Subject: Re: Re[2]: [linux-audio-dev] peakfiles and EDL's
From: Robert Schrem (Robert.Schrem_AT_WiredMinds.de)
Date: Wed Feb 28 2001 - 10:56:08 EET
On Tue, 27 Feb 2001, you wrote:
>
> > And important note to add is that depending on the peak file bin size,
> > low frequencies you will see the magnitude go up and down (real low as
> > you have calculated).
> >
> Good point. Since the purpose of peakfiles is to produce a graphic
> display of the envelope of the signal, then the number of samples
> represented by a single peakfile sample must be high enough to avoid
> having the display reveal frequency information for low frequency
> signals. In light of this I suggest raising the number of samples
> represented from 2048 to at least 4096, or maybe higher, since 2048
> corresponds to an audible frequency with 44.1 khz audio.
Can't follow you: Why dows 2048 correspod to an audible frequency
with 44.1 khz audio?
> I have noticed that some programs display half envelopes, showing only the
> + half. This may be because their peakfiles use absolute value, and
> therefore store only one value per peakfile sample, or it may be a
> feature that allows more tracks to be displayed simultaneously by
> reducing the vertical space per track by 50%. I find full envelopes
> much more natural to look at.
Well I think you need only to compute one peak value for a
sample data block: Max = abs(all samples for a block)
I still don't understan what information we gan if we compute
seperate min and max peak values.
To display only the absolute value on screen on the y axis
would double the resolution of the peak data display on screen
(you would have the double number of pixels for each peak value).
You don't need to display something that looks like a waveform
if it is an evolope. Maybe the display should show a waveform
display for close up's when you work with the real sample data
and switch to envolope mode if you zoom out. I think this would be
a 'honest' solution...
robby
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