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Rescaling from 480p to 540p is STUPID

Porcupine
02-05-2006, 04:50 PM
I am angry now. After owning the Toshiba 30" HDTV for about 2 weeks I have decided that what it does when displaying regular TV (DVD, most videogames, Standard Definition broadcast, etc) is indeed upscale 480p/i (line doubling for interlaced signals) to a 540p signal. I think I can see the artifacts introduced by vertical scaling with my eyes. This is STUPID. Why the heck would the people who make these TVs be so stupid as to do this? Can't they see that the quality is diminished? It would have been better to simply display 480 lines as 480 lines and cut off 60 lines as overscan, which is easily done I think.

I am annoyed at CRT HDTVs now. I chose them over LCD HDTVs because I felt they would not need to upscale their image to fit the native resolution, like LCDs do. But they still do. They do a much better job of it than LCDs, since 480p is a lot closer to 540p than 720p (the worst possible number, halfway in between 480 and its closest integer multiple), but it is still a rescaling and quality is still lost. Regular analog TVs will display standard sources better than HDTVs in many ways.

BTW, the Toshiba manual claims it upscales to 1080i, but it is sort of incorrect. It upscales to 1920 x 540 and displays as 540p, not 1080i. I believe most/all HDTVs do the same thing with SD signals, from when I look at them in the store.

Also if my current thoughts are true, then it is even more pointless to buy a 4:3 fullscreen aspect ratio HDTV like the Sony 27HS420. One big positive of that design I felt was that they could display traditional 4:3 standard definition material in progressive scan 480p with the true best quality and no rescaling artifacts. However probably they will be stupid and rescale and display as 540p anyway, so what is the point? Unless Sony is smarter than Toshiba, but at this point I'm thinking this is what all TV makers do since they don't seem to care enough about true quality.

Are there still any CRT EDTVs on the market that display in a true native 480p? I don't care whether widescreen or fullscreen. I know there are still many EDTV LCDs and Plasma but I want CRTs because they aren't fixed pixel displays and so they are the only type of TV that can possibly display both anamorphic widescreen and fullscreen without rescaling *if* done right.

Porcupine
02-05-2006, 05:22 PM
Hmm. I am not 100% sure though. Maybe these HDTVs don't rescale 480p to 540p. I can still hope, I guess. I have to watch more different source materials and own my TV longer before I am sure. I was gonna delete my message but now it's too late. ^_^; Oh well, if what I said is true though then all my crazy rantings still apply.

Porcupine
02-05-2006, 06:54 PM
Hmm, I've totally changed my mind now. Since then I've put in all sorts of different DVDs into my player and tried to check for rescaling artifacts, but I don't see them anymore. I think it was only those one or two shows I was watching that were maybe mastered in a funny way. I also mostly try to look at subtitles rather than the show itself since those are DVD player-generated and hopefully should be clean and pure.

It does look to me now that CRT HDTVs are doing the right thing and *not* rescaling 480p to 540p, instead simply not drawing 60 lines. Hurray! :) Too bad I can't delete my own topic oh well.

1080PsF
02-06-2006, 09:25 AM
It does look to me now that CRT HDTVs are doing the right thing and *not* rescaling 480p to 540p, instead simply not drawing 60 lines. Hurray! :) Too bad I can't delete my own topic oh well.

Where are you coming up with 540p no such thing. Can you explain what you are you talking about. If the monitor switched to 540p the vertical height would be half size making the aspect ratio 3.56:1. :eek:

BobY
02-06-2006, 10:20 AM
All Toshiba CRT-based HD displays (and probably other manufacturers as well) can be set to convert incoming 480p to either 540p or 1080i, as they are the same scan rate and they can avoid reconfiguring the scan and having to optimize the circuitry for different scan rates.

All other incoming rates that are supported get converted to 1080i (maybe 720p can also be converted to 540p--the manual is confusing on that point and I don't have a 720p source to check it on).

This allows you to avoid re-interlacing progressive material if you don't want to. It doesn't affect the picture size, as the input is being rescaled, just as rescaling it to 1080i doesn't alter the aspect ratio.

*Any* standard input other than 1080i is being rescaled, that's the way all the CRT-based HD displays that I know of work, otherwise they would need to reconfigure the scan circuitry for each different scan rate. Rescaling is cheaper and easier.

For fixed-pixel displays, any input other than what *exactly* matches the resolution of the panel is being rescaled, including 720p if the display isn't 720 pixels high.

pfh
02-06-2006, 04:06 PM
The 540p can also be handy for game consoles as they tend to display, based on the game, better than interlaced res's.

Porcupine
02-07-2006, 03:26 PM
Yeah, I wonder when the PS3 comes out, will the system support native resolutions of 1920x540p, as I suspect some gamers including myself might actually find that preferable to 1920x1080i for gaming applications where things may be in constant motion. Furthermore, I wonder if the PS3 would output 1920x480i for those with regular TVs.

I'm not saying that regular TVs can truely display 1920 horizontal pixels, but in reality neither can most CRT HDTVs. The PS3 is supposed to render all games internally at 1920x1080p anyway so it should be simple to output all 3 "reduced" resolutions above if desired, without even changing any of the computations.

