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I'm getting 15 IRE, not 7.5, why?

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Dave Po
I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 4:37:32 pm

My broadcaster told me our video looks to be 15 IRE. I need some help tracking down the problem and how to fix the problem.

I'm shooting DVCPro 50, editing in FCP, exporting through a AJA IoLA to a Digibeta deck through composite video from the AJA to the deck.

I just took a look at the camera (Panasonic SDX-900), it is Setup at 7.5 (bummer). I also talked to AJA, and they said that the IoLA adds 7.5 IRE, but they said if the video is already at 7.5 it shouldn't double it up to 15IRE. So I don't believe this is the problem. Another reason to believe that the camera isnt the problem is that I used FCPs color bars for printing to tape. They would measure my black level of 15 IRE from the color bars, right? not the video that comes after the color bars?

... so if they are measuring the color bars, which are 15 IRE, it is getting doubled up somehow outside of FCP because I don't have Proc Amp on or anything else. Could it be my deck that is adding the 7.5 on top of what is coming through the AJA? I checked the deck (Sony DVW-2000) and the Setup was set to "Preset". Could that preset be 7.5? I can change it to 0, think that would fix it? If that isn't the problem, could I counteract the problem by setting the decks setup to -7.5IRE?

If you have any answers to these questions or any tips on what might be the problem, it'd be much appreciated! I also need to know ASAP.


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Mark Suszko
Re: I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 6:21:25 pm

Is something unterminated somewhere on their end?


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Dave Po
Re: I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 7:10:01 pm

What do you mean? I guess I dont understand what you mean by unterminated.



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Jan Crittenden Livingston
Re: I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 7:01:18 pm

[Dave Po] "IoLA adds 7.5 IRE, but they said if the video is already at 7.5 it shouldn't double it up to 15IRE. So I don't believe this is the problem. Another reason to believe that the camera isnt the problem is that I used FCPs color bars for printing to tape. They would measure my black level of 15 IRE from the color bars, right? not the video that comes after the color bars?"

Hi,

Turn of the IO's 7.5. Record to DVCPRO50. It will be fine at that point the machine they are playing it back on is set up to add 7.5. So you add 7.5 and they add 7.5 then you have 15. Turn it off on the DVCPRO50 recording. It should never have it. The broadcaaster adds it for all the analog TVs out there, Digital recordings should never have it.

Now if you have 15 on the tape, boy I don't know how you did that as the 7.5 setting on the camera is only for the analog output.


Hopes this helps,

Jan

Jan Crittenden Livingston
Product Manager, HPX500, HVX200, DVX100
Panasonic Broadcast & TV Systems



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Dave Po
Re: I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 7:41:40 pm

"Turn off the IO's 7.5."
- do you mean my AJA IOLA? Is that even possible?

I don't quite understand you. Why would specs ask for 7.5 IRE if they are going to be adding an extra 7.5 IRE?

The more I'm thinking about it, the more I think that the digibeta deck's Setup, which is set to preset, is adding the extra 7.5 IRE.



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Bob Zelin
Re: I'm getting 15 IRE, not 7.5, why?
on Mar 4, 2009 at 8:50:26 pm

I know the answer to this question.
You will not like the answer.

No one wants to buy scopes until they get their tapes rejected by the broadcaster. Well, now its your turn. You will NEVER determine what is going on until YOU put a waveform monitor on your equipment -one piece at a time. You may find out that your broadcaster is an idiot, and their staff has no idea of how to evaluate levels, or THEY are doing something wrong. But you won't know this until you have a waveform montior. Can't afford one - borrow one, rent one, or go to a post house that has one.

Almost all analog outputs have their setup level set to 7.5 IRE. If you have an HVX-900, this is a digital camera, so it's SDI or HD-SDI output would have a setup level at ZERO, but it's ANALOG output would be at 7.5. If you take the analog output and go into a product (like an AJA), it doesn't "add" another 7.5 IRE to the setup - it keeps it the same.

We can go back and forth on this all day long - try this, try that -but it all means NOTHING, because you will try these suggestions, without a scope, send off your tape, and it will get rejected again. YOU MUST GET YOUR HANDS on a waveform monitor.

Remember, there are analog waveform monitors, and digital waveform monitors - analog looks at anlaog signals, and the setup level is 7.5 IRE as specified by RS170A standards. Serial Digital scopes will display an SDI (not an HD-SDI) signal, and the SAME signal will drop the setup level to 0 IRE (or digital 16).

I know that this is not the answer you want, because you dont' want to spend any money, but you play in the big leagues, this is what you suffer with.

Bob Zelin




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Dave Po
Amen brother
on Mar 4, 2009 at 9:30:25 pm

Amen brother! ...fact is, I don't pay bills, no scope for me :(

I am just trying to understand everything so I have a better understanding of what the problem could be.

For the reference we have an SDX-900 not an HDX-900. We are shooting standard def not high def.

So if the camera is set to "7.5%" does that do a fake digital black level adjustment that results in about 7.5 IRE? So the DIGITAL setup level would or wouldnt be 0? I know normally digital black level is set to 0. But the camera "IRE" level is set to 7.5. So it is my understanding it is NOT 0 digital black level. Am I right?

"If you take the analog output and go into a product (like an AJA), it doesn't "add" another 7.5 IRE to the setup - it keeps it the same."

