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TV system conversion



 
 
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  #11  
Old March 18th 17, 06:27 PM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Default TV system conversion

On Sat, 18 Mar 2017 16:16:46 -0000, "NY" wrote:

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?


I wonder how important the output frame rate really is nowadays, as
just about anything with a screen seems capable of displaying any
frame rate and any resolution, switching seamlessly between them
whenever necessary. My TV screen has to display the outputs of a
couple of Freeview PVRs, a Bluray player, a computer and an Amazon
box, and briefly shows some numbers indicating these technical
parameters whenever a new source is selected. I've seen 60, 50 and 24
flash up in the corner of the screen depending on what I'm watching,
but the rest of the time I can't even tell which it is. There would
only be a problem combining material from different sources, but
anyone making a video production would presumably ensure that all
their own material was to the same standards, so it could be edited
together without any discontinuities. As long any given programme was
consistent within itself, I doubt if anybody would notice.

Rod.

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  #12  
Old March 18th 17, 06:55 PM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 1,931
Default TV system conversion

On Sat, 18 Mar 2017 14:58:56 -0000, "NY" wrote:

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.


As far as I know, they're the same. The Sony cameras I remember
working with had plug-in boards for the different sections, the last
one being the encoder. Different boards were available for different
countries, but between the countries that used 625/50 I think the
encoder was the only board that needed to be changed, the rest of the
camera being the same.

For 525/60 the two line delay in the aperture corrector would need to
be different so that board would need to be a different one, but for a
tube camera the rest of it would be very similar. I think the video
processor board, which included things like gamma correction and white
clipping, was always the same.

I never encountered a chip camera that was switchable between 525 and
625, so some of the digital stuff must have been different, but I
think they used the same colour separating prisms, so must have used
essentially the same video processing.

Rod.

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  #13  
Old March 18th 17, 09:08 PM posted to uk.tech.digital-tv
NY
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Posts: 986
Default TV system conversion

"Roderick Stewart" wrote in message
...
On Sat, 18 Mar 2017 16:16:46 -0000, "NY" wrote:

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?


I wonder how important the output frame rate really is nowadays, as
just about anything with a screen seems capable of displaying any
frame rate and any resolution, switching seamlessly between them
whenever necessary. My TV screen has to display the outputs of a
couple of Freeview PVRs, a Bluray player, a computer and an Amazon
box, and briefly shows some numbers indicating these technical
parameters whenever a new source is selected. I've seen 60, 50 and 24
flash up in the corner of the screen depending on what I'm watching,
but the rest of the time I can't even tell which it is. There would
only be a problem combining material from different sources, but
anyone making a video production would presumably ensure that all
their own material was to the same standards, so it could be edited
together without any discontinuities. As long any given programme was
consistent within itself, I doubt if anybody would notice.


Frame rate is less important until you try to mix shots of 25 and 30 fps -
unless you have software and a file format which allows change of frame rate
during a programme. Otherwise some conversion has to take place, and 30 to
25 or 25 to 30 is not pretty, even when it is done well, and it rarely is by
consumer software.

As you say, the ideal is to use the same standard throughout, which is why
the ability to run mini cameras at 25 as an alternative to 30 would be
great. I presume 25 fps cameras are available for broadcast use, but not at
consumer-affordable prices.

  #14  
Old March 19th 17, 12:40 PM posted to uk.tech.digital-tv
NY
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Posts: 986
Default TV system conversion

"Wolfgang Schwanke" wrote in message
...
"NY" wrote in
:

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.


That's not a conversion artefact but a defect of SECAM. You get (sorry
used to get) those streaks with native SECAM reception. Of course
conversion can't remove them.


I knew about crosshatch patterning but not about streaks.

I suppose if BBC/ITN did a deal with a French/Russian station they'd have
access to the original in-studio PAL before conversion to SECAM for
broadcast, but if they had to use an off-air signal (maybe cheekily
"acquiring" the footage without permission!) then they'd get SECAM
artefacts.

