> On May 22, 5:02 pm, "dtsao" <tsaod...@yahoo.ca> wrote:
>
> > Hi,
>
> > I need to build a digital filter for a sound signal. The SIF filter must
> > remove the video portion of the channel and be compatible with worldwide
> > standards and have good rejection.
> > From Matlab, it looks like this requires a tremendous amount of
> > coefficients if built using FIR. So I wonder, does anyone know if a SIF
> > filter MUST be linear phase? Or can it be done using an IIR? And what
> > would be the effect if the sound was not passed through a linear phase
> > filter.
> > Thanks.
>
> I don't think anyone can tell you what your filter's requirements are.
> Linear phase is nice, but as you said, you can trade it off for a
> lower-order IIR filter. What format is the sound signal in? Is it
> digitally-encoded, or is it an analog signal? If your sound is analog,
> then you might be in luck; the human ear doesn't care too much about
> distortion of phase response; in many cases, you can design a filter
> that will meet your magnitude requirements and still have normal-
> sounding output.
>
> Jason
If the sound signal is modulated, for example FM, then couldn't
nonlinear filter phase produce distortion in the demod output?
John