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Inverse Discrete Wavelet transform

Started by luoky_sg July 7, 2008
Below is a reply by Jani Huhtanen in another old thread...

>Below is a diagram of the synthesis part of the wavelet transform (one >level): > >y0[n]--UpSample--x0[n]--G0(z)--z0[n]-- > + ---> z[n] >y1[n]--UpSample--x1[n]--G1(z)--z1[n]-- > >Say that y0[n] and y1[n] are defined for n=1..8 (i.e. 8 samples). After >UpSample x0[n] and x1[n] are defined for n=1..16 (i.e. 16 samples), where
> > x0[2*n] = y0[n], > x0[2*n+1] = 0, > >and > > x1[2*n] = y1[n], > x1[2*n+1] = 0. > >At this point the sample count has doubled from 8 to 16 for both detail
and
>approximation parts. Next these upsampled signals x0 and x1 are filtered
by
>G0 and G1 respectively. This does not increase the sample count. > > >Jani Huhtanen >Tampere University of Technology, Pori >
In regards to this topic, I am still trying to understand DWT. After upsampling is done, Zeros are inserted between the coefficents(8 samples becomes 16 samples). After filtering/convolution is done, does the zeros change to some other value(ie. IDWT change the zero to a non-zero value)?