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Old February 10th, 2004, 06:31 PM   #1
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I'm all perplexed: video scopes

Ok, in Vegas 4, you have your video scopes. I was using the waveform monitor to look at something, and saw, to my dismay, that my blacks were near 0, and not 7.5. There was no "7.5" mark currently displayed, so I'd have had to guess where that was on the scope. Then I thought to check the settings on the scope, and noticed an unchecked box with "7.5 IRE setup" written next to it. I checked it, thinking it would simply add a dotted line at the 7.5 mark to the scope, and instead, all the information displayed on the monitor, the values of my video levels, jumped up, making the lowest value on there near 7.5. What did I just do? Why did the IRE values change? How do I know if this stuff is NTSC broadcast acceptable? I thought the IRE values were absolute, that is, a certain level of black registers as "x number" on the IRE scale, and now it seems it ain't so.
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Old February 11th, 2004, 08:13 AM   #2
 
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Checking the 7.5 ire setup box merely adds 7.5 to all the input values. I don't really know why SoFo wrote it this way, but, the only usefulness of that checkbox is when the "Broadcast Colors" plugin with 7.5 IRE setup is being applied to a track. The intent is to match(calibrate) the vectorscope to a 7.5 IRE input.
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Old February 11th, 2004, 01:04 PM   #3
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So. . .I should uncheck it if I want to see the "true" values? I don't use the broadcast colors plugin, at this time. Is there a better, cheap (or even better, free) software waveform monitor I could acquire, that would work with Vegas 4?
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Old February 11th, 2004, 01:34 PM   #4
 
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Sadly, waveform monitors/vectorscopes are quite expensive, even on Ebay. The situation is that any analog US-NTSC device with an analog output(VCR, DVD set-top player,etc.) will automatically add a 7.5 IRE bias to source material. Digital devices(DV players, cameras) working thru firewire, output 0 IRE, as that's the DV standard. If you want to output a digital signal to an analog NTSC monitor, you need to add the 7.5IRE bias. The best way to add the bias is with a proc amp(process amplifier), available for moderate cost. I am using a DVP-4, available from www.elitevideo.com. Alternatively, you can add the 7.5 IRE "correction" with the Broadcast Color filter. If you show your video on an NTSC analog monitor, you must add this bias or your blacks will be clipped, and that's not pretty. If you will only display on a computer monitor(digital), don't worry about setting the 7.5 IRE bias on your editted streams.
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Old February 11th, 2004, 02:06 PM   #5
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Well, I'm using a Sony NTSC 14m2u monitor to. . .uh. . .monitor my work. I guess that's analogue? So I should just apply the broadcast color filter?
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Old February 11th, 2004, 02:31 PM   #6
 
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Josh...

It really depends on your final product and how you've calibrated your NTSC monitor.


How are you distributing your output, DV tape or VHS? If you ditribute with DV tape, be sure to note to your customer whether or not you've applied the setup level to the video, and generally, you can go either way. If you distribute via VHS, definitely use the Broadcast Color filter.


Also, be sure to set up your monitor brightness in the right way. You do this by viewing an NTSC colorbar chart and setting the brightness so the center and left pluge bar just blend into each other while you are feeding it a colorbar chart at the right 7.5 IRE bias.
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Old February 11th, 2004, 03:07 PM   #7
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Distribution is a toughie. . .I was hoping to have one all around one. . .the only reason I'd put it on VHS, for sure, at least right now, is for screeners for film festivals (I think screeners is the right word--the one you send them to consider you for submission, NOT the one they actually show if you're accepted). Does the XL1s' bars have the 7.5 bias? or Vegas' ?


Ok sorry. . .I just did a test in Vegas by applying the Broadcast colors filter to a clip, and rendered one out without the 7.5 IRE setup added, and one with it, and I can't tell them apart. Am I not supposed to be able to?
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Old February 11th, 2004, 03:18 PM   #8
 
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DV never has 7.5 IRE bias!!!....not a DV cam, not Vegas(unless you use the Broadcast colors filter). DV, by definition, is 0 IRE setup. The 7.5 IRE is needed only when final display is on an NTSC analog display, like a TV monitor. If you capture in DV, process in DV, display in DV, you never need to do anything to the setup level.

