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Scaled output slightly peaking over 100 IRE?
I’ve just been confronted with IRE levels going over 100 on a job with several TV episodes. I’ve always monitored Scaled, the render panel however has been set to AUTO and for some reason some of the clips are indeed way over 100IRE at times.
So I made an isolated test. Found a clip that went up to almost 120 IRE, rendered both scaled and unscaled.
So is Scaled really 100IRE, and not a single value more? I’m checking it in ScopeBox. The peaks are going slightly over. The attached image shows one clip after render. Upon monitoring from Resolve it flats out at 100IRE.
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18 Replies
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it would be good to compare with other scopes?
maybe it is just on 100 and scope box goes mad or this 120 one was ok on scope box ?
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Margus
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I’ll make a video/screencapture tomorrow to show you how the waveform in ScopeBox behaves in the different monitoring situations.
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Broadcast safe 625 video 100 IRE = 700 mV (Pal)
Broadcast safe 525 video 100 IRE = 714 mV, max allowed: 120 IRE (NTSC)That’s why I don’t like this IRE-scale.
And it’s used for analog signals not digital values. So it depends on the DA-converter if full scaled or legal scaled signal will match the desired values.But in case of your screenshot: values around 120% in all RGB-channels can’t result in Y-Value around 100%! I guess there is a bug in your scope.
Regards
Knut -
I think I made myself unclear. Sorry.
The random clip in one of the episodes shows 120IRE when Resolve is set to monitor Unscaled.
When monitored Scaled, it flats out to an even line on 100IRE or just below.When I have rendered this clip, Scaled, and playback outside Resolve, it’s becoming fuzzy like the picture shows, peaking at something like 102IRE or somewhere there about.
However,setting the Waveform in ScopeBox to show the scale in 10-bit Scale shows a peak at 1023.
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As I understand it, IRE is useless in the digital world.
If a digital scope shows IRE or voltage of a digital signal it shows how an ideal da-converter would create the analog signal.
Mathematicaly 1023 should result nearly 109% not 120, so it’s a bug?An real analog device can’t build an ideal signal. It will produce overshoots on high contrast and will show a fuzzy signal-line there.
Thats one reason why a real waveformmonitor has a lowpass-filter (not only to disable the chroma in a composite-signal) -
Makes sense to me.
Looks like I’ll have to add Broadcast Safe filter in FCP for the previous episodes for now.But no matter what I do – the rendered files always seem more fuzzy, and goes a little beyond the values I see when I monitor directly from DaVinci.
If you’re not familiar with ScopeBox, it’s an application that can take any input device and produce scopes. In the Mac with ScopeBox I have the first generation Decklink HD Extreme.
I can’t think of anything else than the rendered files being the sinner. It must be something in the render process.
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Do not be so sure as calibration is since of its own in software or hardware.
Really good would be putting this material to some hw scope or ultrascope for that matter.
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Margus
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There’s a Harris scope in the building somewhere. I’ll see if I can get my hands on it.
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Can’t access the Harris scopes today.
Dan told me to test with a 1D Data to Video LUT. Certainly helped a whole lot, yet it’s very fuzzy after render.I think this image attached speaks for itself. Click it to see full size.
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now the question is which one of those is idiot.
FCP 7 ?
We will wait and see how it goes with real scope.
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Margus
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