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Rescaling from 480p to 540p is STUPID

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Old 02-05-2006, 04:50 PM   #1  
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Thumbs down Rescaling from 480p to 540p is STUPID

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.
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Old 02-05-2006, 05:22 PM   #2  
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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.
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Old 02-05-2006, 06:54 PM   #3  
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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.
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Old 02-06-2006, 09:25 AM   #4  
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Quote:
Originally Posted by Porcupine
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.
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Old 02-06-2006, 10:20 AM   #5  
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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.

Last edited by BobY; 02-06-2006 at 10:29 AM..
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Old 02-06-2006, 04:06 PM   #6  
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The 540p can also be handy for game consoles as they tend to display, based on the game, better than interlaced res's.
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Old 02-07-2006, 03:26 PM   #7  
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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.
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Old 02-07-2006, 03:32 PM   #8  
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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.
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Old 02-07-2006, 03:40 PM   #9  
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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.
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Old 02-07-2006, 05:13 PM   #10  
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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...
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Old 02-07-2006, 08:59 PM   #11  
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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!

Last edited by ja2935; 02-07-2006 at 09:16 PM..
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Old 02-07-2006, 10:50 PM   #12  
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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
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Old 02-08-2006, 01:11 AM   #13  
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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
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Old 02-08-2006, 10:48 AM   #14  
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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...
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Old 02-08-2006, 01:38 PM   #15  
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Quote:
Originally Posted by BobY
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
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.
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