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Owning Palette: Discrete Wavelet VIs

Installed With: Advanced Signal Processing Toolkit

Decomposes a signal according to the level you specify and reconstructs the signal from the frequency bands you select.

Example

Dialog Box Options

Block Diagram Inputs

Block Diagram Outputs

Dialog Box Options

Parameter	Description
Data Source	Specifies whether this Express VI reads data from a block diagram input terminal or from a file. From terminal specifies that this Express VI reads data from a block diagram input terminal. From file specifies that this Express VI reads data from a file. This Express VI can read data from waveform, WAV, or TXT files. The valid format of a TXT data file is a file that contains only a 1D real array.
File Path Configuration	Contains the following options: File path—Specifies and displays the path to the file from which this Express VI reads data. This option is available only if you select From file in the Data Source section. Ask user to choose a file each time this VI runs—Specifies whether this Express VI displays a dialog box that prompts you to select a file each time this Express VI runs. This option is available only if you select From file in the Data Source section.
Original and Reconstructed Signal	Displays the original and reconstructed signal.
Wavelet Transform and Subband Selection	Contains the following options: Frequency bands—Specifies the subbands or the parts of subbands to use to reconstruct the signal. The discrete wavelet transform decomposes a signal into a series of dyadic frequency subbands. Zoom out—Zooms out the frequency bands near DC, which is the origin of the x-scale of Frequency bands. Zoom in—Zooms in the frequency bands near DC, which is the origin of the x-scale of Frequency bands. Select all—Selects all the frequency bands. Click this button to reconstruct the image from the approximation coefficients and the detail coefficients of all the frequency bands. Levels—Specifies the number of levels in the discrete wavelet analysis. Levels must be a positive integer no greater than log2(Ls), where Ls is the length of the signal. Wavelet—Specifies the wavelet type this Express VI uses for discrete wavelet analysis. The default is db02. You can choose from the following options: Customized Wavelet Haar—Orthogonal dbxx—Orthogonal, Daubechies coifx—Orthogonal, Coiflets symx—Orthogonal, Symmlets FBI—Biorthogonal biorx_x—Biorthogonal where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. Note  The orthogonal wavelets are not redundant and therefore are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and therefore are suitable for signal or image feature extraction.
Functions	Displays the following graphs: Analysis scaling—Displays the scaling function of the analysis filter bank. Analysis wavelet—Displays the mother wavelet of the analysis filter bank. Synthesis scaling—Displays the scaling function of the synthesis filter bank. Synthesis wavelet—Displays the mother wavelet of the synthesis filter bank.
Filters	Displays the following graphs: Analysis lowpass (G0)—Displays the coefficients of the lowpass analysis filter G0(z). Analysis highpass (G1)—Displays the coefficients of the highpass analysis filter G1(z). Synthesis lowpass (H0)—Displays the coefficients of the lowpass synthesis filter H0(z). Synthesis highpass (H1)—Displays the coefficients of the highpass synthesis filter H1(z).
Parameters Settings	Contains the following options: Wavelet Type—Specifies the type of wavelet this Express VI uses to design a customized wavelet for discrete wavelet analysis and reconstruction. You can select the Orthogonal or Biorthogonal option. Product of Lowpass (P0=G0*H0)—Specifies P0, which is the product of the lowpass analysis filter G0 and the lowpass synthesis filter H0. Contains the following options: P0 type—Specifies the type of P0. The default is Maxflat. You can choose from the following options: Maxflat Positive Equiripple General Equiripple Note  This option is available only if you select the Biorthogonal option in the Wavelet Type section. Zero pairs at pi (P0)—Specifies the value of p in the Maxflat filter P0(z), where P0(z) = (1+1/z)^(2p)*Q(z). This option is available only if you select the Maxflat option in the P0 type section. # of taps—Specifies the number of coefficients of P0(z). The length of P0(z) must be 4p–1, where p = 2, 3, …. This option is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section. Passband—Specifies the normalized cutoff frequency of P0(z). The value of Passband must be less than 0.5. Passband is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section. Factorization (Type of G0)—Contains the following options: Filter type—Specifies how this Express VI factors P0 to G0 and H0. Contains the following options: Arbitrary—Specifies that no restriction exists on the placement of zeroes. Minimum Phase—Specifies that the zeroes of G0 are located inside the unit circle, except for the zeroes at pi. Linear Phase—Specifies that if one zero belongs to G0(H0), the reciprocal of that zero must belong to G0(H0). B-Spline—Specifies that except for some zeroes at pi, all the zeroes of P0 belong to H0. Zeroes at pi (G0)—Controls how many zeroes at z=–1 belong to G0(z). This option is available only if you select the Maxflat option in the P0 type section. The maximum value of this option is 2p, where p = the value of the Zero pairs at pi (P0) option.
Zeroes of G0 and H0	Shows the distribution of the zeroes of P0(z), G0(z) and H0(z). This Express VI uses this distribution to factor the zeroes of P0(z) into the zeroes of G0(z) and H0(z). Because the filter coefficients of P0(z) are real, all the zeroes of P0(z) are symmetrical with respect to the x-axis. Consequently, this Express VI displays only the upper half of the plane.The blue crosses represent the zeroes of G0(z), and the red circles represent the zeroes of H0(z).Click on the zero you want to select to switch the zero from that of G0(z) to that of H0(z) and vice versa. All the zeroes belong to G0(z) or H0(z). Selecting different values for Filter type puts different constraints on the selections of zeroes. For example, if you select Linear Phase for Filter type and select a zero for one filter, the filter automatically contains the reciprocal of the zero. Refer to the Wavelet Analysis Tools User Manual for more information about the different types of factorization.

Block Diagram Inputs

Parameter	Description
error in (no error)	Describes error conditions that occur before this VI or function runs.
Signal	Specifies the block diagram terminal of the data you want to load. This input is available only if you select the From terminal option in the Data Source section.
File path	Specifies the file path of the data you want to load. This input is available only if you select the From file option in the Data Source section.

Block Diagram Outputs

Parameter	Description
Reconstruction	Returns the reconstructed signal.
error out	Contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces.

This Express VI operates similarly to the following VIs and functions:

WA Discrete Wavelet Transform
WA Inverse Discrete Wavelet Transform

Example

Refer to the Multiresolution Analysis - 1D Signal VI in the labview\examples\Wavelet Analysis\WAGettingStarted.llb for an example of using the Multiresolution Analysis VI.