syncing audio in Final Cut Studio with external .wav

When recording audio for video, it's usually a good idea to record 48kHz, since that is the frequency at which audio is typically delivered when it's part of video. In your case, with an existing 44.1kHz recording, Final Cut will convert the audio on playback, or you can render your audio once and FCP won't have to convert in real time any more each time you play it. You can also use QuickTime or many audio tools to convert from 44.1kHz to 48kHz. There should be no problem with having the audio recorded at 44.1kHz, it's just not the most direct route.

As far as synchronizing picture and audio goes, that's just a matter of shifting them (relative to each other) on the Final Cut timeline. To do that, you need some kind of reference that tells you if they are in synch. A slate is useful for this. Recording reference audio with your HV30 is also a good idea, then you can see the two waveforms on top of each other and adjust them until they "match". Other helpful references are camera flashes.

- Martin

MacMike1 said:

thanks for the input.
is there a easy way to sync the video and audio on the timeline? i read somewhere that i can use mark points. any idea how i can do this?
the only way i managed is manually shifting the audio track and trial and error until the video suits the audio.
after i did that the audio and video is in sync. however, 10 minutes later in the video footage its out of sync again. any idea why? is it because the audio is 44khz? how do i make it 48khz? you said quicktime how do i do that? sorry i am very new on mac and final cut pro.

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I had this same problem with footage. I have these old 80's music videos that were on BETA TAPE!! I wanted to archive them and in doing so decided to use mp3's for the audio to clean them up. The video would fall behind at some points/catch up/then slow down again. The easiest solution I found was to make cuts in the footage and adjust the speed of playback accordingly. Not sure if it would be noticeable on your footage, but it's spotless on mine!

MacMike1 said:

but how is this possible?
if i recorded video and audio at the same time of the same event how is it possible that it is out of sync? if i sync minute 00:01:00 audio and video how can 00:15:00 be out of sync? the movie is not longer or the audio. i am not completely understanding this. hope someone can clarify.
thx mike

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Yeah sorry, I don't have a technical answer as to WHY it happened. For me it happened because it was recorded on tape and the tape it self is very old (1984) and was not kept in optimal conditions. Hopefully somebody could answer that one, I'm kinda curious myself. My GUESS would be it has to do with the framerate of the video recording vs. rate of the audio recording. Not sure if you have a musical ear or not, but did you notice if the audio vs. video sound were in the same key?

MacMike1 said:

is there a easy way to sync the video and audio on the timeline? i read somewhere that i can use mark points. any idea how i can do this?

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You can set a marker in FCP by pressing the 'M' key. Make sure the clip that you want the marker to be attached to is selected before you press M. Having a marker in the video clip and a separate marker in the audio clip, where the two markers represent the same event (such as a slate), you can then easily shift one of the clips to match the other and get it roughly right. For the final finetuning, down to the last frame or two, I usually just try it out and see if it gets worse or better if I shift it a frame to the right or left.

after i did that the audio and video is in sync. however, 10 minutes later in the video footage its out of sync again. any idea why? is it because the audio is 44khz? how do i make it 48khz? you said quicktime how do i do that?

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How much does it drift away? 44.1 vs. 48 kHz is such a big difference, you would notice the drift within a couple of seconds. It sounds like your drift is less significant, i.e. noticable only over longer periods of time? My guess is that the timing devices that drive your camera and recorder are not 100% accurate, and thus drift away over time. Unless you synch them using timecode or similar mechanisms, that is to be expected, just nowhere near as much as you experience. I routinely record an hour and more using dual system (i.e., video and audio recorded on separate devices), and between the beginning and end of the tape there's never more than a frame or two that I need to correct.

I haven't verified this, but I've read posts saying that the latest Soundtrack Pro has a way to change the timing of audio. So, if you know excatly how long the audio is vs. how long it should be in order to match your video, you could correct it that way. But really, using high-quality recording gear, this shouldn't be a problem in the first place.

- Martin

How much room do you have on whichever harddrive you're importing to?

30 minutes of video is going to suck up about 5 or 6GB of drive space. I'd want to have 10GB free (at least!) before importing that 30 minutes's worth. And the more the merrier, because your drive doesn't have to work as hard hunting for somewhere to write to when there's plenty of acreage to graze in, so to speak.

If your drive is almost full (or even getting close) you might find your machine skips frames of video on import, and that it generally has a hard time keeping up with the data flow. I'm wondering whether this could be part of your synching problem.

MacMike1 said:

i managed with soundtrack pro to change the sample rate. and i sync it in final cut pro. and again. it is after couple of minutes out of sync.

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Changing the sample rate is actually not what I tried to suggest. That should have no impact on the synchronization (or lack thereof), because Final Cut will adjust for it on playback, and it'll sound virtually the same.

What I was referring to is changing the actual duration of the sound. Soundtrack Pro 2 can do that; look for "Audio Stretching Tool" in the manual. If the rate of drift is constant, that might be able to get your picture and sound all synched up.

i was recording the video directly to my laptop with firewire and i was recording the sound with wavelab on a PC directly coming out of the mixer.
i dont understand why there is a difference of 1-2 seconds after almost 5-6 minutes. and it get gradually more. hope you can help or anyone else.

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It shouldn't happen, that's all I can say. A second every five minutes means you are drifting by a frame each 360 frames (or off by about 0.3%), that's just magnitudes worse than anything I've ever encountered with digital recorders. But then again, mixing up sample rates (44.1 kHz vs. 48 kHz) would be way worse, so I don't believe that's your problem.

- Martin