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

[Brian Daniels]

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)


-- 
Question with boldness even the existence of a god;
because if there be one he must approve of the
homage of reason more than that of blindfolded fear.

--Thomas Jefferson, Aug. 10, 1787


Brian Daniels                  bitmage at bellsouth.net
      http://www.eviloverlord.net