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dsp.SubbandSynthesisFilter System object

Package: dsp

Reconstruct signal from high-frequency and low-frequency subbands

Description

The SubbandSynthesisFilter object reconstructs a signal from high-frequency and low-frequency subbands.

To reconstruct a signal from high-frequency and low-frequency subbands:

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

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

    Note:   Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Construction

H = dsp.SubbandSynthesisFilter returns a two-channel subband synthesis filter, H, that reconstructs a signal from its high-frequency subband and low-frequency subband. Each subband contains half the bandwidth of the original signal.

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

H = dsp.SubbandSynthesisFilter(lpc,hpc,
'PropertyName',PropertyValue,...)
returns a two-channel subband synthesis filter, H. The object has 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 coefficients

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 synthesis 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 internal states of subband synthesis filter object
stepReconstruct signal from high- and low-frequency subbands

Examples

expand all

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent step syntax. For example, myObject(x) becomes step(myObject,x).

Decompose a signal into low frequency and high frequency subbands using the subband analysis filter. Reconstruct the signal using the subband synthesis filter.

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] = ha(u); % Two channel analysis
y = 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 Synthesis Subband Filter block reference page. The object properties correspond to the block parameters, except:

  • The SubbandSynthesisFilter object does not have a property that corresponds to the Input processing parameter of the Two-Channel Synthesis Subband Filter block. The object only performs sample-based processing and always maintains the input frame rate.

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

Introduced in R2012a

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