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Decklink SP with Vegas and Waveform Monitor confusion.
Okay… so, recently picked up a Decklink card to work with Vegas 6, and I’m having a bit of a time getting my output levels to jive with the Vegas Waveform monitor.
So, here’s what’s going on. My footage is aquired on DVCAM, captured through Vegas, then rendered to 24p, color corrected, filtered, etc. etc. and finally rendered down to the Sony YUV codec, to work with the Decklink card (which looks killer, btw) So… here goes the confusion.
According to the Decklink, it’s outputting 7.5ire (it’s switched on in the prefs)… so, I assume the ‘black’ that Vegas is outputting (normally 0ire in DV), either from the timeline, or from a media generator, should be 7.5ire on the NTSC monitor (through the Decklink). But, it appears darker than the ‘black’ the Decklink is outputting when there is no signal (which could very well not be 7.5 I suppose). So, is the ‘black’ coming through the Decklink from Vegas 0, or 7.5? When I switch the decklink from 7.5 to 0 (Japan), it appears darker on the NTSC monitor. When I put bars out from Vegas, through the Decklink calibrate my monitor, then switch to DV the bars are darker (again because of the 0ire vs. 7.5ire with the Decklink). So, that would lead me to believe the Decklink IS infact, outputting 7.5ire – and all is well, or… maybe not?
So, where the confusion comes in… what’s really black, and is what the Waveform monitor in Vegas telling me correct? Should I be using Studio RGB and 7.5 ire setup options both in the Waveform monitor? And if so, then I assume 0 in the Waveform monitor, is actually 7.5? Or, is 0 actually 0 (which would make 7.5, 7.5). OR, should I have the Studio RGB off, and just use the 7.5ire setting?
My head hurts.
Thanks for the help.
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5 Replies
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don’t know about decklink ??
Vegas generated media operates on the 0-255rgb scale ..
so if you are looking at the waveform set to studio 16-235 scale then the blacks in generated media will be -4ire and 235rgb whites will read 100 ire .. 255rgb will read 108 ire ..text in Vegas i believe defaults to 255rgb = 108 ire …
however under the 0-255 scale (boxes unchecked) generated media blacks will read 0 ire and whites at 255 rgb will read 100 ire ..
note that Vegas dv codec and i believe the YUV are 601 spec’s = 16-235rgb on a 0-100 ire scale ..
note that the microsoft codec, QT , mpeg are not 601 and they read 0-255 which will read 0-100 ire ( all boxes unchecked)…soooooooooo as you can see not all 0 ire’s are equal .. a 0 ire black under 0-255rgb is black and 16 rgb will be 7.5 ( that is USA ntsc set up) .. under 601 on the studio 16 rgb to 235 scale that once you set black to the middle 16rgb black bar ( SMPTE color bars) then the 16rgb is BLACK on a USA NTSC monitor/TV …
soooooooooooooo why does the ole usa have to make everything so difficult ? ?? 29.97 ? 23.96 ?? 24fps , 30fps , set up ??? inches , feet ? etc .. why does europe only have 25fps = i guess they just don’t know what they are missing!!
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I’m going to have to sit in front of Vegas and work out the options that donatello outlines above – for some reason they’re very slippery and hard to hold in my head! I do recall that adamwilt.com has some discussion of this subject as well. There it is.
mikelinton – presumably you are using the decklink to output to betaSP for broadcast? If so, you really need to hit the spec, one way to get this done will be to strap a real waveform monitor across the decklink outputs. With that piece in place you’ll solve this puzzle in about 5 minutes and be able to stand up to a broadcast engineer with confidence.
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Thanks Seth… Yah, I wish I had a waveform monitor – but like I said, I dumped it a few years back… I’m going to see if I can track one down. You are right, this is going out to BetaSP for broadcast – hence my confusion with the Dekclink adding 7.5ire to the mix. In the past, we’ve kept it all in DV format, then in the final mix to go out to BetaCAM we’ve adjusted levels to insure something close to within NTSC spec, before going to the deck. In effect, adding a 7.5 setup by boosting blacks, and making sure whites are within spec – if it was being dubbed (longer format stuff), from a pro DVCAM deck to BetaCAM we made sure to NOT mess with black levels, and use the ‘setup’ functionon the pro deck, to add 7.5 to keep things legal (of course, compressing our whites where need be)….
Anyway… thanks for the article link too – Its a good refresher…
I’ll let you know what I find out….
Cheers.
Mike
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Thanks Donatello… That’s pretty much my understanding of things… If 16,16,16 is 0ire, and the Decklink adds 7.5ire, then are we at 7.5ire from the Decklink. So, I guess where the confusion begins is with generated black media – I should be setting this to 16,16,16, and that should maintain the Studio RGB spec, and give me 7.5 ire on the Decklink. That makes sense… I just totally “brain fartted” on the whole 16,16,16 vs 0,0,0…
What was kinda buggerin’ me up, was from I could find on BMDs website – it says something about it being impossible to output ‘illegal’ signals, because of the 7.5 setup… and another article I read, relating to Final Cut said DON’T adjust black levels at all, as the Decklink will add 7.5 (or, because it’s Quicktime – is FCP working at 0-255, or 16-235?) So, not taking into account the fact Vegas’ black is actually below 0ire, that’s what was messing me up… I was thinking, for some dumb reason, it would essentailly ‘boost’ Vegas’ 0,0,0, RGB to 7.5 ire. But, actually it’s just boosting it to 0ire.
Okay… to recap… Assuming the black level in my captured footage reads around 16,16,16 RGB in Vegas (0ire with the Studio RGB switch on), then the Decklink is adding 7.5 – my footage should be great, rock solid everything is cool, black levels sitting at 7.5ire at the end. If I generate black media in Vegas, set its RGB values to 0,0,0, it should be 0ire on the Decklink… If I set the black levels in the generated media to 16,16,16 that should be 7.5ire on the Decklink… Okay, thanks… I’ve been confusing myself… what was throwing me off is, if black in the footage is 16,16,16, I was kinda thinking that would appear as closer to 15ire… I wasn’t thinking about the 16-0ire ‘offset’ so to speak… in the past, I’ve always color corrected manually, used the Broadcast Colors filter and not having the additional 7.5 setup – I was somehow thinking it would all end up brighter than it really is.
Man… long way to go for a drink of water… I’m still going to try and track down a Waveform monitor, and double check it…
Anyway, thanks for the help! Sorry about the long-rant…
Mike.
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also in generated media don’t forget to set the WHITES to 235rgb ( they default to 255rgb)
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