Overrendering internally at 1920x1080p will still help subtly on any display, as it will act as an automatic anti-aliasing tool of sorts for 3D graphics. All the last-generattion game systems (XBox, Dreamcast, GameCube) EXCEPT the PS2 already used overrending (they all render internally at 640x480p and waste half their scanlines, just for the sake of a cleaner, less "aliased" image) and it payed off for them, while Sony learned their lesson and are doing the right thing with the PS3.

Porcupine
02-07-2006, 03:32 PM
And when HDTV CRTs switch to 540p mode (the Toshibas DO go into 540p mode automatically for 480i input, NOT 1080i as the manual claims) they reconfigure their electron guns so that each field is not offset from the other by 1 line. This is the exact same as regular TVs have done since the beginning when they are fed 240p input (only used in old videogame systems for 2D games like Street Fighter and Super Mario, etc).

I am 99% sure that holds true at least for Toshiba and Sony CRT HDTVs, regardless of what anyone else says. In the case of the Sonys it is easy...just look with your eyes and you CAN see scanlines in the 540p mode only (horizontal black lines between the drawn lines). While in HDTV mode the Sonys obviously are interlacing (same look as a 480i regular TV, personally I can even see every field being drawn with half the lines, alternating per field).

With the Toshibas, even in 540p you CANNOT see scanlines but I think I figured out that is because their beam focus is too fat and/or dot pitch too poor and so it fills up all the space on the TV regardless. The Toshibas still look completely different when in 1080i interlaced mode and I can see the classic vertical "shimmering" effect of interlaced TV.

Porcupine
02-07-2006, 03:40 PM
Also, regarding the Toshibas, I'm still not sure whether they rescale 480p to 540p, or simply chop off the extra lines, but they DO change at least some parts of their scan attributes any time you change screen modes. They won't change the scanning frequency (still 540 lines at 60 Hz) but they can change the amount of analog screen stretch/positioning/etc as desired for their different modes.

I know this because I can go into the Service Menu and set screen parameters for the various screen modes (fullscreen, TheaterWide, Normal, etc) independently, and each time you hit the "Pic" button your remote to change the mode, the TV blanks out for a second and resizes their display (they may also do a digital rescaling between these modes, I dunno, but they can ALSO do an analog one, that's for certain). I used this to my advantage when setting up my TV the way I like it. If one wants, you can get FullScreen/TheaterWide123/Normal to by default look exactly the same as each other (dunno why you would want to, though).

So the Toshibas if they wanted do have the capability to selectively stretch "chop off" for 480p sources, or display everything for 540p/1080i.

BobY
02-07-2006, 05:13 PM
So you're saying the Toshibas convert both 480i and 480p to 540p?

It does look that way to me, too, as my non-progressive DVD player definitely looks smoother than I would expect an interlaced signal to look...

I don't see how they could just "chop off lines", they must be scaling and scan converting, as the lines must be drawn faster to display 540 lines in the same amount of time as 480 lines...

ja2935
02-07-2006, 08:59 PM
I believe I have seen posted an explanation of the 540p 'trick'. I think it is really two identical interlaced 540i fields. In other words it still fills 1080 lines but instead of two unique interlaced fields as in 1080i/30, it is two identical fields one after the other so the frame refresh rate is still 30Hz. This means it is really a line doubler.

On my tv I cannot see any difference when viewing a DVD at 1080i or 540p - they both look pretty good and better than an EDTV because of the reduced 'screen door' effect. Also, as most movies are made at 24 frames/sec, 30Hz is quite fast enough!

BobY
02-07-2006, 10:50 PM
It seems to me there must be more to it than that, as that would cut the motion capture rate in half (a true 480p signal will be updating at 60Fps, displaying the same frame twice would effectively drop the rate to 30Fps. Although the frame rate of 1080i is 30Fps, motion is captured at twice that rate because it is captured in each field). If it does reduce the motion capture rate, I would think that would be noticable...

I'm not sure why it would need to do that, though. The 480p signal would already supply 480 lines at 60Fps, all the scaler would need to do is rescale it to 540 lines at 60Fps. The question I have is how does it get the 540 lines to fill a screen meant to display 1080 lines. It can't fill in gaps between lines on alternate fields as this would be back to interlacing and would flicker even if the two lines were the same. It can't draw each line twice as that would be the scan rate equivalent of 1080p, which I'm sure is beyond these sets (they can't even do 720p). The only way the "display the same field twice" trick would work is if there is no offset between the two fields, which wouldn't fill in the gaps between lines.

Are they stretching the height of the pixels in the analog domain to make the lines thicker? I just don't see any gaps between the lines...

I'm having a hard time wrapping my mind around this:confused:

woodman44
02-08-2006, 01:11 AM
I just entered the HD scene a few weeks ago with a 50" Zenith plasma. Here is a site that looks like it can explain the different modes of HDTV and the difference between (i)interlaced & (p)progressive.
http://www.alvyray.com/DigitalTV/default.htm

BobY
02-08-2006, 10:48 AM
Yes, I've been to that site many times and I have a high regard for Alvy Ray Smith and his work (he co-founded Pixar back in the George Lucas days and they created the foundational work for all of the CGI you see in movies today). I do think his "rename 1080i to 540i" is a bit of a publicity stunt to get people to consider that true 720p is visually better than 1080i in practice and is much easier to process.

