Difference in PQ between component and dvi?

Discussion in 'Displays' started by Bart_R, Jan 12, 2006.

  1. Bart_R

    Bart_R Stunt Coordinator

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    Hi everyone: quick question:

    In what areas (and how substantially) does the picture quality improve when you go from a component connection (and progressive scan dvd-player) to a dvi-connection?

    Will there be less pixellation, more sharpness, a more stable picture? What exactly? For example, I now notice that the mid-plane area is not as much in focus as the background or the foreground. It's only when people get into (medium) close up range that they will get really sharp. Will there be any improvement in this area, perhaps?

    Thanks beforehand...

    [​IMG]
     
  2. John S

    John S Producer

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    Assuming both conections are solid. It should help like solid backgrounds like sky, or maybe foggy scenes. This is where analog to digital conversion and scaling artifacts can usually be seen if you look for them.


    But, I digress. In reality, both connections should be tried, because often for hooking up and two given devices Component will be better. Digital video connections are still pretty new, oddities can arise in color translation and image positioning on the screen with DVI and HDMI. Sometimes a device (DVD Players) will have known issues with it's digital output, but have glowing praise for it's component output and visa versa as well.


    Cleare as mud right???? [​IMG]
     
  3. Mort Corey

    Mort Corey Supporting Actor

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    Can't comment on DVD as a source as i don't have a player with a digital output. With my HD cable box I did see a slight improvement using the DVI connection to my PDP vs a component connection. Not a great deal of difference, but enough to choose one over the other.

    Mort
     
  4. John S

    John S Producer

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    On that note, I am getting ready to order the digital video cables to hook up my dish box. Runnign on component now.


    This silly M1 connector input for my HDCP DVI has delayed this change for me some.
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    Guys!

    Both methods are fully suffiecent for transmitting the full signal without problems. Analog component video is YPbPr, DVI is digital RGB. HDMI also adds digital component video capability in the form of YCbCr, and increased bit-depth capabilities which may be useful in certain situations where that can be taken advantage of.

    Really, if perfectly implemented, there should be NO difference between the two, but as is often the case implementation is not perfect. There are many examples where one is visibly better than the other for this reason, but not for any inherent capability differences when talking about component video sources.
     
  6. Bart_R

    Bart_R Stunt Coordinator

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    Thanks everyone, for the quick replies. It's interesting that the two connection methods do not inherently differ in quality. I readily assumed DVI is better. Still, while I can understand dvd's performing equally, shouldn't HD sources be better of with DVI?

    Also, what of VB? I got a hint of that on my PJ (Panny 900) (That is, I think that's what I'm seeing), and I was wondering if it would lessen or disappear with a DVI instead of a component feed...

    So Mort, could you describe where the difference lies for you between the two connection types?

    Btw, I've ordered a second Panny 900 just to see if the VB is less present on that unit. I'm then allowed to send the worse one back to the (internet) store.

    Cheers...
     
  7. ChrisWiggles

    ChrisWiggles Producer

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    No, because Vertical Banding is inherent to the display. No change in input method or quality will affect this.

    I hope you can resolve your VB issues on the 900, they can vary unit to unit, hopefully you can get one that has very minimally visible VB. It's a very nice projector, especially at that price, enjoy!
     
  8. Bart_R

    Bart_R Stunt Coordinator

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    Re: Chris



    Yeah, I like the Panny quite a bit (btw, is "very minimally visible VB" as good as it gets? What I mean is, is there always VB present on this PJ, or can it be completely absent as well?). Especially the first few days I was very overwhelmed. I projected it on the wall and it looked very nice. Then I hung my frame on the wall with the bo cloth loosely attached to, or rather folded over, it. Even nicer! I watched a few movies on it ('The Perfect Storm' and 'War of the Worlds'): no problem. Then, after almost a week I began noticing small lines or rather, a sort of vertical grid that appears (is visible) in light blue or light green solid color patterns (I think I first saw it in 'Finding Nemo'). And then of course I kept on seeing it; even in less solid color patterns. I tried to counter it by messing with the flicker adjustment menu, but this confused me. I got some level numbers off of a review site (whereby the VB was supposed to diminish), but those levels made the individual colors (R,G,B) even more flickerish than they were, which I don't think is the objective.

