Subject: Re: [linux-audio-dev] Dithering idiots
From: Juan Linietsky (coding_AT_reduz.com.ar)
Date: Tue Jun 18 2002 - 03:00:51 EEST
On Mon, 17 Jun 2002 11:42:55 +0100
Richard Bown <bownie_AT_bownie.com> wrote:
> I'm know this has been asked and answered before in some manner but
> I'm currently thick and low on ideas and none of my searches are
> working.
>
> When generating a graphical preview of an audio file at various
> different resolutions you obviously get slightly different pictures
> of the same envelope depending on how you extract and interpret the
> sample information at the dithering resolution you require.
>
> I'm pretty sure I was playing around with some kind of interpolation
> algorithm a while ago that (I assumed) would give this consistent
> view at the various resolutions I required. I just never got it to
> work and now can't remember how it worked, what it did or where it
> was. I'm pretty sure it was on a website someone linked on LAD or
> ALSA but I could be wrong.. What I do remember is that it had
> separate attack and release paramters and, hmm, that's where I run
> out of steam.
>
> Any clues much appreciated.
>
For displaying waves I do the following, it may be nonstandard but it
works
pretty well:
for each pixel, I average the + and - peaks of all the samples in the
range
of the pixel coordinate and the next one, then just draw a vertical
line
from the - to the + average. This basically shows accuratedly
the envelope of the the sample in any resolution.
Juan Linietsky
> Thanks,
> R
> --
> http://www.all-day-breakfast.com/rosegarden
> http://www.bownie.com
>
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