[miamicanes]

Do high-end European "100hz" TVs show real, honest-to-god 100hz progressive output, or are companies like Sony and Phillips up to just as much mischief over there as they are over here -- taking huge liberties with terms like "progressive" and "100hz" to market displays that knowledgeable computer users would sneer at if they saw the real specs laid out in computer terms?


Offhand, I can think of a few ways a marketing department could define 100hz PAL:


* deinterlace broadcast 540i50 to 540p50, then render each field in 1/100th of a second two times in a row -- creating beautiful, rock-solid flicker-free 100hz progressive output. And then we all wake up, and remember that TV manufacturers are scum who'll do anything to shave $1.37 off the manufacturing cost of a TV intended to sell for $3,000+.


* deinterlace broadcast 540i50 to 540p50, then use each newly-created pseudo-progressive frame to create two 100hz interlaced fields. Under this scheme, broadcast field #1 (odd) would correspond to rendered field #1 (odd), broadcast field #2 (even) would correspond to rendered field #4 (even), and rendered fields #2 (even) and #3 (odd) would be figments of Faroudja's imagination (*grin*). Technically, the source WOULD be deinterlaced, and the scanrate would technically be 100hz, but I'd personally beat the living crap out of any salesperson who tried to convince me such a display were 100hz progressive.


* some god-awful scheme even worse than the second... dispensing with Faroudja entirely, and just buffering each pair of fields for display twice. This evil scheme would render PAL field #1 in 1/100th of a second as the display's odd scanlines, PAL field #2 in 1/100th of a second as the display's even scanlines, then repeat. On one hand, it wouldn't flicker... but I suspect the output would stutter badly, since it would constantly be taking "2 steps forward, 1 step back" as it updated the display.


So... am I close with any of them, or do 100hz European TVs do something entirely different altogether?

 

[trivial]

I thought about acquiring a 100Hz PAL TV a long time ago, for use with a PAL-capable video card. One thing is certain: they do not decode or display 540p100. If they did, they'd also be theoretically capable of 720p60 (disregarding dot/grille pitch), and would be sought-after by videophiles everywhere.


Watch out for those "computer terms", which turn out to include anything a hobbyist could figure out but which someone who "does this stuff for a living" is financially unmotivated to investigate. You will come to believe that people in other technical fields are true idiots if you expect them to follow your speech when it takes that line. Believe me. I'm having real trouble adapting myself to the office space in which I find myself for such reasons.

 

[jckessler]

I don't think there's any deinterlacing going on in 100Hz PAL sets. My understanding is that they simply redraw the each field twice while retaining the interlacing.


576i50 -> 576i100


It's like increasing the refresh rate on your monitor. No processing is being done to the picture. The goal is to reduce flicker...

 

[Otto J]

* some god-awful scheme even worse than the second... dispensing with Faroudja entirely, and just buffering each pair of fields for display twice. This evil scheme would render PAL field #1 in 1/100th of a second as the display's odd scanlines, PAL field #2 in 1/100th of a second as the display's even scanlines, then repeat. On one hand, it wouldn't flicker... but I suspect the output would stutter badly, since it would constantly be taking "2 steps forward, 1 step back" as it updated the display.


Spot-on. Well, kind of. There are generally two generations of 100 Hz tvs. The first generation just repeated each field, to show 100i images. field#1, field#1, field#2, field#2. A steadier picture (I don't know the english word for flicker that isn't line flicker??) than 50 Hz, but the line flicker would still be 50 Hz, so the picture isn't completely flicker-free.


Second generation (dubbed Digital Scan in the case of Philips, Digital Plus from Sony and so on) shows field#1, field#2, field#1, field#2. Flicker-free image, but severe stuttering on motion. Useually you can turn this feature off, and choose between the two modes.


Some (few) actually has progressive scan capability, but I'm not sure how good it actually is. Progressive scan is nowhere near as widespread "overhere".


The best way to show a totally flicker-free, stutter-free image would certainly be to de-interlace the picture to 25 frames, then show all frames 4 times (or just 3, for 75Hz). The problem is that tv is recorded in 50i, so the conversion is, as you know, not that simple. And, 25 Hz simply isn't enough to show stutter-free motion in any form. Never noticed stuttering in the cinema? 24 Hz is a mistake from the beginning. AFAIK, all cinemas show each frame twice anyway, effectively showing 48P. Why on earth haven't they startet filming in 48 Hz, to minimize jutter? (or, like, 120 Hz! Would down-convert flawlessly to 60P or 60i AND 24P anyway)


Well, what I was going to say was: Because of all the various stuttering, from many different causes (low framerate, repeating of interlaced fields, MPEG-processing) Philips turned up with a feature called Natural Motion. What Natural Motion basically does is adding interpolated fields. Instead of repeating the same 2 fields, the image consists of a total of four fields. Field#1, Field#1A, Field#2, Field#2A. Each new field (1A, 2A) is an interpolation, so that you are showing 100i flicker-free but avoids the stuttering because of repeated fields (on Pixel Plus sets actually 75i. Pixel Plus increases resolution, but puts too much strain on the processing to make 100Hz available) . The result is near-perfect motion, even better than a true progressive picture. The drawback is pretty heavy artifacts because of the interpolation. But believe me, when you've seen a picture with Natural Motion, any other kind of display, including the cinema, stutters like mad! Then you realise, that even HDTV with 60P isn't perfect enough. You still basically have 24 pictures from the original film, which just isn't enough. In my opinion, we need a higher frame rate on the original shooting. You wouldn't believe how much detail is lost, not because of the lack of resolution, but because of the low frame-rate.