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Timecode on programme-as-broadcast archive material



 
 
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  #1  
Old October 12th 17, 11:07 AM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,187
Default Timecode on programme-as-broadcast archive material

This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?

  #2  
Old October 12th 17, 01:29 PM posted to uk.tech.digital-tv
Bill Taylor[_2_]
external usenet poster
 
Posts: 35
Default Timecode on programme-as-broadcast archive material

On Thu, 12 Oct 2017 12:07:21 +0100, "NY" wrote:

This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?


You'll notice that there's a clock before 10:00:00:00. If you start
the programme at 00:00:00:00 the clock would run from, say
23:59:30:00, which can be a trifle disconcerting.

10:00:00:00 was the BBC convention for complete programmes, but
inserts could be run from any time code which seemed appropriate.
  #3  
Old October 12th 17, 04:45 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,187
Default Timecode on programme-as-broadcast archive material

"Bill Taylor" wrote in message
...
On Thu, 12 Oct 2017 12:07:21 +0100, "NY" wrote:

This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?


You'll notice that there's a clock before 10:00:00:00. If you start
the programme at 00:00:00:00 the clock would run from, say
23:59:30:00, which can be a trifle disconcerting.

10:00:00:00 was the BBC convention for complete programmes, but
inserts could be run from any time code which seemed appropriate.


Ah, of course. I was forgetting that a VT or film would need to start
running from a few seconds before the 00:00:00.00 point to allow for the VT
countdown clock. And as you say, it would look odd to see 23:59:30 in this
run-up. I suppose starting at 10:00:00 rather than (for example) 01:00:00
has the advantage that you just ignore the tens digit and then you have the
elapsed time of the programme (assuming it does not run for more than 10
hours).

  #4  
Old October 12th 17, 05:04 PM posted to uk.tech.digital-tv
The Other John[_2_]
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Posts: 53
Default Timecode on programme-as-broadcast archive material

On Thu, 12 Oct 2017 12:07:21 +0100, NY wrote:

This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?


Early time code based video tape editors were unable to cue up a tape for
an edit at 00:00:00:00 because a 10 second pre-roll would need to be at
23:59:50:00 which the edit controller would see as 23+ hours into the
tape. In other words it couldn't handle a negative pre-roll, I don't know
if later ones could but of course now it's all non-linear editing they can
handle anything.

--
TOJ.
  #5  
Old October 12th 17, 07:01 PM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,807
Default Timecode on programme-as-broadcast archive material

I'm not sure what you mean, but on old video tape there was always time
allowed for everything to stabilise, I seem to recall.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"NY" wrote in message
o.uk...
This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?



  #6  
Old October 12th 17, 08:13 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,187
Default Timecode on programme-as-broadcast archive material

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?




"Brian Gaff" wrote in message
news
I'm not sure what you mean, but on old video tape there was always time
allowed for everything to stabilise, I seem to recall.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"NY" wrote in message
o.uk...
This is probably a weird, obsessive question...

I've noticed that if you see a programme from a tape archive (eg BBC's
Windmill Road) with burnt-in timecode, the TC often begins at 10:00:00
rather than 00:00:00. An example is
https://www.youtube.com/watch?v=Yf3zE0x_dkI Is there a reason why they
chose to begin the TC at a "zero" of 10:00:00?



  #7  
Old October 12th 17, 10:29 PM posted to uk.tech.digital-tv
Graham.[_12_]
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Posts: 404
Default Timecode on programme-as-broadcast archive material

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.

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.

--

Graham.
%Profound_observation%
  #8  
Old October 13th 17, 09:37 AM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,187
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.

  #9  
Old October 13th 17, 09:43 AM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 322
Default Timecode on programme-as-broadcast archive material

On 12/10/2017 14:29, Bill Taylor wrote:
On Thu, 12 Oct 2017 12:07:21 +0100, "NY" wrote:


You'll notice that there's a clock before 10:00:00:00. If you start
the programme at 00:00:00:00 the clock would run from, say
23:59:30:00, which can be a trifle disconcerting.

10:00:00:00 was the BBC convention for complete programmes, but
inserts could be run from any time code which seemed appropriate.


It's still the convention for all UK broadcasters, Ref Page 23:-

https://dpp-assets.s3.amazonaws.com/...DPPGeneric.pdf



--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #10  
Old October 13th 17, 09:48 AM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 2,131
Default Timecode on programme-as-broadcast archive material

On Thu, 12 Oct 2017 23:29:24 +0100, Graham.
wrote:

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.

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.


The use of timecode also had to be given some thought when recording
raw material on a shoot, the two main methods being "run/record" and
"time of day", each with its pros and cons depending on what type of
shoot it was.

Run/record meant that the timecode would be zeroed at the start of
each tape and the generator, built into the recorder, would only
advance the time while the machine was recording. This would mean that
the timecode would also be an indication of the amount of tape used,
which would help to keep track of it and avoid running out in the
middle of a take. This would be most useful when shooting with a
single camera. It would also be possible to continue using the same
tape on a second day by setting the timecode generator to whatever
value had been reached previously.

Time of day meant just what it says; The timecode generator would run
continuously so the timecode would be the same as the time of day.
This would be useful on a multicamera shoot where the material would
have to be synchronised later. All recorders would either be fed from
a master generator, or each would have its own built-in generator and
they'd all be set carefully at the start of the day. This inevitably
meant a more extravagant use of tape, because if partially used tapes
were used on a second day, there was a possibility of a "timewarp",
where earlier timecode values could occur at later parts of the tape,
which could confuse the editing equipment when searching for material.
Typically, time of day recording would be used with multiple
camcorders where the tapes (or cassettes) would be the smaller sizes
anyway, so there would be some waste but not so much.

Rod.
 




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