DVD on 800x600 PJ from HTPC

Discussion in 'Desktop & Laptop Computers Forum' started by spamboy, Nov 20, 2002.

  1. spamboy

    spamboy
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    I'm not sure if this should be on the PJ forum, but as more of a computer geek I feel more comfotable here ;-)

    I've noticed on the newer entry level sony and panasonic widescreen projectors the resolution is 858x484. Looking at the DVD Faq from http://www.dvddemystified.com/dvdfaq.html#3.4.1 it mentions that the horizontal resolution of DVD is 720 pixels.

    Why do these pj's have the larger resolution? How is is used? From my experience with computer LCD's running anything but the native resolution produces poor results, so is the image modified to fit the wider panel? I'd rather have a pixel by pixel display.

    I'm mainly asking as I'm thinking of buying a pj second hand, which is most likely going to be 800x600 (as I'm on a limited budget), if I'm playing dvd's will there be any scaling involved to fit on the panel?

    Thanks,

    SB
     
  2. buns

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    I cant answer fully, but i use my sanyo plv30, which is a 800x600 panel, for dvd playback through my pc..... there is no extrac scaling done, at least not to my knowledge......certainly the results are great.

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  3. Mr.D

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    Its the resolution of 16x9 NTSC unsquished
     
  4. spamboy

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    Thanks for this, does this mean that they would have a problem with PAL, with it's higher vertical resolution?

    Also, I assume this means that PAL widescreen has a horizontal resolution of 1020 or so, is this correct?

    Sorry for the stupid questions, but the faq's available deal with things in a very TV, rather than computer orientated way.

    Thanks,

    SB.
     
  5. buns

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    No Pal problems for me!

    I agree the FAQ's cover hardware more than software and its application..... have you had a chance to do searches at avsforums?

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  6. Peter Parker

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    I've an old Davis DLS8 pj and I drive it with an htpc.

    No problems at all with resolution, and due to 16:9 images being resolved at 800 x 450, both PAL and NTSC are scaled to this resolution.

    I don't see any difference between the two except when I forget to change the scan rate. :)

    Gary.
     
  7. Mr.D

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    Well thats the thing: the panel only really carries enough resolution for NTSC so you won't notice any appreciable increase in quality with PAL discs even if it is there ( debatable).

    I use an HTPC into my ae100 and the difference between PAL and NTSC is negligble (its running at 60Hz too to match the panel).
     
  8. Peter Parker

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    I wonder if the PAL/NTSC resolution difference is noticable on a 1024x768 or greater resolution pj.

    I'm thinking of upgrading soon, and until I get a demo, I'd be interested in hearing from owners of pjs with higher resolutions.

    Gary.
     
  9. spamboy

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    I'm beginning to think that due to the restricted (less than pal) size of the lcd some of the widescreen home cinema projectors could be worse for htpc use than an 800x600 one. A clear article on dvd resolution is http://www.hometheaterhifi.com/volume_6_4/feature-article-enhanced-widescreen-november-99.html which states the horizontal resolution is 720. One thing that confuses me is if there is a fixed horizonal resolution and a variable vertical resolution between pal and ntsc, how is the aspect ratio preseved?

    Does this mean more scaling? Argghhh......

    I sort of had the hope that you could extract the data from the disk and display a pixel by pixel representation of the data on the lcd. It's becoming clear that this is not the way that TV wants to work. Any ideas why?
     
  10. MAW

    MAW
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    That's quite a hotly debated subject, I'm in the 800x600 camp, nice and bright, HCPC driven. If the panel is good, ie fine panel structure, the picture is virtually as good as anything I've seen demo'd, and all at reasonable cost. Certainly, anything except the PTAE 100 that claims to be for home cinema will have more horizontal pixels, for which the salesman can find a long winded justification, and a quite exraordinary price tag. Someone shoot me down now!

    Scaling is the death of picture quality if not done brilliantly, the ideal dvd pj would have a horizontal res. of 720 IMHO, except that you'd see the pixels if you are closer than about 1.8 times the screen width. That's the only justification for more dots, they're smaller so you can sit closer, and Yoda looks bigger...

    Some PJ's have an option to display component vid. at 'native resolution' ie bypass the internal scaler. I've not tried that function with mine, it seems OK without, but in the interests of science, I'll get around to it one rainy W/E
     
  11. Peter Parker

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    720 x 480 or 720 x 576 is the unstretched anamorphic image of a 4:3 DVD. You need a scaler to stretch it to 848 x 480 or 1024 x 576 or an anamorphic lens (i.e. Pamamorph or ISCO) .

    If a pj was only 720 pixels wide, in order to keep the correct aspect ratio, the image height would only be 405, the same as a letterboxed image.

    That's why the AE100 is around 848 x 480, and why you need something like a 1024 wide pixel array for PAL sources to realise their full resolution. Then you may notice a difference between PAL and NTSC DVDs, depending on bitrate and the quality of the authoring of course.

    Gary.
     
  12. Mr.D

    Mr.D
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    Ahem...

    Pal video pixels are non-square: although the resolution of the image is 720x576 the image needs to be displayed with a slight horizontal stretch to 768. If you were to do a direct 1:1 mapping of 720x576 to a 720x576 inset into an 800x600 panel the image would actually be distorted slightly: So you'd effectively need to scale the image to 768x576. So bang goes your non scaling idealness anway unless your digital panel; projector has rectangular pixels.

    Most of us are going to be watching 16x9 material. Whilst the resolution of this will be 720x576 it needs to be displayed as 1024x576 to look undistorted.

    Either way is that you will involve scaling somewhere for correct display.
     
  13. MAW

    MAW
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    I had fondly imained that a 4:3 dvd image was 720x576. So if that's the widescreen ratio, with non-square pixels, what do they do with 4:3 stuff, there's lots about and it's not all pan and scan.
     
  14. Mr.D

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    Its all 720x576 resolution regardless of aspect ratio.

    The actual correct size of the image is 768x576 for 4x3 and 1024x576 for 16x9.

    Video is non-square pixel if you display it on a square pixel display device you have to do some sort of sub-pixel scaling.
    On a CRT its handled by the raster size ( draw interval or some such archaic nonsense)

    Resolution , image size and aspect ratio are all different things.
     
  15. MAW

    MAW
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    So everything is in the scaling, no matter what res your PJ is. I'm still impressed by mine, must have a good scaler then. I've recently started using a RGB scart to VGA lead for TV watching via STB, a clear improvement over s or composite. Obviously with DVD it's all down to your graphics card, I'm off to the shops then!
     

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