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Is it possible to separate display quality from video processing quality?

Discussion in 'Plasma TVs' started by NicolasB, Aug 8, 2003.

  1. NicolasB

    NicolasB
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    It strikes me that a lot of the difference between one plasma or LCD TV and another at in-shop demonstrations is probably down to differences in the video processing circuitry. Specifically in the abilities of the screen's in-built deinterlacing and video scaling.

    However, the chances are than an external scaler/deinterlacer will do a better job, if you're prepared to spend enough money. So, this raises two questions, the second of which is probably the more important:

    1) Can one save money by buying a screen that actually doesn't have its own scaling and deinterlacing circuitry at all?

    2) Is the answer to the question "which screens have the best image quality for the best price?" going to be different if you know in advance that you're going to be using an external scaler/deinterlacer than it would be if you're depending on the screen's own capabilities?
     
  2. jmack

    jmack
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    not techie but

    the iscan ultra does a better job than the inbuilt one on my toshiba not that is does a bad picture,
    why not go for a older model like panny 4 series and get a iscan to do all the work?
     
  3. mattsimis

    mattsimis
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    And where would one find an "older model"?

    Ive havent seen any Panny4s in the past two months of web searching.



    Matt
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    1: Yes You can buy many plasma's without terminal boards. They will accept RGBHV on HD15 sockets. Saves you a few bob

    2:Yes again.

    Gordon
     
  5. trooper1212

    trooper1212
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    on a related note.

    Is the quality of the new displays too good for home sources at present?

    My plasma shows up every inconsistency and problem with any source, I can see mpeg artifacts, posterisation etc... much more clearly on the plasma than I ever could on the RP TV or LCD projector. Skin tones in particular show posterisation more readily now that the softness of the RP has been taken out.

    I love the form factor of plasma, and the quality can be outstanding, but typical sources just aren't up to the job at present.

    roll on HDTV...
     
  6. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I think much of what you are seeing may be due to your plasma's processing....I wouldn' t use plasma as a critical viewing display to work out where the artifacts are coming from.....


    Gordon
     
  7. Rob.Screene

    Rob.Screene
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    From my brief experience, I think there are two major factors here:

    a) Deinterlacing or film pulldown removal to get to progressive scan.
    b) Scaling the progressive video to the panel's native resolution.

    Using a progressive scan DVD player is probably the most cost effective way to avoid the panel having to do a), but it still needs to scale, and from an analog signal too, unless a DVI input it used.

    I would assume the de-interlacer's like the Iscan's can at the very best look as good as a reasonable progressive scan DVD. Especially as most deinterlacers use an analog component input, whereas the progressive dvd players get it straight from MPEG2.

    SDI straight in to the panel is digital but still requires deinterlacing before scaling, so a) bites us again.

    It would be interesting to hear how progressive scan via DVI in to a panel looks, both with 480p/576p (the panel scaling) and 720p/768p, etc, as the mon<mumble>itsu 880 player is reported to do.

    You'll still want an analog deinterlacer with/without scaler for any analog video sources though. Pity any SDI/PDI/DVI mods for Digital Satellite or Cable, or TIVO boxes aren't readily available yet?

    Q: Does this mean good deinterlacing/scaling and minimal solarisation is possible on any panel with the right scaler or HTPC?

    Rob.
     
  8. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Rob: Answer to your final question is no. Unless you are going in DVI then perhaps....I have to look in to it. With an analogue feed though you are still limted by the displays adc's at least.

    Also not all progressive scan DVD players take the MPEG2 data to work with. One famously fantastic DVD player takes YPrPb and digitises it immediately after the MPEG decoder. Also not all MPEG decoders themselves are of same performance.

    Gordon
     
  9. Rob.Screene

    Rob.Screene
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    Gosh, that's a nice touch, can you mention the famously fantastic model?

    cheers,
    Rob.
     
  10. Joe Fernand

    Joe Fernand
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    Hello all

    Its the one (with the plug in board) who's masters are undergoing a full scale appraisal of the Consumer AV market at present.

    Best regards

    Joe
     
  11. StooMonster

    StooMonster
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    NicolasB

    Internal vs. external scaling and deinterlacing?

    As I understand it, and from what I have tested, deinterlacing has the greater effect on PQ than scaling. RI=RO and all that.

