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Owning Palette: Discrete Wavelet VIs

Installed With: Advanced Signal Processing Toolkit

Computes the multi-level undecimated wavelet transform (UWT) of signal. This VI returns the approximation coefficients at the largest level and the detail coefficients at all levels for a 1D signal input and returns the approximation coefficients and the detail coefficients at all levels for a 2D signal input. The approximation coefficients and the detail coefficients at all levels are the same size as signal. The results of the undecimated wavelet transform have the translation invariant property, which is helpful in robust feature extraction and pattern recognition. Wire data to the signal input to determine the polymorphic instance to use or manually select the instance.

Details  Examples

Use the pull-down menu to select an instance of this VI.

Select an instance WA 1D Undecimated Wavelet Transform (waveform)WA 1D Undecimated Wavelet Transform (array)WA 2D Undecimated Wavelet Transform

WA 1D Undecimated Wavelet Transform (waveform)

	signal specifies the input signal.
	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 1D signal or the minimum dimensional size of the 2D signal. The default is –1, which indicates that the VI sets levels as the largest integer no greater than log2(Ls).
	wavelet specifies the wavelet type to use for the discrete wavelet analysis. The default is db02. The options include two types: orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (FBI, Biorthogonal (biorx_x)), where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. The orthogonal wavelets are not redundant and are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and are suitable for signal or image feature extraction. If you want to use other types of wavelets, do not wire this input. Instead, use the Wavelet Design Express VI to design the wavelet you want and wire the resulting analysis filters to the analysis filters input.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	analysis filters specifies the coefficients of the lowpass analysis filters and the highpass analysis filters for the wavelet you specify. If you specify a value for analysis filters, the VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the analysis filters and the corresponding synthesis filters. lowpass specifies the coefficients of the lowpass analysis filter, which the VI uses to compute the approximation coefficients. highpass specifies the coefficients of the highpass analysis filter, which the VI uses to compute the detail coefficients.
	UWT coef contains the approximation coefficients and the detail coefficients from the multi-level undecimated wavelet transform concatenated into an array of waveforms starting with the approximation coefficients at the largest level followed by the detail coefficients at all levels in descending order.
	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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

WA 1D Undecimated Wavelet Transform (array)

	signal specifies the input signal.
	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 1D signal or the minimum dimensional size of the 2D signal. The default is –1, which indicates that the VI sets levels as the largest integer no greater than log2(Ls).
	wavelet specifies the wavelet type to use for the discrete wavelet analysis. The default is db02. The options include two types: orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (FBI, Biorthogonal (biorx_x)), where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. The orthogonal wavelets are not redundant and are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and are suitable for signal or image feature extraction. If you want to use other types of wavelets, do not wire this input. Instead, use the Wavelet Design Express VI to design the wavelet you want and wire the resulting analysis filters to the analysis filters input.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	analysis filters specifies the coefficients of the lowpass analysis filters and the highpass analysis filters for the wavelet you specify. If you specify a value for analysis filters, the VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the analysis filters and the corresponding synthesis filters. lowpass specifies the coefficients of the lowpass analysis filter, which the VI uses to compute the approximation coefficients. highpass specifies the coefficients of the highpass analysis filter, which the VI uses to compute the detail coefficients.
	UWT coef contains the approximation coefficients and the detail coefficients from the multi-level undecimated wavelet transform. The first row of UWT coef contains the approximation coefficients at the largest level. The other rows contain the detail coefficients at all levels in descending order.
	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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

WA 2D Undecimated Wavelet Transform

	signal is the 2D input signal.
	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 1D signal or the minimum dimensional size of the 2D signal. The default is –1, which indicates that the VI sets levels as the largest integer no greater than log2(Ls).
	wavelet specifies the wavelet type to use for the discrete wavelet analysis. The default is db02. The options include two types: orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (FBI, Biorthogonal (biorx_x)), where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. The orthogonal wavelets are not redundant and are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and are suitable for signal or image feature extraction. If you want to use other types of wavelets, do not wire this input. Instead, use the Wavelet Design Express VI to design the wavelet you want and wire the resulting analysis filters to the analysis filters input.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	analysis filters specifies the coefficients of the lowpass analysis filters and the highpass analysis filters for the wavelet you specify. If you specify a value for analysis filters, the VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the analysis filters and the corresponding synthesis filters. lowpass specifies the coefficients of the lowpass analysis filter, which the VI uses to compute the approximation coefficients. highpass specifies the coefficients of the highpass analysis filter, which the VI uses to compute the detail coefficients.
	UWT coef contains the approximation coefficients and the detail coefficients from the multi-level undecimated wavelet transform. Each element of the array contains the 2D UWT results of one level. The ith element stores the approximation coefficients and the detail coefficients at level i+1. low_low contains the approximation coefficients from the lowpass analysis filtering on each row and each column. The low_low coefficients are a low-resolution approximation of the original 2D signal. low_high contains the detail coefficients from the lowpass analysis filtering on each row and the highpass analysis filtering on each column. The high-frequency signal along the column direction influences the low_high coefficients. high_low contains the detail coefficients from the highpass analysis filtering on each row and the lowpass analysis filtering on each column. The high-frequency signal along the row direction influences the high_low coefficients. high_high contains the detail coefficients from the highpass analysis filtering on each row and each column. The high-frequency signal along the diagonal direction influences the high_high coefficients.
	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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

WA Undecimated Wavelet Transform Details

The following illustration shows an example of a three-level undecimated wavelet transform, where you set the levels input of this VI to 3. The length of the input signal is 16 points.

where the subscript indicates the up-sampling by a factor of m. Using information in the previous illustration, you can see that the UWT coef output contains the approximation coefficients of the largest level and the detail coefficients of each level.

In addition, compared to the discrete wavelet transform, the undecimated wavelet transform does not have sub-sampling. Therefore, the output of each level has the same length as the input signal.

Undecimated discrete wavelet transform is translation-invariant. In other words, when the input signal shifts with certain taps, the output coefficients shift by the same taps, which is important for robust feature extractions, such as peak detection.

Refer to A Wavelet Tour of Signal Processing for more information about the undecimated wavelet transform.

Examples

Refer to the following VIs for examples of using the WA Undecimated Wavelet Transform VI:

• High-order Discontinuity Detection VI: labview\examples\Wavelet Analysis\WAGettingStarted.llb
• Undecimated Image Decomposition and Reconstruction (UWT) VI: labview\examples\Wavelet Analysis\WAGettingStarted.llb
• Undecimated Signal Decomposition and Reconstruction (UWT) VI: labview\examples\Wavelet Analysis\WAGettingStarted.llb