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TV system conversion



 
 
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  #1  
Old March 18th 17, 04:50 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 1,458
Default TV system conversion

At the time when when I was a baby the only way was to point a camera at
a screen. Results were unimpressive.

By 1964 things had moved on and conversion was electronic. The equipment
had 2,000 transistors and occupied two full height racks.
http://ieeexplore.ieee.org/stamp/sta...number=5266568

I have just bought a gadget that converts TVI and AHD to HDMI, VGA, and
CVBS. It handles 720p and 1080p at all frame rates. All VGA modes are
supported. CVBS is PAL or NTSC, 25 or 30fps.

This device is the size of a paperback book and cost £55. It works
perfectly. I would love to go back in time and show it to the engineers
of 1950!

If anyone's interested it's a Scatterbox CNV200.

Bill
  #2  
Old March 18th 17, 05:32 AM posted to uk.tech.digital-tv
Brian-Gaff
external usenet poster
 
Posts: 549
Default TV system conversion

Yes those first moon pictures were only sent at a low frame rate, and the
way we all saw it was a long persistence phosphor tube and a camera pointing
at it. the more recent re mastering of the images was done electronically
from the raw data stored in an Australian ground station. It was on spools
of tape which also contained the data hence the low frame rate. I'm told by
those who have seen them that they are a heck of a lot better.
The later missions of course used dedicated data systems for the colour
pictures.

I remember that we at Racal-Decca had to hastily come up with a way to
record radar displays for the CAA. The first solution knocked up very
quickly was a philips N1702 with bnc video in and out and the same idea of a
camera and it looked at a traditional radar screen.

I'm sure I'm not going to get thrown in clink for revealing this top
secret device..:-)
Brian

--
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
"Bill Wright" wrote in message
news
At the time when when I was a baby the only way was to point a camera at a
screen. Results were unimpressive.

By 1964 things had moved on and conversion was electronic. The equipment
had 2,000 transistors and occupied two full height racks.
http://ieeexplore.ieee.org/stamp/sta...number=5266568

I have just bought a gadget that converts TVI and AHD to HDMI, VGA, and
CVBS. It handles 720p and 1080p at all frame rates. All VGA modes are
supported. CVBS is PAL or NTSC, 25 or 30fps.

This device is the size of a paperback book and cost £55. It works
perfectly. I would love to go back in time and show it to the engineers of
1950!

If anyone's interested it's a Scatterbox CNV200.

Bill



  #3  
Old March 18th 17, 08:48 AM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 1,906
Default TV system conversion

On Sat, 18 Mar 2017 04:50:20 +0000, Bill Wright
wrote:

At the time when when I was a baby the only way was to point a camera at
a screen. Results were unimpressive.

By 1964 things had moved on and conversion was electronic. The equipment
had 2,000 transistors and occupied two full height racks.
http://ieeexplore.ieee.org/stamp/sta...number=5266568


That was just the line-store equipment for converting between
standards with the same field rate, e.g. 405 and 625, with the output
field rate being locked to the input. The one they eventually
developed for converting between 625/50 and 525/59.94 in colour was a
monster occupying 7 or 8 racks as I recall. The delays were
implemented by modulating an RF carrier and using piezoelectric
transducers to send it as a sound wave of 30MHz (even higher than bats
can hear!) through variously sized glass blocks. It had to be kept
switched on all the time so it didn't drift oput of spec.

I have just bought a gadget that converts TVI and AHD to HDMI, VGA, and
CVBS. It handles 720p and 1080p at all frame rates. All VGA modes are
supported. CVBS is PAL or NTSC, 25 or 30fps.


This device is the size of a paperback book and cost 55. It works
perfectly. I would love to go back in time and show it to the engineers
of 1950!


I often find myself thinking the same sort of thing every time I pick
up a smartphone. I think my younger self would be impressed to see
one, not only with how clever it was to make such a thing, but how
stupid it was to make a portable gadget so fragile.

Rod.

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  #4  
Old March 18th 17, 02:15 PM posted to uk.tech.digital-tv
Graham.[_12_]
external usenet poster
 
Posts: 334
Default TV system conversion

On Sat, 18 Mar 2017 04:50:20 +0000, Bill Wright
wrote:

At the time when when I was a baby the only way was to point a camera at
a screen. Results were unimpressive.

By 1964 things had moved on and conversion was electronic. The equipment
had 2,000 transistors and occupied two full height racks.
http://ieeexplore.ieee.org/stamp/sta...number=5266568

I have just bought a gadget that converts TVI and AHD to HDMI, VGA, and
CVBS. It handles 720p and 1080p at all frame rates. All VGA modes are
supported. CVBS is PAL or NTSC, 25 or 30fps.

