[24hoursupport] Re: The Myth Of The 100-Year CD-Rom

  • From: Madrachod@xxxxxxx
  • To: 24hoursupport@xxxxxxxxxxxxx
  • Date: Wed, 9 Feb 2005 01:41:53 EST

 
In a message dated 2/8/2005 1:29:55 P.M. Eastern Standard Time, 
chizotz@xxxxxxxxx writes:
Magnetic tape has (this is basic so don't hold me to specifics) a stripe down 
one edge that contains timing ticks, and the rest of the tape width is used 
to store the actual analog data, usually sound information. Stereo recorders 
broke that area down into two stripes, one for each channel.
    I've never heard of these timing ticks and I've been dealing with 
recording tape for a good 35 to 40 years now.
    And, I don't recall video tape having them either.  I've been dealing 
with that stuff for at least 33 years now, back when it was still only 
available 
on open reels.  The video record head spins around at a very fast pace and 
records the picture onto the tape at an angle like this: \\\\\\\\\\\\\\\\\\\\  
Each of those lines is equivalent to one pass of the video head.  There are 
actually two heads on the cylinder that spins around.  Each of those lines is 
probably also equal to one frame, but I'm not absolutely sure about that.  As 
far 
as I know, the modern video tape machine doesn't use ticks at all, it just 
very quickly adjusts itself to the correct speed that the tape was recorded at. 
 
That's why the machine has to spend a few seconds tracking when you first pop 
a tape into it.  It spends about 1 second adjusting to the correct speed and 
the next few fine tuning to that speed so that the playback will match up with 
the record.  Record a video tape at one speed for a few minutes, or even a few 
seconds, and then stop tape and set it to record at a different speed.  When 
you play the tape back from the start, when it get's to the point where you 
switched speeds, you'll hear the sound speed up or slow down dramatically 
within 
about half a second.  That's because the machine is adjusting itself to the 
correct speed.  It's also going to have to track again to adjust to the new 
playback speed of the tape.
    With audio tape the speed is adjusted by the person operating the 
machine.  What good are ticks when you can fine tune the speed (the pitch) 
while you 
play or record the tape?
 
                            Dale

 


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