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Upscale then down?

Discussion in 'Projectors, Screens & Video Processors' started by sekrof, Dec 18, 2004.

  1. sekrof

    sekrof
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    I've been wondering whether there is any technical/picture quality benefit in have my iScan HD+ output the highest resolution possible (that is compatible with my Panasonic Plasma), and then letting the plasma downscale the image to it's native resolution?

    i.e.

    Would:

    DVD RGB out at 720p (?) -> iScan, convert to 1125i -> RGB to Plasma, plasma downscales to 480p

    be better than:

    DVD RGB out at 720p -> iScan, convert to 480p -> RGB to Plasma, displays at 480p

    NB. I may have confused my p's & i's :clown: ... which is hopefully better than p's & q's (!) ... hopefully you understand though. Basically would the picture improve by using the build in plasma scaler to downconvert, or is it better to give it something that will display at it's native resolution. Hope someone can help.
     
  2. Joe Fernand

    Joe Fernand
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    Sekrof

    Way too many cooks in your signal path :)

    If your playing R1 and R2 Standard Definition discs its best to set your player to output 480i and 576i - that way you'll make best use of your DVDO iScanHD+.

    Very few DVD players have the ability to Output a Progressive signal in RGB format – its more likely to be YPbPr if its Analogue.

    Some DVD players will enable Digital RGB or Digital YPbPr via HDMI or DVI – though again try to avoid using any up-scaling in the DVD player and stick to 480 and 576 Interlaced (or Progressive if you must)

    Keep in mind the iScanHD+ is a Standard Definition (SD) processor if your inputting Analogue signals - if you input 720P and or 1080i RGB or YPbPr it merely acts as a switcher for those signals it cant ‘process' them.

    I have found through lots of test that the 480P Panasonic Displays do look very good if you input a 720P signal and let the Display downscale 720P to the 480 line array.

    I'd avoid outputting 1080i from your iScanHD+ - your not making use of its deinterlacer and instead relying on the Displays deinterlacer.

    I'd also suggest an ISF Calibration is well worth the money (£250) if you've gone to the expense of a decent Display and Video Processor.

    Best regards

    Joe
     
  3. sekrof

    sekrof
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    Thank you Joe.

    I think I must have been 'dreaming' about 720p output from my DVD player - it is infact only outputting interlaced on RGB (what plant was I on?!). The DVD player is a Sony DVD DVP-NS900V - 480i output ???

    Over the weekend I spent an age pondering options and playing with the HD+ - what an amazing piece of kit !!!!!! I tried outputting just about every output (format) resolution using various inputs (Component, S-Video, Composite etc) - and the best result I found was simply to avoid any reliance on the Panasonic's image processor; simply get the HD+ to output the panies native resolution/format (852x480) progressive.

    I found the HD+ supports the panies native resolution within it's list of selectable options (PLA1), but I had to play around quite a lot with the image placement adjustments to get an good fit. However, after using plenty of the HD+ test-cards, I've managed to ensure the panie doesn't 'touch' the signal it receives.

    I didn't find this, but I think I'll have to revist and try this one again. Thank you for the information Joe.

    One element I'm still confused by is the Frame Rate Conversion feature of the HD+.

    I've read the sticky posts in this forum, and that excellent article explaining progressive scan/3:2 pulldown and 2:2 pulldown, but it still doesn't help me on this one:

    I assume that most UK input devices (DVD Players etc) output at 50Hz (?), if this is true, then should I locked my framerate output on the HD+ at 75Hz or 50Hz? It would seem logical that having 3 progressive frames output for 75Hz would give a better (smoother) picture (in progressive) than 2 ??? The HD+ default is unlocked at 59.94Hz - very confusing.

    Also, the 60Hz frame rate by default is locked at 60Hz (1:1) - but surely this would mean every 10th frame will be repeated ? isn't it better to leave this unlocked at 59.94Hz ?

    Any help on this would be extremely helpful.... :lease:
     
  4. Jasonjo

    Jasonjo
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    I am not as experienced as Joe, but I have had my Iscan HD with my SD Panny PWD6 for quite a while and have played a fair bit:

    720p does seem to give the nicest overall image, not "light and day" over and above 480P, but enough to justify leaving it on this setting (I think it is now called 720p-50 to signify 50Hz). Kinda weird as you would think native would be best...just shows that you need to play and see what looks best TO YOU. Obviously at 720p the horiz res test pattern wont look correct.

    And yes, you do fart about quite a bit to get the screen to align for 1:1 mapping.

    The newer firmwares seems to default 50Hz as outputed to 60Hz in order to allow NTSC to play on PAL screens (cos DVDO are US based I guess)...I think you are probs best to output 50Hz as 50Hz to avoid judder. You can have a go with 75Hz, but from memory this is not one of the standard FR supported by the Panny, as it only likes 48, 50 & 60. You can confirm this with the judder pattern. The only slight advantage to outputting 50Hz as higher is that it seems to get rid of the slight flicker you can get with 50Hz mode on the Panny (noticeable on block areas of colour). You may also want to try 60Hz output as 48Hz as this looks pretty smooth although I tend to notice the flicker a little more, so have left it on the default of 60Hz.

    Cheers :thumbsup:

    JJ

    P.S. I did a review of the HD on here a while ago, this may be worth a look for some of my other feedback thoughts...
     
  5. sekrof

    sekrof
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    Thank you Jasonjo - I'll have a play with the 720p mode & the frequencies you mention and see what looks best to me. :)

    Do you, or anyone else, know much about the impact of the H & V settings used to align the picture (on the HD+, rather than Panny) ?