This device is the size of a paperback book and cost 55. It works
perfectly. I would love to go back in time and show it to the engineers
of 1950!

If anyone's interested it's a Scatterbox CNV200.

Bill


I think you've already seen this, and I must redo it sometime, now I
have built a Band I modulator and the picture is miles better.
https://www.youtube.com/watch?v=T2oNculjoQc
An obsolete PC with webcam running Vidblaster and WinModelines, which
coaxes half the dual-head graphics card to output 405 lines (or 625 or
813, 525 etc.)

It's still not a real-time system converter, but I question why anyone
would want one, I am perfectly content to digitise analogue TV content
first and import the resulting digits.




--

Graham.
%Profound_observation%
  #5  
Old March 18th 17, 02:38 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 933
Default TV system conversion

"Graham." wrote in message
...
I think you've already seen this, and I must redo it sometime, now I
have built a Band I modulator and the picture is miles better.
https://www.youtube.com/watch?v=T2oNculjoQc
An obsolete PC with webcam running Vidblaster and WinModelines, which
coaxes half the dual-head graphics card to output 405 lines (or 625 or
813, 525 etc.)

It's still not a real-time system converter, but I question why anyone
would want one, I am perfectly content to digitise analogue TV content
first and import the resulting digits.


Excellent bit of work.

I notice you're getting some 1Hz beating between the pictures on the TV and
your video camera for making the Youtube video. I've just looked at the
"Stats for Nerds" and I see that you shot your Youtube video at 24 rather 25
Hz, so that's why! Maybe in the interests of perfection you should use a
normal 25 Hz camcorder next time :-)

Before the National Media Museum got rid of their TV gallery (a criminal
waste to consign all the equipment that had on show to behind-the-scenes
tours only) they had three screens showing the same recorded pictures:
405-line, 720x576 SD and 1920x1080 HD. I wonder whether they used similar
equipment to you for down-scaling the HD original to 405-line mono, either
via a modulator or a direct tap into the composite video feed within the TV.


I do wonder what planet the National Media Museum are on: first they got rid
of the excellent Tim Hunkin "how TV works" demos, then the Calendar News
studio showing the petrol fire in Summit Tunnel, and all the
behind-the-scenes work to produce a live news programme, and now they have
got rid of most of the TV gallery. What will be left? The still-photography
gallery (which is still good), lots of stuff aimed at children who just like
w**king the buttons, and a few temporary and slightly pretentious galleries
of various photographers' work. Last time I went (before the demise of the
TV gallery) I was fairly underwhelmed, and I bet I would be even more so
now.

It's a shame that when the Museum of the Moving Image on the South Bank in
London closed, more of the displays from there didn't find themselves at the
Bradford museum.

  #6  
Old March 18th 17, 02:56 PM posted to uk.tech.digital-tv
external usenet poster
 
Posts: 162
Default TV system conversion

On Saturday, 18 March 2017 04:50:22 UTC, wrote:
This device is the size of a paperback book and cost £55. It works
perfectly. I would love to go back in time and show it to the engineers
of 1950!


Ah, 1950 (not that I remember it of course), education was useful, houses were affordable, healthcare was available and jobs were secure.

And only another 6 years of sweet rationing to go!

Owain


  #7  
Old March 18th 17, 02:58 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 933
Default TV system conversion

"Bill Wright" wrote in message
news
At the time when when I was a baby the only way was to point a camera at a
screen. Results were unimpressive.


I remember in the 1970s on News at Ten, you'd occasionally get footage of
breaking news stories in NTSC-land (eg USA, Japan, Africa or South America)
which had the tell-tale rapid 5 Hz flicker and geometric distortion which
showed the the UK news crew had taken (with or without permission!) local
footage and re-photographed the screen with their film or video camera -
presumably because there wasn't time to get a standard-conversion done. Not
pretty, as you say.

What always used to intrigue me was that you could always spot local TV news
footage from France or Russia, even though no line or frame rate conversion
is necessary between SECAM and PAL. As far as I know, French and Russian
equipment records in PAL and only converts to SECAM for transmission (for
ease of mixing captions on top of footage, and to use more widely-available
rather than niche-market equipment), so you'd think that UK news teams would
be able to get a clean copy without any SECAM-to-PAL artefacts like speckle
and streaks on the edges of saturated colours.

Does SECAM use the same gamma and black level as PAL, or do you get the same
problems as with NTSC where their pictures look very artificial and
plasticky. Mind you, even on NTSC tellies, US pictures look odd, in a way
that is difficult to define - something to do with contrast and tonal range.
Admittedly it was on a multi-standard TV (NTSC/PAL/SECAM) that my sister
bought in the UK for when they lived in the US for a while, so maybe the
NTSC signal was being decoded using the PAL gamma constant, though you'd
think a true multi-standard TV would cater for differences like that.

