16-235 Broadcast safe? at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > Open DV Discussion

Open DV Discussion
For topics which don't fit into any of the other categories.


Reply
 
Thread Tools Search this Thread
Old November 22nd, 2004, 06:18 PM   #1
Major Player
 
Join Date: Jul 2004
Location: springfield, OH
Posts: 344
16-235 Broadcast safe?

Can someone explain to my why computer graphics have to be adjusted with output levels between 16 and 235 for digital video?

I just read this in DV magazine and still photos do look better on my video monitor when they've had their contrast reduced to those output levels.

Another question: Why don't programs like Vegas and Premiere automatically adjust graphics when they're added to the timeline.
__________________
Tony

"Good taste is the enemy of creativity" - Picasso

Blog: http://www.tonyhall.name
Tony Hall is offline   Reply With Quote
Old November 23rd, 2004, 12:02 AM   #2
Hawaiian Shirt Mogul
 
Join Date: Nov 2001
Location: northern cailfornia
Posts: 1,261
for vegas just add the broadcast filter FX to the output and that will adjust 16-235 ... Vegas codec is 16-235 spec ... premiere use to (don't know about currently ?) default to using microsoft DV codec which is 0-255 ...also QT is 0-255 ...
for your stills/graphic's if you are using photoshop CS then you can set it up to NTSC spec ...
Don Donatello is offline   Reply With Quote
Old November 23rd, 2004, 11:29 AM   #3
Major Player
 
Join Date: Jul 2004
Location: springfield, OH
Posts: 344
Ok, thanks for the info. There seems to be more than one way to adjust your image for broadcast and I found the difference in the two methods to be a bit curious.

First there's "computer RGB to studio RGB". This method makes changes that you can see on the vectorscope, waveform, and histogram. It adjust's the image's RGB levels to between 16 and 235, it compresses the information as you can see the pattern on the waveform get compressed vertically.

Then there's the options under "broadcast colors". This method doesn't actually change the colors, it just clips off any information that falls outside the legal broadcast range. If you watch the waveform, you can see everything above 100 and below 0 just disappear. I wonder what the usefulness of this is and why anyone would choose that over the first method.

I don't shoot video for broadcast... mostly as a hobby and practice for my script that I'm working on. Converting photos using the "computer RGB to studio RGB" method seems to improve the contrast range of the image on my video monitor, but other than that... is there any real reason to do so? Should I make a habit of applying this filter to photos for footage that will be shown on a television? Lastly, would you convert to "studio RGB" for something you were editing for film? Hope someone can answer this or at least give me a good link to go to.
__________________
Tony

"Good taste is the enemy of creativity" - Picasso

Blog: http://www.tonyhall.name
Tony Hall is offline   Reply With Quote
Old November 23rd, 2004, 06:41 PM   #4
Inner Circle
 
Join Date: Jun 2003
Location: Toronto, Canada
Posts: 4,750
Everything above 100IRE and below 0IRE are illegal colors. If your material is going to broadcast, they may clip the colors off like the broadcast safe filter does.

On the low side:
In North America, 7.5IRE is the level for black. Anything under 7.5IRE is not supposed to appear on your TV. Mis-calibrated TVs will be able to show colors under 7.5IRE however. If you run NTSC bars and tone to a TV and see all three pluge bars then you are seeing less than 7.5IRE (the pluge bars are 3.5IRE, 7.5IRE, and ?11.5?IRE - you are supposed to barely see the 11.5IRE one).

Anything under 0IRE will start to interfere with synchronization pulses.

On the high side:
Anything too high will interfere with the audio subcarrier.
Glenn Chan is offline   Reply With Quote
Old November 23rd, 2004, 07:18 PM   #5
Warden
 
Join Date: Mar 2002
Location: Clearwater, FL
Posts: 8,267
Tony, you may also be interested in this post from several months ago.
__________________
Jeff Donald
Carpe Diem




Search DVinfo.net for quick answers | Where to Buy? From the best in the business: DVinfo.net sponsors
Jeff Donald is offline   Reply With Quote
Old November 24th, 2004, 12:19 PM   #6
Major Player
 
Join Date: Jul 2004
Location: springfield, OH
Posts: 344
<<<-- Originally posted by Glenn Chan : Everything above 100IRE and below 0IRE are illegal colors. If your material is going to broadcast, they may clip the colors off like the broadcast safe filter does.

