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Discussion Starter · #1 ·
How many of us would like to see the DVD player manufacturers use VGA ports on their machines?? I know i would, if it saved me the trouble of a transcoder, and with many TV's and PJ's offering VGA-in, with superior quality, i think the market would be hot. How difficult would it be to add a port (and circuitry, if needed)? I think they can do it.

This kind of compromise makes me mad - just like going with RCA ports instead of BNC for component connections. :mad: :confused: Why the hell not?


That's my rant for the day, thank you for listening.
 

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They have an "internal" scaler/de-interlacer for installation in MPEG-2 products (like DVD players). Not quite as cheap as your BNC->RCA connector problem, but the results are fantastic.
 

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VGA output is a violation of the macrovision license or something to that effect. I believe macrovision simply doesn't work over VGA output. I have only heard of Chinese manufacturers using VGA output (Chinese manufacturers ignore as many of DVDs licenses and rules as they can).
 

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NTSC over VGA does not work well with digital projectors. CRT displays however are another matter.
 

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I have VGA out on my Daewoo dvd player. I dont' use that port much though. Only if I need to take a dvd player and projector on the road for some reason which I haven't had to do in a while.
 

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Discussion Starter · #7 ·
Why doesn't it work well with digital projectors? Are there timing issues involved?

I understand the Crapovision issue though. %$#%#$ :mad: :mad:
 

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Mark,


Why do you say VGA into TV's and PJ's ........ offers superior quality??? I read this as you meaning superior quality to [also] component in?


Everything I've read says Y/Pr/Pb and VGA produce the same video quality - with VGA just un-bundling the H/V sync signals.


(I have VGA input available on my RPTV, but opt to use the Y/Pr/Pb inputs instead so I maintain control of certain video parameters that I would lose using the VGA input.)
 

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Quote:
Originally posted by Mark Laarson
Why doesn't it work well with digital projectors? Are there timing issues involved?
The projector's input might assume that on RGB input with 480 lines, that each line has 640 dots rather than 720 that DVD has.


I do have to question the need for Macrovision on VGA out - I can't think of anyone making a consumer video recorder that can record an analog VGA signal! 'tis easier to rip the DVD anyway, with better results too.
 

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Right on the mark Jeff. 640x480x60Hz uses the exact same timings for horizontal and vertical synch as 720x480x60Hz (progressive NTSC - 480p). There's a slight difference of course - but most digital projector ADCs and processor have trouble distinguishing that, and so uses the wrong sampling rate and scaling. The result is a loss of horizontal resolution - and scaling artifacts. Usually 480p is output through component and thus it's possible to program the projector to use different timings because it's a different type of signal.
 

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Can someone please explain to me how 720 dots fits onto a monitor with 640 pixels across. Is it scaled reverse-anamorphically ?


Thanks,


CG
 

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fredzy,


You're actually asking two questions really - and I'm not sure which one you are talking about.


The first one is the issue we're discussing. For the sake of argument I'm going to assume a digital display device (as a CRT doesn't have this problem I mention). The easiest way to handle this is to think of it as an analog signal being sampled. Think of just one horizontal line. Divide that into 720 parts. Now think of a line that's the same length, but instead divided into 640 parts - this is the sampling being done. Overlay that 640 part line over the 720 line, and you see what parts of the original 720 pixels are actually sampled by the process. In addition the pixel widths are not the same - and so some of the sampling will be across two pixels instead of one. This has an ugly tendency to confuse the A/D converters and make some of the pixels brighter or darker than they're supposed to be. A slight vertical banding effect can be seen as a result of that.


The second is how do you fit 720x480 DVD into a 640x480 desktop on your PC (scaling done by the computer). A computer has different ways of scaling (linear, bicubic etc etc) and which one the player uses has an effect on how good the results are. In this case you're actually downscaling the DVD so it fits the resolution. As a result pixels/lines have to essentially be dropped. The different scaling algorithms have different ways of doing this, but the end result is always that you lose effective resolution. For anamorphic DVDs it's even worse as then you have to scale 720x480 down to 640*360 - which means you're losing even more resolution.
 

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Pnichols:

Quote:
Everything I've read says Y/Pr/Pb and VGA produce the same video quality - with VGA just un-bundling the H/V sync signals.
I have tried 2 outputs from an NRS to a plasma this way and can confirm they both produce the same picture quality.
 

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Frode -


Thanks for that very coherent explanation. From what you say, the data on a DVD is stored as a digital representation of a analog signal, rather than a pure digital frame. Therefore the digital nirvanna of going from disc to projector (via DVI) is impossible without at least one D->A conversion, sigh!


Nevertheless I am still confused about what the native resolution of an anamorphic disk would be after de-squeezing it vertically 33%. Is it 720*1.33=957 ? My projector is 850 * 600, which is supposed to be ideal for DVDs ?!?


CG
 

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fredzy :

Quote:
Therefore the digital nirvanna of going from disc to projector (via DVI) is impossible without at least one D->A conversion, sigh!
Would this be true if you have a DVD player with the SDI modification? From what I’ve read on this forum, it sounds like it would be all digital to a DVI output. Of course, there would have to be an SDI-capable scaler in the middle with DVI out (e.g. Leeza or CS-1) or a player with DVI out.
 

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Quote:
Originally posted by fredzy

[BNevertheless I am still confused about what the native resolution of an anamorphic disk would be after de-squeezing it vertically 33%. Is it 720*1.33=957 ? My projector is 850 * 600, which is supposed to be ideal for DVDs ?!?[/b]
Each "dot" on an NTSC DVD is by definition non-square. The aspect ratio of real data points stored is 1.5:1, however, the actual image that it represents would either be 1.33:1 or 1.78:1. The display does its own "scaling", as it were, to correct for the difference.
 

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fredzy,


You never mentioned DVI in your original post - and this thread is about VGA, which is analog ;). VGA is the problem, not DVI.


With DVI (and SDI) it's slightly different as then you'll get the original 720x480 pixels and it's up to the HTPC or display device to scale that so it fits the panel resolution. Since that's a digital format there are no synchronization issues as I've outlined above.


As for anamorphic "resolution", if you think square pixels just take the vertical resolution*16/9. So it's 480*16/9=853. The resulting resolution when stretched to correct aspect ratio is thus 853*480 - in square pixels. Your projector would thus chop off 1 pixel on one side, and two on the other - and then display it with black bars above and below the picture. If it had just been SVGA projector you'd have to reverse the calculation - 800*9/16=450, which means you're essentially dropping 30 lines of picture information to fit the panel.
 
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