🚀 go-pugleaf

In article <wilf.667759065@rigel.sce.carleton.ca> wilf@sce.carleton.ca (Wilf Leblanc) writes:
>jbuck@galileo.berkeley.edu (Joe Buck) writes:
>
>>[deleted]
>
>>Example of CD salespeak: pushing oversampling as an advanced technical
>>feature.  Oversampling is simply inserting zeros between the digital
>>samples and thus increasing the sampling rate.  It's used because then you
>>can use cheaper, less complex analog filters; it reduces the system cost.
>>Still, some sales critters think it's an advanced technical extra.
>
>This kills me too.  Especially 8x oversampling !
>(I always thought oversampling was used because analog filters usually
>have a horrible phase response near the cutoff.  However, if you want
>to spend enough money, you can get very near linear phase response
>with an analog filter.  So, you are right).
>

I also understand that oversampling increases the 'transition region'
of the filter thus allowing for lower order filters.  However, the sharper
the cutoff, the more ringing will be present in the step response.  This
ringing might be below audible levels though.  Comments?

As for the CD's that do not oversample, what type of filter is generally used?
Theoretically, the transition region for the filter is about 4.1 Khz  
(cutoff frequency is 20Khz and stopband at 44.1-20=24.1 Khz) but in 
practice I think you could get away with much more since there shouldn't
be much energy above 12Khz which extends the transition region to about 
12Khz.  Nevertheless, to get the necessary attenuation (which is what, 
40 dB+?) in 12Khz is a demanding spec.

So what type of filter?  Chebyshev type 2? 

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 Chris Wein                           | cjwein@watcgl.waterloo.edu 
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