Re: Fwd: Re: Re[2]: [linux-audio-dev] peakfiles and EDL's

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Subject: Re: Fwd: Re: Re[2]: [linux-audio-dev] peakfiles and EDL's
From: Paul Davis (pbd_AT_Op.Net)
Date: Thu Mar 01 2001 - 19:44:23 EET


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.

i don't disagree that for the purposes of spotting clipping, it would
work to use abs(), and display the entire curve using positive values
above an axis. but it wouldn't fit in very well with what most people
think of when they see a waveform display, and it misses the critical
distinction between a peak meter and a waveform display.

--p


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