In this case, though, we are talking about an approach to progressive that Toshiba uses in their CRT-based HDTV's. It's not a progressive signal per se, it's a way they display a signal to make it look progressive (or a way to display an already progressive signal). I'm trying to understand how Toshiba specifically creates their 540p image on the display...

ja2935
02-08-2006, 01:38 PM
It seems to me there must be more to it than that, as that would cut the motion capture rate in half (a true 480p signal will be updating at 60Fps, displaying the same frame twice would effectively drop the rate to 30Fps. Although the frame rate of 1080i is 30Fps, motion is captured at twice that rate because it is captured in each field). If it does reduce the motion capture rate, I would think that would be noticable...

I'm not sure why it would need to do that, though. The 480p signal would already supply 480 lines at 60Fps, all the scaler would need to do is rescale it to 540 lines at 60Fps. The question I have is how does it get the 540 lines to fill a screen meant to display 1080 lines. It can't fill in gaps between lines on alternate fields as this would be back to interlacing and would flicker even if the two lines were the same. It can't draw each line twice as that would be the scan rate equivalent of 1080p, which I'm sure is beyond these sets (they can't even do 720p). The only way the "display the same field twice" trick would work is if there is no offset between the two fields, which wouldn't fill in the gaps between lines.

Are they stretching the height of the pixels in the analog domain to make the lines thicker? I just don't see any gaps between the lines...

I'm having a hard time wrapping my mind around this:confused:
The point is that the 1080i CRT sets are interlaced and scan 540 lines at 60Hz - one frame is two interlaced scans (fields) and so each new frame is generated at 30Hz. The 540p merely sends the same information twice displaced by one scan line so as I said before it is really a line doubler in order to use all 1080 lines. It is unlikely that many people could detect a 30Hz flicker - most people can't detect much above 25Hz.

Porcupine
02-08-2006, 02:07 PM
OK I have done yet more testing on this and I now think everything in my initial post was correct. So good thing my rant was kept, because HDTV makers deserve to be shot for their stupidity.

But anyways, first let me clarify these other recent discussions that have been going on here. I'm claiming (and you don't have to believe me) that what I say IS correct because I simply see these things with my trained "bionic" vision. And in several cases the Toshiba manual has been blatantly wrong when explaining certain technical things, so don't always trust what it says.

The Toshiba and Sony CRT HDTVs, and most likely all HDTVs can and do reconfigure their electron guns to either output 1080i or a TRUE 540p. When in 540p mode, the electron guns DO scan the exact same scan lines 60 times a second. The Sonys DO leave visible black scanlines when in progressive mode. Just go to Best Buy, open the Sony menu, and switch between "Interlaced" and "Progressive" mode and check the difference with your eyes. The scanlines can't be more obvious in 540p, and the interlacing can't be more obvious in 1080i (image gets bouncy and just plain looks interlaced, but steady black "scanlines" are not visible). BTW the signal Best Buy feeds to their CRT HDTVs is a 480i regular analog coax cable feed.

The Toshibas do not allow you to choose between 540p and 1080i when a 480i signal is fed (the manual states this as well). You can change the option in the menu but the screen mode WILL NOT CHANGE. Therefore if you see no difference with your eyes between the two modes that may be because you are feeding a 480i signal. Whenever feeding a 480i signal, the Toshibas upscale and display as true 540p. NOT 1080i (the manual is lying). In the case of Toshiba, you cannot see visible black scanlines because their beam width is too thick, however the image IS truly 540 progressive.

If you feed 1080i or 720p into the Toshibas they always upscale to 1080i, I think (I haven't been able to test this yet due to no source, but I don't see any reason to doubt this).

Now, if I configure my DVD player to output 480p through the component cables, that is the ONLY way to get the Toshibas to switch selectively between 540p and 1080i. ANY OTHER input and the 540p/1080i menu select option HAS NO EFFECT. The manual states this. Furthermore, when I do switch between 540p and 1080i on a DVD player *which has been correctly set up to output 480p* I see a huge difference in my screen image. 540p mode looks exactly the same as the same DVD player displaying 480i. 1080i mode looks totally different. It's in this mode that the lines are doubled (a second time) from 540 to 1080 and simply redrawn twice. But the end result look is different. A stationary image might look "the same" but you can ALWAYS see the interlacing effect of your TV in 1080i, if you have trained your vision to see things quickly.

Porcupine
02-08-2006, 02:10 PM
As to being able/unable to detect flicker, there is a reason computer monitors have selectable refresh rates. Most have selectable refresh rates of typical values such as 60 Hz, 72 Hz, 75 Hz, 85 Hz, and 100 Hz. And observant (and it helps to be young) people CAN tell the difference between all these screen modes simply by checking the amount of screen flicker.

Porcupine
02-08-2006, 02:22 PM
And back to the original topic, I am once again very pissed to realize that CRT HDTVs (at least the Toshibas, but probably all) do rescale 480 lines to 540 lines to display. That is dumb because a resampling is done and causes information to be lost.

