i realize there may be other more eficient means with the advent
of cheap digital capture but this was more of a hobby project for
fun and **Learning** exercise as VCRs are very cheap and easy to
come by

so the idea is to get a standard issue VCR and modify to become a
time lapse recorder say something like 5 fps , 1 fps or 1
frame every 5 seconds

how much can a standad VCR be slowed before significant
degradation in image quality ?

is this mod possible ? what sort of changes to make ?

my own thoughts from my limited VCR undersranding are these
issues :

1. This mod makes no sense if the tape record capacity can not be
increased so tape movement needs to be changed
1a. slowed down easier i suspect but image quality threshold
is problem
1b. stop and go to *BUT* more complex with timing and
gettting tape up to speed from full stop and the mechanical plus
electrical problem with the go part
1c. slow down speed up combo to eliminate the issues with
complete stop and go
2. Recording Head speed and timing with the tape movement ?
3. Playback issues. can such a tpe be played in any VCR or just
the time lapse

4. Just use a Different technology like some digital storage
capture and take a pics at desired frame rate

robb wrote:

> i realize there may be other more eficient means with the advent
> of cheap digital capture but this was more of a hobby project for
> fun and **Learning** exercise as VCRs are very cheap and easy to
> come by
>
> so the idea is to get a standard issue VCR and modify to become a
> time lapse recorder say something like 5 fps , 1 fps or 1
> frame every 5 seconds
>
> how much can a standad VCR be slowed before significant
> degradation in image quality ?
>
> is this mod possible ? what sort of changes to make ?
>
> my own thoughts from my limited VCR undersranding are these
> issues :
>
> 1. This mod makes no sense if the tape record capacity can not be
> increased so tape movement needs to be changed
> 1a. slowed down easier i suspect but image quality threshold
> is problem
Impossible. There is a minimum tape advance for the head to lay down a
track (remember its helical scanning) that can be played back with a
head of normal width. The timelapse recorders I used to work on
although often based on a deck similar to those in high end domestic
units, always had custom upper drums, capstan motors and servo circuits.

> 1b. stop and go to *BUT* more complex with timing and
> gettting tape up to speed from full stop and the mechanical plus
> electrical problem with the go part

Not insurmountable on a machine with an EP recording mode that retracts
the tape to half load and stops the capstan on extended pause. If the
tape remains in contact with the drum, it will wear through the tape so
the pause mode is designed to end (either to stop or Play/Record) after
a couple of minutes. Some decks throw in an occasional frame advance in
pause for the same reason.
> 1c. slow down speed up combo to eliminate the issues with
> complete stop and go
*worse* problems than pausing to half load. The drum speed is tied to
the video frame rate. Pro timelapse recorders dont mess with the drum
speed though I remember one model that had dynamic drum tilt to maintain
the tracking and did dynamically vary the capstan speed. Everything
else drove the Capstan like a stepper motor (actually usually like a
servo but definately in discrete steps). They also have nice features
like alarm inputs to go to a higher quality mode when a PIR gets
triggered and alarm outputs for faults like mechanism failure, broken
tape, end of tape or no tape to let you hook up an autodialler to notify
the boss.
> 2. Recording Head speed and timing with the tape movement ?
> 3. Playback issues. can such a tpe be played in any VCR or just
> the time lapse
Tapes from the high end ones that could step the capstan with enough
accuracy could be played on a normal VCR, but the quality sucked
compared to playback on the original deck.

Also, *all* VHS timelapse recorders are incredibly tough on tapes. If
you want usable evidence, a new tape *every* week was more or less
essential, as was a timecode stamp on the video.
>
> 4. Just use a Different technology like some digital storage
> capture and take a pics at desired frame rate
>
*yes* but nowdays you want it to be solid state rather than HDD based
for long term reliability. The future is probably network camera
based. You might be able to do something worth-while if you add Video
capture and a SD or MMC card interface to that 8051 board of yours, but
the sensible thing to do if you want to experiment with the technology
is to look at PC compatible SBCs with a CF card rather than a HDD.
Development can be done on an ordinary PC.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

"robb" <some@where.on.net> wrote in message
news:13oh8ssg284gtf6@corp.supernews.com...
> i realize there may be other more eficient means with the advent
> of cheap digital capture but this was more of a hobby project for
> fun and **Learning** exercise as VCRs are very cheap and easy to
> come by

Much easier to hook the same camera you plan to use to your PC. I'm sure
there must be free S/W to do this on the web.

