Please Explain 'Black Level' Enhancement

Discussion in 'Playback Devices' started by James Edward, Jan 19, 2004.

  1. James Edward

    James Edward Supporting Actor

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    My new Mits DD8040 has a 'black level' on/off toggle in the mode menu. My set (Tosh57HX81) easily looks better with the control set to off. Blacks are deeper, colors appear more saturated, and the picture looks almost 3-D.

    What exactly is this control doing? My old Toshiba SD-5700 did not have this control, but was able to display the THX backdrop in the Optimizer menu. The new player does not.

    Thanks for any replies...

    BTW, the picture improvement was well worth the expense($188).
     
  2. Lewis Besze

    Lewis Besze Producer

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    The Black level is devided to 100 IRE's.The US NTSC consider totally black at 7.5 IRE,however the Japanese system starts from 0 Ire, which here in the US we refer to it as "blacker then black".Sygnificance of this comes at when you calibrate your TV. If you use 0 Ire as starting point[or enhanced black level]on your DVD player and proceed with a calibration,other sources like regular broadcast TV or cable might look too bright in comparison since it uses a different scale to begin with. So in a nutshell turn it off[EBL]if you use your monitor for other sources as well and your calibration will look good for both once it's done.
     
  3. Don_Berg

    Don_Berg Supporting Actor

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    Yes it selects between black at 0IRE or 7.5IRE. For component video output 0IRE is considered the proper standard and looks best to me. For composite/s-video interlaced output 7.5IRE is normally used.
     
  4. Lewis Besze

    Lewis Besze Producer

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    The difference will manifest itself on the TV's black level controll only,it won't provide any better picture after calibration is done properly.However if you preffer to use it by all means, do it.
     
  5. Don_Berg

    Don_Berg Supporting Actor

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    Not true, I find only with 0IRE can I get the picture setup just right. With 7.5IRE setting, I can't get it looking the same by adjusting the TV's controls to try to match it.
     
  6. Lewis Besze

    Lewis Besze Producer

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    Then maybe your display doesn't track black levels accuratelly.As you pointed out the difference is the 7.5 IRE,I see no difference in theory to switch that on the DVD player or adjust it on the TV.If you see a difference then one of the equipments is "faulty".It also depends what test disc you use. VE uses the 0 IRE,Avia uses the 7.5 IRE setting.
     
  7. ChrisWiggles

    ChrisWiggles Producer

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    This is not the case. Test discs can't control IRE at all, all they can control is the video contained on them, which is not locked into IRE values, which is solely an analog voltage issue.
     
  8. James W. Johnson

    James W. Johnson Screenwriter

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    Agreed, the Mits 8040 looks great with the Black Level off howver it has ONE MAJOR BUG ...you have to reset the black level every time you use the player.

    If you dont mind then the 8040 is about as good a 480P picture that can be had from a progessive player.
     
  9. Lewis Besze

    Lewis Besze Producer

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    I didn't say it controls it, I said test patterns are created as such.VE was designed to accomodate[test] players that can pass "blacker then black".
     
  10. ChrisWiggles

    ChrisWiggles Producer

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    Your statement is based on a misconception of what is referred to when we're talking about blacker than black with regards to DVD and digital video. It is unrelated to whether or not NTSC setup is present (which determines whether black is output at 0, or 7.5 IRE).

    Either disc will work just fine whether a player is set to 0, or 7.5 IRE. Blacker than black is *not* black "below 7.5 IRE" per se. Using a 7.5IRE setting will not "lose" information between 0 and 7.5 as is often (and incorrectly) assumed on the forums.

    When discussing BTB in digital video, we are discussing black that is below reference black *digitally.* Video is encoded in steps from 1-254, with reference black at digital 16, and white at digital 235. Values above, and below these points are headroom and footroom (for a few reasons preserving these values are important, unfortunately too many product engineers don't take heed or understand this), that we can refer to as blacker than black, and whiter than white information.

    All this information is purely digital, and is totally unrelated to IRE, which is a representation of the voltage of an ANALOG video signal. IRE *only* enters the picture when the digital video is translated into an analog output from your player.

    American NTSC uses a setup pedestal, which assumes that black will be output at 53.57mV, or 7.5IRE. Black (digital 16) will be output in these situations at this voltage, and blacker than black data (
     
  11. Don Keener

    Don Keener Auditioning

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    Chris,

    Agree... I did some experimenting with my Denon 3910 and its 0/7.5 adjustment and its DVI normal/enhanced setting. I found that in all combinations except IRE 0 and DVI enhanced that pluge was properly passed without black 'crush'. That suggests/confirms that the NTSC DVD MPEG stream and decoder maps reference black to d16 (if it didnt, you would never see the BTB pluge pattern). The function of IRE 0/7.5 seems to be to inject (additional?) 'setup' probably at the MPEG decoder level. The DVI normal/enhanced determines how the YCC is mapped into RGB... RGB can map d16 to d16 (normal) or d0 (enhanced).

    What I stuggle with is why I would ever change the IRE 0/7.5 from 0? d16 should map to IRE 7.5 on the component outputs (?). Is there other format DVD's that set black at d0 and need the insertion of pedistal at the MPEG decoder?

    I have IRE set to 0 and DVI set to normal and all looks great and passes pluge just fine. What I cannot confirm is that black is being output over the DVI at d16 but analysis makes me think that it is. Opinions welcome.

