Re: [buildcheapeeg] EDF and DDF file formats

From: Sar Saloth (sarsaloth_at_yahoo.com)
Date: 2002-03-13 16:58:19


>
> > What would be our minimum resolution be (if any)? Would we ever
> > have, say, < 1 second, and thus have several "chunks" per second?
>
>Yes, definitely. For ProComp, you could use 1/32 sec, which gives 8
>EEG samples and 1 of each of the other samples.
>
> > Is that why you have chosen to represent this as a floating point
> > value?
>
>I used floating point because maybe there is some device out there
>that basically samples at 256Hz, but sends out lower-rate info once
>every 10 samples, which means 1/25.6 sec intervals, which isn't a nice
>fraction.
>
> > And what determines this duration when the file is being stored? Is
> > that something we need to configure via software options?
>
>I think you can make it as small as is sensible for your device. This
>could be hard-coded -- e.g. 1/32 sec for the ProComp. For pure EEG
>devices, we could send out one sample at a time, i.e. use 1/256 sec
>intervals. I can't see a problem with that (although in EDF they seem
>to prefer longer blocks).

What is the lower limit for data record size in EDF? I haven't been able to
find that.

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