Forums

flanger effect, audio interpolation

Started by omal...@gmail.com February 15, 2006
Hey,

I'm implementing a flanger effect as part of a guitar effects processor
on an ADSP-21364 development board.  A Flanger effect is produced by
adding a single delay to the current input sample, the length of the
delay is dictated by a sin wave which i have in aa lookup table. This
implements a comb filter.

My problem is that on top of the desired output I am also getting a
'police siren' like sound which is a sin wave produced by the
imperfections involved when the sin wave calculates a non-integer
delay.

I have tried to overcome this problem using linear interpolation which
was an improvement but not a complete solution.  I then implemented a
4-point cubic  interpolation algorithm which didn't seem to improve
things much more.

My question is, can anyone suggest a decent interpolation algorithm
suitable for this audio application?


Many thanks 


Ronan

Do you have a sample program?
Perhaps you need to stabilize the comb filter, i.e. multiply the delayed 
value by some factor smaller than one?

omalley.ronan@gmail.com wrote:
> Hey, > > I'm implementing a flanger effect as part of a guitar effects processor > on an ADSP-21364 development board. A Flanger effect is produced by > adding a single delay to the current input sample, the length of the > delay is dictated by a sin wave which i have in aa lookup table. This > implements a comb filter. > > My problem is that on top of the desired output I am also getting a > 'police siren' like sound which is a sin wave produced by the > imperfections involved when the sin wave calculates a non-integer > delay. > > I have tried to overcome this problem using linear interpolation which > was an improvement but not a complete solution. I then implemented a > 4-point cubic interpolation algorithm which didn't seem to improve > things much more. > > My question is, can anyone suggest a decent interpolation algorithm > suitable for this audio application? > > > Many thanks > > > Ronan >