Talk:Daubechies wavelet

message: Should the table of the "Orthogonal Daubechies Coefficients" have several fewer columns? The way it is now, the table does not fit in my browser window (on a 19" screen), and I doubt having that many numbers adds any value to the article. Also, maybe only on my screen, the table at the bottom overlaps the pictures. Probably, the pictures should all be aligned to the right. Comments? Oleg Alexandrov 18:49, 8 Mar 2005 (UTC)
thread_title: Formatting issues

message: I have another question about this tutorial. The analysis coefficients are given in the page, however is it possible to derive the corresponding coefficients for synthesis filter banks from the coefficients already given? —The preceding unsigned comment was added by 137.205.8.2 (talk) 16:04, 21 April 2007 (UTC)
replies: text: Hi, please read again the article, the algorithm for the synthesis coefficients is already there. In short, one just has to reverse the analysis sequence. That's why the Daubechies wavelets are orthogonal (or CQF).--LutzL 08:01, 23 April 2007 (UTC)
replies: text: PS: Sorry, the wavelet part of WP was messed around by different authors without ever getting into a consistent state. The part that is refered to as "above" dealing with this problem is now in an extra page orthogonal wavelet.--LutzL 08:05, 23 April 2007 (UTC)
thread_title:  A question about coefficients of Synthesis filter banks 

message: The provided code does not work "as is" in Matlab as the paragraph above it would lead you to believe.     Matlab does not come with a function 'S' by default, so some further explanation is needed.
If there are other libraries or extensions necessary to make the code run, or if the user needs to run any preliminary expressions, then that should be stated clearly.  Likewise it should also be indicated if any of the functions or variables in the code refer to any possible user-defined functions or variables.  —Preceding unsigned comment added by 98.199.61.19 (talk) 22:09, 28 April 2008 (UTC)
replies: text: Ehm, S is the input Signal? A simple array of length N (even)? Nevertheless, it should be explained.--LutzL (talk) 07:12, 29 April 2008 (UTC)
replies: text: There are more problems. The article claims that the detail coefficients are [x(3), -x(2), x(1), -x(0)], but if you look at the output from the code (I could not understand the code itself at all, it does way too much magic for me) and scale it by sqrt(2) you can see that the coefficients used are [-x(3), x(2), -x(1), x(0)], ie. the signs are reversed. Which is "wrong" -- the code or the article? -Sesse (talk) 16:22, 5 May 2008 (UTC)
replies: text: Both sign versions are correct, one only needs to take care when implementing the inverse transform. There is no way to decide which version is better.--LutzL (talk) 09:57, 6 May 2008 (UTC)
replies: text: The article should state that this is the LIFTING SCHEME implementation of the D4 wavelet transform and refer to the paper of Sweldens and Daubechies where the lifting coefficients are given.Goossensb (talk) 16:46, 15 May 2008 (UTC)
thread_title:  Working matlab code? 

message: What is the benefit of using the wavelet values normalized to sum up to 2?
For example for D4, I frequently see the values
  0.4829629131445341, 0.83651630373780772, 0.22414386804201339, -0.12940952255126034
Which are not normalized, but the direct values \frac{1+\sqrt(3)}{4\sqrt{2}} etc.
--138.246.2.177 (talk) 16:57, 4 November 2010 (UTC)
thread_title:  Unnormalized wavelet values 

message: Upon trying the code (direct copy/paste) in Matlab with S being a column vector of 512 elements between 0-255 (e.g., image row), the result (after transform and inverse transform) did not come anywhere close to being the original array.  In my most recent attempt the sum of the absolute values between the original S and final S (after forward and inverse transform) was 10703.  My best guess is that there are some issues with the ends of the arrays.  — Preceding unsigned comment added by 216.45.196.90 (talk) 20:44, 26 August 2011 (UTC)
replies: text: Did more testing on this code.  Forward transform was good, inverse transform needed some minor changes.  I have verified the changes with Octave.  Found this link to be quite helpful.  — Preceding unsigned comment added by 216.45.196.90 (talk) 21:00, 29 August 2011 (UTC)
thread_title:  Matlab: Part II 

message: I'm to lazy to read all of the article, but I can see directly that it's missing a section about the applications of Daubechies wavelets. That's probably what is the most interesting to read about, so they should be mentioned in the article. —Kri (talk) 21:32, 20 November 2012 (UTC)
replies: text: Please consult discrete wavelet transform and wavelet compression and tell there (and if necessary here) what is missing.--LutzL (talk) 13:14, 21 November 2012 (UTC)
replies: text: A section about the applications is what is missing. —Kri (talk) 16:05, 21 November 2012 (UTC)
thread_title:  Applications?