Subject: Re: [linux-audio-dev] Final Scratch, custom kernel?
From: Lance Blisters (geoff_AT_lek.ugcs.caltech.edu)
Date: Tue Oct 08 2002 - 05:02:30 EEST
Great! What are you using to decode the audio signal? How can
other software program against it?
As there are several implementations of timecode-on-vinyl, perhaps
the authors can agree on a format for realtime position/rate data.
I can imagine other custom controllers which would fall into this
category. I don't suppose there is an existing standard of some sort
which would be sufficient?
-geoff
On Mon, Oct 07, 2002 at 04:28:26PM -0400, Juan K. wrote:
> here's how i do it:
>
> 1st channel:
> 1.5khz control tone
>
> 2nd channel:
> bits encoded as follows:
>
> 0 : 1 3khz cycle
> 1 : 2 6khz cycles
> marker: 1 1.5khz cycle
>
> so each timecode looks like this:
>
> marker cycle
> encoded 0
> checksummed bit sequence
> encoded 1
> marker cycle
>
> each one ends up being about 8ms. so my "latency" is better than theirs!
> [i'm pretty sure finalscratch's 12ms assumes the record is moving at
> normal speed]
>
> since the frequencies are multiples of each other, the crosstalk from the
> cutting head or even from the cartridge that gets used is mitigated
>
> the 0 and 1 starter bits help figure out what's going on depending if the
> record is playing backwards or forwards
>
> counting zero crossings works...but don't forget to filter out the low
> frequencies [like 80hz and below], since the noise from the person's hand
> will fuck things up
>
> i'm fiending to buy one of the finalscratch control records [the guys at
> platinum are telling me they're gonna be like 25 dollars], to see what
> they're doing
>
> --
> John Ketchpaw
> kungfu_AT_alumni.cmu.edu
>
> On Mon, 7 Oct 2002, CK wrote:
>
> > I read:
> > > Well i guess encoding absolute time should not be too hard.
> > > A simple solution could be to have the two stereo channels with different
> > > frequencies, with the ratio corresponding to the radial position.
> >
> > forget it there is no such thing as a clean channel separation on
> > vinyl.
> >
> > regards,
> >
> > x
> >
> > --
> > chris_AT_lo-res.org Postmodernism is german romanticism with better
> > http://pilot.fm/ special effects. (Jeff Keuss / via ctheory.com)
> >
> >
>
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