Frank - What do you mean by your last sentance. There is a very clear
difference between progressive scan and non-progressive scan. I recall
prior to buying the LG existing owners had shown photographs of
detailed images with and without.
Does this mean that you don't have any personal experience of
progressive scanning?
Interested in why you would think it's not applicable.
To be honest, I'm in no position to give an opinion on this issue
(that's why I phrased my last statement as a question). I don't have
access to any progressive scan AV equipment, and my understanding of
this term is very rudimentary. I suppose a simplistic definition is to
say that progressive = non-interlaced, and non-progressive =
interlaced. Here's another definition:
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http://www.jvc.com/support/index.jsp?pageID=1&faqID=10
Progressive Scan Output
Video output that carries a video signal in which each horizontal line
follows the next--unlike an interlaced output, which presents the
odd-numbered horizontal lines, then the even-numbered horizontal
lines, and so on. Progressive-scan video has less flicker and fewer
motion artifacts than the traditional interlaced-scanning method.
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Notice that the author cites reduced flicker and "fewer motion
artifacts" as being benefits of progressive scannning. However, I
would think that current LCD displays would be relatively immune to
flicker and "motion artifacts" due to their relative long response
times (16ms?). In fact, 20 years ago CRT CAD monitors used long
persistence phosphors to circumvent flicker problems due to low
refresh rates.
Another problem with interlaced CRT displays is "interlace jitter".
This URL seems to describe this effect quite well:
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http://moliere.byu.edu/digital/oilwater.html
Instead, each frame actually consisted of two fields that were scanned
to the face of the TV's cathode ray tube in succession. The first
field was placed on alternating scanlines, and the second field was
"interlaced" onto the lines left vacant by the first field.
Due to the difficulty of beginning the scan of each line at the
precise point of the preceding and subsequent lines, the interlacing
of the two fields causes jitter on the screen.
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I see interlace jitter on both my 68cm LG and my 80cm Sanyo TVs
(although the latter has additional vertical jitter issues). It is
most noticeable when viewing text or long, thin horizontal lines. I
would think that an LCD display would be immune to this problem
because odd and even lines of information would be written precisely
on every scan, ie there would be no synchronisation issues.
Here is another definition of interlace jitter:
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http://www.gisdevelopment.net/glossary/i.htm
Thus, a single, still video image of 1/30 of a second duration
consists of two interlaced fields of the source video signal.
Displaying a single frame of interlaced video causes vertical jitter.
This jitter is especially pronounced when an image contains horizontal
lines. This is called umpire shirt jitter on conventional broadcast TV
and can be seen along the black and white edges of an umpire's shirt
or along the sharp horizontal edges of large letters. This effect can
cause eye strain. Interlace jitter is best overcome by using a monitor
with long-persistence phosphor. This phosphor holds each line longer
until it can be refreshed by the next scan.
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- Franc Zabkar
