[TriLUG] Recording Eric Raymond's Talk(s)

[Tanner Lovelace]

On Fri, 2003-02-07 at 16:39, Brian Daniels wrote:
> On Fri, Feb 07, 2003 at 04:31:00PM -0500, Tanner Lovelace wrote:
> > On Fri, 2003-02-07 at 16:15, Jeff Jackowski wrote:
> > 
> > > For LP mode, the tape is run slower, but the data format is the same. The 
> > > only degradation will be an increased error rate, which still won't happen 
> > > often, but it will happen maybe 2 to 5 times per tape. The rest of the 
> > > time it'll look the same as SP mode. Just have that playback problem to 
> > > work around.
> > 
> > Actually, Jeff, please look at the URL I posted previously (in Mozilla,
> > because Konqueror and Safari seem to give a 404 on it).  LP mode for
> > miniDV does *not* run slower, but it does adjust the width of the
> > tracks from 10 microns to about 6 microns.  If two different miniDV
> > players aren't perfectly aligned, then there can be problems.
> > 
> 
> 
> To jump in here: (off-topic!)
> 
> It makes the track width narrower by slowing down the tape.  The video 
> heads are inside a spinning drum that is mounted at an angle to the tape.  
> The heads pass over a diagonal slice of tape as the drum rotates:
> 
> -------------------
> /  /  /  /  /  /  /  ----> tape motion
> ------------------
> 
> if the tape moves slower then the head passes get packed closer together:
> 
> ------------------
> //////////////////  --> 
> ------------------
> 
> This packs more data into the same space, giving you the increased 
> recording time.  But it makes the tolerances very tight, increasing the 
> chance of errors when the data is read.
> 
> --Brian (who's dealt with this too much in DAT drives)

Hmm... according to the web page (and web pages are never wrong, eh? ;-)
"In both modes the head drum spins at 9000 rpm and has to be able to
accurately position each head over it's respective track on a moving
tape."

BTW, here's a mirror of that page:
http://www.trilug.org/~jeremy/minidv_sp_vs_lp.htm

Cheers,
Tanner
-- 
Tanner Lovelace | lovelace(at)wayfarer.org | http://wtl.wayfarer.org/
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