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PAL / NTSC conversion

 
 
Den Murray
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      06-15-2007
Hello All

I'm in the US and I have a Cyberhome DVD player - it's region-free, but that
is incidental to my question.

1) When I play a PAL DVD from the UK or Australia my DVD player reads the
PAL encoded DVD but outputs an NTSC signal - to allow my TV to correctly
display the picture. All is good except that the picture can be a little
jerky if there is fast movement - I assume that this is part of the frame
dropping that occurs during the conversion.

2) I also have an external video standards converter - a TenLab TR21 - that
will convert a PAL signal to NTSC. If I play a PAL DVD and output PAL from
the DVD and run it through the video standards converter and output an NTSC
signal to the TV the picture is also fine - perhaps of marginally poorer
quality than in (1) above, but not jerky.

Can someone explain to me what is different between the two ways of getting
an NTSC signal to the TV from the DVD and why the difference in jerkiness
and clarity?

Thanks!


 
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Kimba W. Lion
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      06-15-2007
"Den Murray" <(E-Mail Removed)> wrote:

>Can someone explain to me what is different between the two ways of getting
>an NTSC signal to the TV from the DVD and why the difference in jerkiness
>and clarity?


Do you really have to ask why a piece of equipment that costs $740 works
better than one that costs $30? I know the concept of "bargain", but
really...

You're converting a 625-line picture, 25-frames-per-second stream to a
525-line picture, 30fps stream. This requires RAM and interpolation. The
quality of the result depends on the amount of memory, the available
computing power, and the skill of the programmer(s) behind the product,
all of which presumably cost money.

If you can remember what professional broadcasters delivered from PAL
sources just a few years ago, even the quality of the CyberHome is
astoundingly good. In fact, it's probably the high overall quality that
makes the jerkiness of the picture stand out.
 
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Jukka Aho
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      06-15-2007
Den Murray wrote:

> I'm in the US and I have a Cyberhome DVD player - it's region-free,
> but that is incidental to my question.
>
> 1) When I play a PAL DVD from the UK or Australia my DVD player reads
> the PAL encoded DVD but outputs an NTSC signal - to allow my TV to
> correctly display the picture. All is good except that the picture
> can be a little jerky if there is fast movement - I assume that this
> is part of the frame dropping that occurs during the conversion.
>
> 2) I also have an external video standards converter - a TenLab TR21
> - that will convert a PAL signal to NTSC. If I play a PAL DVD and
> output PAL from the DVD and run it through the video standards
> converter and output an NTSC signal to the TV the picture is also
> fine - perhaps of marginally poorer quality than in (1) above, but
> not jerky.
> Can someone explain to me what is different between the two ways of
> getting an NTSC signal to the TV from the DVD and why the difference
> in jerkiness and clarity?


The DVD player probably resorts to frame-doubling (not dropping!) to
keep things in sync. Every 6th frame (or so) will be doubled. Hence the
jerkiness.

The external video standards converter might use frame-blending,
instead - i.e., it it captures, stores and mixes several adjacent frames
together, in a moving window, with varying degrees of opacity. (Think of
the "onion skinning" techniques that cartoon animators use:
<http://en.wikipedia.org/wiki/Onion_skinning>.) This will give a
smoother impression of motion as nothing is ever duplicated straight
away, but at the same time, everything that moves will get faint shadow
images around it from the previous (and following?) frames.

You could try capturing the output of you standards converter to a
computer and analyzing the individual frames there (and perhaps making a
direct comparison to the original MPEG-2 frames on the DVD.) Of course,
a PAL test disc with some suitable test material would come handy here.
(A ball rolling across the view, or a timecode display burned into the
picture, or something similar.)

Professional standards converters may also apply sophisticated motion
estimation techniques. You might want to take a look at these documents:

"Motion Science - A New Option for Standards Conversion"
<http://studio-systems.com/broadfeatures/JulyAug2001/Motion/32.htm>

"The Engineer's Guide to Standards Conversion"
<http://www.snellwilcox.com/community...e_center/engin
eering_guides/estandard.pdf>

"The Engineer's Guide to Motion Compensation"
<http://www.snellwilcox.com/community...e_center/engin
eering_guides/emotion.pdf>

--
znark

 
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skibbet@yahoo.com
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Posts: n/a
 
      06-17-2007
The ratio for PAL and NTSC is very different in the number of lines so
I copy PAL DVD into Movie Maker and Export as NTSC it is very time
consuming on slower computers but it works for me. I have yet to find
any convert programs that convert any format to another without some
quality loss or other unwanted results. So when I have formats other
than Avi for editing I use Quicktime Pro then export files or use
Movie Maker and save as to my computer. You can get the new Dazzle for
importing files into your computer and it reads everything for the
most part then you can export back out from your computer it is done
in real time so again time consuming. Hope that helps...

