Hi guys!
I'm working a bit on a filterbank were I'm mapping subbands to
channels using a mapping matrix in this fashion (8 subbands to 4 channels):
1000
1000
0100
0100
0010
0010
0001
0001
I'd like to make this mapping logarithmic, but i can't seem to get my
head around it.. Anybody got any ideas?
Thank you in advance,
Christian
Filterbank mapping
Started by ●April 15, 2009
Reply by ●April 16, 20092009-04-16
Hello,
I'm working on a similar project. A possible logarithmic mapping would be:
the first subband to the first channel
the next two subbands to the second channel
the next four subbands to the third channel
... and so on
Ok, you won't see the exact logarithmic function in this example, it was just intuitively drawn out of a logarithmic plot.
A basic ideea would be that you draw the needed logarithmic function (or any other function you might be interested in, for instance power law) plot on a coordonate system. On the Ox axis you then draw the subbands. Out of this you can determine the channels on the Oy axis. This is very easily done in Matlab.
Now, I would have a question too :) Could you please tell me how you decide upon the central frequencies of the bandpass filters?
Thanks, and I also hope I was of any help.
Paul
Hi guys!
>
>I'm working a bit on a filterbank were I'm mapping subbands to channels using a mapping matrix in this fashion (8 subbands to 4 channels):
>
>1000
>1000
>0100
>0100
>0010
>0010
>0001
>0001
>
>I'd like to make this mapping logarithmic, but i can't seem to get my head around it.. Anybody got any ideas?
>
>Thank you in advance,
>Christian
>
I'm working on a similar project. A possible logarithmic mapping would be:
the first subband to the first channel
the next two subbands to the second channel
the next four subbands to the third channel
... and so on
Ok, you won't see the exact logarithmic function in this example, it was just intuitively drawn out of a logarithmic plot.
A basic ideea would be that you draw the needed logarithmic function (or any other function you might be interested in, for instance power law) plot on a coordonate system. On the Ox axis you then draw the subbands. Out of this you can determine the channels on the Oy axis. This is very easily done in Matlab.
Now, I would have a question too :) Could you please tell me how you decide upon the central frequencies of the bandpass filters?
Thanks, and I also hope I was of any help.
Paul
Hi guys!
>
>I'm working a bit on a filterbank were I'm mapping subbands to channels using a mapping matrix in this fashion (8 subbands to 4 channels):
>
>1000
>1000
>0100
>0100
>0010
>0010
>0001
>0001
>
>I'd like to make this mapping logarithmic, but i can't seem to get my head around it.. Anybody got any ideas?
>
>Thank you in advance,
>Christian
>
Reply by ●April 21, 20092009-04-21
Hi Paul,
thank you for your help, I think I've got it working now.
As for filterbank frequencies, I'm using an FFT filterbank, where the size of the FFT will determine the number of channels. The channel frequencies will then be evenly distributed across the desired frequency spectrum.
Hope this helps.
Christian
thank you for your help, I think I've got it working now.
As for filterbank frequencies, I'm using an FFT filterbank, where the size of the FFT will determine the number of channels. The channel frequencies will then be evenly distributed across the desired frequency spectrum.
Hope this helps.
Christian
