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What res HTPC into VSM

Discussion in 'TAG McLaren Audio Owners' Forum' started by GrahamMG, Nov 29, 2004.

  1. GrahamMG

    GrahamMG
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    Ok guys.
    Anyone care to offer the best res to feed the VSM with from a DVI HTPC? All that software scaling and image smoothing etc. is doing my poor HTPC in and I've run out of faster processors...... John? BTW VSM output is set to 1280x720 which is the native res of the DLP panel showing the picture.
     
  2. JohnMulcahy

    JohnMulcahy
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    If your graphics card will run at the native res of the disc (720x480 or 720x476) you could try that, eliminating scaling for the HTPC, but it probably will not have a lot of effect on processor load (if any). What res is the HTPC running at? Most can run 1280x720 native using Powerstrip.
     
  3. GrahamMG

    GrahamMG
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    Hi John.

    Naturally I can run the HTPC at 1280x720 without any issue but........ I have the feeling that the VSM might make a better job of motion smoothing and scaling than using half a dozen different software plugin's hence the processor load..... I can set the PC to output 720x480/576 but I've not found a way of making that automatic depending on PAL or NTSC original source material. If I set the HTPC to output 1280x720 I'm not sure what the VSM does with it..... Hence the question :rolleyes: Just searching for the ultimate image as usual....
     
  4. Bogi

    Bogi
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    Hi Graham

    Maybe a tad bit OT but have you tried a higher resolution? I've found that for fixed panel displays feeding the projector a higher res than its native resolution actually improves the pic. The down scaling feature seem to make it better in most cases.

    But then I don't have a VSM, just a plain ol' Lumagen Vision... :)
     
  5. GrahamMG

    GrahamMG
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    1:1 pixel mapping is what everyone should strive for, everything else tends to look less sharp, i.e. drive the screen digitally directly pixel for pixel. This is what scalers and decent graphics cards should be doing. I personally haven't seen a pj/plasma downscale a picture sucessfully to rival 1:1 pixel mapping and I've seen a few........ but I'm not saying it isn't possible if you would care to illuminate me....
     
  6. JohnMulcahy

    JohnMulcahy
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    If you feed the VSM 1280x720 with output res also set to 1280x720 it will not do any scaling, though you can still apply the various picture trims. Ideally you would use a player that outputs interlaced over HDMI (such as the Arcam DV79) and feed that into a processor's DVI input, you can try that with the VSM but it will use the scaler's de-interlacer rather than the SiI504.
     
  7. Bogi

    Bogi
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    Hi Graham

    In a way it depends what you're after. For a razor sharp picture that shows a Windows desktop, then yes, a 1:1 pixel is what to strive for. However, if one looks for a more "film" like experience then I've found that somehow the picture looks more pleasing when putting a higher rez into the fixed display and letting it downscale.

    But you guys play in a different league than I, so no worries.

    Cheers :)
     
  8. GrahamMG

    GrahamMG
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    Hi John.
    Yes understood, I think I'm up against the PC being de-interlaced by nature and the slightly less than perfect pans on some material is I assume almost certainly down to the de-interlacing rather than the scaling, I'll fiddle with 720x480/576p output and see what the VSM makes of it, at least I can get rid of some of the programs I've been trying to get a perfectly smooth image and give the CPU a night off.....
    What would you think might be the result if I actually sent the DLP a 1920x1080 from the VSM (assuming I can) and let the Barco downscale, I'll assume less sharp but maybe smoother pans? I think I'm at trading one for the other time..... Time to fiddle with the VSM picture trims......

    Hi Bogi.
    The PC res is what you set it to regardless of if its showing the desktop or not, a 16:9 format DVD file fills the screen at 1:1 mapping if both PC and display are the same res. It is this acuracy of picture that many wish to achieve, I can see however that winding the res up and letting the display downscale will soften the image slightly and give a more "film like" image. Of course hi-def material is downscaled on most current (mid sector) fixed panel devices (with some exceptions) and looks much better than DVD but most is at 720p and it isn't a happy accident that high end DLP's are all 1280x720..... I won't get into the 1080i is better than 720p discussion as many will say it is the same thing really but.........
    I'm just curious what others have found and settled on so I can try them out before passing judgement but at the moment I'd say that you must scale DVD material to the native res of a fixed panel (and the sweetspot of a CRT for that matter) one way or the other (pulldown/pans/jaggies all need to be tamed) and high-def 720p/1080i material is just chucked straight at the display assuming it is 1280x720 panel res. Just how our ancent NEC plasma looks so much better with high-def (into the panel res of only 848x480) 720p material is hopefully down to the HTPC as the same movie looks dire when fed from the DVD player, someone willing to give a definative answer to why a low res panel can look so much better with a signal that it can't possibly use to its best advantage....? :lease: I'll ignore cost for now.....
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Graham,

    If you are feeding analogue source to a digital device (through its analogue inputs) then what Bogi suggests can prove effective. If you are going digitally then pixel for pixel is more often the best solution. Bogi's scaler is an analogue only device.

