Model based prediction in a critically sampled filterbank
The present document relates to audio source coding systems. In particular, the present document relates to audio source coding systems which make use of linear prediction in combination with a filterbank. A method for estimating a first sample ( 615 ) of a first subband signal in a first subband of an audio signal is described. The first subband signal of the audio signal is determined using an analysis filterbank ( 612 ) comprising a plurality of analysis filters which provide a plurality of subband signals in a plurality of subbands from the audio signal, respectively. The method comprises determining a model parameter ( 613 ) of a signal model; determining a prediction coefficient to be applied to a previous sample ( 614 ) of a first decoded subband signals derived from the first subband signal, based on the signal model, based on the model parameter ( 613 ) and based on the analysis filterbank ( 612 ); wherein a time slot of the previous sample ( 614 ) is prior to a time slot of the first sample ( 615 ); and determining an estimate of the first sample ( 615 ) by applying the prediction coefficient to the previous sample ( 614 ).
1. A method, performed by an audio signal processing device, for determining an estimate of a sample of a subband signal from two or more previous samples of the subband signal, wherein the subband signal corresponds to one of a plurality of subbands of a subband-domain representation of an audio signal, the method comprising
determining signal model data comprising a model parameter;
determining a first prediction coefficient to be applied to a first previous sample of the subband signal; wherein a time slot of the first previous sample immediately precedes a time slot of the first sample; wherein the first prediction coefficient is determined in response to the model parameter using a first lookup table and/or a first analytical function;
determining a second prediction coefficient to be applied to a second previous sample of the subband signal; wherein a time slot of the second previous sample immediately precedes a time slot of the first previous sample; wherein the second prediction coefficient is determined in response to the model parameter using a second lookup table and/or a second analytical function; and
determining the estimate of the sample by applying the first prediction coefficient to the first previous sample and by applying the second prediction coefficient to the second previous sample;
wherein the method is implemented, at least in part, by one or more processors of the audio signal processing device.
2. An audio signal processing device configured to determine an estimate of a sample of a subband signal from two or more previous samples of the subband signal, wherein the subband signal corresponds to one of a plurality of subbands of a subband-domain representation of an audio signal; wherein the audio signal processing device comprises
a predictor calculator configured to
determine signal model data comprising a model parameter;
determine a first prediction coefficient to be applied to a first previous sample of the subband signal; wherein a time slot of the first previous sample immediately precedes a time slot of the first sample; wherein the first prediction coefficient is determined in response to the model parameter using a first lookup table and/or a first analytical function; and
determine a second prediction coefficient to be applied to a second previous sample of the subband signal; wherein a time slot of the second previous sample immediately precedes a time slot of the first previous sample; wherein the second prediction coefficient is determined in response to the model parameter using a second lookup table and/or a second analytical function; and
a subband predictor configured to determine the estimate of the first sample by applying the first prediction coefficient to the first previous sample and by applying the second prediction coefficient to the second previous sample;
wherein one or more of the predictor calculator and the subband predictor are implemented, at least in part, by one or more processors of the audio signal processing device.
3. A non-transitory computer-readable storage medium comprising a sequence of instructions which, when executed by a computer, cause the computer to perform the method of claim 1 .