Today it is much easier to record sync sound because of the on board microphones that most digital video cameras have as well as the multitude of XLR attachments so that you can plug external microphones right in and record on the same track as the video. Though this is possible, it is not always optimum to record sync sound. Sync sound tends to not come in quite as clear as well recorded non–sync sound as to much information going to one source may compromise it. You will find that having the on site sound mixer use a field recorder can be a great choice for getting exactly the kind of sound you want. Whether this is an older DAT recorder or one of the more contemporary digital 702 field recorders, you are going to have to sync the files up later when you are editing. You will often have these audio files in the Aiff format and you are going to have to sync that to what may have been exported as QuickTimes when you captured the film stock or digital video files. Here is a quick over view on how to easily sync the QuickTimes to your Aiff files.
Sync QuickTime and Aiff
Go into the large QuickTime file that you may have for all of the footage and make sub clips for each take or scene. If your bulk footage is already exported to several individual QuickTime files then you may not need to do this. Take this clip and get it into the viewer of Final Cut Pro, or whatever non-linear editing system you choose to use, and mark in and out points and then go to Modify and Make Subclip. Make sure that each of these video clips are named so that you can find them easily in the Browser.
Bring the Aiff audio track into the viewer. Do the same process of marking the in and out point for the specific scenes. You are going to want to use the clapper sound as where you should mark for the beginning of the scene and just make sure that the out mark is before the next clapper sound. Make sub clips for each of these audio segments as well. Allow that Aiff audio sub clip to have the same title as its video mate.
Bring the sub clip for each video and audio sample and match them up so that the clapper sound matches the clapperboard in the video. This will sync the audio track with the video track and the sound will then match perfectly, as long as you matched the clapper appropriately. You can then do this for each pair of sub clips on their own individual sequences. If you need to you can then export them individually as QuickTime videos, or just save each sequence as its own clip in the Browser for further editing.