Interpolation with JAVA like MATLAB

Walker wrote:

> >
> >Thaks you have understand what I would like :). It would be great if I
> >find a rate converter like "interp" in Matlab...It's too compplicate to
> >implement it :S.
> >
> >Carlos Vargas
> >
>
> I have an implementation:
>
> 1. Interpoling signal with "rate-1" zeros:
> for example if rate = 3
> Signal: 2 1 4 6 7 ...
> Signal zeros: 2 0 0 1 0 0 4 0 0 6 0 0 7 0 0 ...
>
> 2. Make a simetric sinc with 5-6 lobules at each side, and sample it with
> "rate"-samples at each lobule. (Principal Lobule "rate"-samples from 0 to
> 1 and "rate"-samples from -1 to 0).
>
> 3. Convolve Signal zeros with that sinc.
>
> Note: If you take more lobules (for example 35 at each side) the result
> will be better, but we will have a large transitory in the signal result.
>
> Can somebody make it better? It would be great, if somebody konw how to
> eliminate that transitori without cut it.

Sampling the sinc function is a good approach. By windowing the sinc
samples you can noticably improve transition bandwidth and stopband
attenuation. See:

http://www.dspguide.com/ch16.htm

Regards,
Andor