HDMI doesn't pass blacker than black? - AVS Forum
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post #1 of 206 Old 03-30-2004, 10:34 AM - Thread Starter
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Gary Merson recently stated in his Perfect Vision review of the Pioneer PRO-1110HD 50" Plasma TV that while using its HDMI input "...the Pioneer would not display test signals from a DVD below 7 IRE, commonly known as “blacker than black.†A Pioneer spokesman said this was part of the HDMI standard."

Anyone know anything more about this?
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post #2 of 206 Old 03-30-2004, 11:12 AM
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I think this "blacker than black" thing is meant for calibrating analog TVs. Digital TVs with DVI or HDMI inputs have to following Video spec that specifies 16 as black and 235 as white. Anything out that range will be clipped. If your digital TV can display blacker-than-black, the normal black will be light gray.
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post #3 of 206 Old 03-30-2004, 11:20 AM
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1. The guy from Pioneer is wrong.
2. This is a bug in the current generation HDMI transimtter and you will only encounter when you feed HDMI to DVI. If you feed HDMI to HDMI then you are OK. The problem is the color space converter in the HDMI transmitter is clipping head and toe room. It does have two modes, expanded and normal and even in normal, it clips. Silicon Image is aware of the problem. I pointed it out to them last year while beta testing some early HDMI products.

It is possible to bypass this if you feed RGBHV to the HDMI transmitter and not let it perform the conversion in the case where you have to use DVI compat mode.
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post #4 of 206 Old 03-30-2004, 11:21 AM
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Quote:
Digital TVs with DVI or HDMI inputs have to following Video spec that specifies 16 as black and 235 as white. Anything out that range will be clipped.
It is not supposed to be clipped, that is the bug. It is on their list to fix.
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post #5 of 206 Old 03-30-2004, 11:34 AM
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Thanks for point that out.
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post #6 of 206 Old 03-30-2004, 11:41 AM
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Quote:
Originally posted by sspears

2. This is a bug in the current generation HDMI transimtter and you will only encounter when you feed HDMI to DVI. If you feed HDMI to HDMI then you are OK. The problem is the color space converter in the HDMI transmitter is clipping head and toe room. It does have two modes, expanded and normal and even in normal, it clips. Silicon Image is aware of the problem. I pointed it out to them last year while beta testing some early HDMI products.
Ah, so this is what Kris cryptically referred to a couple of weeks ago in a post he made. Thanks for stating what the problem is. Now I'll remove the DVD players with HDMI output from my list since I'd have to use an HDMI-DVI conversion.
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post #7 of 206 Old 03-30-2004, 11:49 AM
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CRAP! I am expecting delivery of the HD Tivo unit this week (#193 on the pre-order list from VE). The unit has HDMI out, which I was planning on running using the supplied HDMI to DVI cable into my Gefen DVI switch and out to my DVI in on my HT1000 projector.

"The problem is the color space converter in the HDMI transmitter is clipping head and toe room." Should I be too concerned about this? How the hell to you calibrate a non-DVD source anyway? It's not like they broadcast Avia...
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post #8 of 206 Old 03-30-2004, 12:18 PM
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Hold the phone. sspears what you are saying I'm going to have issues with blacker than black if I get the Toshiba 5960 (HDMI connection) to my Panny TV with a DVI connection? So I will not be able to calibrate my display? Or my PQ will suffer on all DVD's?
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post #9 of 206 Old 03-30-2004, 12:27 PM - Thread Starter
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Quote:
Originally posted by sspears
1. The guy from Pioneer is wrong.
2. This is a bug in the current generation HDMI transimtter and you will only encounter when you feed HDMI to DVI. If you feed HDMI to HDMI then you are OK. The problem is the color space converter in the HDMI transmitter is clipping head and toe room. It does have two modes, expanded and normal and even in normal, it clips. Silicon Image is aware of the problem. I pointed it out to them last year while beta testing some early HDMI products.

It is possible to bypass this if you feed RGBHV to the HDMI transmitter and not let it perform the conversion in the case where you have to use DVI compat mode.
Thanks, but I'm confused. Gary used "DVI-equipped sources (DVD players and satellite boxes)" with a DVI-HDMI cable. In other words, he was feeding DVI to HDMI, the reverse of what you describe.
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post #10 of 206 Old 03-30-2004, 01:00 PM
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Then it was either Gary's source or the the display. The problem is only on the transmitter side.

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(#193 on the pre-order list from VE).
I am 62 on the list. :)

If the TiVo converts to RGB prior to the HDMI part, then no problem. Or if you upgrade your display to native HDMI, then you are OK.

Jim, yes, that is what Kris was talking about.
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post #11 of 206 Old 03-30-2004, 01:35 PM
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So if I buy a 59AVI and use my Samsung DLP display, the display will not show balcker than black because of the HDMI converter in the Pioneer is being feed into the Samsung with DVI ?
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post #12 of 206 Old 03-30-2004, 01:55 PM
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I don't know if the 59AVi uses the HDMI part to convert to RGB. You will also loose above white, which is visible.

