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Audio coming into FCP low
We are shooting on Panasonic HDX900 cameras (dvcpro). When our audio guys set tone @ -20dB in the field, we always have to add gain to the audio in post. We started asking them to set tone @ -12dB to give us a hotter signal. The audio sounds fine but we’re still having to add gain to all audio. This has happened with many different audio guys, many different gear packages, and many different locations.
On the post side we are capturing from DVCPRO 1400 Decks, decklink cards and we are pulling everything in via HDSDI.
Any thoughts?
Thanks in advance!
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17 Replies
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What level does the -20 tone comeback at on your system? You should align your system to the -20 tone from the source media. Broadcast standards are tone @-20dbfs and nothing hotter than -10dbfs.
Eric
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Hello Steve and welcome to the Cow Audio Forum.
Tone at the camera at -20 is correct. Where you roll after that makes a difference.
Tone at 0 from the mixer to -20 on the camera is used to calibrate the two systems so you can know with some certainty by looking at the mixer meters what’s getting to the camera.
With this calibration, I usually peak my mixer at + 14. That means the camera is seeing -6 dB. That’s 6 dB of “Oops” room. Make sure the mixer displays peak meters, not just RMS.
Set up a trial and record this way. See what happens when you bring that into FCP.
Regards,
Ty Ford
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Sound recordists are “very sensibly” nervous about running the audio too hot in the field. They calibrate their mixer ppm 4 to a -20 on the camera. Then hit a 6 on the mixer thats fine. BUT be aware that the input electronics of many cameras dont like it as hot as that and can create distortion, which is a sure fire way of YOU not hiring THEM again.
When youre in the field, you dont know what coming next as it “live” unlike those of us in post where we can rewind and do it again. So if a mixer recordist lines up mixer and camera correctly, but then allows audio to go over the ppm 6 – it will be off his scale very soon. And so, how loud was it? Did it clip, or distort. No one knows until the editor rings him and tells him it all needs to be re shot. Whos paying then.
And anyway the levels arent an issue really in the edit, as when it goes to the dubbing mixer, he can and will fix issues like that with far greater tools at his disposal than any FCP can ever have!
It is going for a dub right??When you say it plays back low. do you mean that a -20 tone on camera input doesnt make a -20 playback on the FCP. Then that an FCP issue. You should find that those tones come in and playback (with the fader at an unadjusted 0 position) at a PPM 4 in the edit suite. Is this not the case.
Peter
Post Production Dubbing Mixer
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Peter,
Let’s call it like it is. There are any number of cameras that I have worked with that are out of calibration if they were ever IN calibration. Audio is not a yes/no situation. Circuitry can go somewhat wong.
A DSR500 from Boston came here (with operator). When I alerted him to strange clipping sounds well below 0 (like -10) on his camera’s meters he say not to worry, “all the sound guys say that.”
When he got back home, the audio was clipped. Upon inspection, he found his camera was out of spec. Fortunately, I had been recording very clean mp3 files for transcription. BUT THE CAMERA WAS BROKEN.
Any camera that can’t take level to 0dB without clipping is either designed incorrectly or components have shifted values and it’s BROKEN. Shame on the designers if they can’t get it right. Shame on the operator if he/she doesn’t send the camera in for maintenance when problems like this occur.
For audio people in the field, here’s my advice. When you hear clicks in the phones that sound like clips, double check all levels. Look at the camera’s meters. If they are below 0 dB and you’re hearing clips, record some audio with these clicks and then play it back. The clicks should be audible in exactly the same place upon playback. If they aren’t, there’s something else out of alignment. Make sure your mixer ‘s meters are set to read peak, not just rms. Make sure you’re not sending line level to an input set to mic level.
If they are there and you’re sending line level to the camera, try switching mixer and camera to Mic Level and recalibrate to -20. Simply switching from line to mic (or vice versa) without recalibrating tones is NOT good enough. See if the problem goes away. The few times I have run into this clipping problem, switching to Mic Level has solved the problem. Yes, there may be some low level noise you wouldn’t hear if you were feeding line, but underrecording with no real way to tell what level your working with is just not acceptable. Alert the camera operator of the problem and anyone above them (in a nice way) so that the problem may be corrected.
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field GuideWatch Ty play guitar -
Thanks for the info fellas! I’m certainly no audio expert so the advice helps. Here’s what we’ve come up with on the issue.
If the field guy sends his tone down the line and calibrates the it to -20dB, we get a clean signal here however we’re having to add a lot of gain to get it to a reasonable level. The DVCPRO camera and all DVCPRO decks clearly indicate (with the tone marker)-20dB as the level for tone.
If the field guy sends his tone down the line and calibrates it to -12dB, we get a clean signal that is much more in line with the audio levels we’d like to see and we still might add a touch of gain here and there. I totally understand that the field guy’s job is to capture what’s happening in a world where nobody knows what will happen next and he/she needs to be a bit conservative. With that said, we’ve had pushback from the field guys when asking them to set tone at -12dB
I personally have set a mixer and cam up to test and have had no trouble setting tone to -12dB and screaming as loud as possible into a mic. If I scream bloody murder I can make it clip but the HDX900 seems to handle this just fine.
I’m hoping to be able to better explain the issue at hand to any field guys so that we can all be on the same page. I would have thought, “me client, you getting paid” would have been enough but it looks like I’m going to have to learn some techno babble on this one.
Thanks agian guys!
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Ty
Youre entitled to your opinion, as is everyone.As a studio guy who has complained about cautious levels from the field myself over the years, I was surprised – but I can tell you that it is the opinion of a great many highly regarded UK recordists that cameras input electronics do differ in what levels they can accept before distortion, (not clipping) and this is not a fault, but circuitry design.
This is not my opinion, but feedback from field recordists on the topic.
PeterPost Production Dubbing Mixer
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Steve,
what mixer are they using?
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field GuideWatch Ty play guitar -
Tone level is one thing. Actual dialog level is another. Perhaps the sound guys are just recording the dialog level too low. Keeping the dialog level peaking at +10 at the mixer and -10 on the camera should solve your “low level” issues.
Eric
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Several different ops and different mixers. SD 442, PCM, etc..
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Peter,
Sorry. Not buying it. Zero is zero.
If you’re telling me that the camera craps out before 0 dB. It IS a design flaw.
We’ll still be friends regardless,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field GuideWatch Ty play guitar
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