  #8  
Old March 18th 17, 03:32 PM posted to uk.tech.digital-tv
Graham.[_12_]
external usenet poster
 
Posts: 334
Default TV system conversion

On Sat, 18 Mar 2017 14:38:44 -0000, "NY" wrote:

"Graham." wrote in message
.. .
I think you've already seen this, and I must redo it sometime, now I
have built a Band I modulator and the picture is miles better.
https://www.youtube.com/watch?v=T2oNculjoQc
An obsolete PC with webcam running Vidblaster and WinModelines, which
coaxes half the dual-head graphics card to output 405 lines (or 625 or
813, 525 etc.)

It's still not a real-time system converter, but I question why anyone
would want one, I am perfectly content to digitise analogue TV content
first and import the resulting digits.


Excellent bit of work.

I notice you're getting some 1Hz beating between the pictures on the TV and
your video camera for making the Youtube video. I've just looked at the
"Stats for Nerds" and I see that you shot your Youtube video at 24 rather 25
Hz, so that's why! Maybe in the interests of perfection you should use a
normal 25 Hz camcorder next time :-)


I don't know, but I didn't think *that* was the problem.
I was using an iPad. I notice that Big Clive has abandoned his iPad,
he was forever complaining about flicker and lack of control, and is
using something different now and has other problems noticeably with
sound.
What I thought was the problem was the crude arrangement I had to
inject the video into the set.
I hadn't finished restoring the set, and I had not built a modulator,
so I injected the video onto the grid of the video amp. As I no longer
have a suitable isolation transformer to power the set I used a cheap
UPS and a 12v 20A PSU as an inverter to provide 230V isolated from
earth. The UPS uses a ceramic resonator as its frequency reference.
The UPS output was not true sign-wave and was far from ideal, There
was some visible hum present,

Before the National Media Museum got rid of their TV gallery (a criminal
waste to consign all the equipment that had on show to behind-the-scenes
tours only) they had three screens showing the same recorded pictures:
405-line, 720x576 SD and 1920x1080 HD. I wonder whether they used similar
equipment to you for down-scaling the HD original to 405-line mono, either
via a modulator or a direct tap into the composite video feed within the TV.


I do wonder what planet the National Media Museum are on: first they got rid
of the excellent Tim Hunkin "how TV works" demos, then the Calendar News
studio showing the petrol fire in Summit Tunnel, and all the
behind-the-scenes work to produce a live news programme, and now they have
got rid of most of the TV gallery. What will be left? The still-photography
gallery (which is still good), lots of stuff aimed at children who just like
w**king the buttons, and a few temporary and slightly pretentious galleries
of various photographers' work. Last time I went (before the demise of the
TV gallery) I was fairly underwhelmed, and I bet I would be even more so
now.

It's a shame that when the Museum of the Moving Image on the South Bank in
London closed, more of the displays from there didn't find themselves at the
Bradford museum.


A friend of mine donated a Dynatron to the Vintage Wireless Museum in
South London.

https://www.youtube.com/watch?v=gQdoqYD8jLY

I suspect they use the de facto standard device viz the Aurora
standards converter. All that will do is convert from 625 and show a
factory set stored still, usually a test card.

It seems to me that my rig would be far more flexible for a museum,
and I would like to run them side-by-side to see if my picture quality
matches that of the Aurora.
--

Graham.
%Profound_observation%
  #9  
Old March 18th 17, 04:16 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 933
Default TV system conversion

wrote in message
...
On Saturday, 18 March 2017 04:50:22 UTC, wrote:
This device is the size of a paperback book and cost £55. It works
perfectly. I would love to go back in time and show it to the engineers
of 1950!


Ah, 1950 (not that I remember it of course), education was useful, houses
were affordable, healthcare was available and jobs were secure.

And only another 6 years of sweet rationing to go!


And still King George VI on the throne. And no-one had ever heard of
Coronation Chicken :-)


I think the biggest technological advances are in size of cameras. I still
find it hard to get my head round the fact that you can use a camera that is
little bigger than a matchbox to record HD pictures for several hours onto a
wafer about the size of your little fingernail. Shame that all the ones of
that size (GoPro, SJCAM 5000, various dashcams) can only record in
US-standard 30 fps, and aren't switchable to 25 fps for the European market,
which means you have to endure jerky movement if you try to blend footage
from one of those cameras with footage from a proper 25 fps camcorder, as
every 5th frame of the 30 fps is dropped (Adobe Premiere doesn't do anything
fancy with interpolation!). I wonder if it's true 30 fps or 29.97 fps?

 




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