The only way to know is to try it using DVE.
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post #13 of 206 Old 03-30-2004, 02:15 PM
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Thanks Stacy. From what I've been reading, people with that combo have written that the picture is fantastic which make me think that if it is an issue most people aren't noticing. According to Kris' report, it does pass blacker than black through HDMI. Where could you find out whether it converts before the HDMI or in fact uses it. Would Pioneer support know ?
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post #14 of 206 Old 03-30-2004, 08:40 PM
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Quote:
Originally posted by andrew jc
Hold the phone. sspears what you are saying I'm going to have issues with blacker than black if I get the Toshiba 5960 (HDMI connection) to my Panny TV with a DVI connection? So I will not be able to calibrate my display? Or my PQ will suffer on all DVD's?
I don't know for sure, but I would assume that Toshiba uses their own (touted) HDMI chips - not Silicon Image. Of course Tosh may have worse problems. (hopefully not :) )

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post #15 of 206 Old 03-31-2004, 05:12 AM
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I'm trying to decide between the Denon 2900 and Pioneer 59AVi DVD players to use with a Panny 50PHD6UY plasma with DVI. I have been trying to find out if the Pioneer would have an advantage in video quality because of its HDMI output despite its lower ranking in the "secrets" article. I am planning on purchasing this plasma in part because of its great black levels. Will I lose this advantage if I choose the Pioneer over the Denon?
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post #16 of 206 Old 03-31-2004, 06:56 AM
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I wonder if this HDMI "problem" with Pioneer DV-59ai has anything to do with the "old" firmware version 1.306 or/and if it´s solved in version 1.406?
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post #17 of 206 Old 03-31-2004, 07:38 AM
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Quote:
Originally posted by PGriff1051
Thanks Stacy. From what I've been reading, people with that combo have written that the picture is fantastic which make me think that if it is an issue most people aren't noticing. According to Kris' report, it does pass blacker than black through HDMI. Where could you find out whether it converts before the HDMI or in fact uses it. Would Pioneer support know ?

IMHO, this clipping bug of HDMI transmitter should not affect your PQ as normal DVD movies do not use "blacker-than-black" or "whiter-than-white" range. It will be hard to proper caliberate your TV using the test disc though.
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post #18 of 206 Old 03-31-2004, 07:59 AM
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I guess my question is whether or not people who own a 59 AVI and are using a digital display via its DVI input have issues setting black ? I'm about a week from getting the 59AVI, but I can also get a 5900.

I currently have a 2900 and think the picture is great, but I want to enjoy my Samsung 467 to its fulliest. I've also owned a Denon 4800 (video Dac blew) 2 3800's (both skipped and froze even after they "fixed" the problem) 2 2900's (first one blew a video dac). To say that I'm a little concerned with owning a Denon right now since I seem to have issues everytime I get one would be an understatement.

The Pioneer has two cue issues, yet they are the same isues that my 2900 has and I have yet to notice and I just can't justify $600 for the Denon considering my luck.

Audio is not an issue since I won a Musical Fidelity A324 Dac and there are currently about 5 SACD titles that I own and want to own.
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post #19 of 206 Old 03-31-2004, 09:51 AM
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IMHO, this clipping bug of HDMI transmitter should not affect your PQ as normal DVD movies do not use "blacker-than-black" or "whiter-than-white" range.
Yes you do. Video is 8-bit and that from 1-254. 16-235 is 7.78 bits. If you clip below 16 and above 235, you have just tossed .2 bits of data.

The bits below black should not be visible when your display is calibrated, but those above 235 are. With that said, values below 16 and above 235 are still used for scaling and dither operations that take place in the display or DVD player.

Just to give you an idea, 8-bit video is capable of 256 levels of gray. 10-bit offers 1024 levels of gray. We can see ~1600 shades of green, ~700 shades of red and ~400 shades of blue in controlleld lighting conditions. 8-bit video is not enough, so every bit counts, even if it is just .2 bits. :)

If you want to see what happens when white is clipped, find a scene in a movie with a light source. Those values often go above 235. I like to use the NASA sequence on DVE or the Boo in the restroom sequence on Monsters Inc to demonstrate what you loose when you clip above white.

I use talented Mr. Ripley to show what happens when you clip below black. You end up with a pasty blacks.

I believe only Silicon Image makes HDMI chips today, so Toshiba is using the Silicon Image part.
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post #20 of 206 Old 03-31-2004, 10:05 AM
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In mid-December Toshiba announced that it was rolling out both HDMI receivers and HDMI transmitters. It was sampling chips at that time, so they may now be in full production.

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post #21 of 206 Old 03-31-2004, 11:11 AM
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I missed the Toshiba announcement, thank you Steve. I hope they get it right.
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post #22 of 206 Old 03-31-2004, 01:12 PM
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Quote:
Originally posted by sspears

I am 62 on the list. :)
How did you find out what number you are on the VE list?

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post #23 of 206 Old 03-31-2004, 01:13 PM
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Quote:
Originally posted by sspears

I am 62 on the list. :)
How did you find out what number you are on the VE list?

