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Phase Issues inherent in Final Cut Timeline?
So for years, I’ve been loading clips into Final Cut and they been out of phase. A Boom and a Lav that sound great in stereo (and on set) but as soon as you pan them to mono, they sound thin and out of phase. While I always thought it was suspect for two radically different types of mics in two radically different positions to be so perfectly out of phase, I just chalked it up to that. I also record music and understand the delicate balance of mics and phase cancelation etc. Usually, it seems prevalent with mics in stereo pairs that are similar distances from the instrument. It is also almost always much more subtle than how extreme it is in Final Cut.
Just recently I started doing some really low budget run and gun stuff and am working with an old MONO Shure mixer. I run a lav and boom into the mixer, mix them on the fly and send a mono signal to a stereo splitter to my HV20 camera so that the mono signal is recorded onto two separate channels. WHEN I LISTEN BACK IN THE CAMERA, IT SOUNDS FINE.
Here’s where it gets weird. When I load a clip into a timeline in FCP with two identical mono clips as if they are stereo tracks, they are out of phase. Now this is panned hard left and hard right. It sounds like a telephone effect. Now, if I pan them in the center, it gets much thinner still and the volume drops a good 50 percent or so. If I delete one of the tracks and only play one of the mono tracks, it sounds great and full like it did on set. I look at the tracks grouped as a stereo track and they are exactly out of phase. The peak of one track pointing up is pointing down on the 2nd track. The tracks actually look like perfect mirror images of each other rather than identical tracks being slightly shifted with the peaks and nulls not aligning. The only possibility I can think of other than Final Cut having some fundamental phasing issues is that the splitter I’m using is inverting the signal, but again, it sounds fine in the camera. Also, it seems if the tracks are panned hard left and right, i shouldn’t have any phasing issues. For years I’ve suspected that the timeline is set as inverting the phase by default but now that I’m working with two identical mono signals, it seems to confirm it.
Anyone else notice this?
Is there a setting I’m overlooking?
Why is there no phase inversion plug in?It’s obviously an easy fix in my situation, but for separate mics on separate channels it gets much more complicated unless you bring it into a DAW. Seems like an unnecessary step that most people shouldn’t have to deal with. It’s also a scary thing in that even if you did mix in a DAW, when you bring your stereo track back into FCP, there would be phasing issues.
replied 16 years, 2 months ago 5 Members · 14 Replies
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14 Replies
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How are you monitoring your audio?
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I usually monitor through fairly cheap computer speakers plugged into the 1/8″ headphone output of my tower. With this latest project, i was monitoring through the speakers in my laptop as i’m out of town. I’ve also noticed the problem at a place i freelance at through an Aja card into midlevel MAudio monitors.
-Chris
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It’s always been the way FCP works for me, but it varies shoot to shoot. If you output dual mono tracks (instead of panning your mono tracks to stereo and playing back stereo), you won’t get it.
Or simply hide one of the audio tracks by clicking the track visibility orb on the far left of the timeline.
Jeremy
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How do you capture from the camera? Is it possible there is a wiring problem between your deck/camera and the computer?
XLR connections should be wired as such:
Pin Function
1 Chassis ground (cable shield)
2 positive polarity terminal (“hot”) (+)
3 return terminal (“cold”) (-)Tech-T Productions
http://www.technical-t.com -
I digitized the HV20 footage via firewire through Imovie and import the files into FCP (the hv20 is particularly buggy with FCP) but I’ve had the same problem with the HVX200 and other cameras using the P2 import tool.
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[Chris Walldorf] “but I’ve had the same problem with the HVX200 and other cameras using the P2 import tool.”
It’s really easy to alleviate, though.
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Well, firewire rules out my initial idea.
Lets see…….It could be incoming audio to the camera being out of phase, but you say that it sounds fine on headphones straight from the the camera. So, I think that you are correct then in assuming some kind of funkyness going on in your computer. I never used iMovie before. Any chance there is a setting or something going on there?
Tech-T Productions
http://www.technical-t.com -
[Terry Mikkelsen] ” but you say that it sounds fine on headphones straight from the the camera.”
Most likely because the camera is sending a dual mono split L&R.
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Most likely because the camera is sending a dual mono split L&R.
Oh, that would suck if the camera were not outputting true stereo sound through the headphone output. But again, if the audio were out of phase as it was getting into the camera and then the camera combined them for a dual mono output, then the headphones would have that “telephone” out of phase cancellation sound.
Tech-T Productions
http://www.technical-t.com -
My point is that there is no phase cancelation in the files, it’s very easy to listen to one channel or the other in FCP or listen to a dual mono (instead of stereo) output to hear each channel separately. Or simply lower the level of one of the channels. There’s a bunch of ways to ‘fix’ this, although I don’t really see it as a major problem.
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