Hello I am trying to do some data compression using the DWT techniques but i have encoutered some problems. Once i have set the threshold values, all the DWT coefficients that were less than the chosen value were reduced to zero which was the purpose. But on the other hand i would like to reconstruct the signal using only the remained coefficients without using those coefficients replaced with zeroes. This also will affect the length of the signal ( the number of samples). IS it possible (or correct) to just reconstruct the signal with the remained samples? Thanks
Wavelet data compression
Started by ●September 12, 2006
Reply by ●September 12, 20062006-09-12
Umutesi Faith wrote:> > Hello > > I am trying to do some data compression using the DWT techniques but i > have encoutered some problems. Once i have set the threshold values, all > the DWT coefficients that were less than the chosen value were reduced to > zero which was the purpose. But on the other hand i would like to > reconstruct the signal using only the remained coefficients without using > those coefficients replaced with zeroes. This also will affect the length > of the signal ( the number of samples). IS it possible (or correct) to > just reconstruct the signal with the remained samples? > > ThanksYes. Reconstruction will lead to least squares sense optimal reconstruction when those coefficients set to zero are not available. -- Jani Huhtanen
Reply by ●September 13, 20062006-09-13
Ok, i will try and see what results i get! By the way i did not understand what you meant by "least squares sense optimal reconstruction"! Thanks! ******************************************************************>Yes. Reconstruction will lead to least squares sense optimalreconstruction>when those coefficients set to zero are not available. > >-- >Jani Huhtanen > >
Reply by ●September 13, 20062006-09-13
Umutesi Faith wrote:> Ok, i will try and see what results i get! By the way i did not understand > what you meant by "least squares sense optimal reconstruction"! > Thanks! > > ****************************************************************** > > >>Yes. Reconstruction will lead to least squares sense optimal > reconstruction >>when those coefficients set to zero are not available. >> >>-- >>Jani Huhtanen >> >>If one considers the zeroed coefficients as missing, then straightforward reconstruction leads to minimum error in least squares sense. This, because we are dealing with orthogonal projection (well, actually this might not hold for biorthogonal case). -- Jani Huhtanen Tampere University of Technology, Pori