If you want to show DV on analog display, like a TV screen, you need to add the 7.5 IRE black setup via a proc amp. If you add the 7.5 IRE black setup, you need to add the Broadcast Colors filter to your NLE to prevent black clipping.

Getting more confused? Don't feel bad..it's a hard thing to grasp.

Ummm..your test clip...

it will be hard to see a difference because all the filter does is remap the blacks. the overall result is a slight redux in signal bandwidth, hopefully unnoticeable. You'd need to run both clips thru your monitor, with 7.5 setup added, to see the difference in the blacks. Clipped blacks usually have a muddy appearance rather than pure black. The inverse, that is no setup added on display but the broadcast color filter set to 7.5 IRE, will reduce the bandwidth, as I said, but, will probably go unnoticed.
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Old February 11th, 2004, 03:36 PM   #9
 
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Let me try to explain it another way...

Here in the good ole US of A, TV analog broadcast devices, which includes a TV set, a VCR, and US market DVD players, they all clip the input video signal below IRE7.5 and above IRE95. So, if you have a video source with RGB colors mapped anywhere below RGB16 and above RGB235, your signal will be arbitrarily clipped. The result of clipping is muddy blacks and blown out hi-lites. The audio analogy is like trying to feed a hot signal to an audio amplifier and clipping the peaks of the signal. In order to avoid clipping, the Broadcast Color filter remaps any colors below IRE 7.5(RGB16) to RGB 16 or above and above IRE95 to RGB235 or below. The remapping is done in a rather smooth curve so no banding occurs.

So, if you're viewing your editting on an analog monitor(AKA TV monitor) you've gotta ask yourself what that monitor is setup for, NTSC standards or not. If it's set for NTSC standard (7.5 IRE setup) then any signal you feed it below 7.5 IRE wil get clipped.

Does this help any?
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Old February 11th, 2004, 03:46 PM   #10
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Yes. . .uh. . .sort of. Basically, the idea is, depending on final output, I may or may not want to use the added setup. If I somehow get something shown on VH1, for instance, I would have to reformat it with the added setup so that when it airs, it doesn't look like ass. . .correct? And that goes for anytime it'll be played through an NTSC device like a VCR, or DVD player, at a a film festival, also right? If not, though, don't worry about it?

And you need the proc amp in conjunction with the broadcast colors filter, correct?
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Old February 11th, 2004, 03:55 PM   #11
 
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yeah, I think you're getting it.
If you want to monitor your video image on your TV monitor, or play it to your TV monitor with your computer as the source signal(VEGAS4, or whatever), and see it with the same setup level that you'd see it in broadcast, then you need to put a proc amp at the TV monitor input to properly clip the signal coming from your digital source....does that make sense?

Does anyone know whether the S-video or composite video output of a standard video card, like a Matrox Parhelia or a Radeon 9800, output with the 7.5 setup level already added? If these cards already add the 7.5 setup level, you don't need the proc amp. I don't know the answer to this question.
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Old February 11th, 2004, 04:02 PM   #12
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I can tell you I have a pretty old video card, an NVidia Diamond Viper 770D, and that my firewire card is a $75 Pyro 1394 (or whatever that number) basic card.


Guess what I found? While searching through my monitor's various menus, there's a setting that allows you select either 7.5 or 0 IRE as the setup. When I moved it to 7.5, BAMMO! Everything got darker. . . When I went into the NLE, and using the software video scope for reference (with 7.5 setup turned off), and started raising the brightness level till the darkest darks were around 10 IRE, it started to look okay.
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Old February 11th, 2004, 04:09 PM   #13
 
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ta-daaa!
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Old February 11th, 2004, 04:15 PM   #14
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So, I guess if intend my distribution medium to be film fests, maybe TV shows, whatever, I should shoot as well as edit with the 7.5 bias? And I'm guess this is one of the reasons people's stuff looks so dark on the web?
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Old February 11th, 2004, 04:18 PM   #15
 
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1-yes
2-I dunno
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