    Gordon
     
  10. GrahamMG

    GrahamMG
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    Hi Gordon.
    Of course, I didn't realise the Lumagen to which Bogi referred was analogue only.
    I was firmly in "digital" mode.......
    Whilst I have your attention, which Lumagen's would best be suited to a HTPC in case I get really keen on making sure I test all the ways of feeding a fixed res panel.....? Money seems no object at the moment as I'm in full "I'll make this better if it kills me" mode.....
     
  11. Eric Walter

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    Hi Graham,

    This can be done. Any decent HTPC should be running the macro utility Girder, even though it's not free anymore: http://www.promixis.com/

    There is a plugin for Girder called DVDSpy, it will supply events to Girder that carry information about inserted DVDs, including if it's PAL or NTSC. A Girder macro triggered by such an event can then set a resolution, preferably through PowerStrip. The resolution to set may of course also depend on the discs aspect ratio for those not using a scaler separate from the PC. In my case, I'm running a 1440x720 resolution on my CRT at 50Hz for PAL and 47.952Hz for NTSC.

    Regards, Eric
     
  12. JohnMulcahy

    JohnMulcahy
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    Hi Graham,

    What do you not like about the pans? If there is motion judder then I guess you mean with region 1 material i.e. 3:2 pulldown. To even that out you will need to use a processor that can do sequence-locked 3:2 to 2:2 48Hz or 3:3 72Hz conversion - That doesn't make the pans smooth of course as the source is still only changing at 24fps, but the judders are then more uniform than with 3:2 which is probably preferable. Or you could watch the R2 version and have smoother pans plus higher resolution :). Can't recall whether the Lumagen firmware currently handles sequence-locked 3:2 -> 2:2/3:3 though I think it does - no doubt Gordon can oblige :)

    If the problem is combing on pans then you need better de-interlacing.

    Projector behaviour when fed resolutions greater than its native resolution rather than less is entirely down to the way the respective decimation and interpolation filtering has been implemented.

    When scaling up, the interpolation filters must by their nature roll off some response at the top end of the input signal's range, hence soften the image a little, otherwise there will be aliasing artefacts - a consequence is that the scaled up image will have slightly less HF extension than the source, though this can be partially compensated by adding HF lift (sharpness) at the expense of some ringing.

    The decimation filters must limit the input signal to the bandwidth of the panel's native resolution, but that means they will still preserve more HF extension from an HD input that you can ever get by scaling up an SD input, so (provided the panel's resolution is above 720x480 or 720x576) HD input downscaled should look better than SD upscaled.
     
  13. GrahamMG

    GrahamMG
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    Hi Eric.

    Yep I was aware of Grider and its many various ways of getting it to "almost" work ;) , trouble is it doesn't really work that well with files from the hard disk whch is where all the movies are.....Can DVDspy work with these or is it just DVD disks in the DVD-rom drive?
     
  14. GrahamMG

    GrahamMG
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    Hi John.
    Thanks for the insight, well put as usual.
    Yes the pans do suffer slightly from motion judder and yes it is NTSC original material and American sourced hi-def as well........
    I had assumed that pulldown was the issue and not at all sure how I improve this on a DVI-D PC output without going back to warming up the CPU, Imagine graphics (just down the road from me!) are talking about a PCX hardware decoder card but that is not available yet....
    Sequence locked pulldown, I assume that is in the PSM and therefore bypassed if I feed the 192 the PC output which is already de-interlaced?

    I'll have a word with Gordon......(e-mail coming mate)....


    Ref, upscale/downscale, well I can get a picture that is very very nice from DVD based material (which is upscaled) and way better than any DVD player we have around here so all that horsepower and software must be doing something right and frankly there isn't a lot in it compared to 720p material from the States (Fifth Element always used for testing!). Sharpness doesn't seem to be an issue although that is a personal preference adn there are far too many places to alter that for my liking.....

    Regarding downscaling, yep that is what I see on the plasma and as the HTPC is bypassing any processing in the display I must be on the right track.
     
  15. Eric Walter

    Eric Walter
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    Hi Graham,
    certainly true that it's hard to get complicated Girder setups to work reliably. DVDSpy will not work for files from hard disk. Might be worth a try if it works for ripped DVDs when they are mounted as an image, though I never tried that.
    Regards, Eric
     

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