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: Tom Pincince (stillone_AT_snowcrest.net)
Date: Fri Mar 02 2001 - 01:07:12 EET


> Here is where I see a problem. I use the peak envelope for clipping, and
> for a 'general' idea when mixing. My main problem right now has to do
> with content. If you take the RMS value of the peak, I don't see that as
> being overly more helpful.
>
Not the RMS value of the peak, the RMS value of the entire 2048 (or
whatever) samples.

> Are you concerned with the power of the
> signal? If so, then a spectral power representation is what would
> help, maybe even with phase data for mix prediction. When I get quite a
> few tracks, I always have the fun of going through and tweaking the
> volumne curves and eq to keep from getting clipped signals.
>
If your mixer app is float, you shouldn't have to do this. If you hear
clipping, turn down the master fader. If your mixer app is integer or
you specifically want to reduce the amplitude of hot spots in individual
tracks for gain maximization in the final mix, use a compressor plugin.
This is precisely what compressors are for.

> What I am
> actually working on from a conceptual point of view is a 'sound print'
> function. I am trying to develop a way of a file that contains fft output
> data that can be drawn behind the waveform as a thermal map. This can
> help to identify hotspots in songs and apply filters for those hotspots
> when they are causing clipping with other tracks. Also, with a phase
> related information too, you could select some tracks and generate a
> display of the 'mixing' potential, a rude prediction of the contents being
> mixed.
>
>
> What do you all think about this? I have been writing it in perl right
> now (just because working with the canvas with Perl/Tk is so fast). Would
> anyone benefit from the things I have described if I could come up with
> some algorithms that were fast and have a good deal of correlation?
>
It sounds to me like you are well on your way to creating a multi-band
batch compressor, and it would be a useful thing. Don't worry about the
clipping (phase) stuff though. Float mixers really do eliminate that
issue (unless you like to apply 500 db of boost at 100 hz to lots of
tracks simultaneously).

Tom


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