720p/1080i/1080p resolution

Discussion in 'Playback Devices' started by 1inxs, Nov 25, 2007.

  1. 1inxs

    1inxs Auditioning

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    I first want to say "I enjoy the HT forum". I currently use a Sanyo PVL-Z5 projector which I understand to be at 720p resolution. I am ordering a Sanyo PVL-Z2000 1080p projector. I have decided to jump into the HD world and purchased a Toshiba HD-A30 DVD (1080p) player which upconverts standard DVDs. I have two (2) questions. If the projector (or monitor) and DVD player are both capable of 1080p what is the resolution of a standard DVD when it has been upconverted ? What limits the resolution on upconverting a standard DVD?
     
  2. Stephen Orr

    Stephen Orr Screenwriter

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    Welcome to the forum, Robert. I've been here a few years and, although we never meet face to face, we all become family.

    If I understand correctly, it really depends on the player and maybe even your display. I have a Sony 46in XBR connected via HDMI to a Toshiba HD player that upconverts my SD discs to 1080i. Some look terrific, some not so much.
     
  3. Clinton McClure

    Clinton McClure Casual Enthusiast
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    Hi Robert, and welcome to the Forum. The maximum resolution of an SD-DVD is 540 lines. A standard SD-DVD player can only output 480 of those 540 lines. (Absurd, I know.) An upconverting player takes the entire 540 lines and sends them to the display working in 1080 mode, which allows the display to then display all 540 lines from the source. Some up-converting SD-DVD players need to be connected to the display via HDMI cables to be able to upconvert, while others like the Oppo can be connected using component cables.

    To answer your question, the resolution of an upconverted SD-DVD will be displayed as 1080i, although it is not a true 1080 lines of resolution. You will also need to connect your HD-A30 to your projector with an HDMI cable to upconvert.
     
  4. Sanjay Gupta

    Sanjay Gupta Supporting Actor

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    Actually it's not absurd, but rather just a limitation of the NTSC system used in the US. NTSC DVDs are limited to 480P while PAL DVDs are 540P.
     
  5. Jonathan Kaye

    Jonathan Kaye Second Unit

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    576p, to be pedantic.[​IMG]
     
  6. Sanjay Gupta

    Sanjay Gupta Supporting Actor

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    You are absolutely right, the funny thing is I knew that all along. Anyhow here I am wondering where did I came up with the '540' from and then I realized it was from the prior post. I guess the power of suggestion should not be taken lightly.
     
  7. troy evans

    troy evans Screenwriter

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    So, even if you set your player at 720p/1080i you're only getting 540 lines max regardless? If that's the case, does it matter setting the resolution above 480p? Why does the display read that 720p/1080i is being displayed when you hit the display button of the tv itself ? Just wondering.
     
  8. Sanjay Gupta

    Sanjay Gupta Supporting Actor

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    Let me try and explain. Your US NTSC DVDs output a maximum of 480p lines of resolution. An upconverting player will upscale the 480p DVD to 720p/1080i/1080p, depending on what you set in your player and ofcourse that would depend on what your diplay is capable of. You have to keep in mind that this upconverted signal will only be output via the HDMI output. In other words the regular 480p DVDs will be upscaled upto 1080p but it is still a pseudo resolution and not as good as an original 720p/1080i/1080p picture from an HD disc. Is this pseudo upscaled signal better than the original 480p? For well mastered DVDs the answer is yes, but for DVDs that are poor quality to begin with, you can expect an even worse picture.

    PS: There are some older DVD players, which do not conform to the DVD standards and thus will output an upscaled DVD signal via the component outputs also.
     
  9. troy evans

    troy evans Screenwriter

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    Thank You Sanjay. Now, when I watch my dvds and I get a poor picture in the 720p/1080i settings will the picture for those poorer sd dvds look better at the 480i/480p settings? Is upconverting actually causing more degradation of the signal in this case?
     
  10. Clinton McClure

    Clinton McClure Casual Enthusiast
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    Oops! I didn't realize NTSC DVDs were limited to 480p, I thought only the NTSC players were. My bad. [​IMG]
     
  11. Sanjay Gupta

    Sanjay Gupta Supporting Actor

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    Yes, in most cases of poorly mastered DVDs, upscaling will only multiply the problems.
     
  12. AmusingistheDawn

    AmusingistheDawn Stunt Coordinator

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    How can you make it so the avr doesn't automatically upscale the image then? I'm having similar issues.
     
  13. Nathan Eddy

    Nathan Eddy Second Unit

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    I've never owned an upscaling DVD player--I jumped straight to BD player. However, don't modern TVs upscale already? (My Pany TH-50PX80U, for instance.) I mean, when I'm watching a DVD on my HDTV via my DVD player, isn't the picture being presenting in the native resolution of the TV? How could it not? A 1080 (or 768 in my case) TV shows *everything* in it's native resolution. And I don't see any "missing" lines on my screen (no black lines in the picture, at least). So doesn't this mean that a DVD is being upconverted to the native resolution of the TV screen?

    I guess I'm confused what the difference is between up-conversion and simply presenting a DVD on an HDTV without up-conversion. Is the image smaller without up-scaling (due to fewer lines presented)? If it's not--if it's the same size--then it seems like there has to be some up-scaling going on, even without an up-scaling DVD player.
     