I have, since I bought my TV, been perplexed by why my image seems fuzzy, especially in the vertical direction. Now I know the reason, it is because of the rescaling. I still think CRT HDTVs still rescale far better than most/all LCD HDTVs, but the sad truth is that they should not have had to rescale at all. And TV makers are idiots for doing it. It is easy to just display 480 lines and leave the last 60 lines BLACK. This would result in a higher quality image, but they were too dumb to do it. The 60 black lines could have been cut off as overscan (on a CRT monitor, you simply resize the image with the Menus/Service Menus...this is done in an analolg way so no quality is lost) if they are annoying. If not, just display them who cares. The quality will still be much better.

Also, from toying around with the Service Menu to indirectly gather information about how my TV works, I'm sure now that the various screen modes of the Toshiba (Full, Normal, TheaterWide123) DO digitally rescale/zoom the image to fill the whole 540 vertical lines. You can further resize the image in an analog way through the Service Menu though, as I said. For example I can resize TheaterWide3 to have the same aspect ratio as Fullscreen (widescreen) mode. However then there will be black areas at the bottom and top of the screen because the digital rescaling has been done and cannot be altered. The reason the TheaterWide modes don't really look badly rescaled is because you are comparing to Full/Normal modes which are ALSO rescaled. So you don't even know how clear an unscaled image would be on your TV because there is no way to tell.

I'm fairly sure an unscaled 480 line image would look MUCH better on these TVs. My image quality is highly unsatisfying, especially with videogames, I've noticed, where it is more obvious that resampling has been done and the image looks slightly fuzzy in the vertical direction. A good 480p CRT EDTV would probably do a much better job, but I dunno if any are made. Maybe some companies other than Toshiba don't resize 480p to 540p. If true I'd really like to know. I doubt it though, so I am very angry at the TV industry right now. They think that consumers won't notice all these things and that they can get away with it, or they are too stupid to notice these things themselves.

Porcupine
02-08-2006, 02:32 PM
When watching true 1080i HDTV sources (which I will do at some later time, probably when the PS3 and the next-gen HD DVD formats come out) most likely the image will look better just as much from the increased resolution as from the simple fact that it is not rescaled. These tube HDTVs can't really display 1920x1080 anyway, since most only have 800 to 1400 lines of horizontal resolution, plus there are color convergence errors, etc. But displaying an image in the correct, completely unscaled native resolution, will make it appear much sharper (in some sense a native image could be considered twice as sharp as a rescaled image).

And here is one last piece of info for Toshiba owners. The other major lie in the owner's manual is regarding TheaterWide 1 mode. It does NOT "stretch the sides of the screen but leave the center mostly untouched" as claimed. It does not do a differential stretching like that. It simply stretches the image uniformly by a certain horizontal amount, and also cuts off a certain vertical amount. The same as all the other screen modes. You may (and probably will, as I did also) IMAGINE the effect described in the manual. However that is due to your TVs design and not the TheaterWide 1 mode. That effect is present in all modes of the Toshiba, even Fullscreen/Normal. The Toshibas have really bad geometry, like most/all flat screen CRTs it seems.

The above applies to the 30" and 26" models only. I dunno about you ja2805 because you have a 34HF84 which is genuine Toshiba-made and may be different.

BobY
02-08-2006, 09:58 PM
ja2935-

I don't think that's how it works in the 540p mode. If it is taking the progressive image and displaying it as two alternating, 540-line fields which are offset, it's not progressive, it's interlaced (essentially synthesizing 1080i with a line doubler, not 540p).

It doesn't matter if the second field is identical to the first, if it's offset, then each raster line is alternating between being active and being blank and it will look interlaced. It will also have jerky motion as the display will be updating motion at half the rate as the input and would be throwing away every other 540p frame as they would be coming in at 60Hz, not 30Hz. That doesn't make sense to me. It shouldn't be any trouble to rescale the 480p image into a 540p image and display it as 540 lines at 60Hz. The problem is filling the black space between the lines where the second field would go in an interlaced 1080i presentation. Porcupine says Sony doesn't do anything about the space and you just see black lines between the active lines, while Toshiba make each line thicker to fill in the space.

I'm pretty sure what I'm seeing is not alternating fields interlacing to fill the gaps between lines, as there is no trace of flicker or combing. I have always been able to easily detect interlacing (it gives me headaches if I watch for any length of time), but I've never seen a 1080i display with a 1080i signal before, so I could be wrong about what I'm seeing...

Porcupine-

If I understand you correctly, you're saying the Toshibas are actually scaling both 480i and 480p to 540p, and using the line doubler trick to display 540p as 1080i when that option is selected. If that's the case, why wouldn't they let you select between 540p and 1080i on a 480i signal?

If upscaling upsets you, you bought the wrong TV :) The Toshibas rescale everything except 1080i. At least it's upscaling. If they were to downscale 720p to 540p, then line double it to 1080i, that would be sad...

1080PsF
02-08-2006, 10:23 PM
Porcupine-

If I understand you correctly, you're saying the Toshibas are actually scaling both 480i and 480p to 540p, and using the line doubler trick to display 540p as 1080i when that option is selected. If that's the case, why wouldn't they let you select between 540p and 1080i on a 480i signal?


