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Old October 13th 17, 09:37 AM posted to uk.tech.digital-tv
NY
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Default Timecode on programme-as-broadcast archive material

"Graham." wrote in message
...
On Thu, 12 Oct 2017 21:13:18 +0100, "NY" coalesced
the vapors of human experience into a viable and meaningful
comprehension...

Brian, what I was meaning is that the timecode - or at least, the burnt-in
timecode that is displayed on-screen in examples such as the in-house
version of an episode of Blue Peter that I mentioned - starts at
10:00:00.00
(ie 10 hours, zero minutes etc), I was expecting it to start at zero
hours,
but now people have talked about needing a time code for the run-up
stabilisation time before the start of the programme, I can see why a
pre-zero time of 23:59:30 would be a bad thing.

And I can see why they chose 10 rather 01 as the starting hour, because it
allows you to mentally or literally mask off the leading digit and get a
time which at any instant is the true elapsed time since the start.


By the way, were there ever times when a programme spanned more than one
tape? Did they have a means of the first VTR (when it reached a designated
TC) triggering the run-up of a second VTR and then seamlessly switching
transmission from one to the other at the correct frame?



I don't know how often they *did* do it, but they certainly had the
technology *to* do it as that is how editing was done.


True. I hadn't thought of that, but yes to do editing they needed the
technology for a first VTR to cue up a second one (into record mode, rather
than play mode),

I still can't get my head (pun not intended) around the cut-tape editing of
2" quad tape - to be able to get the joint sufficiently accurately timed
that there was no glitch requires superhuman skills, rather like gluing a
broken CD back together; it's hard enough with a 78 or LP record. I realise
that the actual joint is between one head pass and the next, but there's
still plenty of scope for timing errors.

Presumably once a tape has been cut-edited it must never be bulk-erased or
the electronic "sprocket hole" timing marks of a new recording could occur
in the wrong place, putting the joint in the path of the spinning head - or
did they have an absolute ban on recording over cut tape, even if the timing
marks were still in place?

I remember my dad bought a device for editing camcorder footage onto VHS. It
used a control bus for the Hi-8 camcorder (the source) and an IR emitter
that you trained with the VHS recorder's remote. You then calibrated it with
a special signal that displayed countdown numbers and you examined a test
recording to see what your VHS machine's in and out delays were. It worked
fairly well, though VHS was never 100% reproducible in its pre-roll times,
and you still got the coloured patches at the point where the new recording
kicked in. It was painfully slow if you wanted to use shots in different
parts of the source tape, and you had to be careful that the VHS deck didn't
come out of pause mode if it was kept waiting too long :-)

I'll tell you about something that was routinely done at Granada in
the mid '80s, because I saw it for myself. When Coronation St was to
be played out from VTR they cued up a pair of C format machines, the
second one carrying a copy that was called "the guard", so should
anything go wrong, like a head clog, the operator could very quickly
switch to the other machine.


I can imagine this happened quite often for very popular programmes. I
presume mission-critical equipment is on uninterruptible power supplies and
the two playout machines are on different UPSs.