    One question on pedistal... does it only apply to 'Y' or chroma too? Seems like should just be Y.
     
  12. ChrisWiggles

    ChrisWiggles Producer

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    If there are any DVDs that are so far off as to use digital 1 as black, that would be hopefully caught before they were manufactured, because that's a serious mastering error. 0 is not usable for image data AFAIK.

    Are you using a digital or analog connection method? IRE setup change should affect the digital output.

    There may be some other option that affects a digital output, perhaps switching between studio RGB, and expanding to PC RGB, which is undesireable if you can avoid it.

    Your qustion is fairly confusing to me, so perhaps you should read through this:

    http://www.hometheaterforum.com/htfo...light=Avia+Pro
     
  13. Don Keener

    Don Keener Auditioning

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    Thanks Chris,

    Awesome pointer.. Good read.

    I am currently using DVI and have also played with component with the Denon.

    I was struggling as to why I would ever want to set my player to anything other than IRE 0 black level (thus why the setting existed) and the thread you pointed to seemed to clarify that with a component or digital connection you DONT want anything other than 0 unless the monitor has calibration range difficulty. Additionally, that the 7.5 IRE setup is really targeted for composite or S outputs and NOT component or digital. I think that point is really being missed by many (me included till now) as not too many folks that are in the forums are using composite or S.

    My question about d0 black on DVD was trying to rationalize why such a 'black level' ire setting existed. Given what the thread taught.. its pretty clear that the reason has nothing to do with d0 black media but with composite or S connections.

    The second adjustment the 3910 has is as you said... mapping to either Studio RGB or PC RGB. Denon calls them 'normal' and 'enhanced' respectively. I have mine set to normal (reference black at d16).

    Now here is a question.... If the player was connected via composite or S, was set at the the IRE 0 setting, and playing DVE outputting pluge, would the BTB bar be visable? My bet is NO. If the same situation were component connected, then the answer would be yes. (assumes that display brightness is high enough to make it visable if it was there)
     
  14. Lewis Besze

    Lewis Besze Producer

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    I got my information from those discs mentioned above,and it seems that you simply go beyond the laymen terms described in those discs.I have a feeling that the producers wanted to avoid the "technobable" you used here,so if you think that should be icluded please feel free to direct your rant to them next time!
     
  15. Steve_L_B

    Steve_L_B Stunt Coordinator

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    I don't think that Chris's "technobabble" is ranting. He is trying to clarify a common misconception and misunderstanding of black level set-up. This is an HT enthusiast forum, and it is the responsibility of all forum members to try educate and correct misinformation. Correctly setting black level is fundamental to good PQ, and I think he is trying to make sure you really understand the differences between the two standard reference levels.

    -Steve
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    Lewis, I don't hold anything against the particular producers, I do know that the makers of Avia did indeed want to include test material that contained BTB/WTW data, however, because of limitations during i believe the mastering stages, Avia was limited to 16-235 in digital data.

    Furthermore, at the time of production, these discs did assume a 7.5IRE NTSC setup, so their labels in IRE are correct for these situations. I do hold some reservations that the patterns are labeled in IRE, because the absolute IRE is not controlled by the disc. In a different playback environment, such as in a 0IRE black output one, those labels are no longer correct, and would need to be recalculated. Unfortunately, this rather "technobabble" idea of what IRE really is got lost on the forums, and mashed in with BTB, which isn't that related.

    The explanations on the discs are very stripped down for reasons to limit confusion. I haven't listened to the explanations on Avia for quite some time, but it does mention that the test patterns for black/white level do not contain blacker than black material, and instruct the user to use the patterns to correctly set black level.

    I don't own VE, and I never bothered with the explanation on DVE, but I can understand users being confused with instructions to utilize the BTB bars in the pluge patterns in setting black level, when many players don't preserve this data. The explanation on Avia gets at this point, in that use of the pattern should be used the same regardless of whether the playback chain preserves BTB data, since no BTB data is on the disc.

    I attempted to elaborate on your statements lewis, as they were wrong in the basic way of associating the presence of IRE setup with the preservation of BTB digital data.

    As explained, the clipping of BTB data can occur at a 0IRE output setting, 7.5IRE output setting, neither, or both, depending on the design. Keep in mind that negative IRE (negative voltages) are legitimate to preserve BTB in a 0IRE setting, and that BTB *can* be maintained in a setting with a 7.5IRE setup.

    Statements that one setting defacto is superior is not the case. The end goal is the same: to make Black which is encoded on the disc, appear black on your display, which is a function of your entire playback chain.

    Don: read through the whole thread again, paying closer attention to Guy's explanation, rather than Jim's, which are a little bit out of context.

    There isn't a big reason why 7.5 should be used with composite/s-video, except that inputs of these types will likely be expecting blacks at this IRE. The end result, wich proper adjustment range should be the same in any combination.

    If you have a number of inputs, it makes sense to have them all at the same output level, so you needn't readjust your display's black level with changes in source. However, many times the outputs are not exact anyway, so just because say, an HDTV receiver and a DVD player are set to output black at 0IRE doesn't particularly mean one or both might be a little off and need slight adjustment. This is why individual calibrations for inputs can come in handy, and why you should hopefully calibrate your entire video chain, not just parts of it, to display things correctly.
     

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