On the low side:
In North America, 7.5IRE is the level for black. Anything under 7.5IRE is not supposed to appear on your TV. Mis-calibrated TVs will be able to show colors under 7.5IRE however. If you run NTSC bars and tone to a TV and see all three pluge bars then you are seeing less than 7.5IRE (the pluge bars are 3.5IRE, 7.5IRE, and ?11.5?IRE - you are supposed to barely see the 11.5IRE one).

Anything under 0IRE will start to interfere with synchronization pulses.

On the high side:
Anything too high will interfere with the audio subcarrier. -->>>

Ok, thanks for the info. I've got my monitor calibrated to 0IRE and I don't intend for the footage to be broadcast, so I think I'll be OK staying between 0 and 100. Didn't I read somewhere that DVD players are set up at 0IRE? Yeah, that's right... all DV footage is 0IRE although you can have your camera record the same levels as 7.5 IRE.

Oh and thanks for the link Jeff, I always enjoy any information I can get on something.
__________________
Tony

"Good taste is the enemy of creativity" - Picasso

Blog: http://www.tonyhall.name
Tony Hall is offline   Reply With Quote
Old November 24th, 2004, 02:12 PM   #7
Regular Crew
 
Join Date: Sep 2003
Location: Quebec, QC, Canada
Posts: 123
<<<-- Originally posted by Tony Hall :
Didn't I read somewhere that DVD players are set up at 0IRE? -->>>

DVD players sold in North-America have their NTSC output setup at 7.5 IRE to be viewed on standard North-American TV sets. So if you're planning on burning your videos to DVD, don't even bother with the 7.5 setup and work it all the way at digital standards, i.e. 0 IRE. The playback will be OK on your computer's DVD drive for your computer monitor set at 0 IRE, and also OK on your TV set if played on your home DVD player with its A/V output set at 7.5 IRE by default.

The only time it will not be OK is when you play the video tape directly from your DV camcorder to the TV set via the cam's A/V outputs, unless you have a prosumer or pro camcorder with adjustable VTR playback setup.
__________________
Norm :)
Norm Couture is offline   Reply With Quote
Old November 24th, 2004, 04:13 PM   #8
Major Player
 
Join Date: Jul 2004
Location: springfield, OH
Posts: 344
Thanks for the info Norm... that's odd that you can't play footage directly from your camera through the a/v cords to a television (and see what's really there).

I never thought about the conflict of televisions having 7.5 setup and DV cameras having 0 setup.

What's this mean for the guy with a cheap MiniDV camera, without a computer who doesn't do any computer editing and just wants to film family events and watch them on the television through the camcorder? I just won't look right?
__________________
Tony

"Good taste is the enemy of creativity" - Picasso

Blog: http://www.tonyhall.name
Tony Hall is offline   Reply With Quote
Old November 25th, 2004, 10:47 AM   #9
Regular Crew
 
Join Date: Sep 2003
Location: Quebec, QC, Canada
Posts: 123
Yes Tony,
It means that most North-American consumers who watch their footage directly from the cam's A/V output to their TV set find the picture to be somewhat darker than what they see on the cam's LCD. The blacks are "crushed".

That's why their VHS copies also are a little dark and deceiving compared to commercial rental tapes from the video club.
The VHS players do not add setup.

One of my friends has a Canon GL2 and always wondered what the "VTR setup" menu was for. The owner's manual does not explain.
__________________
Norm :)
Norm Couture is offline   Reply With Quote
Old December 6th, 2004, 10:54 AM   #10
Trustee
 
Join Date: Mar 2004
Location: Hilliard, Ohio
Posts: 1,193
Pro and semi pro camers like the DSR-PDX10 can set the black to 0 or 7.5. Check any camera manuals before you buy one so you can get one that operates with 7.5 IRE from the start and you won't really have to worrry about it, unless you do something odd with your footage like send it through Photoshop for rotoscope or something.

