Subject: Re: [linux-audio-dev] peakfiles and EDL's
From: Jörn Nettingsmeier (nettings_AT_folkwang-hochschule.de)
Date: Thu Mar 01 2001 - 20:54:00 EET
Paul Davis wrote:
>
> In message <01030118195401.06627_AT_pc-robert>you write:
> >On Wednesday 28 February 2001 19:57, Paul Davis wrote:
> >> >At least I never felt any neccesarity for two seperate peak meters
> >> >showing the positive and negative peak values of the same signal
> >> >seperatly. Maybe you can you convince me, why I would need this an
> >> >for what purpose.
> >>
> >> i think thats because your peak meters are almost certainly computing
> >> RMS levels, even if they say "peak meter".
> >
> >It depends. The Yamaha 02/R digital mixer, Alesis ADAT recorders,
> >usual DAT recorders and the DR-8 HardDisk recorder display
> >like most digital equipment 'digital' peak data on the peak
> >meters, that's for sure (I'm using these things for years now).
>
> as the author of a few software digital meters, i can explain to you
> that the answer is very simple: peak meters are designed to show
> clipping. it doesn't matter whether the clip is positive or
> negative. hence, zero is at the bottom of the meter, and the clip
> value is somewhere toward the top. and yes, you use abs() to figure
> out the value to display.
>
> but with a "waveform" display, this is rather different. for some
> reason (and who can really tell why?) people expect to see a zero axis
> that is roughly in the middle of the data, and to see amplitude values
> for the wave above and below the line.
if i'm not very much mistaken, you definitely want to know the
direction of a zero crossing to make smooth edits without the need
to crossfade. an abs()ed display does not provide this information.
-- Jörn Nettingsmeier home://Kurfürstenstr.49.45138.Essen.Germany phone://+49.201.491621 http://www.folkwang-hochschule.de/~nettings/
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