    For example, I noticed that the HD+ reports "V Total" & "H Total" as being more than the native resolution of the Panny (seems to add the V/H Porch + the V/H Shift to the V/H Size) - does this have any effect on whether or not the panny 'gets involved' in the picture processing if the effective resolution is now greater than the default native one? .. and is there any side effect on how this might upset the HD+ test-patterns ? (I still haven't managed to get the V Test Line to stop moving!) even in native. Managed the H ones though.

    Any thoughts/comments/guidence gratefully received.

    Happy Christmas!
     
  6. Jasonjo

    Jasonjo
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    Firstly, I assume we are talking analogue connections here, not DVI. I think RGBHV from the HD to the VGA input is the best way analogue wise, which is what I use. All my sources ouput interlaced and I let the HD deinterlace as it is better than most inbuilt deinterlacers ;)

    If you use the 852x480 (PLA1) format this will use 852x480 which is the native res of the SD panel...with this format you should be able to get all the test patterns 100% by using the picture horiz and vertical adjustment on the panel itself. You shouldn't need to use H and V adj on the HD itself with 852x480.

    However, if you use 720p then the test patterns will never be 100% as are sending to the screen in non native res and the screen is therefore doing some scaling to 852x480. The test patterns are designed to only "work" when the screen is doing nothing i.e. accepting a native format. The panel will then be scaling from 720 to 480, which the Panny seems to do very well in order to produce a surprising result for non native.

    The best thing I have found is to start with the test pattern that puts a single white row of pixels all the way around the edge of the screen. Adjust with the panel H and V adjustents until you have this pretty near, then try to use the horiz and vertical test patterns and change the panel H and V until they snap into focus (they will lose the blurring bands). You should be able to move either side of the correct setting and see the correct setting snap in and out of focus.

    As I said, for 852x480 you should be able to get perfect 1:1 mapping, for 720p the horizontal test pattern lines will not be uniform like 852x480 as you are sending the screen more lines than it needs and hence it is scaling to fit.

    So, I guess you have the following options:

    (a) Use default 852x480 and adjust for 1:1 mapping to get native res
    (b) Use default 720p-50 and adjust for pixel alignment and ignore the horiz and vertical test patterns as you are never going to get native res.

    I have just checked and I am currently using the default 720p-50 format (majority of my inputs are PAL). As for frame rates, I lock 50Hz to 50Hz and 60Hz to 60Hz, as with other settings I can notice judder or it introduces more flicker.

    Joe, myself and a few others seem to like (b), but if (a) looks better to you then go for it!! :)

    Let us know how you get on :thumbsup:

    Cheers

    JJ

    P.S. You may want to check out the Video processor forum over at www.avsforum.com as a chap called Dale from DVDO gave some good tips on setting up the HD.
     
  7. sekrof

    sekrof
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    Yes, all analogue.

    Exactly what I do.


    I have found that I did have to position everything as the PLA1 image was not correctly mapped. I used the HD+ to do this - but I guess it would be better to do this at the Panny end. I'll have a go.


    I tried this combination last night, and I must say it looks better than the native res - so I guess the panny is doing something right here :)


    I assume you mean alter the H/V settings on the panny, rather than HD+, I'll try this.

    I have to say (b) works very well for me - but I can't stand the 50-50 lock, I can see the flicker - probably comes from working for too many years on beautiful high hertz CRT monitors :)

    I like to leave the 50 & 60 Hz framerate unlocked - seems to make the picture quite nice on all inputs Sat & DVD (both interlaced to the HD+).

    What can I say fellahs - thank you for the help so far, the setup is looking better & better ... but I know as soon as I'm happy I'll just have to change to an entire HD system end to end (well, we can all have a dream at this time of year) :)

    Thank you once again. I'll go play more.

    :smashin:
     
  8. gizlaroc

    gizlaroc
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    What plant?? I would guess a purple skunk or silver haze?? ;)
     
  9. sekrof

    sekrof
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    Crushed rose bush! :laugh:
     
  10. Jasonjo

    Jasonjo
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    So do you output 50Hz as 50Hz and 60Hz as 60Hz, but just leave unlocked?

    TBH I didn't realise there would be a difference between locked and unlocked if the input and output were the same...

    Also, you are correct in your assumption, you should be able to just use the H and V picture settings on the panel itself when using the PLA1 and 720p-50 formats.

    JJ
     
  11. sekrof

    sekrof
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    When I set the HD+ Framerate for the 2 options, 50 & 60 Hz, I select 'unlocked' for each, and accept the default 59.94.

    From studying the article all about progressive scan http://www.avdeals.com/classroom/Proscanexplained.htm, 59.94 is the perfect number to ensure that when the conversion (3:2 pulldown) happens from interlaced to progressive, I won't see every 10th frame repeated (as you would if you selected 60Hz-60Hz).

    This may not be the perfect number for 50Hz inputs (I seem to remember the article doesn't cover 50Hz), but the effect on the picture seems ... well, nice. And it is how the HD+ is factory set (for 50Hz framerates).
     
  12. Jasonjo

    Jasonjo
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    Yeah...dont forget the default is to cover displays which cant display PAL, but not necessarily the best option for all...

    Does the 50Hz=>60Hz not introduce judder for you?

    JJ
     
  13. sekrof

    sekrof
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    If I use the Test Pattern - Judder - then yes, there is some, but strangely the picture seems better than locking at 50/60 Hz. Odd - might just be me though. :)
     

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