  #15  
Old March 19th 17, 05:05 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 7,539
Default TV system conversion

On 18/03/2017 14:58, NY wrote:

Does SECAM use the same gamma and black level as PAL,


Yes

or do you get the
same problems as with NTSC where their pictures look very artificial and
plasticky.


You are talking in the present, none of this is relevant any more, and
from the mid 80s, the only place in France you'd find a SECAM coder in
use, (in the Tx chain) was the transmitter site.

The French in recent decades did everything before the transmitter as
PAL, then from the early nineties as component video (just as we did,
with our PAL encoders way downstream too) (BBC regional studios
excepted)

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.


Not any more, it's a digital component world, contemporary American TV
pictures are as good European ones. Better you might argue, coz they are
running at 30 frames/Sec not 25.


--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #16  
Old March 19th 17, 05:37 PM posted to uk.tech.digital-tv
Alan White[_3_]
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Posts: 62
Default TV system conversion

On Sat, 18 Mar 2017 16:16:46 -0000, "NY" wrote:

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?


The GoPro Hero4 Silver and the GoPro Hero5 both record 1080/50.

--
Alan White
Mozilla Firefox and Forte Agent.
By Loch Long, twenty-eight miles NW of Glasgow, Scotland.
Webcam and weather:- http://windycroft.co.uk/weather
  #17  
Old March 19th 17, 08:18 PM posted to uk.tech.digital-tv
NY
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Posts: 986
Default TV system conversion

"Wolfgang Schwanke" wrote in message
...
"NY" wrote in
:

That's not a conversion artefact but a defect of SECAM. You get (sorry
used to get) those streaks with native SECAM reception. Of course
conversion can't remove them.


I knew about crosshatch patterning but not about streaks.


By crosshatch pattern do you mean cross luminance? Yes that's slightly
worse with SECAM as well, but not badly. The typical "SECAM fire" I was
talking about consists of blue/red/magenta streaks to the right of
sharp edges.


What I remember at times was a fine +/- 45 degree lattice pattern (like a
garden trellis) overlaid on patches of certain colours. Was that how SECAM
showed cross-luminance.

Here's a clip that shows SECAM fire under more typical conditions. It has
blue/red streaks on bright spots almost throughout, but not in a

disturbing way.

https://www.youtube.com/watch?v=HkyqVuIyuP4



Yes, the coloured patches to the right of the bright areas (and even
not-so-bright ones) is fairly typical of what I remember. It's particularly
noticeable around https://youtu.be/HkyqVuIyuP4?t=23m58s on the men's medals.

The lettering on the banner at https://youtu.be/HkyqVuIyuP4?t=16m5s seems to
have horizontal banding. Obviously there's a a lot of motion blur as the
camera pans past it.

Gordon Bennett! That's one hell of a hairdo that the woman interviewer has
https://youtu.be/HkyqVuIyuP4?t=25m36s - the amount of hairspray she must
have used would destroy the ozone layer! Is the windshield on her microphone
big enough? :-)

Interesting that the filmed inserts such as
https://youtu.be/HkyqVuIyuP4?t=33m57s don't have anywhere near as much
colour streaking to the right of everything. Lower contrast, perhaps?

The one thing I haven't seen examples of is the sharp pointed horizontal
spikes to the right of saturated areas.

Good old Leonid Brezhnev with his black-slug eyebrows:
https://youtu.be/HkyqVuIyuP4?t=6m40s . I'd forgotten about him.


Was SECAM thought to be technically superior to PAL (maybe replacing one set
of artefacts with another) or was the main motivation for the French
developing it the "not invented here" syndrome of PAL?

  #18  
Old March 19th 17, 10:02 PM posted to uk.tech.digital-tv
Chris Youlden[_6_]
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Posts: 3
Default TV system conversion

On 19/03/2017 18:05, Mark Carver wrote:
On 18/03/2017 14:58, NY wrote:


You are talking in the present, none of this is relevant any more, and
from the mid 80s, the only place in France you'd find a SECAM coder in
use, (in the Tx chain) was the transmitter site.


