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From: maj@hpfinote.HP.COM (Mike Jassowski)
Newsgroups: sci.electronics
Subject: Re: Digital recording on a VCR
Message-ID: <15880005@hpfinote.HP.COM>
Date: 19 Jan 90 21:03:30 GMT
References: <21254@siemens.siemens.com>
Organization: Hewlett Packard CICD
Lines: 29

/ hpfinote:sci.electronics / henry@utzoo.uucp (Henry Spencer) /  9:46 am  Jan 18, 1990 /
>In article <13400@cit-vax.Caltech.Edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes:
>>me and a friend have wondered how tough it would be to record a stream of
>>digital pulses on a vcr tape and play them back (i.e. cheap HD backup, speed
>>doesn't really matter). We tried putting the serial port though an op-amp
>>and recording it on cassette tape, however we had some trouble...

I had some luck recording digital on audio tapes.  I had to modulate the
digital information.  Audio recorders have trouble with DC; if you have 
several ones/zeros in a row, it starts to look like DC.  A little filtering
the output restored the informtion.
>
>VCRs are not like audio recorders; they know that their input is a video
>signal and tinker accordingly.  (For example, as I recall, they record sound
>and picture separately on the tape, meaning they know how to take a video
>signal apart.)  You're going to have to make your digital data look like
>video, at least to the extent of having sync pulses, I'd guess.

Most VCRs have separate "video in" and "audio in" ports, as well as the
RF connection.  If you used these, there may be less artificial video
stuff that needs to be done.  My thesis advisor claimed that an audio
type signal into the video port should work, but you would still have to
modulate any digital information (although I never tried it).  To give
this a try, you might just attempt an audio recording through the video
input, and see if it is distorted on playback.
>-- 
>1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
>1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
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