  14. Joseph DeMartino

    Joseph DeMartino Lead Actor

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    Nathan, you're basically correct. All HDTVs and projectors that user a fixed-pixel array (which basically means everything other than CRT-based systems and a few old plasma TVs) are inherently progressive and incapable of displaying anything other than their own native resolution. Given a standard def signal they will de-interlace it and scale it to that resolution (720p, 768p or 1080p.) Given a 720p signal a 720p set just displays it. Same with 1080p to 1080p. Given a 1080i signal a 1080p set just de-interlaces it, with no other processing needed. A 768p LCD panel is going to re-scale anything anyway, so it makes as much sense to have the DVD player send a 480i or 480p signal to it.

    Now, it can be the case that the de-interlacer and/or the scaler in a DVD player can be better than the one in the TV - or vice versa. It all comes down to the combination of player and TV you're dealing with. So it isn't like there's no point to an upconverting player. (And if you have a CRT-based RP HDTV or projector - which were a lot more common a few years ago - you'd find one quite useful.)

    I have a 56" JVC H-DILA RPTV (true 720p) and a Sony upconverting DVD player. After playing around with various settings on both and doing a/b comparisons, I simply can't tell the difference between the player upconverting the discs and the TV doing the job. YMMV.

    Regards,

    Joe
     
  15. Stephen Tu

    Stephen Tu Screenwriter

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    A lot of half-true, somewhat garbled info in this old resurrected thread ... I'll try to correct to the best of my knowledge:

    Standard NTSC DVD has pictures made up of 720(w)x480(h) pixel frames. To be absolutely accurate, the frames are split up into fields, since old CRT sets were interlaced and display half the frame each pass, alternately drawing the odd lines & even lines. And actually there are 525 total lines, not 480, 480 is the actual picture data, the rest are the "vertical blanking interval" and not visible (also contains stuff like closed caption info). But 480 is what we care about so we say DVD is 480i. The stuff Clinton said above about "480 of 540 lines" is nonsense. 540 lines of res is a theoretical limit based on older standards of measuring resolution based on how many vertical lines could be drawn in a circle inscribed in a 4:3 set, and is basically 0.75 * the 720 figure above, has nothing to do with the 480 along the other dimension or the figures for PAL.

    A progressive scan DVD will reconstruct these 720x480 frames which correspond to individual film frames. And usually repeat them in a 3:2 pattern to correct for the difference between film which is 24 frames/sec and TVs which normally expect 60 frames/sec, with the exception of some of the newest TVs which will also accept 1080p at 24 frames/sec.

    OK, now you have a 720x480 picture, but a newer tech LCD/plasma/DLP etc. TV that has 1920x1080 (or 1366x768, or 1280x720, or whatever) pixels to fill. Since pretty much everyone wants their screen filled up, you have to scale aka upconvert aka upscale at some point. No matter what equipment you have, something is going to have to scale up. You can upconvert at the DVD player itself, if your DVD player has that feature; you can upconvert at the AV receiver, if the receiver has that feature; and if neither of those two do it, the TV will do it. On a fixed pixel set, you cannot avoid upconversion! If you turn off the feature on your DVD, all that means is your TV does it instead. Upconversion can only be avoided on older CRT based sets with a native 480p scan rate.

    And if the TV has a native resolution that doesn't match the output of the DVD/receiver, it will scale a 2nd time to get to that native res. E.g. 1080p upconverting DVD -> 768p plasma, the plasma will end up downscaling from 1920x1080 to 1366x768. Multiple scaling operations generally aren't desirable, so in this type of situation often better result would be obtained by just using 480p out from the DVD and letting the plasma scale 480p->768p.

    Now no matter what your resolution is fundamentally limited by the original 720x480 on the disc. You can't create detail out of thin air. To get more detail you need Blu-ray. What you are looking for in upscaling is mainly to get the picture to fill your screen without creating visible artifacts, and without softening the picture too much to avoid those artifacts. Different equipment use different chips with subtly better/worse algorithms at doing this. So if you have multiple equipment that can upscale, you can experiment to see which does it best by disabling/enabling the feature on each & seeing the results. And if your TV has good enough scalar, really you don't need upconversion feature in DVD or receiver at all.

    The differences between scalars is not huge, IMO most people with smallish
     
  16. Nathan Eddy

    Nathan Eddy Second Unit

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    Stephen, thanks a lot. Fantastic information, there.


    Okay, so do I have to change the resolution my BD player is outputting each time I switch between watching a DVD or a BD, to get the best picture? You said I don't want multiple scaling going on (TV + player). So to my 768p TV, I should output 480p for DVDs and 720p for BDs? That seems like a pain to change the settings each time. My player (Sony 550) does have an auto setting for resolution. I suppose that's what it is for? Does it sense my TV resolution send the correct one depending on the resolution of the source?
     
  17. Stephen Tu

    Stephen Tu Screenwriter

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    You don't have to; the differences are rather small & it's not unlikely you won't be able to tell. Also you should try both 1080i (1080p if your set supports it) & 720p options for BD to see which you prefer if you can notice any difference.

    Auto setting for resolution just picks the highest res your TV's HDMI input supports. If you want auto-fallback to 480p for DVD, you could use component instead of HDMI.

    Just experiment, really I think most people won't readily notice a difference between the various reasonable combinations of settings/connections for regular DVD, especially on regular program material rather than test pattern torture tests.
     

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