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'[OT] PIC to generate sync for VCR to record data'
2000\02\08@141627 by Martin McCormick

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       I remember reading about those digital Sony interfaces in the
eighties.  If I recall, they used 32,000 samples per second so they
weren't directly compatible with CD systems, but they probably sounded
quite good anyway.

       Older VCR's need to see at least a vertical sync at the
correct rate in order to record at a uniform speed.

       I even read that some public television station in Boston used
to broadcast an experimental digital feed of classical music
performances through one of those Sony devices and the audience was
instructed to tune their VCR to that channel and then feed the video
out to the correct input on their digital converter and the result was
digital radio.

       I think if you just want to use an older VCR to record audio,
all you need is a source of a good sync signal.  I do this all the
time and just tune in a channel to provide a signal to make the sync
circuitry happy and then feed audio in to the auxiliary input jack.
It makes for some very strange video tapes, I am sure, but the sound
is steady.  With one of the digital systems, you could have two stereo
channels plus the linear edge track for yet another audio channel.

       Thanks for mentioning the name of the Sony F1.  I have
always wanted to find one of those, but had forgotten what it was
called.


Martin McCormick

andy howard writes:
>Many of the earliest digital audio recordings were done on video
>recorders, using a Sony F1 PCM adaptor. In those days "real" digital
>recorders cost a small fortune so the Sony/video recorder system gained
>a lot of friends by being some two orders of magnitude cheaper(!)

2000\02\08@165830 by andy howard

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> I remember reading about those digital Sony interfaces in the
> eighties.  If I recall, they used 32,000 samples per second so they
> weren't directly compatible with CD systems, but they probably sounded
> quite good anyway.

The ones I have seen *have* been 44.1kHz sampling rate - In fact I was
once told that the 44.1k sample rate was chosen for compatibility with
the F1 (and with the various professional versions which had PCM numbers
AFAIR. They were *much* too expensive for the kind of places I worked in
those days.)  The reasoning being that in Europe the PAL TV system used
625 line at 50 Hz field rate (=25Hz frame rate).  Three full samples
could be fitted per line and 37 lines were used for frame sync, in-line
data services etc. so the sample rate was 3*25*588= 44100.

That may have been the fanciful musings of an old engineer, but I was
convinced by it at the time. Certainly the PCM machines were around
before CDs were ever on sale. I don't know how that would work out with
the US frame and line rates though. Maybe they stole a few extra lines
from the frame sync area.

I do recall that the very first ones were 14 bit so maybe that was what
you were thinking of, pretty soon they were made switchable 14/16 bit.


>         I even read that some public television station in Boston used
> to broadcast an experimental digital feed of classical music
> performances through one of those Sony devices and the audience was
> instructed to tune their VCR to that channel and then feed the video
> out to the correct input on their digital converter and the result was
> digital radio.

It's amazing what can be achieved if you try. In the late 70's or early
80's the BBC here in the UK used to send software to accompany a
computer literacy programme on the audio channel of the TV signal for
people to record on their cassette recorders (this was in the days when
a cassette was de rigeur for any home computer).

I was hugely impressed by Norman Gillespie's account today of recording
the entire AM band on a VCR too.


> Thanks for mentioning the name of the Sony F1.  I have
> always wanted to find one of those, but had forgotten what it was
> called.

Nostalgia eh?

If you're thinking of buying one then look for the PCM1xxx series which
were the professional version of the F1 and cost a king's ransom in
their day. I recall a friend of mine hiring one in the early 80s for
around 800 US dollars per day!












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