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Discussion Starter · #1 ·
(this is my first post, so please be gentle...)


I've read the information in the FAQ regarding ALiS and i've seen Hitachi's propaganda, so I have a basic understanding of how this system works. I've also searched the forum archive for more info, but I've not found anything that satisfies my concerns:


since it uses a 60Hz interlace of non-scanned alternating lines corresponding to a refresh of 30 times per second, and since that nearly matches (I think) the interlaced broadcast signal, why do so many people on this forum regard this as inferior design? I would expect a perceivable decrease in saturation due to half the lines being lit at any 1/30 of a second moment, but that should be correctable with picture setting controls. But what other problems are there?


I've been unable to do thorough subjective comparison so far due to there being so few plasma displays in the stores I've visited so far, but what I have seen seems to support ALiS displays as having comparable PQ to some of the highly regarded non-ALiS displays. I think I could perceive a slightly less sharp edge to the ALiS pixels from very short distances, and I might have been able to see a subtle flicker effect. Is this where the forum members find fault?


I don't think I will ever really have the opportunity to test any display using my criteria before purchasing. For one thing, although I've seen same-source DVDs on multiple screens, I don't expect to be able to view a test pattern. Has anyone tried comparing ALiS with non in this way?


Thank you for your help.
 

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A lot of it has to do with scaling, in my opinion. Compare the 1024 Alis to a 768 50" (vertical lines) panel. Now, suppose the panel is being fed a 480i signal (dvd, or SD TV)...


The 1024 display will have to more than double the size of the image on every frame. (2.13 times or so)

The 768 progressive will have to a) de-interlace the source and then b) scale the progressive frame from 480 lines to 768 - an increase of just 1.6 times...


Most displays have a pretty good handle on simple de-interlacing. 3:2 pulldown can be used, or some motion-handling routines. Thus the progressive frame formed from the interlaced can be very good with little loss of information. So basically what you are left with is the Alis needs to scale the image a lot more (over double, vs just a 60% increase) than the progressive panel. Perhaps that is one reason.


Also, since the panel is inherently interlaced, all of the interlacing artifacts will remain, no matter what is done. On the progressive displays they can be eliminated... I'm sure that helps overall PQ quite a bit.


In general, the more scaling, the worse off one is. This is backed up by the fact that *most* people regard the 852x480 Panny panel to be the best for displaying DVD and SD resolutions.


Why isn't the Alis better for straight 1080i signals? Well, at that point I think the problem (aside from the inherent interlacing) becomes general poor quality of the display. (poor contrast, blacks, etc.)
 

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Felgar, it sounds as you are messing some things up.

The ALIS panels are 1024i, which means 2 sets of 512 pixels height. When scaling interlaced content the 240 odd lines are scaled to 512 and the 240 even lines are scaled to the other 512 even pixels. Doing that is very different from how you must do it on a 768 progressive panel, as it doesn't have odd and even lines.

First the image needs to be deinterlaced, which is more or less a troublesome process depending on the source material.

After deinterlacing, the picture is now 480p and can succesfully be scaled to 768 pixels height.

I would think it should give an edge to the ALIS panel being able to handle interlaced content, interlaced.

IIRC, when displaying 1080i, 28 pixels on top and buttom is discarded and the image is then directly mapped to the panel, again giving an advantage to the ALIS panel.


In theory the ALIS panel sound nice, but as Felgar wrote, it's probably because of general poor quality of the display that they look not as good as normal panels.
 

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Quote:


In theory the ALIS panel sound nice, but as Felgar wrote, it's probably because of general poor quality of the display that they look not as good as normal panels.
well said- I bought an ALIS panel,got flamed for it, and now see they were right-


there are so many better panels out there...


Mark
 

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I think our basic problem with this technology is the return to Interlaced technology. Originally, this technology was created because CRTs and video sources simply couldn't match the necessary frame rate.


So, instead of trying to push the issue, they divided the image into two fields. This causes line flicker and an endless list of other artifacts that progressive technology has been trying to correct in the 90s.


So, more and more we're seeing technology settle on progressive frames as a substantially more stable technology that can give us a better image using the same bandwidth.


So technologies returning to interlaced imaging for one reason or another drives us insane. This includes 1080i and ALiS. Since 1080i would be turned into 1080p relatively easy (a matter of opinion here), that's easy to overlook. However, ALiS cannot be turned progressive.


As a matter of personal preference, some people like it and some don't.


I don't.
 

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Discussion Starter · #7 ·
Thank you for your replies.


I, too, have my doubts concerning reintroducing interlacing to what was once hoped to be a progressive medium. my technophilic reflex forces me to mistrust ALiS as a compromise.


BUT, my limited subjective experience has been that the newer ALiS displays hold their own fairly well against the glorified Panasonics.


What I find especially counterintuitive is that the 32" ALiS panels I've seen nearly match the 42" Panasonics they've been shown next to (3 different shops). The 32" display has a vertical resolution of 852 lines, so the math doesn't seem to favor it for interlacing (then again, I'm mathematically dyslexic). Perhaps the smaller dot pitch has something to do with it, but the picture is very smooth and rich.
 

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We have talked about the general suckiness (perhaps we should have a synonym section in the FAQ where suckiness and ALiS are the first entries - just kidding Joshy - have fun ;)) of the glass used in ALiS panels before and the general suckiness of the internal scalers used also (AVM in the Fujitsu 4242 notwithstanding - which I am giving the benefit of the doubt to because I have only ever seen a 1080i source with it). If you are interested this thread actually digs up some useful info from a PAL user who likes ALiS (Some ALiS supporters here say that ALiS is great for the higher rez PAL standard but, conversely, a lot of UK owners here and on www.avforums.com disagree):
http://www.avsforum.com/avs-vb/showt...IS#post1399075


WRT the 32" Sony, take a look at Pete Putmans review (the projector expert link) to see a favorable view point:
http://www.avsforum.com/avs-vb/showt...ht=pete+Putman
 

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You are right Esben, I was a little off there. But, in reviewing your statement, you note that "240 odd lines are scaled to 512". This boils down to what I was saying. Each frame is more than doubled when it's scaled.


But for progressive, first you deinterlace which I claim can be done fairly well, esspecially on DVD where you can do it perfectly. Then second, you scale the progressive frame much less than the Alis panel has to scale its material.


Maybe I'm off on the wrong track here... Sorry if I am. More thinking out loud than anything.
 

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In my experience, CKarras, both look fabulous. I believe, however, that the 1080i looks even better than the ABC (but that may have more to do with the quality of ABC's HD transfers than anything about the resolution; on the Pio 503 -- my current panel -- I am more often blown away by the non-ABC stuff).
 
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