Audio Problems with MP3 Files

Posted on by Larry

[ This article was first published in the January, 2009, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]


José Antonia Donoso writes:

I’ve had two problems with audio lately that I hope you can help me with; none of the audio articles I found in your page could do it. The first one is related with using files in the Mp3 format: Every once in a while, the MP3 files seem to make some sort of “auto-render” or “corrupted” render which is not undoable.


The second problem I was hoping you could help me with is related to audio also: I was editing material recorded with a miniDV camera, with two different audio sources: in some scenes I used material coming directly from the camera, while for others I received a CD with WAV files recorded by a (sort of) sound engineer. I edited, rendered, made a DVD with it and it was all good. Then I was requested to make a master in miniDV also.


To my surprise, when listening to the “product” through the camera I was recording in, the audio lost a lot of level in a point. That point was a dialogue received as a WAV file, which didn’t seem corrupt or damaged. And, to add to my surprise, if I put earphones on the camera output there was NO loss of level in that dialogue. ??? I tried different ways: panning both channels to the center, panning them to the opposite side they had so far, but nothing. I then exported some audio renders of the dialogue as WAV, AIFF, MOV. I used FC, Compressor, and MPEG streamclip. The problem (or symptom) remained the same: when listening to THAT file (a single line of dialogue), it was almost mute if I listened through the camera I was recording to, but OK if I listened my timeline in FC or (???) through the camera’s earphones. I should also make clear that I did listen to the recorded tape, and yes, the audio problem was there. Eventually I erased one of the audio channels in the timeline, panned the remaining one to the center, checked the levels and the problem was solved.

Larry replies: Thanks for writing — and for your excellent questions.

First, Final Cut Pro HATES MP3 files – your solution to convert them to AIF before editing in iTunes is the best way to work. You can do the same thing using Soundtrack Pro. Final Cut expects to work with uncompressed audio. That means all your audio should be converted to either AIF or WAV before importing it into Final Cut.

Here’s an article that explains how.

If you are still getting breakup, my suggestion is that somehow an MP3 sneaked onto your timeline or you will need to reconvert the file using other software. I’ve never had problems using AIF files in FCP.

The second problem is caused by audio phase cancelation. This is most often caused by using microphone cables that are not wired the same way. The audio signals are recorded “out of phase.” While each channel sounds fine when listened to separately, like on headsets, when you combine the two channels into a mono track, each cancels the other out and the level drops. You can fix this either by deleting one channel, which you did, or by using the Analysis tab in Soundtrack Pro to fix it.


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