wavelte packet reconstruction

hi,

actually i decomposed the signal with wpdec() and measured each node using wpcoef now i have to adjust those signals before reconstruction.

anybody pls help me in which manner the signal can be adjusted before reconstruction to get the better signal.

 thank u in advance

Answer 1

[Wayne King]

Yes, you can use wpthcoef(), that does what you want.

Unless you have a very specific way you want to modify them beside hard or soft thresholding. If that is the case:

Read the terminal node coefficients with

cfs = read(T,'data');

Keep the approximation coefficients

tnodes = leaves(T);
app_coefs = read(T,'data',tnodes(1));

Change cfs the way you want. Let coefs be the changed coefficients.

Put the new coefficients in a tree.

Tnew = write(T,'data',coefs);

Place the approximation coefficients back.

   Tnew = write(T,'data', tnodes(1),app_coefs);

Answer 2

[Wayne King]

Hi, You can use wpthcoef or wpdencmp for denoising. Or you can simply modify the terminal nodes of your original tree, then create a new tree and use write to write your new coefficients to the terminal nodes.

Answer 3

[thangam]

thanks for ur kind reply sir. ya actually i tried wpdencoef and wpthcoef and i got some output.

but i need to adjust each node signal separately and i adjusted some of the nodes and modified new coefficients by write command. but i did not get clear output. in some of the nodes while adjusting it shows invalid node value. so pls give me an for the procedure to adjust the each node signal sir.

Answer 4

[Wayne King]

Hi, It doesn't make sense in a wavelet packet tree to adjust each node separately because the higher levels nodes depend on the terminal nodes. It's not like a wavelet tree where you can modify just the detail coefficients.

You should decompose the signal down to whatever level you wish and just modify the terminal nodes. By definition, everything above it will be modified.

Answer 5

[thangam]

thanks for ur help sir.

so i used 3 level([c,l] = wavedec(x,3,'db1');) means then

Is i have to change all the nodes of 7, 8, 9, 10, 11, 12, 13, 14 sir.

Actually i changed those nodes by giving some values, and the signal was got modified but i did not get clear output. so in which manner i have to adjust the nodes either by defining threshold values by any command or any other process sir.

thank u in advance sir

[Wayne King]

wavedec() does not give you a wavelet packet transform. That gives you a wavelet transform, so which did you do?

[thangam]

just for example i gave that one sir.

actually i am doing with wpt = wpdec(y,3,'db3'); sir

Answer 6

[thangam]

just for example i gave that one sir.

actually i am doing with wpt = wpdec(y,3,'db3'); sir

Answer 7

[Wayne King]

Then just modify the terminal nodes.

[thangam]

ya i got idea. thanks for your kind help sir.

Answer 8

[thangam]

is there any procedure to modify those nodes sir

[Wayne King]

wpthcoef