SECAMs advantage was always its robustness in the transmission chain.
The old analogue distribution networks comprising miles of microwave
circuits didn't cause differential phase and gain like they did PAL.

I don't know whether the French ever carried out RBS tests, but if they
did it would be interesting to know the quality of picture received at
the end of a multihop rebroadcast similar to the BBC having all
transmitters on RBS from CP to Scotland.



The French in recent decades did everything before the transmitter as
PAL, then from the early nineties as component video (just as we did,
with our PAL encoders way downstream too) (BBC regional studios pted)

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.


Not any more, it's a digital component world, contemporary American TV
pictures are as good European ones. Better you might argue, coz they are
running at 30 frames/Sec not 25.


+1

A couple of years ago I watched an NFL match on a fairly large tv in a
bar in Boston, MA and was extremely impressed with the quality.




--

Chris

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  #19  
Old March 20th 17, 06:54 AM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 1,931
Default TV system conversion

On Sun, 19 Mar 2017 23:16:08 +0100, Wolfgang Schwanke
wrote:

What I remember at times was a fine +/- 45 degree lattice pattern (like
a garden trellis) overlaid on patches of certain colours. Was that how
SECAM showed cross-luminance.


I think the cause is that SECAM is FM, hence the colour carrier is
always present at full amplitude.


It's always present at *some* amplitude. There is a filter to reduce
its amplitude at its unmodulated frequency, i.e. where there is no
colour, though it's never zero.

[...]

SECAM was invented before PAL. I think it's fair to say that regarding
picture quality PAL is better, but SECAM is said to be more robust
especially under poor reception. France's insistance on using it
instead of PAL was partly political to protect its domestic industry,
and so was their campaigning in the Eastern block. Conversely the
inventor of PAL claims in a book that he had no support from the German
government, and all the campaigning for PAL abroad was entirely
Telefunken's initiative. But he is biased, so maybe he's not telling
the whole story. In any case there was a lot of politics going on.


Does anyone know what "PAL" really stands for? All the books I've seen
give it as "Phase Alternation Line" or "Phase Alternation Linewise",
but I've always assumed that it must have been named in German and
the English translation contrived to keep the same initials, hence the
rather inelegant phrase that we've become used to. Perhaps the
original name is something neater in its own language?

Rod.

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  #20  
Old March 20th 17, 07:03 AM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 243
Default TV system conversion

On 19/03/2017 23:02, Chris Youlden wrote:
On 19/03/2017 18:05, Mark Carver wrote:
On 18/03/2017 14:58, NY wrote:


You are talking in the present, none of this is relevant any more, and
from the mid 80s, the only place in France you'd find a SECAM coder in
use, (in the Tx chain) was the transmitter site.


SECAMs advantage was always its robustness in the transmission chain.
The old analogue distribution networks comprising miles of microwave
circuits didn't cause differential phase and gain like they did PAL.


Yes, which is why the USSR adopted the system. The chroma channel in
SECAM was intrinsically FM. I can remember playing with a SECAM SPG, and
turning the chroma signal up and down in amplitude, it made no
difference until the 'quieting point' to the received picture.
The downside was the triangular noise spectrum for FM, so I don't
now how it fared there ?

I don't know whether the French ever carried out RBS tests, but if they
did it would be interesting to know the quality of picture received at
the end of a multihop rebroadcast similar to the BBC having all
transmitters on RBS from CP to Scotland.


Umm, good question !

Not any more, it's a digital component world, contemporary American TV
pictures are as good European ones. Better you might argue, coz they are
running at 30 frames/Sec not 25.


+1

A couple of years ago I watched an NFL match on a fairly large tv in a
bar in Boston, MA and was extremely impressed with the quality.


Yes, same for me, 18 months ago, on a tour of Boston and New England.
Very impressive, and also the D-Sat platform Direc TV that we had in
some of our B&B rooms.


--
Mark
Please replace invalid and invalid with gmx and net to reply.
 




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