Echo or Off Timing Recording?

So I do amateur audio/video editing, and I recently started helping some friends do an interview style podcast. We use 1 camera and a few mics. But when I load up the files and begin editing, I notice that the audio from the camera and one of the mics doesn’t line up. It starts out fine, but as the recording goes on, the audio falls out of sync and begins echoing. Now, I know about dropped frame rates and the such being a possible issue, but I really think it may be a settings thing I’m just not catching. Here’s my set up:

Audacity (for Mac) 2.0.0 and Mac OSX ver. 10.6.8
Recorded standard 44100Hz, 16bit
MXL 990 USB mic

Sony Handycam hdr-cx100 AVCHD 1440 x 1080
Dolby Digital 2ch 48000Hz compressed

I use Premiere Pro with a project audio format of 48000Hz - 32bit floating. Is this happening because of the hz/bit settings?

If you record two digital things, then sample rate sync becomes a serious issue. Nobody can maintain perfect 48000. If your mic is running at 48001 and the camera is running at 47998, then the composite is eventually going to drift out of sync.

When you use Apple Aggregate Device to get two USB microphones to record at once, the Mac will ask you which one you want to use as the timing master. You can’t use both.


If you only have one microphone that does this, then the easy fix is to sell it. You can use the “Change” tools within Audacity to slow down or speed up the track, but they never come out perfect and you will need to do that to every recording you make from now to forever.

There are compromises. You can figure out that the mic drifts off one frame every five minutes and rip out two frames every ten minutes. Games like that.

Start taping a person trading a book and get them to clap loudly and visibly every five minutes. Edit later to tell how far off it actually is.

You’re doing the consumer version of this.


Thanks Koz, I’ll keep that in mind and tweek some things next time we record.