    Therefore the first step is to improve the deinterlacing. iScan Ultra does a better job than most internal chipsets, and it's SiI504 chipset is used in some scalers too. There are other deinterlacers out there, and many solutions; but the deinterlacing chipset is what gives you biggest bang for buck.

    Replacing internal scaling with external scaling may have some incremental benefit -- i.e. a better interpolation algorithm. However, this can be off set by losing key functionality of some screen's internal scalers...

    ...which is, that as well as interpolating pixels, screens with bit depths higher than 24-bit (17.6 million colours) upscale the colour depth too (e.g. to 30-bit or 1 billion colours) when image size scaling. So, when scaling they will take DVD's 24-bit image and scale it's size up, but using more colours and shades than original image during the interpolation -- so it gives a more blended image.

    Personally I haven't seen any scalers claiming that they are more than 24-bit, so I'm assuming that none are -- but I am sure to be corrected by a more knowledgeable poster.

    Therefore, with high bit-depth screens you may be better just using a deinterlacer, or outputing your scaler/deinterlacer with no scaling, to take full advantage of the higher bit depth imaging.

    StooMonster
     
  12. NicolasB

    NicolasB
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    The fact that an external scaler/deinterlacer can produce better results than a built-in one is hardly surprising. That wasn't my question. What I'm interested in is this: if it is generally accepted that (say) Panasonic, Fujitsu and Pioneer plasma screens produce about the best picture possible, does that remain true when the screens' scalers and deinterlacers are taken out of the equation?

    Or do other (perhaps cheaper) screens suddenly draw level with the front-runners under those conditions because it was their in-built video processing that was causing the comparative lack of quality, rather than anything to do with the actual screen?
     
  13. StooMonster

    StooMonster
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    NicolasB, I did seem to have missed your point entirely. :zonked:

    Perhaps one should consider different brands that use the same glass.

    Some comparisons could include:
    50" Panasonic, Toshiba, and Fujitsu all using Panny glass;
    alternatively 50" Pioneer and Sharp using Pio glass;
    or even ALiS 42" Fujitsu, Hitachi, Phillips, and Sony using Fuji/Hitachi glass.

    In these three groups, the physical screens are the same; the electronics behind them (inputs, deinterlacer, scaler, etc.) all vary by manfacturer.

    Yes, they produce noticeably different results with same glass. Therefore I would suggest that it is their in-built video processing that causes the comparative lack of quality, rather than anything to do with the actual physical screen.

    StooMonster
     
  14. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Nicholas,

    That's what I thought you were getting at. I'm not sure though is the answer. Something that may well be shown at Event2 I suspect.........

    Gordon
     
  15. StooMonster

    StooMonster
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    Hrm... Point would be can you bypass all their internal gubbins with your lovely external scaler? Which I guess is why Key Digital PIO768P is so eagerly anticipated.

    As above, deinterlacing is almost a no-brainer; depending on screen. Scaling is a little bit more complex...

    Again, my question would be does your external scaler match the the glass of your screen -- if your screen can display, say, 1 billion colours (30-bit depth) via it's internal scaler do you want to limit it to an external scaler with 16.7 million colours (24-bit depth)?

    Unless, of course, your potential lovely new scaler has colour capability to 30-bit depth too. ;)

    StooMonster
     
  16. Gordon @ Convergent AV

    Gordon @ Convergent AV
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  17. tbrar

    tbrar
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    Stoomonster,

    Thats an interesting point. In my experience no you certainly do not, and is something worth checking for all potential scaler purchases.

    I recently had on loan an Aurora X-Tune. This is the stand alone version of thier TVP-1000 card for the Pioneer MXE. The loan was to evaluate the video processing and scaling in anticipation of the UK release of their cards for the MXE.

    I chose to send the box back quite quickly, as I was none to impressed.

    After some playing around, reading secifications, back and forth with the manufacturers it became aparent the fundimental reason for this was its Video processing (which by-passed the MXE's internal) was based upon eight bit Video Processing, 24 Bit Depth - 16.7 Million Colours. As you know the MXE's has 10 Bit Video Processing, 30 Bit Depth - though displays 576,000,000 colours.

    The result was although the deinterlacing was fair and better than the panels, the actual represntation on the panel was to me very muted in comparison to the MXE's own. There was a definate decrease in range of colour and depth and therfore to my percieved PQ.

    My current Lumagen Vision works on 10 Bit Video Processing, just in case you were wondering.


    Tony
     

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