I'm try to decipher why progressive scan video is considered better
then interlaced.

Assuming that we are not dealing with old 1930's phosphors, would it be
fair to say that the following 2 images would be of the exact same
quality:

480i camera --> 480i display
480p camera --> 480p display

formats and you get jaggies?

Can I conclude that:

Progressive scan TVs are considered to be better, MOSTLY because DVD
are encoded from film, which is essentially a progressive scan source.
That is, the source and display are both progressive scan.

<wdoe***@yahoo.com> wrote in message
Read this:

http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html

Everything you need to know about progressive scan.

Thanks.  Yes, I had seen that article before and it does seem to make
the most sense.  They are essentially confirming that progressive scan
is NOT better than interlaced per se, rather a progressive scan image
is better when the source is progressive scan (such as film).

What had me confused is that a good percentage of the information on
the web seems to be quite wrong (what else is new about the internet).
Most articles make crazy statements about interlaced images having
"half the resolution", or gaps between the lines in interlaced images
(as if progressive scan images have fatter lines or something).

It really shouldn't matter how the image is displayed (from top to
bottom, bottom to top, sideways, from the centre out) as long as the
source is scanned in the same manner.

Joshua Zyber wrote:
Show quoteHide quote

wdoe***@yahoo.com wrote:

That's a correct conclusion if we're talking about content that was
produced _natively_ as interlaced fields or _natively_ as non-interlaced
frames. Neither system benefits when it's being converted to the other
system.

But note that the refresh rate / frame rate matters, too. 60 Hz (60 *
1000/1001 Hz) "progressive scan" display is not ideal for
film-originated content. 24 fps film-originated video would be best
displayed with a non-scanning display that updates the pictures 24 times
a second, or with a scanning display that flashes the frames two times
(48 Hz) or three times (72 Hz) in a row, like movie projectors do.

The article that you were referred to in the above appears to be mostly
correct but the animated tomato illustration and the animated depiction
of an interlaced scanning pattern appear to give false impressions about
the topic. Both illustrations seem to make a somewhat ludicruous (or at
least inaccurate) claim that your brain would somehow integrate _exactly
two adjacent fields at a time_ into a single picture. You will get a
better description of what is really happening from here:
<http://lurkertech.com/lg/fields/fields.html>.

The "Interlace Scan" illustration also appears to suggest that "Field 1"
would be retained on the screen while "Field 2" is being drawn
in-between its lines. That's not true. The phosphors on modern CRT
screens fade away long before a single field refresh is complete. See,
for example:

<http://en.wikipedia.org/wiki/Image:Refresh_scan.jpg>

Most of the time confusion arises because it is not clearly stated what
kind of a progressive system the writer has in his mind when he is
making these comparisons.

In my previous message to this thread, I gave a link to a Wikipedia
discussion page where I compared three different (but technically
related) "progressive scan" systems to a single interlaced system [1].
For example if you're comparing an interlaced system to a "Progressive
variant A" system, as defined on that page, you _will_ get more visible
gaps between the scanlines (or rather, more discernible scanline
structure) - but note: the gaps are visible in the _progressive_ system,
not in the interlaced system. And, if you're comparing an interlaced
system to a corresponding "Progressive variant C" system (as defined on
that page as well), each field in the interlaced system has only half of
the vertical resolution when compared to the frames in the progressive
system. It all depends on what you're comparing to what.

_____

[1] Here's the link again: <http://en.wikipedia.org/wiki/Talk:Inter
lace#Comparing_interlace_to_progressive>

On 9 Nov 2006 19:49:32 -0800, wdoe***@yahoo.com Gave us:

  Because each field is a fully rendered frame.  Interlacing is a
bunch of zigsaw puzzles stacked together for each frame.

  Progressive gives one a richer rendering of each frame for the eye.

wdoe***@yahoo.com wrote:

1) Non-interlaced video is easier to deal with computers,
image-processing algorithms, and compression algorithms. (And, they're
easier to get your head around, if you're not very bright. Some computer
programmers who try to make video processing products, aren't.)

2) Modern display technologies do not "scan". Only CRTs and the ancient
electromechanical Nipkow disk televisions are based on "scanning",
natively. (It can be argued, though, that it would be possible to
_emulate_ the scanning pattern of a CRT with, for instance, a SED
display.)

3) When "progressive scan" (which is beginning to be a misnomner these
days - see point #2) is applied, it is usually assumed that at least
twice the bandwidth is used for delivering the images. Instead of
drawing, say, 240-line progressive pictures 60 times a second, or
480-line progressive pictures 30 times a second - both of which would
have the same bandwidth as an interlaced 480-line 60 Hz system, you draw
480-line progressive pictures 60 times a second. ("60" in the above is
really 60*1000/1001, and "30", respectively, 30*1000/1001.)

Do you assume those to be faster-decaying or slower-decaying than the
modern phosphors? What is the problem you assume there being with 1930s
phosphors? (This is not a trick question - there just does not seem to
be a consensus about this. Some say the early CRT-based televisions had
faster-decaying phosphors, and insist that interlaced scanning was
designed, in part, to combat this problem. Others maintain that they had
a longer afterglow. Go figure.)

Depends. Do you mean a 30 fps 480p system or a 60 fps 480p system? Still
scenes or motion?

Coincidentally, the Wikipedia article about interlace is currently under
scrutiny. You might want to read the discussion page, where lots have
been said about the relative merits of an interlaced system and the
various "related" progressive systems.

<http://en.wikipedia.org/wiki/Talk:Interlace>

See, especially, my contribution (yes, this is a shameless plug!), where
I compare an interlaced system to three related progressive systems:

<http://en.wikipedia.org/wiki/Talk:Interlace#Comparing_inter
lace_to_progressive>

(Please copy and paste the two parts of the URL together manually if
your newsreader program does not do that automatically.)

That's a real problem whenever some sort of automatic conversion from
interlaced domain to non-interlaced domain is applied, and the source
material alternates between film-originated, "progressive scan" video,
and regular interlaced video.

That's about correct. But note that NTSC (525-line 59.94
fields-per-second) countries have some additional complications due to
the 3:2 pulldown pattern which is used when transferring 24 fps film
frames to video. PAL (625-line 50 fields-per-second) countries
circumvent those problems by speeding up the film by 4 % when it is
transferred to video, so that each pair of adjacent fields comes from
the same film frame.

Also note that in the age of digital television broadcasts it is
possible to shoot real "progressive" (i.e. non-interlaced) 60 fps video
signal - such as 480p/60 or 720p/60 - and display it "as is" on a
non-interlaced display, without any tricks.

Thanks - I've seen so much hype about progressive scan that it is good
to see (in the article you referenced) that people are questioning some
of the crazy reasons that are given for the superiority of progressive
scan.

Jukka Aho wrote:
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