On Jun 14, 11:37 pm, "Den Murray" <(E-Mail Removed)> wrote:
> Hello All
>
> I'm in the US and I have a Cyberhome DVD player - it's region-free, but that
> is incidental to my question.
>
> 1) When I play a PAL DVD from the UK or Australia my DVD player reads the
> PAL encoded DVD but outputs an NTSC signal - to allow my TV to correctly
> display the picture. All is good except that the picture can be a little
> jerky if there is fast movement - I assume that this is part of the frame
> dropping that occurs during the conversion.
>
> 2) I also have an external video standards converter - a TenLab TR21 - that
> will convert a PAL signal to NTSC. If I play a PAL DVD and output PAL from
> the DVD and run it through the video standards converter and output an NTSC
> signal to the TV the picture is also fine - perhaps of marginally poorer
> quality than in (1) above, but not jerky.
>
> Can someone explain to me what is different between the two ways of getting
> an NTSC signal to the TV from the DVD and why the difference in jerkiness
> and clarity?
>
> Thanks!



 
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Bill Vermillion
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Posts: n/a
 
      06-21-2007
In article <mmAci.178980$(E-Mail Removed)> ,
Jukka Aho <(E-Mail Removed)> wrote:


>The external video standards converter might use frame-blending,
>instead - i.e., it it captures, stores and mixes several adjacent
>frames together, in a moving window, with varying degrees of
>opacity. (Think of the "onion skinning" techniques that cartoon
>animators use: <http://en.wikipedia.org/wiki/Onion_skinning>.)
>This will give a smoother impression of motion as nothing is ever
>duplicated straight away, but at the same time, everything that
>moves will get faint shadow images around it from the previous
>(and following?) frames.


Back in the last 1960 or early 1970 frame, a person I used to work
with got into video quite heavily.

He had 3 network connections coming in and would record the
nightly news from CBS/NBC/ABC and then ship them via air to
Puerto Rico so they could watch the world news stories with
only 1 day delay. It seems so strange in this day of satellites.

Then he bought the first Marconi standards convertor shipped to the
US. It cost him $250,000 [in 1970 dollars].

He got a contract to convert all the ABC Wide World of Sports
from NTSC to PAL for European distribution.

I last saw that device in a warehouse where our old ISP was
located. It was about 6 feet tall. Had plug-in cards that were
about 12" high and 18" deep. And it was no longer operational
as some of the chips used in that device were no longer being made.

The logo from the rack was saved, and all the cards were recycled
to get the gold from the contacts.

And now we can get semi-reasonable translations in $30 DVD players.
That's about an 8000 times price difference. And of course the old
tapes he was converting from were the 2" quad machines which
were good for their time - but had their problems.

Bill

--
Bill Vermillion - bv @ wjv . com
 
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Mike S.
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Posts: n/a
 
      06-21-2007

In article <(E-Mail Removed)>, Bill Vermillion <(E-Mail Removed)> wrote:
>In article <mmAci.178980$(E-Mail Removed)> ,
>Jukka Aho <(E-Mail Removed)> wrote:
>
>
>>The external video standards converter might use frame-blending,
>>instead - i.e., it it captures, stores and mixes several adjacent
>>frames together, in a moving window, with varying degrees of
>>opacity. (Think of the "onion skinning" techniques that cartoon
>>animators use: <http://en.wikipedia.org/wiki/Onion_skinning>.)
>>This will give a smoother impression of motion as nothing is ever
>>duplicated straight away, but at the same time, everything that
>>moves will get faint shadow images around it from the previous
>>(and following?) frames.

>
>Back in the last 1960 or early 1970 frame, a person I used to work
>with got into video quite heavily.
>
>He had 3 network connections coming in and would record the
>nightly news from CBS/NBC/ABC and then ship them via air to
>Puerto Rico so they could watch the world news stories with
>only 1 day delay. It seems so strange in this day of satellites.
>
>Then he bought the first Marconi standards convertor shipped to the
>US. It cost him $250,000 [in 1970 dollars].
>
>He got a contract to convert all the ABC Wide World of Sports
>from NTSC to PAL for European distribution.
>
>I last saw that device in a warehouse where our old ISP was
>located. It was about 6 feet tall. Had plug-in cards that were
>about 12" high and 18" deep. And it was no longer operational
>as some of the chips used in that device were no longer being made.
>
>The logo from the rack was saved, and all the cards were recycled
>to get the gold from the contacts.
>
>And now we can get semi-reasonable translations in $30 DVD players.
>That's about an 8000 times price difference. And of course the old
>tapes he was converting from were the 2" quad machines which
>were good for their time - but had their problems.


I'm told that, for major events intended for international broadcasts,
the biggies still use separate NTSC and PAL video cameras because the
standards conversion is not perfect even now.


 
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