    Being as my 7-day return period had just expired when I noticed the problem, I called the site if they would want to send me another model, after which I could return one of them. After some objections (and tips like: "you should go to Panasonic") the manager there apparently agreed with my proposal. So the new one will arrive this tuesday.

    I'm somewhat weary of what will happen. If the new oe turns out to be even worse (or similar) I don't have much leeway anymore. Maybe, just maybe they would allow for me to order the Z4, but I doubt it. (and of course, I haven't even seen the Z4 in action yet, so it'd be quite a gamble on its own. But it does have less VB-problems, or so I heard...).

    Alright, I'll end it right here, since I'm getting way off-topic here.

    Thanks again for your comments...
     
  9. ChrisWiggles

    ChrisWiggles Producer

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    Well, it doesn't hinge exactly on the output as much. If you're looking at upscaling players, it will be over DVI/HDMI pretty much exclusively anyway. Some displays can handle and take advantage of 10 or 12-bit component from HDMI, so a player that can process and output at that bit-depth can help, but that's not too common. Most displays won't be able to take advantage of this, either they won't accept that input, or even if they do they may have a bottleneck where the display itself goes to 8-bit or comparable to 8-bit and it sort of defeats the benefits of the higher-bitdepth feed.

    As for the AE900, I don't know how bad your unit is, obviously it's imossible to know based on description, but I think most people don't notice VB too much, and the 900 can get it down to where it's pretty minimal and only rarely visible to picky eyes.
     
  10. Bob McElfresh

    Bob McElfresh Producer

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    I heard a PodCast with Joe Kane (author of Digital Video Essentials) and one of the commentators asked Joe about current problems in HDTV. His answer was "the connection".

    He uses video analysis equipment and has discovered problems feeding a HDTV with an analog source. These problems are related to the digital->analog conversion in the source box, and the analog->digital conversion in the television. These 2-generations of conversion are not usually visible - but he has seen it while working with his test-patterns and doing work on next-gen televisions.

    I have not heard of many people here who could see any differnce doing a A/B comparison between component and DVI/HDMI (at least with a DVD player as the source). But when someone like Joe Kane talks about it - I'm tempted to upgrade to a DVI input from my HDTV cable box.

    (I'm less worried about 480 sources than I am about the 720).

    HDTV Guys
     
  11. ChrisWiggles

    ChrisWiggles Producer

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    Say Bob:

    I think I listened to that one, and frankly I found his comments there somewhat strange/surprising. I think everyone is going to be using digital connections eventually, but I still think it's implementation issues that will cause there to be differences. There is more room for degradation in analog domains than there is with digital signals which more or less work, or not work. I've definitely seen digital connections be visibly worse compared to analog, I've also seen adjustments and outputs for digital signals be clipped and implemented in strange ways. So in an ideal situation, yes I would go digital all the way, but in ideal situations also, analog should be sufficient to transmit the signal without degradations as well. So in terms of "weaknessses" I would disagree with Joe on that one, I don't think that digital connections themselves have inherent capability advantages. Nor would I characterize that as the main weakness.

    I should note that I do use a CRT FP display, but my opinion is also informed by seeing a lot of digital displays too, including some like the Sharp 11k/12k that look better with analog, and many digital sources that do bizarre things with the digital outputs. If you look at close comparisons, there's also issues of the signal capabilities, and things like RGB are better than component, so how do you easily compare digital component video via HDMI to analog RGB?
     