In 480p this would mean that the video on the disc was film based and 480i would mean that it is video based. If it is film based then you can remove the 3:2 and de-interlace it and make it a progressive signal but if it is video based you can't do that because each field is discreet.

Porcupine
02-09-2006, 03:47 AM
> I don't think that's how it works in the 540p mode. It doesn't matter if the second field is identical to the first, if it's offset, then each raster line is alternating between being active and being blank and it will look interlaced.

That's right! You have good eyes, just like me.

> I'm pretty sure what I'm seeing is not alternating fields interlacing to fill the gaps between lines, as there is no trace of flicker or combing.

Exactly. I see the same in properly-working 540p modes. And I have confidence in my vision, as do you. :)

> If that's the case, why wouldn't they let you select between 540p and 1080i on a 480i signal?

There is no reason why they couldn't have let you do this. The Sony Wegas DO allow you to do this (I did it in the store). Toshiba simply decided not to.

> If upscaling upsets you, you bought the wrong TV The Toshibas rescale everything except 1080i. At least it's upscaling.

Yeah. But still...wah wah. I am upset I am angry lol. I hate all the CRT HDTV makers. They should have been smart enough to handle 480p as non-scaled 540p with 60 blank lines. Die die they must die. ;) I wish I had superpowers like Magneto so I could destroy all the dumb HDTVs in the world and make better ones appear out of thin air.

I'm still wavering with what I'm gonna do regarding my current HDTV crisis. I've got 3 weeks left to return my new Toshiba 30HF85 before I'm stuck with it. Problem is, if I return it I dunno what to get in its place as all CRT HDTV brands seem to have their own pitfalls these days.

BobY
02-09-2006, 08:20 AM
In 480p this would mean that the video on the disc was film based and 480i would mean that it is video based. If it is film based then you can remove the 3:2 and de-interlace it and make it a progressive signal but if it is video based you can't do that because each field is discreet.

I'm not saying they didn't make that assumption (obviously they cut corners all over the place), but that assumption isn't necessarily true. A non-progressive DVD player will display movies as 480i (they're encoded as 480i on the disk) and a progressive DVD player will display video-based content at 480p (since it is synthesizing the progressive image from an interlaced image). Hopefully they are basing the reverse pull-down on the field/frame sequence and not whether the input is progressive or interlaced...

> That's right! You have good eyes, just like me.

Actually my eyes are pretty bad, but I'm sensitive to flickering, including interlaced displays, fluorescent lights and incandescent lights on dimmers.

> There is no reason why they couldn't have let you do this. The Sony Wegas DO allow you to do this (I did it in the store). Toshiba simply decided not to.

Maybe their processor is not fast enough to scale it, de-interlace it and double it to 1080i. It wouldn't need to de-interlace a progessive signal, so it's less work. Doesn't seem likely, though, it's not much effort to double it to 1080i (as opposed to upscaling it to 1080i using line interpolation).

> I wish I had superpowers like Magneto so I could destroy all the dumb HDTVs in the world and make better ones appear out of thin air.

If all the companies that made poorly-executed CRT-based HD sets were gone, there wouldn't be any other HD displays out there either :) I think it's a goal of most of these companies to phase out conventional CRTs, so maybe this is part of their plan...

But if you were Magneto, you could control the beam deflection yourself. I think we can safely assume that Magneto would opt for a CRT-based HDTV--he was a control freak. Talk about tweaking your display ;)

> I'm still wavering with what I'm gonna do regarding my current HDTV crisis. I've got 3 weeks left to return my new Toshiba 30HF85 before I'm stuck with it. Problem is, if I return it I dunno what to get in its place as all CRT HDTV brands seem to have their own pitfalls these days.

Take a deep breath. If you actually *see* disturbing problems on the screen, take it back and rethink your plan. If it's just an intellectual issue--don't worry, be happy. The more I learn about my Toshiba, the less impressed I am with it's engineering, but I still think the picture looks great and I'm happy to keep mine until good-looking, affordable 1920 x 1080p flat panels are available. I'm really intrigued by the new SED technology which seems like it would have all the benefits of direct view displays and none of the problems of CRT (size, weight), LCD (contrast, viewing angle, poor black level) or Plasma (aging/lifetime).

BobY
02-09-2006, 09:33 AM
Oh yeah, there is no reason they couldn't display a 480 line signal as 480 lines, but they would have to reconfigure the scan circuitry, which they are apparently unwilling to do for cost reasons.

You couldn't just "add" blank lines to fill out a 480 line raster to 540 lines, as 540 is still a faster scan rate than 480 (if you have a 60th of a second to draw your lines and you need to draw 540 instead of 480, you have to draw the lines faster to get it done in time). All of the horizontal and vertical deflection parameters would have to be changed to compensate or the aspect ratio and screen size would change).

Bottom line, you would still need to upscale the 480 signal to 540 in order to display it in a 540 line/60 Hz raster, there is no simple solution.

Porcupine
02-09-2006, 08:56 PM
Well, what you would do is simply have your TV be smart, and tell itself to draw some black (or whatever color) bars at the top or bottom of the screen when fed 480i input.

