audio levels in a film.....

[Glen Trew]

As Tim mentioned, you can record right up to max (0dBfs) without a problem. 0dBfs doesn't sound any better or worse than -12dBfs or -20dBfs except for a miniscule about of noise difference (undetectable by most humans).

The standards that often come up, like "-12" and "-20" are only a "zero VU reference" for aligning a mixed and mastered recording or live broadcast to the "0" of a VU meter. "Zero VU reference" is of absolutely zero use for the recording of original tracks (such as film production dialog), hence the nick name for VU=Virtually Useless.

An ideal recording would have the highest level at maximum, and everything else anywhere below maximum that achieves the dynamics that the mixing engineer wants.

There are formulas and equipment that different agencies (like broadcast networks) have come up with to impose limits on perceived loudness and to standardize tasteful dynamic range, but all of these have flaws of their own. Even still, the highest level of a recording should be 0dBfs.

Glen Trew

 

[j1clark@ucsd.edu]

There are formulas and equipment that different agencies (like broadcast networks) have come up with to impose limits on perceived loudness and to standardize tasteful dynamic range, but all of these have flaws of their own. Even still, the highest level of a recording should be 0dBfs.

Glen Trew

Since the meters are not peak detectors, but in fact appear to be averaging, how do you know that you peak amplitude is not clipped when the 'meter' reads 0 dBFS?

 

[Glen Trew]

Which meters are you referring to that are not peak type?

If the meters are VU, you would not know where the peaks are, which is why, for recording original tracks, VU=Virtually Useless. VU meters are for mastering and broadcast. For optimum levels without overload, peak meters are a must.


GT

 

[DrDave]

I think for certain video applications you have to be really careful how you mix the bass. Here you may want to use multiband compression on the bass track. Dense short reverb is pretty much a given with some physical modeling to make sure it sounds like it is in the right space, especially in extreme transitions like leaving a car or phone booth, or modeling ambient sounds like a radio in the distance. To measure digital peaks, you need an inline digital peakmeter, but you can also just render the file and get the peak as part of the render process in most DAWs. The digital peakmeter is good for showing true overs in recording. The standard meters in various gear just take a sample--albeit a very short one--and transients can spike through undetected. Unless you are using some very expensive gear.

 

[CineSound]

im editing a film in fcp and theres a lot of tense scenes with tension building etc. Im taught that audio levels should always stay as -12db... is there any exceptions?

Ask the distributor who's getting the film what their technical requirements are for delivery. Quite a few cable channels and networks have very specific specs for average dialog levels and peak levels. I've had perfectly-good mixes rejected for DVD just because of (very rare) momentary peaks, requiring us to peak-limit everything to -10dBfs.

If you don't have any specs (or don't currently have a distributor), contact one of the major cable channels like HBO, Showtime, or Discovery and ask about technical delivery specifications, which they'll give you at no charge.

Among the things I'm concerned about in final mixes are:

1) the neutrality and isolation of the room (and I think few edit bays will qualify)

2) the quality of the loudspeaker/amp chain

3) the calibrated sound levels at which you're mixing (typically 82dB for a medium to small room, 85dB for large rooms)

4) your metering (peak vs. VU), signal processing, and so on.

These issues are frequently discussed in the post section of the Digidesign User Conference, at this link. It's a very complex area. If you're trying to do this in FCP, my recommendation would be that you just try to get a reasonable-sounding rough mix done for test screenings, and be prepared to do the final mix in a bigger room, preferably by an experienced re-recording mixer.

--Marc W.