Re: [SoX-users] looking for a really tight (48db) lowpass filter with minimal effect on the remaining stuff

[Sergei S. <ser...@ya...>]

Phase response is audibly irrelevant for pure sine sine inputs.

Pre-echoes is a known phenomena on audio CDs, and the root cause is near brick wall anti-aliasing filter.

Regards,
  Sergei

--- On Tue, 1/22/13, Rob Sykes <aq...@ya...> wrote:

> From: Rob Sykes <aq...@ya...>
> Subject: Re: [SoX-users] looking for a really tight (48db) lowpass filter with minimal effect on the remaining stuff
> To: "sox...@li..." <sox...@li...>
> Date: Tuesday, January 22, 2013, 4:17 AM
> ----- Original Message -----
> 
> > From: Sergei Steshenko <ser...@ya...>
> > To: sox...@li...
> > Cc: 
> > Sent: Tuesday, 22 January 2013, 10:46
> > Subject: Re: [SoX-users] looking for a really tight
> (48db) lowpass filter with minimal effect on the remaining
> stuff
> > 
> > Fundamentally, SoX supports biquadds, so any filter
> after its transfer function 
> > is expressed as biquads can be implemented.
> > 
> > My earlier comments on phase vs magnitude response and
> pre-echoes still stand.
> 
> 
> Yes, there are several filters available in SoX one could
> try. I don't think a particularly steep filter is needed,
> but also, I don't think you'll hear much difference.
> 
> E.g. try:
> 
> sox -q "|sox -c2 -np synth 3 sin noise remix 1p-2,2p-22"
> "|sox -c2 -np synth 3 sin noise remix 1p-2,2p-22 sinc -t1k
> -15500" -d spectrogram
> 
> 
> Cheers,
> 
> Rob
> 
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