> All of the horizontal and vertical deflection parameters would have to be changed to compensate or the aspect ratio and screen size would change

The Toshiba TV's built in EEPROM memory contains separate memory data containing the aspect ratio/screen size/etc for each individual screen mode and sometimes even input connector being used (1 for Fullscreen, 1 for TheaterWide1, 1 for Normal, etc....and a whole new set each for the Composite inputs, the Component inputs, HDMI input, etc). You can just check this in the Service Menu. I've made good use of that fact myself, as I've individually resized all my screen modes separately to fit my personal preferences.

Anyway, the problems on my Toshiba do bug me there is no doubt about that. But I can be very picky, and I suspect that I would also be bugged by things on other companies' CRT HDTVs. In any case, I think I will take my current 30HF85 back to Best Buy and exchange for yet another one (my 4th, haha). This one does have a hole in the shadow mask (one of my RGB sets of screen pixels is broken) so I suppose that alone is good enough reason for an exchange. My previous 2 sets did not have any holes in the shadow mask but instead they had dirt stuck inside the protective glass which effectively did the same thing (block out a couple pixels of my image). Also I think the convergence on my current set is not the best it could be (I've had 3 sets so far and each had different convergence looks) although that is okay. The Toshiba quality control is definitely awful these days, at least that much I can say for sure. Some of the other problems I suspect are simply design problems though (like bad geometry, fatter on the right side).

I don't feel bad about wasting Toshiba's money by returning sets, at least. Actually I feel better for making them waste money lol, but I should not let that be a factor that motivates me into returning a set. ;) I wonder how much contribution I will make to Toshiba's TV return rate (last I heard it was around 12% to 20%)?

rbinck
02-09-2006, 10:42 PM
I'm not saying they didn't make that assumption (obviously they cut corners all over the place), but that assumption isn't necessarily true. A non-progressive DVD player will display movies as 480i (they're encoded as 480i on the disk) and a progressive DVD player will display video-based content at 480p (since it is synthesizing the progressive image from an interlaced image). Hopefully they are basing the reverse pull-down on the field/frame sequence and not whether the input is progressive or interlaced...

While the DVD data is stored on the disc as two fields per frame, the fields came from a common film frame, so when those two fields are put back together you end up with the progressive video. They do switch from film mode to interlaced video mode by sensing the 3:2 sequence - there will be a duplicate field or repeat flag when in the film mode. They actually can switch on the fly and depending on the mastering, the switch can happen even when the source is film. Video derived from film is different than interlaced video because both fields are from the same point in time, whereas with interlaced video each field is from a different point in time 1/60th apart.

All of the new TVs with digital chassis will convert every signal to digital video for processing. That means a digital image is formed in video memory and scaled, reverse pulldown, deinterlaced and filtered digitally. It is a simple matter to scale the image to 1080 lines, 540 lines or 480 lines as required by the particular scan rate the TV operates in for any given mode.

BobY
02-10-2006, 09:13 AM
Well, what you would do is simply have your TV be smart, and tell itself to draw some black (or whatever color) bars at the top or bottom of the screen when fed 480i input.

You would still need to change the scan rate. At the normal scan rate for a 480 line image, no matter how smart the TV is, there's no time left to scan more "blank" lines before vertical sync. To add more lines, you have to scan each line at a higher rate. Toshiba was obviously totally committed to implementing only one scan rate.

The Toshiba TV's built in EEPROM memory contains separate memory data containing the aspect ratio/screen size/etc for each individual screen mode and sometimes even input connector being used (1 for Fullscreen, 1 for TheaterWide1, 1 for Normal, etc....and a whole new set each for the Composite inputs, the Component inputs, HDMI input, etc). You can just check this in the Service Menu. I've made good use of that fact myself, as I've individually resized all my screen modes separately to fit my personal preferences.

Is this changing stuff digitally (like altering start times and pixel widths) or is it actually changing the deflection characteristics? To change the scan rate, you have to change the horizontal gain to sweep the whole screen horizontally in a different amount of time and the vertical gain to sweep the whole screen vertically with a different number of lines.

BobY
02-10-2006, 09:22 AM
While the DVD data is stored on the disc as two fields per frame, the fields came from a common film frame, so when those two fields are put back together you end up with the progressive video. They do switch from film mode to interlaced video mode by sensing the 3:2 sequence - there will be a duplicate field or repeat flag when in the film mode. They actually can switch on the fly and depending on the mastering, the switch can happen even when the source is film. Video derived from film is different than interlaced video because both fields are from the same point in time, whereas with interlaced video each field is from a different point in time 1/60th apart.

That's true of a progressive scan DVD player, but the Toshiba sets perform the reverse pulldown in the TV itself. The TV doesn't have access to the flags or information on the field sequence, it can only look at the cadence of the incoming fields. That brings me to a few dumb questions:

If the TV is being fed a progressive signal, since it doesn't have access to the individual fields, it won't be able to detect a film sequence will it?

Or is it true that all prodressive scan DVD players perform reverse pulldown, even if they don't mention it in their specs or manual? If not, using a progressive scan player with TVs that perform reverse pulldown themselves might be a bad thnig...

rbinck
02-10-2006, 12:10 PM
In most cases, if not all, when a TV is fed a progressive signal, the 3:2 reverse pull down would not be possible since it relies on interlaced fields for the 3:2 cadence. I would imagine the TVs would just stay in the video mode.

