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dsp.SubbandAnalysisFilter System object

Package: dsp

Decompose signal into high-frequency and low-frequency subbands

Description

The SubbandAnalysisFilter object decomposes a signal into high-frequency and low-frequency subbands.

To decompose a signal into high-frequency and low-frequency subbands:

  1. Define and set up your two-channel subband analysis filter. See Construction.

  2. Call step to decompose the signal according to the properties of dsp.SubbandAnalysisFilter. The behavior of step is specific to each object in the toolbox.

Construction

H = dsp.SubbandAnalysisFilter returns a two-channel subband analysis filter, H, that decomposes the input signal into a high-frequency subband and a low-frequency subband, each with half the bandwidth of the input.

H = dsp.SubbandAnalysisFilter('PropertyName',PropertyValue,...) returns a two-channel subband analysis filter, H, with each specified property set to the specified value.

H = dsp.SubbandAnalysisFilter(lpc,hpc,
'PropertyName',PropertyValue,...)
returns a two-channel subband analysis filter, H, with the LowpassCoefficients property set to lpc, the HighpassCoefficients property set to hpc, and other specified properties set to the specified values.

Properties

LowpassCoefficients

Lowpass FIR filter coefficients

Specify a vector of lowpass FIR filter coefficients, in descending powers of z. For the lowpass filter, use a half-band filter that passes the frequency band stopped by the filter specified in the HighpassCoefficients property. The default values of this property specify a filter based on a third-order Daubechies wavelet.

HighpassCoefficients

Highpass FIR filter coefficient

Specify a vector of highpass FIR filter coefficients, in descending powers of z. For the highpass filter, use a half-band filter that passes the frequency band stopped by the filter specified in the LowpassCoefficients property. The default values of this property specify a filter based on a third-order Daubechies wavelet.

 Fixed-Point Properties

Methods

cloneCreate subband analysis filter object with same property values
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs of step method
isLockedLocked status for input attributes and nontunable properties
releaseAllow property value and input characteristics changes
resetReset filter states of subband analysis filter object
stepDecompose signal into high- and low-frequency subbands

Examples

Perfectly reconstruct a signal using subband analysis and synthesis filters:

load dspwlets; % load the filter coefficients lod, hid, lor and hir
ha = dsp.SubbandAnalysisFilter(lod, hid);
hs = dsp.SubbandSynthesisFilter(lor, hir);
u = randn(128,1);

[hi, lo] = step(ha, u); % Two channel analysis
y = step(hs, hi, lo); % Two channel synthesis

% Plot difference between original and reconstructed signals
%  with filter latency compensated
plot(u(1:end-7)-y(8:end));

Algorithms

This object implements the algorithm, inputs, and outputs described on the Two-Channel Analysis Subband Filter block reference page. The object properties correspond to the block parameters, except:

  • The SubbandAnalysisFilter object does not have a property that corresponds to the Input processing parameter of the Two-Channel Analysis Subband Filter block. The object assumes the input is frame based and always maintains the input frame rate.

  • The Rate options block parameter is not supported by the dsp.SubbandAnalysisFilter object.

See Also

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