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post #24 of 206 Old 03-31-2004, 01:16 PM
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Are the needles and pins bars in AVIA good for testing below black?
Ie the one where there only two black bars moving left and right etc.
I assumed the darker (Left) bar was below black, and the righthand bar was actual black.
Same with the moving white bars etc.

I do have a copy of DVE, and when i get a chance i can test it properly.

I hope the new Lumagen scaler fools the 868i(59i) into sending it HDMI signals as well as interlaced. It would then kill two birds with one stone as such!:D

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post #25 of 206 Old 03-31-2004, 01:53 PM
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Ok, just tested my 868i/S3 (HDMI to DVI)
I had to adjust brightness from 50 to 60 on the S3 to see the blackest bar.
With brightness set to 50(normal setting), the right hand bar is barely visible but there. The middle bar is visible, and the left bar is hidden.
When brightness on the S3 is set to 60, all three bars are clearly visible.
Now the question is, is the left hand darkest black bar below black?
If yes, then HDMI-DVI does pass below black.
If no, then how can i test for it?
I did flick from component to DVI, but couldn't see anymore black or white info.:confused:

This bug in HMDI could explain my initial disappointment with HDMI(DVI).
But i must admit to using HDMI/DVI all the time now as i prefer the image.(after lots of tweaking!)
If i'm losing picture info, no matter how small then that's not good.

HDMI-HDMI via a video processor is my get out of Jail card, as this has always been my intention. But it is not fair on those who don't wish too(who have DVI displays etc)
But if this HDMI-DVI bug is true, then you wonder why more hasn't been mentioned about it.

Anyway, the image below is via HDMI to DVI on my 868i/S3.
Brightness set 10 points higher to enable photo etc.
http://www.pauldowning.plus.com/images/plugebars.jpg

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post #26 of 206 Old 03-31-2004, 02:04 PM
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It looks like Pioneer is doing the Y'CbCr to R'G'B' prior to the HDMI transmitter, which is great news, meaning you will not hit the bug. The player I have does not do this.

Quote:
With brightness set to 50(normal setting), the right hand bar is barely visible but there. The middle bar is visible, and the left bar is hidden.
That is what you should be set to during normal viewing.

As to your first comment, AVIA does not have any below black or above white you need AVIA Pro for that. DVE does contain as you show in your image.

Can you take an image of the reverse gray ramp? (steps)

Quote:
But if this HDMI-DVI bug is true, then you wonder why more hasn't been mentioned about it.
HDMI is new. There are only a few products on the market.

BTW - In the photo above the top two squares on the right look like one square. Is this because of the flash or because you turned up brightness to take the photo? Just want to make sure. :)

I am tempted to go out an buy the 59AVi. Does the Pioneer let you adjust aspect ratio when sending 720p to the display?
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post #27 of 206 Old 03-31-2004, 05:00 PM
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Stacey, I'm not understanding something you've said. First, you say that a properly calibrated display should not display the values below 16. And then you say that if you clip below back, you get "pasty blacks". Why don't these statements contradict each other?
Thanks in advance!

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post #28 of 206 Old 03-31-2004, 05:16 PM
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Thanks for that great update Stacy. I now feel excited to get the Pioneer, especially since my friend works at Tweeter and is going to allow me to trade in my 2900 for it straight up. (Only paid 850 for the Denon)
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post #29 of 206 Old 03-31-2004, 05:31 PM
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Michael, you won't see the BTB stripe when your display is properly calibrated. (you set brightness where it belongs)

If you actually clip below black (not setting brightness, but a player or processor clipping all values below 16.), then you end up with visual artifacts. Or rather I have seen this pasty look from products that clip at 16. I will see if I can dig up a demo app we wrote that allows you to clip and not clip to see the results.
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post #30 of 206 Old 03-31-2004, 05:55 PM
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You do see the effects of clipping below-black. One reason is that changing a sample doesn't just affect the waveform in the local area - it affects several samples to the left and right. So any scaling or digital resampling operations are affected because the sample values have been changed, and the frequency spectrum of the waveform is changed in the analog domain.

I strongly think, though, that the primary reason that clipping below-black looks so bad is that on a CRT you see below-black information, even if the CRT is properly calibrated. A bright image on screen raises the effective black level, so the below-black shadow details on an otherwise black screen are raise above absolute black, and are visible. (This is demonstrated well in the scenes discussed in Talented Mr. Ripley.)

Telecine operators use CRT monitors to adjust levels, and they adjust the levels manually from scene to scene. Given the black-level retention characteristics of all CRT monitors, even professional grade, they would certainly at times dial the blackest parts of the image into the "below-black" range. And that image will look perfect on a perfectly-calibrated CRT monitor. A digital display that is designed to mimic a CRT will also raise the black level slightly when the image is bright, and will also display below-black detail.

Ultimately it doesn't matter what the reasons are - below black shadow detail is visible. I've had this demonstrated to me many times, on my own and with Stacey. There's a reason the video engineers who designed the digital video spec reserved so much space below black and above white.

Above white is really a misnomer - all movies have above-white information in them. All of them. Clip above-white and every bright white object loses every bit of detail. It looks terrible.

Don
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