BobY
02-10-2006, 04:05 PM
More confusion for me! That would mean the Toshiba set could only do reverse pulldown on a 480i input, which, according to Toshiba, gets scaled to 1080i, not 540p. Can you do reverse pulldown on an interlaced signal and *not* end up with a progressive output?

I'm beginning to think that all Toshiba is doing is scaling all inputs (except 1080i) to 540p, then line doubling to 1080i.

This is an important question for me, do all progressive scan DVD players perform reverse pulldown on film-based video even if they don't mention it in their specs? I would hate to get a progressive scan player and find out that it not only doesn't do reverse pulldown but it prevents the set from doing reverse pulldown as well...

rbinck
02-10-2006, 04:31 PM
I can't speak to all DVD players. If the set does reverse pull down it will do it based on sensing the 3:2 cadence. If the DVD player has removed it, the TV can't sense it. By definition a progressive player would have to deinterlace the signal.

Here is a link that should help:
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

Porcupine
02-10-2006, 04:33 PM
The very definition of a progressive scan DVD player is one that does 3:2 pulldown correctly and outputs a truly progressive signal to your TV. If your DVD player does the pulldown, then your TV will receive 480p and should be smart enough not to pulldown again.

Even with a progressive scan DVD player, you can choose to force it to output 480i through S-Video or composite cable (or possibly menu-select 480i even through component). In which case, your HDTV will do the 3:2 pulldown for you if it is turned on (in "Film" mode).

But I think 3:2 pulldown is overrated. I never use it. My cheapo $60 Samsung progressive scan DVD player does not do it well. It combs (feathered edges) often so it is unacceptable. Maybe better DVD players will do a better job of it. My Toshiba 30HF85 set to "Film" mode does 3:2 pulldown much better, but I still see it comb once every 5 minutes or so. So I turn it off too. I always leave my Toshiba perenially in "Video" mode, in which it never combs but I am also not sure how it is doing the line doubling.

I think even in Video mode the Toshiba does do 3:2 pulldown sometimes (also sort of referred to as a "weave") but it will revert to a simple line interpolation of the current field at other times (called a "bob") when it senses it has no fields to weave together. I'm very pleased with the performance of the Toshibas in Video mode, I have no complaints currently whatsoever. It also looks the same as the Film mode to me, except it never combs. It doesn't look any less steady or more fake/interpolated...

Porcupine
02-10-2006, 04:47 PM
> Is this changing stuff digitally (like altering start times and pixel widths) or is it actually changing the deflection characteristics?

Some of the Service Menu geometry-altering options are digital, but most are analog. I can tell the difference because when something is an analog change and I really move the settings far away from normal, the screen will start to warp and get all funny shaped in various ways. When something is digital and I move the settings far from normal, no "side-effects" will occur.

The horizontal centering option in the Service Menu is digital. It simply moves the image you see left/right within the TV's computer memory. But the horizontal stretch option is analog (if you scrunch it up too much it'll get really weird). The vertical centering option is analog. If you push it up super far things will get weird, the image doesn't just move upward like in a videogame. The vertical stretch option is analog. Just some examples. :)

Porcupine
02-10-2006, 04:50 PM
There are a LOT of options in the Service Menu for correcting vertical geometry problems so that is why I have no real complaints about vertical stretch/straightness/geometry on my Toshiba. But there are few options for addressing horizontal geometry problems. Even of the ones that exist, some of the ones that might be useful are digital and don't help. :P

BobY
02-10-2006, 05:25 PM
I'm willing to believe that all progressive DVD players perform reverse pulldown, but it's certainly possible to produce a progressive image without reverse pulldown. The reverse pulldown is re-sequencing the fields to prevent the errors that can occur when unrelated fields are combined into the extra "generated" frames. There's no reason that has to be an inherent component of progressive scan, but, on the other hand, there's no reason not to do it either.

Regarding the Toshiba TV's, it doesn't seem to me there is any way it could perform reverse pulldown on already progessive signals (which presumably have already been corrected so it wouldn't matter) and if it performs reverse pulldown on 480i signals, then the result will be a progressive signal, not 1080i as Toshiba states. Unless at that point they re-interlace the resulting progressive image.

I think I'm going to order the service manual for my Toshiba to try to find out what they really are doing. It will probably display a true 1080i input correctly, but I'm suspicious that by "converting to progressive", Toshiba means "only displaying half the lines the set is capable of displaying" and that by "converting to 1080i" Toshiba means "only taking half the lines the set is capable of and displaying them twice alternately with an offset".

rbinck
02-10-2006, 09:39 PM
First let's start with a block diagram of a typical digital TV:

http://www.highdefforum.com/gallery/data/511/TVblockDiag.jpg (http://www.highdefforum.com/gallery/showphoto.php/photo/270/cat/511/page/4)
The main differences from brand to brand will be in the technology of the video processing, deinterlacers, noise reduction, scalers, etc., but the basic block diagram will be the same. (I didn't draw this diagram, I lifted it from cirrius.com.)

