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Audio meters
Any idea what the scale of the FCP X audio (VU/peak) meters relate to? Does 0 equal the previous 0 in FCP 7? Is it 0 VU (analog), which would be -20dB on a digital scale? Or maybe -12dB. Since the headroom is only 6 dB, it seems like it doesn’t quite relate to digital standards. Ideas?
– Oliver
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16 Replies
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Oliver
Did you try exporting some audio clips from FCP 7 with known audio levels (say -6db, -12db, -20db) and then bring them into FCX and see how they line up? That should provide some reference.
Cheers
Andy -
[Andy Mees] “Did you try exporting some audio clips from FCP 7 with known audio levels (say -6db, -12db, -20db) and then bring them into FCX and see how they line up?”
When I posted this morning I didn’t have time to check that. I’ve since run a quick test. T&B in FCP 7 set to -20 in a timeline and then I exported a self-contained QT file. It also shows up as -20 in FCP X. In theory a file should be clipping after 0 on this type of scale, so what are the other 6 dB of headroom? Seems that you shouldn’t actually exceed 0 when mixing in FCP X either.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
Am I misunderstanding something here?
I thought that exceeding 255 (digital value clipping) was ALWAYS catestrophic in the digital realm.
Oliver, are you saying that there’s some “hidden” headroom being applied in FCP-X and that the -20db out of FCP-7 which (as you indicate) imports as -20 in FCP-X is somehow a different level.
I’m confused.
“Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions.”-Justice O’Conner
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Bill,
By 255 you mean video right? This is the audio. In FCP 7 the meters go to 0, which would be the point where the audio hits distortion. In FCP X they go to +6. In my past experience, -20 in FCP 7 matches -20 on a digital VTR via SDI using a Decklink or Kona card. So, FCP 7 has been using a scale consistent with the broadcast world and the audio mastering world. When I create a clip in FCP 7 with tone at -20 this imports into FCP X also with the tone at -20. So presumably 0 in FCP 7 (clipping) would equal 0 in FCP X, which appears to be 6 dB lower than the clipping limit. That’s what I’m trying to figure out.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
I’m a bit confused as well. But FCPX appears to be using Soundtrack Pro’s model which also peaks at +6.
I threw Deftones “Elite” into FCP X and Soundtrack Pro. It peaks at between +1 and +2 in both. What is interesting is that if you place it in an FCP timeline and open the audio mixer it peaks at around the same levels there as well. Which makes me wonder if we all have been misinterpreting how FCP classic handles audio.
Or am I missing something significant?
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Not sure myself. Yes, I see that STP is +6 on the meter, too. However, when I open a mastered commercial piece of music (these typically cram the signal to the max) the peaks in STP read no higher than +.2 (not +2). I opened the same cut in BIAS Peak (its meter tops at 0) and I get the same basic levels, meaning it hits at 0 on the peaks. So I’m not sure why your track reads as high as it does.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
Just ran a quick test. I took a track and crammed the levels up to the max, slamming the meter at +6. The second version was raised so the levels danced at or above 0. Both were exported and opened in Peak. Both read with a max level of 0, but clearly the +6 version was more clipped, with a waveform largely sheared off at top and bottom. Neither was unpleasing sounding, of course it was a ZZ Top track 😉 So, kinda hard to tell to begin with. I would say, stay conservative with levels and assume that anything over 0 will be clipped. Since FCP X is using floating point processing, there’s probably some graceful clipping on peaks, but I wouldn’t want to routinely slam the meters.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
Sorry I was unclear.
I was using the 255 video clipping idea to reflect how a signal over WHATEVER digital max setting is baked into the software – in audio OR video causes CATESTROPHIC wave form breakdown.
Back in my young FCC license radio days – we all understood that there was a gentle “soft-clipping” area (represented by the red “technically over-modulated” but still very much usable (and sometimes DESIRED) part of metering.
When the change to digital came – we had to re-order our thinking to understand that if you took digital meters to work like analog ones – you were risking DISASTER.
When I read your post, I thought you were suggesting that FCP-X might improperly map levels such that one could inadvertently be shielded from audio levels that would FAIL in FCP-X.
IF, on the other hand, these values ARE being mapped properly – we can relax about it.
That’s what I was trying to get at. Does metering in FCP-X lead you to a functional and destructive “brick wall clipping” situation such as one faces in 255 video – or is it reliable as a way to set audio levels.
Simple as that.
“Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions.”-Justice O’Conner
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So you’re saying Apple has programmed something akin to analog “soft clipping” into FCP-X?
If so, that’s going to REALLY help a new generation of FCP editors to avoid messing things up.
I guess everything old IS new again – if you wait long enough!
“Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions.”-Justice O’Conner
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[Bill Davis] “So you’re saying Apple has programmed something akin to analog “soft clipping” into FCP-X?”
I don’t know. Merely, that there was no harsh clipping or obvious digital garbage.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com
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