Subject: Re: [linux-audio-dev] Direct Stream Digital / Pulse Density Modulation musing/questions
From: Denis Sbragion (d.sbragion_AT_infotecna.it)
Date: Mon Jul 28 2003 - 16:50:14 EEST
Hello Anders,
At 14.00 28/07/2003 +0200, you wrote:
>It becomes even more interesting when you bring in dither. Then you can
>represent signals whose amplitude is less than one bit, and you can
>increase time resolution to infinity.
...
well I agree with anything else you have written but here there's a basic
relation that sets a limit on time resolution of a linear system:
df * dt > 1/2
Here d is "delta" and not "differential", f is frequency and t is time.
This relation applies to any signal and/or any linear system. So the
limited bandwith of a PCM system sets a lower limit on time resolution. For
sure dithering allow for the almost complete use of the available time
resolution, and also increasing the semple rate increase time resolution,
but as usual the big question is: does it matters to our ear? I think no,
and with this respect I completely agree with you.
Bye,
P.S. I have yet to test the latest BF with fftw3. My RedHat 7.3 has a
bugged gcc which fails to compile the sse support for fftw3, losing much of
the advantages of fftw3. I filed a bug report and I'm waiting for an answer
from RedHat.
-- Denis Sbragion InfoTecna Tel: +39 0362 805396, Fax: +39 0362 805404 URL: http://www.infotecna.it
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