"Ian Malcolm" <valid.address.in.signature@invalid.invalid> wrote
in message news:fmahu8$kcp$1@inews.gazeta.pl...
> robb wrote:
>
> >
> > so the idea is to get a standard issue VCR and modify to
become a
> > time lapse recorder say something like 5 fps , 1 fps or 1
> > frame every 5 seconds
> >
> > my own thoughts from my limited VCR undersranding are these
> > issues :
> >
> > 1a. slowed down easier i suspect but image quality
threshold
> > is problem
>
> Impossible.
>
> > 1b. stop and go to
>
> Not insurmountable on a machine with an EP recording
>
> > 1c. slow down speed up combo to eliminate the issues
with
> > complete stop and go
>
> *worse* problems than pausing to half load.
>
> Also, *all* VHS timelapse recorders are incredibly tough on
tapes
>

Thanks for help/ideas Ian,

Impossible, not insurmountable and worse ...

I guess i have enough of those kinds of projects going right
now. i think i might reconsider and try out the pc capture as
you suggested.

thanks again for help,
robb

Inline:

"robb" <some@where.on.net> wrote in message
news:13oh8ssg284gtf6@corp.supernews.com...
>i realize there may be other more eficient means with the advent
> of cheap digital capture but this was more of a hobby project for
> fun and **Learning** exercise as VCRs are very cheap and easy to
> come by
>
> so the idea is to get a standard issue VCR and modify to become a
> time lapse recorder say something like 5 fps , 1 fps or 1
> frame every 5 seconds
>
> how much can a standad VCR be slowed before significant
> degradation in image quality ?
>
> is this mod possible ? what sort of changes to make ?
>

There is an awful lot of mechanism inside of a typical VCR. One of the
typical parts is a set of gears that drive the tape. If you yank it all
apart, and switch out the gears (which sounds like a nightmare to me) you
might be able to get it to run more slowly.

> my own thoughts from my limited VCR undersranding are these
> issues :
>
> 1. This mod makes no sense if the tape record capacity can not be
> increased so tape movement needs to be changed
> 1a. slowed down easier i suspect but image quality threshold
> is problem

Well, yeah. If you consider the quality differences between SP and LP on a
typical VCR, and extrapolate that out to 1/5 fps, well... I'm not sure how
they encode the video signal, but at a slower speed, the errors are going to
be more obvious.

> 1b. stop and go to *BUT* more complex with timing and
> gettting tape up to speed from full stop and the mechanical plus
> electrical problem with the go part
> 1c. slow down speed up combo to eliminate the issues with
> complete stop and go
> 2. Recording Head speed and timing with the tape movement ?
> 3. Playback issues. can such a tpe be played in any VCR or just
> the time lapse
>
> 4. Just use a Different technology like some digital storage
> capture and take a pics at desired frame rate
>

This is by far the easiest approach. You can buy off the shelf cards that
will record off the line. Get a 500GB disk (I saw one yesterday for $80 at
Fry's), and you can record in real time for about a year. (no, not
really...) You probably have a computer, so adding a disk and a video card
to the computer is easy. If you got ambitious, you could even try to write
some software to sample the output stream from the video card at 1/5 fps.

Here is a capture device for $20:

http://www.tigerdirect.com/applications ... CatId=1425

you could hack the remote to make it do the 1/5 fps thing.

Regards,
Bob Monsen

On Sat, 12 Jan 2008 06:27:22 -0500, robb wrote:

> i realize there may be other more eficient means with the advent
> of cheap digital capture but this was more of a hobby project for
> fun and **Learning** exercise as VCRs are very cheap and easy to
> come by
>
> so the idea is to get a standard issue VCR and modify to become a
> time lapse recorder say something like 5 fps , 1 fps or 1
> frame every 5 seconds
>
> how much can a standad VCR be slowed before significant
> degradation in image quality ?
>
> is this mod possible ? what sort of changes to make ?

If your "standard" VCR has a pause button, then it can be slowed
to zero, and left there until the head wears a hole in the tape.
Or the tape wears a hole in the head.

I saw a VCR once that had a slo-mo playback that could be slowed
down to almost zero - the tape would just advance one frame per
"bip", as it were. (the frames are recorded on diagonal tracks
and read helically, one after the other.)
http://electronics.howstuffworks.com/vcr3.htm

So, if you have the talent to hack into the tape advancer thing
that gives the slo-mo playback (assuming your VCR has it), and
the cojones to hack into the video circuitry and make it record
on those passes instead of play, you could do it.

But it is definitely NOT a beginner-level project.

Good Luck!
Rich