Sean McHenry
__________________
ĎI donít know what Iím doing, and Iím shooting on D.V.í
- my hero - David Lynch

http://www.DeepBlueEdit.com
Sean McHenry is offline   Reply With Quote
Old December 6th, 2004, 11:45 AM   #11
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
Most cameras like the PDX10 have a setup switch that works incorrectly, bumping digital black levels from 16 to about 32, which produces and illegal black value on the digital tape. That's because the analogue outputs don't ever add setup, so the camera cheats by boosting the black in the digital domain - which is wrong.

It's also wrong to talk about IRE with regards to digital video. That's because IRE is an analogue measurement. You can't measure digital video with an analogue measure!!!

All digital video uses the 16-235 range, wether it be DV, DVD, DigiBeta etc.

Setup, or 7.5IRE is purely an analogue phenonema and should only be talked about while talking about analogue video or else you are making no sense what-so-ever.

As for monitoring your DV in your home edit suite with a camera or deck that does not add setup on it's analogue outs - if you calibrate your monitor to your deck / NLE system, then you will be seeing accurately what is on your digital tape or NLE.

The only time you need to worry about setup is when dubbing a VHS client copy, say. Either buy a proc amp, or make a DVD and dub the VHS from that as most north american DVD players correctly add setup on the analogue outs.

Graeme
Graeme Nattress is offline   Reply With Quote
Old December 7th, 2004, 03:40 PM   #12
Trustee
 
Join Date: Mar 2004
Location: Hilliard, Ohio
Posts: 1,193
Interesting. I was under the apparently incorrect impression that the setup only controlled the analog out of the camera.

I am not sure why I thought that as it was actually recording that way.

On the other hand, if you are artifically bumping the digital, in the DA conversion are you saying it isn't 7.5 on the output of that DA conversion?

Why would somebody like Sony go through the trouble of adding a 7.5 option which had to cost them some money to engineer and implement bother?

This is news to me so I am interested in this one. I have always shot at 7.5 believing it to be the correct setup. I have to go hit the manual now.

Thanks for the input Graeme
__________________
ĎI donít know what Iím doing, and Iím shooting on D.V.í
- my hero - David Lynch

http://www.DeepBlueEdit.com
Sean McHenry is offline   Reply With Quote
Old December 7th, 2004, 05:03 PM   #13
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
For Sony to add something simple in the digital domain is cheap - to add it to the analogue, more expensive, and they're Japanese anyway, so don't need it themselves.

Yes, bumping the digital will give the right black output of analogue, but your NLE and tape are now working in the wrong range, and you've lost 16 or so levels of brightness which will reduce the quality of the recorded picture. Your NLE will want to work in a different range so some effects might not work right.

So, don't use it, and either use the DVD method, or the proc amp method for analogue.

Graeme
Graeme Nattress is offline   Reply With Quote
Old December 7th, 2004, 07:45 PM   #14
Trustee
 
Join Date: Mar 2004
Location: Hilliard, Ohio
Posts: 1,193
OK, I see what you are saying here but, if I set to 7.5 and bring the video into my Avid via firewire, the output should be correct I would think if I go to say a quicktime ref file as the input for the DVD content.

You have me wondering about the flow I have been working with now. I'll have to check the levels, import some footage and call up the waveform to check it out.

I do know that the DVRack metering shows correct 7.5 on the firewire if I set it to be 7.5. Then again, we are still in digital.

I'm not really doubting htis, I just need to verify things with my own tools. Let you know what I find out one way or the other.

Sean
__________________
ĎI donít know what Iím doing, and Iím shooting on D.V.í
- my hero - David Lynch

http://www.DeepBlueEdit.com
Sean McHenry is offline   Reply With Quote
Old December 8th, 2004, 08:16 AM   #15
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
If you set it to 7.5 and bring it digitally into any NLE, then it will be WRONG.

7.5 is not correct on firewire, SDI or any other digital way of transfering video. It would be correct if it were 0%, but anything else is wrong. No digital video has setup - ever, or else it's wrong.

Graeme
Graeme Nattress is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > Open DV Discussion

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 09:35 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network