  12. Bart_R

    Bart_R Stunt Coordinator

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    Ok, some of the talk is going quite over my head here, but it's nevertheless fascinating. Perhaps I'll get there with you, when I'm more into it.

    But anyway...


    I suppose that is as good as it gets then. That's kind of a shame, since I was under the impression that VB isn't a necessary by-product of LCD projectors, but that it sometimes happens. Even if this sometimes is actually quite often, according to Projector Central, it nevertheless points to a defect, or error/inaccuracy in the production process of the panels.

    One final question then (for now). While watching movies on my PJ, I've noticed horizontal bands going through the subtitles at times, and I've seen the same phenomenon (at least, I think it falls under the same "problem") in sudden movements, usually with red(ish) color patterns. (e.g. nemo/marlin quickly turns around and his fins get a little "stripey". The same goes for Bruce Willis doing a double take when he watches (while turning twice) Vincent Vega hug Marcellus Wallace in the (redly lit) bar). I thought that maybe it had something to do with the quality of the player and/or its handling of the progressive scan signal/connection. Some terms came up while googling. I think what I'm looking at here is something called "combing" artefacts, which can (also) happen on/with progressive displays or connections.

    So, my questions are as follows:

    Does the "problem" I'm describing sound familiar in anyway? If yes, what is it? Is it indeed something called "combing"? And, most importantly, am I looking at a defect of my PJ or a dvd-player that isn't really up to scratch when it comes to outputting this signal via progressive scan? (which isn't unlikely, since the player was quite cheap and has poorer PQ when compared to my other, more expensive player, without progressive scan output). Since I'm in the process of evaluating my (newly bought) PJ, this last question is quite vital. Not that it's a huge problem, but still (when added to the equation it might even make me turn to a wholly different brand alltogether, God forbid...).

    Cheers,
    Bart.
     
  13. ChrisWiggles

    ChrisWiggles Producer

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    Sounds like the chroma bug.
     
  14. Bart_R

    Bart_R Stunt Coordinator

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    Chroma bug? That doesn't sound too good. So it is actually a problem with the projector then?

    EDIT: Looks like I jumped the gun a bit. I did a quick google and it turns out (or very much looks like) it's a dvd problem [http://www.hometheaterhifi.com/volum...ug-4-2001.html]). I quickly browsed the article (I'm at work right now), but even though the subtitle lines don't appear to be discussed, I'll assume it's a result of the same bug...). Anyway, that's good news, in a way (I mean, already knew the dvd player wasn't the top of the line, plus it's far less expensive (to replace/repair) than the Panny 900 PJ). [​IMG]

    Thanks for the quick reply...
     
  15. Randall Wetmore

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    In my experience, DVI is better than component. With DVI, I found the brighter areas of the picture to be less harsh and easier on the eyes; in fact, the whole luminence part of the signal was much more natural. I also found that DVI has a little better clarity than component. I made my comparision with top of the line Blue Jeans component cables running from my HD cable box. I have the Sony KD-30XS955.
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    DVI transmits RGB, there is no luma signal.
     
  17. Randall Wetmore

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    ??? What transports the luminence information then?
     
  18. ChrisWiggles

    ChrisWiggles Producer

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    The RGB signals transmit all the image information, which of course involves luminance. But there is no luma signal in an RGB format of course. There is a difference between luma and luminance. Color difference formats use a Luma signal (not luminance), which is the Y signal, in the case of component it's the Y of YCbCr/YPbPr. RGB are individual, full bandwidth, equally sampled Red, Green, and Blue signals. Component is a luma signal (Y) with two color difference components(chroma).

    I ommitted prime notation here, but it's all nonlinear here of course.
     
  19. LanceJ

    LanceJ Producer

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    Since HDMI and DVI are encrypted connections (I guess because of paranoid Hollywood movie execs [​IMG] ), could the encryption/decryption process be degrading the digital signal in some way? I would think such a process would be strictly math-related so it shouldn't do anything like that, but you never know.
     

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