Audio Drift - Zoom H4n and Canon 700d editing in FCP x

Hi all,

I am having problems with audio drift even with short clips of less than a minute.

I am shooting on a Canon 700d and using a Zoom H4n with lavalier microphone to record audio separately.

When I try to sync up the audio file with the video clips in FCP X there is a noticeable amount of audio drift almost immediately.

Can anyone help me with how to make sure that my audio files and video clips fill the same amount of time?

Cheers,

D

I just did a job with footage and audio from those same two devices, no problems with sync.

What frame rate is the 700D recording at? Also what sample rate is the H4N recording at?

At least one device is recording at a different speed than clip playback speed. You need to figure out which device is not recording and playing back 1:1 "real time" correctly.

Verify all audio on all devices is at 48kHz sample rate. One of them isn't, I suspect the Zoom. Not sure the Canon will even change audio sample rates. But video standard is 48kHz (which can effect sync), at 16-bit (which won't effect sync).

Hi both,

Thanks for getting back to me.

So my Canon movie recording settings were: 1920x1080, 24fps, shutter speed 50. I can't find a way to see what the audio sample rate is on the camera.

The Zoom H4n was set to WAV 48KHZ, 24 bit.

Editing in FCP, the frame rate was 23.98fps.

It seems that the audio file is longer than the video file so even when I mute the audio on the video file, the presenter's lips go out of sync with the audio from the Zoom.

OK, the 700d is known as the Rebel T5i here in the US. It is fixed at 48kHz, can't be changed.

I'd look at the Soom H4n. Does it have a frame rate setting, in addition to sample rate & bit-depth settings? I've seen some of these dedicated recorders let you set a frame rate, which screws with the sample rate in odd ways.

But to verify, I'd open the both files in QuickTime 7 player, if you have it. Command+i will give you the info window that can verify the clips settings accurately. I'd simply verify clip specs in something other than FCPX just to verify the file formatting specs correctly. If both are 48kHz sample rate, sync "drift" should be an issue.

Duration will be different, because you can't his record and stop on two devices at once in absolute perfect sync. But that shouldn't matter.

Are you sync'ing manually, or with FCPX's sync command?

Have you tried to create a real 24 fps project.

Color NTSC per definition is not playing real-world time. Audio does.
That means a 1 second NTSC video plays back in 1,001 seconds. So the timeline is set to a 47952 Hz playback. A 48000 Hz audio will play longer.

FCP X infos are a bit misleading.

- Andreas