Ok, now as you can see there are two areas where video processing occurs. In the case of SD signals there is the magic block called the video digitizer. Here the signals from the analog tuner and the analog inputs are fed to it. In that magic box is where the signal is digitized and converted to a memory bit array and then processed. For the purpose of this discussion we will say a 640x480 pixel memory array. All of the deinterlacing and other video processing has been done by the time the signal is stored in this video array output. they process the SD material at this point because it takes less firepower to do sophisticated processing at 640x480 than it would at a HD resolution, thus less lag time. The output of this video digitizer is then sent to the Video Up Scaler where a video pixel array output is built for the resolution of the display being driven. In the case of a CRT display this would be a 1920x1080 pixel array. In the case of a 1280x720 fixed pixel display, that would be the output size.

Now it is a pretty simple matter to output interlaced video to the CRT tube by outputting the odd lines on one scan of the CRT followed by the even lines on the next pass. If driving a fixed pixel display the lines are transferred line by line.

Now the beauty of digitizing the analog signals allow for digital processing which can allow the processor to look at neighboring pixels in the arrays to achieve a better smoothness when de-interlacing video and to allow for the 3:2 reverse pull down to occur without getting the display out of sync with the 60 fields per second refresh of a CRT or 60 frame per second of a fixed pixel display.

Remember when the 3:2 reverse pull down occurs (the processor operating in the film mode) the effective frame rate out of the SD video digitizer is 24 frames per second. All this gets worked out by just transferring the 24fps video data into the Video Up-Scaler at 24fps and letting the signal be sent out to the display at 60 fields (or frames) per second. By allowing the display output pixel array to be accessed at 60fps the picture will change whenever the next 24fps video arrives, since in the digital realm the input and output to the HD pixel array can asynchronously to each other, the 3:2 cadence is not necessary as it would be if we were dealing with an analog only system where the timing had to be at 60fps throughout.

Notice the HDMI, or DVI if so equipped, is just received and passed to the Video Up-Scaler because there would be no pre-processing required being digital video already. This block diagram does not show HD component inputs, but presumably they would go through a digitizer and then fed to the Video Up-Scaler in a similar path to the HDMI.

To my knowledge, no manufacturer has divulged the inner workings of their video processors in great detail, but you can get an idea by checking out this link: What Is Video Processing (http://www.hqv.com/technology/index1/video_processor.cfm?CFID=&CFTOKEN=19e6d28930aaaa8a-5382ACA5-7E90-E2A3-B0B0A05B613BDD8B)?

Also you may want to check out:
http://www.cirrus.com/en/pubs/appNote/AN_CS493xx_DTV.pdf

Porcupine
02-11-2006, 04:03 AM
> if it performs reverse pulldown on 480i signals, then the result will be a progressive signal, not 1080i as Toshiba states.

I don't want to get involved in all your current arguments, but i just wanted to point out that I did say before that Toshiba converts 480i to 540p, NOT 1080i. And that the manual is WRONG on this. My eyes do not deceive me, and I will believe them over any manual.

It is possible that 480i is converted digitally to 1080i for reasons of simplicity (always do the same thing) and also for the benefit of 1920 horizontal pixels of digital resolution, but afterwards half the scan lines are "thrown out" and the TV does display in a true 540p mode (NOT displaying in 1080i with each scan line displayed twice, which is what the manual and others would have you believe).

BobY
02-11-2006, 09:05 AM
I don't think we're arguing. At least I'm not trying to, I'm trying to understand what's going on.

I see the same thing you do and I had come to the same conclusion until I started experimenting with an upscaling DVD player, which yielded some unusual results.

So far, I see *no* difference on the Toshiba display regardless of whether the DVD player is sending 480p, 720p or 1080i, other than the player shows staircasing on still frames in both 1080i and 720p, but does not show staircasing on the same still frame on 480p, regardless of whether I set the Toshiba 480p mode to 540p or 1080i. This is confusing to me. If the player's progressive scan eliminates jaggies on 480, why doesn't it do it on 720? If the TV is converting 720p to 1080i and that is causing the jaggies, why doesn't it cause jaggies on the 480p signal when set to 1080i?

I see no flickering on any of the modes, not even 1080i from the player. I figure this has something to do with the fact that I'm not sending it a true 1080i signal such as broadcast, rather in all cases 1080i is being created from something else.

Unfortunately, it won't play 480i out the HDMI port and the Component outputs are only 480i or 480p, so I have to change things around to see what happens with 480i compared to 480p.

More to come...

Porcupine
02-11-2006, 12:45 PM
I think the reason could be that your upscaling DVD player does not do a good job of upscaling, while the Toshiba TV either does a better job of upscaling (480p to 1080i) or simply line doubles without interpolation when converting 540p to 1080i.

Different devices can yield very different looks when doing an upscaling, it depends on the method used.

I do see very obvious flickering in 1080i mode (the only way I was able to activate it was by sending 480p through Component on my DVD player, then selecting 1080i from the menu). Toggling between 540p and 1080i the difference in the steadiness of the image was obvious to me. Try reducing the contrast of your TV to zero. That will reduce vertical blooming of the beam and probably make interlaced flickering more obvious (you still won't see scanlines in 540p mode, even with Contrast set to 0 though).