-understood.

"Remember, there are analog waveform monitors, and digital waveform monitors - analog looks at anlaog signals, and the setup level is 7.5 IRE as specified by RS170A standards. Serial Digital scopes will display an SDI (not an HD-SDI) signal, and the SAME signal will drop the setup level to 0 IRE (or digital 16)"

-does this mean a 0 digital black level video when exported through something analog (like an AJA) will have 7.5 IRE? How so? Because 0 Digital black is different from 7.5 analog IRE?



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Bob Zelin
Re: Amen brother
on Mar 5, 2009 at 12:58:09 am

you write -
" Because 0 Digital black is different from 7.5 analog IRE?"

NO - 0 digital black IS 7.5 IRE analog black. This was clearly shown to me when the Leader LV5100D was first released (the first true multi format scope - before the Videotek VTM-200), and with the first AVID Meridian SDI AVID.

On the SAME waveform monitor, when you monitor the SAME signal coming out of an analog out or a digital output, the BLACK LEVEL CHANGES - analog is 7.5 IRE, digital is ZERO. THIS IS THE SAME SIGNAL. It is on EVERY PIECE OF EQUIPMENT SINCE DAY 1 of multi format products (like Digi Beta VTR's). There are menu settings to change this, but there is NO REASON to compensate for this. If you boost setup to 7.5 while monitoring the SDI signal, you are fooling yourself, and the tape op at "the other facility" will setup to what he considers normal, screwing up what you have done.

Let me make one thing perfectly clear for those that do not understand. If you have a monitor (like a Sony PVM series with both SDI and analog inputs), and you switch back and forth between the analog and SDI inputs, THE PICTURE LOOKS DIFFERENT BECAUSE THE BLACK LEVELS ARE DIFFERENT. You don't like this fact - then lets dig up the MORONS at the SMPTE committee that decided all of this in the 1980's, and EXECUTE THEM, becuase they have made all of our lives miserable for at least 2 decades. Who says that the "experts" know what they are doing. Just look at 29.97, 23.98, etc. All of this insanity happened because of B+W TV compatibility.

Get that scope, you will be lost without it. And just remember, you may be doing nothing wrong, and your system is fine, and the "TV station" is wrong- but you can't prove this until you have access to a waveform monitor. My first purchases of test equipment in the linear days were from idiots at post facilities in NY that did not know how to read a scope, and would reject tapes, becuase of their uncalibrated equipment, and inablity to read scopes properly.

bob Zelin




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Dave Po
*angels singing
on Mar 5, 2009 at 6:24:08 am

the heavens opened and here and behold, i have a waveform monitor (on lend from tv station).

Everything I am reading through it, as far as black levels goes, is 7.5 IRE. That is from my AJA, and from the digibeta deck. If I unterminate the digibeta deck, i get 15IRE with whites out of view. That is obviously not the problem because I went to there studio and saw my tape in their monitor, whites where in the correct spot, only thing was, 15IRE black level.

I also ran bars from our standard def, digital camera. (Panasonic SDX-900) If I had the "7.5%" setting on, blacks read at 7.5 IRE on the waveform monitor (which is analog), if I turned the "7.5%" setting off, IRE on the waveform monitor showed 0IRE. This would "disprove" that you (bob zelin) said. But I believe you, I just need an explanation for what I'm seeing.

Soo..... everything looks good on my end. Looks to be their problem. But this is a super legit station, I don't think they'd be cutting engineering corners. Also, I saw them put in another tv show and their bars where correct. But I heard them mention that this other tv show was also having problems. Maybe they just turned there black levels down to 0IRE?



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Bob Zelin
Re: *angels singing
on Mar 8, 2009 at 12:20:38 am

Dave writes -
Soo..... everything looks good on my end. Looks to be their problem. But this is a super legit station, I don't think they'd be cutting engineering corners. Also, I saw them put in another tv show and their bars where correct. But I heard them mention that this other tv show was also having problems. Maybe they just turned there black levels down to 0IRE?

REPLY - no matter how professional a big company may be, it never ceases to amaze me the incompetance of some of these operations. Often, QC rejection happens by a poorly trained tape op, and not the chief engineer, who actually knows what is going on. I suggest that you ask for the chief engineer of the station or company that rejected your tapes, and politely ask him to evaluate your tape for the problem that was claimed. Often, there is NO PROBLEM, and it was "operator error". When you have the right equipment, YOU become the expert.

Bob Zelin




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Dave Po
problem fixed!
on Mar 6, 2009 at 5:52:54 am

Got it fixed!

Just for future reference for anyone with the same problem (doubt it will EVER happen to anyone else), here i the solution, at least in my case.

We have a Sony DVW-2000 DigiBeta deck. In the extended menu (which is turned on or off by a switch that is on a chip board that you have to pull out of the deck) there was a setting, Item Number 713 (video setup reference level), that was not set to default. The master level setting was set to 0IRE instead of 7.5, to understand what exactly that means, take a look at your manual, it explains it, ...sorta. Basically it has to do with adding and subtracting it from inputs and outputs and stuff.

And to sing the praises of having a waveform monitor... I wouldn't have figured out that it WAS fixed, after I fixed it, without it. Get a scope.

If anyone does have this problem in the future, feel free to email me dave -at- savedeth.com



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