Why is my Audio Sync out?

Submitted by Rick Young & Andrew Shanks

NOTE: most of the Audio sync problems talked about below occured in earlier versions of EditDV & Quicktime. Both technologies have come a long way since then and with the exception of a few of issues listed below (1, 3 and 4) you shouldn't have any trouble with Audio sync. For CineStream make sure you are running Quicktime 4.1.2 or greater.

why is the audio out of sync with my video and how can I fix it?

There are various reason for this, some are bugs, some are just niggles with the way EditDV works, but I'll try to cover the main causes here (note there are some problems I have heard of that are just pure mysteries, and for those I have no answers, ...but check these out first anyway).

1. The project was set to the wrong audio sampling rate. This means that when you created a new project, you may have set the Audio for 44.1KHz, when your camera footage has in fact been recorded at 48KHz. This can have strange effects on your sync (although when you render down to the AP track, the new soundtrack will be at the new project sampling rate (although I am unsure as to whether this will bring things back into alignment sync-wise though). So the general rule there is make sure you choose the project sampling rate to be the same as your cameras audio sampling rate (again you can mix sampling rates in a single project, but just be aware that things might get a little strange in the sync department if you do).

2. I encountered the dreaded sync-slip problem which has been reported by
several users of EditDV. I emailed Digital Origin support and received an
interesting response from one of the support guys who has helped me many
times in the past. I advised him of my system - a 9600/200 and said I was
using EditDV 1.6.1 with QT4. His response was:

Remove the Sound Manager extension to the trash, and restart the machine.

Run the QuickTime 3 installer from your EditDV CD, and CUSTOM install
only the Sound Manager.

Quicktime 4's Sound Manager is quite problematic.

After this everything seemed to work fine!!!.

I recently installed EditDV 1.6.1 on my Beige G3/333 running QT4. Again I
encountered out of sync pictures. I tried the above fix and Hey Presto -
everything back in sync.

3. Some Canon cameras have a problem where-by the audio doesn't capture at exactly 48khz, thus the longer the clip the more out of sync the audio becomes in relation to the video. The only way around this is to grab smaller chunks of Video with Audio.

4. Lastly there is the old question as to why when you play audio in the timeline (with video going out the firewire to an external monitor and the audio playing out the computer) the audio is so out of sync with the video. The video and audio ARE actually in sync, even if they don't look it, this is just an annoying little niggle about the way editDV/CineStream works, ...it is to do with the fact that the time it takes for the video to travel out the firewire is different to the time taken for audio to go out the computers speakers, so you get this delay (when you play out to tape at the end, because you are using the firewire for both audio and video, everything will sync up again perfectly). To get around this annoying delay there is a preference setting under LiveDV that allows you to alter the audio delay to suit your system (a good way to test and set this up is to either use a clapperboard or even something as simple as a book hitting a desktop, something that gives you a sharp sound and visual cue, capture into CineStream, put clip in timelinne then tweak the number of frames of delay in the LiveDV prefs until it looks right, ...3 or 4 frames will probably be about right). Also you can play the timeline with both audio and video out the firewire by holding down OPTION key and SPACE BAR. If you are serious about getting your clips cut to the beat and don't trust the audio delay too much you can always use the waveform view of the audio track you're cutting to, make a cut using that visual guide, then check it works by using the OPTION & SPACEBAR technique (note that audio is probably going to get a well needed overhaul before the next revision of CineStream, so many of these problems will hopefully be a thing of the past).

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