montagne

Hi, I'm implementing a continuously variable delay line. Unfortunately I am currently using linear interpolation between samples, and it's prety awful. Does anybody know of a good object for quadratic or cubic interpolation of signals?

Hi, I'm implementing a continuously variable delay line. Unfortunately I am currently using linear interpolation between samples, and it's prety awful. Does anybody know of a good object for quadratic or cubic interpolation of signals?
Thanks


quadratic-or-cubic-interpolator

> Hi, I'm implementing a continuously variable delay line. 

> Unfortunately I am currently using linear interpolation between 

> samples, and it's prety awful. Does anybody know of a good object 

> for quadratic or cubic interpolation of signals?

I don't have an object for this, but I have some C code for an 

allpass interpolation. Would that help? Or do you know how to code 

On Dec 12, 2006, at 11:52 PM, Tim wrote:
> Hi, I'm implementing a continuously variable delay line.  
> Unfortunately I am currently using linear interpolation between  
> samples, and it's prety awful. Does anybody know of a good object  
> for quadratic or cubic interpolation of signals?

I don't have an object for this, but I have some C code for an  
allpass interpolation.  Would that help?  Or do you know how to code  
externals?

-----
Nathan Wolek
nw@nathanwolek.com
http://www.nathanwolek.com


I don't know if I'll have time to make an external, but the code may be helpful. How can I get it from you?

I don't know if I'll have time to make an external, but the code may be helpful. How can I get it from you?
thx
tim.m


> I don't know if I'll have time to make an external, but the code 

> may be helpful. How can I get it from you?

Here you go. Complete with reference on where I found the technique.

************************************************************************ 

float rbb_allpassInterp(float *in_array, float index, long bufferLength,

        float last_out, float *out_ptr)

inputs:            in_array -- name of array of input values

                index -- floating point index value to interpolate

                bufferLength -- length of in_array

                last_out -- value of last output from buffer

                out_ptr -- pointer to output location

description:    performs allpass interpolation on an input array and 

    results to a location specified by a pointer; implements filter as 

    in Dattorro 2: J. Audio Eng. Soc., Vol 45, No 10, 1997 October

returns:        interpolated output

void rbb_allpassInterp(float *in_array, float index, long bufferLength,

    long index_i = (long)index;                    // i

    long index_iP1 = index_i + 1;                // i + 1

    float index_frac = index - (float)index_i;    // frac

    // make sure that index_iP1 is not out of range

    while (index_iP1 >= bufferLength) index_iP1 -= bufferLength;

    // formula as on bottom of page 765 of above Dattorro article

    *out_ptr = in_array[index_i] + index_frac * (in_array[index_iP1] - 

On Dec 13, 2006, at 1:16 PM, Tim wrote:
> I don't know if I'll have time to make an external, but the code  
> may be helpful. How can I get it from you?

Here you go.  Complete with reference on where I found the technique.

/ 
************************************************************************ 
********
float rbb_allpassInterp(float *in_array, float index, long bufferLength,
		float last_out, float *out_ptr)

inputs:			in_array -- name of array of input values
				index -- floating point index value to interpolate
				bufferLength -- length of in_array
				last_out -- value of last output from buffer
				out_ptr -- pointer to output location
description:	performs allpass interpolation on an input array and  
returns the
	results to a location specified by a pointer; implements filter as  
specified
	in Dattorro 2: J. Audio Eng. Soc., Vol 45, No 10, 1997 October
returns:		interpolated output
************************************************************************ 
********/
void rbb_allpassInterp(float *in_array, float index, long bufferLength,
		float last_out, float *out_ptr)
{
	// index = i.frac
	long index_i = (long)index;					// i
	long index_iP1 = index_i + 1;				// i + 1
	float index_frac = index - (float)index_i;	// frac

	// make sure that index_iP1 is not out of range
	while (index_iP1 >= bufferLength) index_iP1 -= bufferLength;

	// formula as on bottom of page 765 of above Dattorro article
	*out_ptr = in_array[index_i] + index_frac * (in_array[index_iP1] -  
last_out);
}

thanks for the code. It looks quite simple. Obviously a piece of cake in C (once you know) but the feedback aspect of the algorithm would make it pretty much impossible in MAX/MSP directly, I believe. Is that correct? From other posts I have seen it seems that a minimum feedback delay of 1 signal vector is required?

thanks for the code. It looks quite simple. Obviously a piece of cake in C (once you know) but the feedback aspect of the algorithm would make it pretty much impossible in MAX/MSP directly, I believe. Is that correct? From other posts I have seen it seems that a minimum feedback delay of 1 signal vector is required?
Thanks.


> Obviously a piece of cake in C (once you know) but the feedback 

> aspect of the algorithm would make it pretty much impossible in MAX/ 

> MSP directly, I believe. Is that correct? From other posts I have 

> seen it seems that a minimum feedback delay of 1 signal vector is 

On Dec 14, 2006, at 8:49 AM, Tim wrote:
> Obviously a piece of cake in C (once you know) but the feedback  
> aspect of the algorithm would make it pretty much impossible in MAX/ 
> MSP directly, I believe. Is that correct? From other posts I have  
> seen it seems that a minimum feedback delay of 1 signal vector is  
> required?

-------------------
Nathan Wolek, PhD --- nwolek@stetson.edu
Assistant Professor of Music Technology
Stetson University - DeLand, FL
http://www.nathanwolek.com

quadratic or cubic interpolator