# Questions tagged [dwt]

DWT denotes discrete wavelet transforms, instances of continuous wavelet transforms that admit a discrete sampling.

33 questions
Filter by
Sorted by
Tagged with
88 views

173 views

### 2D DWT computation order

In 2D the discrete wavelet transform (DWT) of an image using lifting based 5/3 filter, if I perform a row-wise operation first then perform column-wise operation then I will get 4 sub-band LL, LH and ...
138 views

### Raw signal to short for DWT

The algorithm i use to apply a discrete wavelet transform only accept raw-data with a certain number of samples (2,4,8,..128..). I have to either interpolate the raw signal or padding it with zeros (...
40 views

### DWT initialization from nonuniform samples

Let $D\subset\mathbb R$ be compact, let $f:\mathbb R\to\mathbb R$ be a contintinuous function with support $D$. Let $\phi(x)$ be a well-defined scaling function, in the sense that it generates a ...
36 views

### Does each pixel of the original image has a corresponding coefficient for every scale and every direction calculated by the DWT?

I want to take a pixel and find its coefficients calculated by the discrete wavelet transform for every scale and every direction. But as the DWT subsamples images, I don't see how to do that. Do I ...
4 views

17 views

### discrete wavelet transform matrix for vectorized image

Yesterday I asked about how to extract 2D DFT matrix for a vectorized image. Today my question is how can I extract 2D DWT matrix for a vectorized image. Fourier transform have this property that ...
47 views

### Aliasing from downsampling and Nyquist

In a book Conceptual Wavelets in Digital Signal Processing by Lee Fugal 2009 on page 246 the author talks about aliasing present in DWT subbands due to downsampling by 2 and states: Recall from DSP ...
13 views

### Obtaining Continuous Wavelet Transform coefficients from Discrete Wavelet Transform

On an earlier StackExchange question, I read that for a given signal, "From the resulting DWT the corresponding full CWT can be obtained by convolving the DWT with the reproducing kernel of the ...
36 views

### Discrete Wavelet Transform (DWT) Filter Bank

I have some stumbling block in my thesis writing. Do we use the same filter pair while implementing DWT filter bank with downsampling of the filter output, or filters do change also from level to ...
75 views

### High frequencies disappear when applying discrete wavelet transform

Trying to decompose and reconstruct a signal using a to some extent self-made implementation of DWT for some reason fails. The result looks highpass filtered and/or shifted. I wanted to write the code ...
34 views

### What are the constraints in design of discrete orthogonal wavelets?

Can anyone point me to literature that explains a quote from here : Why is a wavelet transform implemented as a filter bank? So not all wavelets can be implemeted perfectly (invertible) with ...
16 views

### Looking for a analytical formula to compute the central frequency of a signal analyzed by a discrete wavelet at a given scale

I am reading this paper by Han et al. (2014). In this article, the authors extract detailed information from geomagnetic data sampled at 1Hz using a daubechies 5 (db5) wavelet: they reconstruct the ...
187 views

### Wavelet transform of a spatial convolution

Does anyone know if there exist a kind of convolution theorem for the discrete wavelet transform (decimated or undecimated)? In other words can I find a simple form of \$W\left[ \int f(t) g(x-t) \, ...
100 views

### Extracting feature from audio track using DWT

Our teacher gave us an assignment: Write a program to transform an audio track to time - frequency domain, and create a vector include at least 4 features extracted from transformed output signal. I ...
249 views

### Programming the IDWT for image processing

I want to program the 2D inverse discrete wavelet transform (only 1 level) in the case of image processing. In the matlab website there's this diagram: now, I want to program the IDWT with haar ...