame for the lost audio frame by performing an inverse frequency transform of a frequency spectrum of the transformed prototype frame, wherein the transformed prototype frame includes the phase shifted spectral coefficients included in the interval Mk and randomized phases of spectral coefficients that are not phase shifted;
- substitute the created substitution frame for the lost audio frame in the previously synthesized audio signal;
- and
- output the previously synthesized audio signal comprising the created substitution frame substituted for the lost audio frame.
Dependencies are inferred from the claim text.