Filterbank (Gyrator ) for Multiband processing

[gtek]

Hi all,

I'm trying to implement a multiband device ( more then 2 bands ) into an older dsp.
Everytime i bounce into processor limits.

Is there a way to implement one filter with multiple taps. ie. bass,mid,treb_lo,treb_hi ?

Now i'm just filtering 4 times (2 bands, left + right ) with 15 taps per filter.

like this:
bass_out_left=fir(....,left,...); lowpass
bass_out_right=fir(....,right,...); lowpass
treb_out_left=fir(....,left,...); highpass
treb_out_right=fir(....,right,...); highpass

Is there a faster way?

grt.

gtek

[Urs]

If your FIR coefficients are symmetric (left side of center looks like right side of center), then the phase would be linear, so you could just substract the lowpass from the input signal to get the highpass.

Cheers,

Urs

[gtek]

Yes, that's right.
Treb_out_left=delayed input - bass_out_left;
But, the delaying of the input takes as much cpu cycles as doing a FIR filter action isn't it?

grt Evert

[Urs]

That depends... if a delay and a substract is less expensive than twice the multiplies, then it's supposedly faster.

Wait... it IS faster, as you can calculate both at once! Just do the substract while you calculate the lowpass. That should be pretty much faster!

Cheers,

Urs

[gtek]

Hmmm,

"Nothing" beats the speed of the Visual dsp's library implemented FIR routine, so this will leave the option for me to recompile the fir source into my own lib.
Well a faster dsp is coming soon, 2000 MFLOPS/s instead of the imaginary 145 MFLOPS/s i do now have. So that will do the trick anyway.

By the way, anyone interested in an ADSP-21061 EZ-KIT?

grt.

Gtek

Evert Verduin