0 vs. 7.5 IRE sources on DVDO processors - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 10-08-2009, 10:07 AM - Thread Starter
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And I thought with the move to Blu-Ray this annoying piece of video history was finally gone - but, man, was I wrong. A bunch of recent japanese Blu-Rays are still mastered with a higher IRE level than the usual American or European movie discs.

Parts of the hardware I use either correct the 7.5 IRE offset automatically (Blackmagic) or allow to set the IRE level manually (Optoma videoprocessor or Pioneer DVD Player), unfortunately others don't (PS3 for Blu-Ray, Sony DVD Player for DVD and my DVDO 50pro processor).

At least once per week I run into a DVD or Blu-Ray which looks completely washed out on my (half-way) calibrated setup due to those IRE offset differences.

I'm wondering if anyone with a 50pro in use can comment on his take on the problem ? How can I calibrate a setup for "japanese mastered" discs when I don't have a testpattern for those IRE levels ? Eyeballing the brightness down and the contrast a bit up is an option, but obviously not the perfect one...
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post #2 of 9 Old 10-13-2009, 07:38 PM
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Assuming digital is used (DVI or HDMI) there is no IRE level. The differences you are seeing are more likely PC vs. Video level. Many displays/sources unfortunately treat RGB incorrectly as PC. YCbCr should always be treated correctly, however. If your display accepts YCbCr (and you can use it source-to-display) it should correct the problem.
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post #3 of 9 Old 10-14-2009, 05:07 AM - Thread Starter
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Thanks for the reply! But no, it's DEFINITELY not a PC vs. Video level problem. It's the fact that japanese DVDs are simply still often mastered with the wrong offset (not Hollywood movies, but japanese movies).
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post #4 of 9 Old 10-14-2009, 06:43 AM
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Quote:
Originally Posted by Fudoh View Post

Thanks for the reply! But no, it's DEFINITELY not a PC vs. Video level problem. It's the fact that japanese DVDs are simply still often mastered with the wrong offset (not Hollywood movies, but japanese movies).

Japan decided to use 0 IRE for black (NTSC-J) while North America chose 7.5 IRE (NTSC-U). Is this what you're referring to? They were "supposed" to move to 16 in the digital realm, but I'm guessing that didn't always happen.

Perhaps there's a Japanese laserdisc with test patterns on it similar to Video Essentials? A Japanese Criterion disc? Would that help?
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post #5 of 9 Old 10-14-2009, 07:39 AM - Thread Starter
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Is this what you're referring to?

probably. Of course my whole setup is calibrated to American/European standards, but I guess some japanese mastering setups are still using the old NTSC IRE offset...

Test Pattern - - none that I can think of. I though maybe a 50pro user could help me out with a "number" (brightness offset) on his setup. Other VPs have a IRE offset setting, but DVDO is unfortunately lacking this option.

I find it highly surprising that not a single 50pro user besides me has ever run into this problem ? No japanese movie admirers here ?
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post #6 of 9 Old 10-14-2009, 02:30 PM
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If a DVD or BD player has an "IRE 0/7.5" setting switch that is implemented when digital video is being used I'd be extremely surprised if it didn't switch between PC and Studio video levels. "Real" IRE 0 vs 7.5 only applies to analog video. Regardless of NTSC Japan and US IRE standards for analog video, Studio level for "black" is 16. If the discs are not PC levels and "black" is not 16, no VP is going to be able to automatically compensate correctly or have an option to "fix it".

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post #7 of 9 Old 10-14-2009, 04:11 PM - Thread Starter
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Sounds reasonably. Next time I run into a "washed out" Japan disc I'll turn the processor to full range RGB while leaving the display set to limited range and see if it's spot on
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post #8 of 9 Old 10-21-2009, 07:26 AM
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I suggest eyeballing the levels and writing down the settings when you get it the way you want. Part of the confusion can also result from some disks with blacker than black content and others without. It is your choice whether to adjust things with the seeing of blacker than black content in mind.

In digital video, black can be mastered as 1 or as 16 on a scale of 0 to 255. (Maybe some non-standard values too.)

In analog video, black can be mastered as 0 or as 7.5 on a scale (IRE values) of 0 to 100. (Maybe some non-standard values too.)

Are you saying that these DVD's were made from analog masters where IRE 7.5 was matched to digital 16? If so then blacker than black (IRE 0 to 7.5) can fall between digital 1 and 15. If you adjusted digital 16 to be display black (using the TV menu), then you will of course bury any blacker than black content.

Or are you saying that IRE 0 was matched to digital 16 but black in the source was IRE 7.5 which would then translate to digital 32 or so? Here source black would appear as dark gray but then blacker than black would be in the 16 to 32 region and should be readily reproducible.

Within the range limits, the brightness and contrast controls let you spread the source black to white range over the display black to white range, for example if incoming black happened to be digital 32, then you can put display black up at 32 if you wished to. (You would do this visually since the numbers 7.5, 32, etc. are probably not shown on the screen or in the menus.) I would not be surprised if there are some non-standard masterings resulting in several different settings to write down and use for different disks.

Remember when lines and logos burned the TV screen? I was at a concert where a musical selection made extremely heavy use of about four of the keys of the piano.
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post #9 of 9 Old 10-21-2009, 07:52 AM - Thread Starter
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Quote:


Or are you saying that IRE 0 was matched to digital 16 but black in the source was IRE 7.5 which would then translate to digital 32 or so? Here source black would appear as dark gray but then blacker than black would be in the 16 to 32 region and should be readily reproducible.

this constellation seems likely. I don't know why, but it is obvious on quite a lot japanese movie DVDs and I've seen it not only on older analogue transfers (where I get it at least), but also on recent digitally mastered movies. Japanese tend to put underscan borders on their discs and the funny thing is that the black of the border is properly set to digital 16 whereas the black in the actual movie is significantly higher. I can't really explain why this is happening over and over again, but I would imagine some analogue preview monitors to be set at IRE 7.5 and nobody ever cared to re-calibrate them for digital DVD mastering.
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