[music-dsp] Re: DC Offset

James Chandler Jr jchandjr at bellsouth.net
Tue Jan 16 14:53:10 EST 2001


> I mean, if your 5 second audio has a component which has 0.001Hz, you will
> percieve it as DC!
> And, **practicaly**, substracting the average off ALL samples when
> processing *LARGE* files, isn't very usefull....
>

Hi, Bram

I hadn't thought of removing DC offset to re-zero non-linear processing,
until it came up here. Excellent idea, which I'll likely implement from now
on.

The main application of DC Offset removal I had seen over the years, was to
remove fixed DC offset induced by inferior ADC converters.

ADC converters are much better nowadays, but older/cheaper soundcards, and
even my 6 year old Sony DAT, produces enough DC offset to make a click when
CD tracks are cued in and out (unless the DC is removed, or the files are
faded in and out on the file heads and tails).

ADC DC offset on soundfiles is usually a fixed long-term amount, and one
would think that removal with an average offset scheme would kill the fixed
offset without having any chance of messing with the phase of low frequency
signals. Scanning a long audio file to find average, then re-writing the
file while subtracting the offset, would only take a few seconds on a
decently fast modern computer.

James Chandler Jr


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