De Emphasis FIR Filter

Steve Pope <spope33@speedymail.org> wrote:
> Randy Yates  <yates@digitalsignallabs.com> wrote:
 
>>I've never understood how preemphasis/deemphasis mitigates bad data
>>converters. Can you please explain it?
 
> AFAIK it does not mitigate "bad" data converters per se;  it mitigates any
> source of additive white noise (an accurate and  properly dithered 
> data converter being an example of such).  It can do this because
> the original audio is not spectrally flat, and the pre-emphasis is
> a poor-man's whitening filter.

Sounds right to me.

FM radio has pre-emphasis for about the same reason.

Vinyl records and audio tape have slightly more complicated equalization
functions, but again the pre-emphasis helps with high frequency 
noise.

-- glen

>An fir version is a different story, you'll definitely want to use an
>optimizer for that. But if your hardware can do either IIR or FIR I don't
know
>why you wouldn't choose IIR. 
>
>Bob

Can someone, please, explain what kind of optimizer? Using already
existing FIR is the only option.

Do others agree that I can use IIR impulse response simulated in some
software as FIR filter coefficients? I am just trying to find the easiest
and quickest method that does not require learning some completely new
concepts.


How do I know if phase matters? I am trying to demodulate audio signal.

Thank you very much for your answers on how to resolve this problem.



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How long is the FIR you get to use?

Have you already tried sampling the analog impulse response and using those as FIR coefficients ? If so how much error did you see in the frequency response ?

Bob