My Audio Track Slows Down in FCP

[Dustin Whitaker]

I hooked up a flash recorder to the sound board, at an event i was shooting, so i could get the best audio. I recorded it as an mp3. In FCP I cued it up to the video and audio from my cameras but after a few minutes it's off. What's up?

[Steve House]

Originally Posted by Dustin Whitaker

I hooked up a flash recorder to the sound board, at an event i was shooting, so i could get the best audio. I recorded it as an mp3. In FCP I cued it up to the video and audio from my cameras but after a few minutes it's off. What's up?

It could stem from a variety of causes but the bottom line is the sample rate clocks of the video and of the file from your flash recorder aren't absolutely rock-solid identical. FCP should let you adjust the length of your audio file to bring it into sync. I'm a Windows guy and not familiar with FCP but perhaps someone else can guide you on the details of how to go about it. One of the problems with consumer MP3 recorders is that their clocks just aren't up to the accuracy required for double-system recording and the MP3 compression introduces additional variables. For best results record to an uncompressed file format such as wav and insure that the audio recorder is set to 48kHz sample rate if you can to avoid the need for conversion when it comes into your editor. (48kHz is the standard for video and is the rate the camera is running at. Music recorders default to the CD standard of 44.1 kHz but some consumer MP3 recorders run at even lower sample rates.)

If the problem is too severe to fix with minor adjustments in the length of the audio file or if the sound gets distorted when you tweak the file length, try playing back the audio in the recorder you used to make it, connecting the analog audio out of the recorder to the audio in on your soundcard and re-record it directly into FCP.

[Seth Bloombaum]

Originally Posted by Steve House

...insure that the audio recorder is set to 48kHz sample rate if you can to avoid the need for conversion when it comes into your editor...

Steve's advice is solid, I'll just emphasize that converting your mp3 to a 16 bit 48KHz aiff should be your first step before you bring it into your project.

[Dustin Whitaker]

Thanks, I converted the mp3 file to an aiff and it doesn't slow down.