Synchronizing Video and Audio

As previously mentioned, Killdeer has 158 takes that might need to have the video and audio recordings synchronized. (Some shots are MOS, which is filmmaking slang for being without sound.) While synchronizing a take is straightforward, even a short task done 158 times begins to add up.

Adobe Premiere has a feature to synchronize audio and video tracks. I presume that feature does the software equivalent of what an editor does manually: find the audio spike for the slate in the camera audio track and in the microphone tracks and align using that. That feature works pretty well, although there are always cases where it can’t find the spike in every track. But because the video tracks are discrete along 1/24 of a second boundaries and the audio tracks are continuous, whether using automatic or manual synchronization there can be a skew between video and audio tracks.

On average, this skew should be no more than 21 milliseconds but I wanted the audio to be exactly aligned with the video. After much grinding of teeth and searching, I discovered a page that talked about Show Audio Time Units, a context menu item that changes the timeline for a sequence from video units, i.e., 1/24 of a second, to audio units, which are effectively continuous. When using audio time units, the audio tracks can be aligned exactly on the slate spike even if it falls between two video frames. Voilà!